AIDS Vaccine Design Immunogenicity Efficacy
Perciani, C. T., W. Jaoko, S. Walmsley, B. Farah, S. M. Mahmud, M. Ostrowski, O. Anzala, K. I. Team and K. S. MacDonald (2017). “Protocol of a randomised controlled trial characterising the immune responses induced by varicella-zoster virus (VZV) vaccination in healthy Kenyan women: setting the stage for a potential VZV-based HIV vaccine.” BMJ Open 7(9): e017391.
INTRODUCTION: A protective HIV vaccine would be expected to induce durable effector immune responses at the mucosa, restricting HIV infection at its portal of entry. We hypothesise that use of varicella-zoster virus (VZV) as an HIV delivery vector could generate sustained and robust tissue-based immunity against HIV antigens to provide long-term protection against HIV. Given that HIV uniquely targets immune-activated T cells, the development of human vaccines against HIV must also involve a specific examination of the safety of the vector. Thus, we aim to evaluate the effects of VZV vaccination on the recipients’ immune activation state, and on VZV-specific circulating humoral and cellular responses in addition to those at the cervical and rectal mucosa. METHODS AND ANALYSIS: This open-label, randomised, longitudinal crossover study includes healthy Kenyan VZV-seropositive women at low risk for HIV infection. Participants receive a single dose of a commercial live-attenuated VZVOka vaccine at either week 0 (n=22) or at week 12 (n=22) of the study and are followed for 48 and 36 weeks postvaccination, respectively. The primary outcome is the change on cervical CD4+ T-cell immune activation measured by the coexpression of CD38 and HLA-DR 12 weeks postvaccination compared with the baseline (prevaccination). Secondary analyses include postvaccination changes in VZV-specific mucosal and systemic humoral and cellular immune responses, changes in cytokine and chemokine measures, study acceptability and feasibility of mucosal sampling and a longitudinal assessment of the bacterial community composition of the mucosa. ETHICS AND DISSEMINATION: The study has ethical approval from Kenyatta National Hospital/University of Nairobi Ethics and Research Committee, the University of Toronto Research Ethics Board and by Kenyan Pharmacy and Poisons Board. Results will be presented at conferences, disseminated to participants and stakeholders as well as published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT02514018. Pre-results.
Li, S. S., N. K. Kochar, M. Elizaga, C. M. Hay, G. J. Wilson, K. W. Cohen, S. C. De Rosa, R. Xu, A. Ota-Setlik, D. Morris, G. Finak, M. Allen, H. V. Tieu, I. Frank, M. E. Sobieszczyk, D. Hannaman, R. Gottardo, P. B. Gilbert, G. D. Tomaras, L. Corey, D. K. Clarke, M. A. Egan, J. H. Eldridge, M. J. McElrath and N. Frahm (2017). “DNA priming increases frequency of T-cell responses to a VSV HIV vaccine with specific enhancement of CD8+ T-cell responses by IL-12 pDNA.” Clin Vaccine Immunol.
HVTN 087 assessed the effect of increasing doses of pIL-12 adjuvant on the immunogenicity of a HIV-1 multi-antigen (MAG) DNA vaccine delivered by electroporation and boosted with an attenuated VSV-Gag vaccine. We randomized 100 healthy adults to receive placebo, or 3mg HIV-MAG (gag/pol, env, nef/tat/vif) DNA vaccine co-administered with pIL-12 at 0mug, 250mug, 1,000mug or 1,500mug intramuscularly by electroporation at 0, 1 and 3 months followed by intramuscular inoculation with 3.4×107 PFU VSV-Gag vaccine at 6 months. Immune responses were assessed after prime, boost and 6 months after the last vaccination. High dose pIL-12 increased the magnitude of CD8+ T cell responses post boost compared to no pIL-12 (P=0.02), while CD4+ T-cell responses after the prime were higher in the absence of pIL-12 compared to low and medium dose pIL-12 (P</=0.05). The VSV boost increased Gag-specific CD4+ and CD8+ T-cell responses in all groups (P<0.001 for CD4+ T cells), inducing a median of four Gag epitopes in responders. Six to nine months after the boost, responses decreased in magnitude, but CD8+ T-cell response rates were maintained. The addition of a DNA prime dramatically improved responses to the VSV vaccine tested previously in HVTN 090, leading to broad epitope targeting and maintained CD8+ T-cell response rates at early memory. The addition of a high dose pIL-12 given with a DNA prime by electroporation and boosted with VSV-Gag increased CD8+ but decreased CD4+ T-cell responses. This approach may be advantageous in reshaping the T-cell responses to a variety of chronic infections or tumors.
AIDS Vaccine Envelope Design
Wang, S., T. H. Wu, A. Hackett, V. Efros, Y. Wang, D. Han, A. Wallace, Y. Chen, G. Hu, S. Liu, P. Clapham, J. Arthos, D. Montefiori and S. Lu (2017). “Screening of primary gp120 immunogens to formulate the next generation polyvalent DNA prime-protein boost HIV-1 vaccines.” Hum Vaccin Immunother: 0.
Our previous preclinical studies and a Phase I clinical trial DP6-001 have indicated that a polyvalent Env formulation was able to elicit broadly reactive antibody responses including low titer neutralizing antibody responses against viral isolates of subtypes A, B, C and AE. In the current report, a panel of 62 gp120 immunogens were screened in a rabbit model to identify gp120 immunogens that can elicit improved binding and neutralizing antibody responses and some of them can be included in the next polyvalent formulation. Only about 19% of gp120 immunogens in this panel were able to elicit neutralizing antibodies against greater than 50% of the viruses included in a high throughput PhenoSense neutralization assay when these immuongens were tested as a DNA prime followed by a fixed 5-valent gp120 protein vaccine boost. The new polyvalent formulation, using five gp120 immunogens selected from this subgroup, elicited improved quality of antibody responses in rabbits than the previous DP6-001 formulation. More significantly, this new polyvalent formulation elicited higher antibody responses against a panel of gp70V1V2 antigens expressing V1V2 sequences from diverse subtypes. Bioinformatics analysis supports the design of a 4-valent or 5-valent formulation using gp120 immunogens from this screening study to achieve a broad coverage against 16 HIV-1 subtypes.
Del Prete, G. Q., B. F. Keele, J. Fode, K. Thumar, A. E. Swanstrom, A. Rodriguez, A. Raymond, J. D. Estes, C. C. LaBranche, D. C. Montefiori, V. N. KewalRamani, J. D. Lifson, P. D. Bieniasz and T. Hatziioannou (2017). “A single gp120 residue can affect HIV-1 tropism in macaques.” PLoS Pathog 13(9): e1006572.
Species-dependent variation in proteins that aid or limit virus replication determines the ability of lentiviruses to jump between host species. Identifying and overcoming these differences facilitates the development of animal models for HIV-1, including models based on chimeric SIVs that express HIV-1 envelope (Env) glycoproteins, (SHIVs) and simian-tropic HIV-1 (stHIV) strains. Here, we demonstrate that the inherently poor ability of most HIV-1 Env proteins to use macaque CD4 as a receptor is improved during adaptation by virus passage in macaques. We identify a single amino acid, A281, in HIV-1 Env that consistently changes during adaptation in macaques and affects the ability of HIV-1 Env to use macaque CD4. Importantly, mutations at A281 do not markedly affect HIV-1 Env neutralization properties. Our findings should facilitate the design of HIV-1 Env proteins for use in non-human primate models and thus expedite the development of clinically relevant reagents for testing interventions against HIV-1.
Bogers, W., S. W. Barnett, H. Oostermeijer, I. G. Nieuwenhuis, N. Beenhakker, D. Mortier, P. Mooij, G. Koopman, E. Remarque, G. Martin, R. P. Lai, A. K. Dey, Y. Sun, B. Burke, G. Ferrari, D. Montefiori, L. Martin, D. Davis, I. Srivastava and J. L. Heeney (2017). “Increased, Durable B-Cell and ADCC Responses Associated with T-Helper Cell Responses to HIV-1 Envelope in Macaques Vaccinated with gp140 Occluded at the CD4 Receptor Binding Site.” J Virol 91(19).
Strategies are needed to improve the immunogenicity of HIV-1 envelope (Env) antigens (Ag) for more long-lived, efficacious HIV-1 vaccine-induced B-cell responses. HIV-1 Env gp140 (native or uncleaved molecules) or gp120 monomeric proteins elicit relatively poor B-cell responses which are short-lived. We hypothesized that Env engagement of the CD4 receptor on T-helper cells results in anergic effects on T-cell recruitment and consequently a lack of strong, robust, and durable B-memory responses. To test this hypothesis, we occluded the CD4 binding site (CD4bs) of gp140 by stable cross-linking with a 3-kDa CD4 miniprotein mimetic, serving to block ligation of gp140 on CD4+ T cells while preserving CD4-inducible (CDi) neutralizing epitopes targeted by antibody-dependent cellular cytotoxicity (ADCC) effector responses. Importantly, immunization of rhesus macaques consistently gave superior B-cell (P < 0.001) response kinetics and superior ADCC (P < 0.014) in a group receiving the CD4bs-occluded vaccine compared to those of animals immunized with gp140. Of the cytokines examined, Ag-specific interleukin-4 (IL-4) T-helper enzyme-linked immunosorbent spot (ELISpot) assays of the CD4bs-occluded group increased earlier (P = 0.025) during the inductive phase. Importantly, CD4bs-occluded gp140 antigen induced superior B-cell and ADCC responses, and the elevated B-cell responses proved to be remarkably durable, lasting more than 60 weeks postimmunization.IMPORTANCE Attempts to develop HIV vaccines capable of inducing potent and durable B-cell responses have been unsuccessful until now. Antigen-specific B-cell development and affinity maturation occurs in germinal centers in lymphoid follicles through a critical interaction between B cells and T follicular helper cells. The HIV envelope binds the CD4 receptor on T cells as soluble shed antigen or as antigen-antibody complexes, causing impairment in the activation of these specialized CD4-positive T cells. We proposed that CD4-binding impairment is partly responsible for the relatively poor B-cell responses to HIV envelope-based vaccines. To test this hypothesis, we blocked the CD4 binding site of the envelope antigen and compared it to currently used unblocked envelope protein. We found superior and durable B-cell responses in macaques vaccinated with an occluded CD4 binding site on the HIV envelope antigen, demonstrating a potentially important new direction in future design of new HIV vaccines.
Emerging Infectious Diseases
Harmon, J. R., S. T. Nichol, C. F. Spiropoulou and A. K. McElroy (2017). “Whole Blood-Based Multiplex Immunoassays for the Evaluation of Human Biomarker Responses to Emerging Viruses in Resource-Limited Regions.” Viral Immunol.
Many emerging viruses such as Ebola and Lassa occur in resource-limited areas of the world. The advent of multiplex immunoassays has facilitated the study of biomarkers of disease since only small amounts of clinical material are required; however, such assays are designed and validated for only plasma or serum. This is a significant impediment when studying infectious diseases in the context of an outbreak in a developing nation. Plasma or serum can be difficult to obtain in the field due to the need for additional processing of infectious materials. Evaluation of multiplex immunoassays using frozen and thawed human whole blood (WB) would permit additional analysis using a more readily available human clinical sample. In this study, frozen and thawed human WB was directly compared with frozen and thawed plasma from normal healthy donors in a series of multiplexed immunoassays for 59 different biomarkers. We demonstrate that most important biomarkers can be evaluated using thawed WB, which will facilitate the study of human cytokine and other biomarker responses to viruses emerging in resource-limited regions.
Wang, J., M. Bardelli, D. A. Espinosa, M. Pedotti, T. S. Ng, S. Bianchi, L. Simonelli, E. X. Y. Lim, M. Foglierini, F. Zatta, S. Jaconi, M. Beltramello, E. Cameroni, G. Fibriansah, J. Shi, T. Barca, I. Pagani, A. Rubio, V. Broccoli, E. Vicenzi, V. Graham, S. Pullan, S. Dowall, R. Hewson, S. Jurt, O. Zerbe, K. Stettler, A. Lanzavecchia, F. Sallusto, A. Cavalli, E. Harris, S. M. Lok, L. Varani and D. Corti (2017). “A Human Bi-specific Antibody against Zika Virus with High Therapeutic Potential.” Cell 171(1): 229-241 e215.
Zika virus (ZIKV), a mosquito-borne flavivirus, causes devastating congenital birth defects. We isolated a human monoclonal antibody (mAb), ZKA190, that potently cross-neutralizes multi-lineage ZIKV strains. ZKA190 is highly effective in vivo in preventing morbidity and mortality of ZIKV-infected mice. NMR and cryo-electron microscopy show its binding to an exposed epitope on DIII of the E protein. ZKA190 Fab binds all 180 E protein copies, altering the virus quaternary arrangement and surface curvature. However, ZIKV escape mutants emerged in vitro and in vivo in the presence of ZKA190, as well as of other neutralizing mAbs. To counter this problem, we developed a bispecific antibody (FIT-1) comprising ZKA190 and a second mAb specific for DII of E protein. In addition to retaining high in vitro and in vivo potencies, FIT-1 robustly prevented viral escape, warranting its development as a ZIKV immunotherapy.
Shan, C., A. E. Muruato, B. W. Jagger, J. Richner, B. T. D. Nunes, D. B. A. Medeiros, X. Xie, J. G. C. Nunes, K. M. Morabito, W. P. Kong, T. C. Pierson, A. D. Barrett, S. C. Weaver, S. L. Rossi, P. F. C. Vasconcelos, B. S. Graham, M. S. Diamond and P. Y. Shi (2017). “A single-dose live-attenuated vaccine prevents Zika virus pregnancy transmission and testis damage.” Nat Commun 8(1): 676.
Zika virus infection during pregnancy can cause congenital abnormities or fetal demise. The persistence of Zika virus in the male reproductive system poses a risk of sexual transmission. Here we demonstrate that live-attenuated Zika virus vaccine candidates containing deletions in the 3′ untranslated region of the Zika virus genome (ZIKV-3’UTR-LAV) prevent viral transmission during pregnancy and testis damage in mice, as well as infection of nonhuman primates. After a single-dose vaccination, pregnant mice challenged with Zika virus at embryonic day 6 and evaluated at embryonic day 13 show markedly diminished levels of viral RNA in maternal, placental, and fetal tissues. Vaccinated male mice challenged with Zika virus were protected against testis infection, injury, and oligospermia. A single immunization of rhesus macaques elicited a rapid and robust antibody response, conferring complete protection upon challenge. Furthermore, the ZIKV-3’UTR-LAV vaccine candidates have a desirable safety profile. These results suggest that further development of ZIKV-3’UTR-LAV is warranted for humans.Zika virus infection can result in congenital disorders and cause disease in adults, and there is currently no approved vaccine. Here Shan et al. show that a single dose of a live-attenuated Zika vaccine prevents infection, testis damage and transmission to the fetus during pregnancy in different animal models.
HIV- Acute Infection
Mabuka, J. M., A. S. Dugast, D. M. Muema, T. Reddy, Y. Ramlakhan, Z. Euler, N. Ismail, A. Moodley, K. L. Dong, L. Morris, B. D. Walker, G. Alter and T. Ndung’u (2017). “Plasma CXCL13 but Not B Cell Frequencies in Acute HIV Infection Predicts Emergence of Cross-Neutralizing Antibodies.” Front Immunol 8: 1104.
Immunological events in acute HIV-1 infection before peak viremia (hyperacute phase) may contribute to the development of broadly cross-neutralizing antibodies. Here, we used pre-infection and acute-infection peripheral blood mononuclear cells and plasma samples from 22 women, including 10 who initiated antiretroviral treatment in Fiebig stages I-V of acute infection to study B cell subsets and B-cell associated cytokines (BAFF and CXCL13) kinetics for up to ~90 days post detection of plasma viremia. Frequencies of B cell subsets were defined by flow cytometry while plasma cytokine levels were measured by ELISA. We observed a rapid but transient increase in exhausted tissue-like memory, activated memory, and plasmablast B cells accompanied by decline in resting memory cells in untreated, but not treated women. B cell subset frequencies in untreated women positively correlated with viral loads but did not predict emergence of cross-neutralizing antibodies measured 12 months post detection of plasma viremia. Plasma BAFF and CXCL13 levels increased only in untreated women, but their levels did not correlate with viral loads. Importantly, early CXCL13 but not BAFF levels predicted the later emergence of detectable cross-neutralizing antibodies at 12 months post detection of plasma viremia. Thus, hyperacute HIV-1 infection is associated with B cell subset changes, which do not predict emergence of cross-neutralizing antibodies. However, plasma CXCL13 levels during hyperacute infection predicted the subsequent emergence of cross-neutralizing antibodies, providing a potential biomarker for the evaluation of vaccines designed to elicit cross-neutralizing activity or for natural infection studies to explore mechanisms underlying development of neutralizing antibodies.
HIV – Assay
Hraber, P., C. Rademeyer, C. Williamson, M. S. Seaman, R. Gottardo, H. Tang, K. Greene, H. Gao, C. LaBranche, J. R. Mascola, L. Morris, D. C. Montefiori and B. Korber (2017). “Panels of HIV-1 Subtype C Env Reference Strains for Standardized Neutralization Assessments.” J Virol 91(19).
In the search for effective immunologic interventions to prevent and treat HIV-1 infection, standardized reference reagents are a cost-effective way to maintain robustness and reproducibility among immunological assays. To support planned and ongoing studies where clade C predominates, here we describe three virus panels, chosen from 200 well-characterized clade C envelope (Env)-pseudotyped viruses from early infection. All 200 Envs were expressed as a single round of replication pseudoviruses and were tested to quantify neutralization titers by 16 broadly neutralizing antibodies (bnAbs) and sera from 30 subjects with chronic clade C infections. We selected large panels of 50 and 100 Envs either to characterize cross-reactive breadth for sera identified as having potent neutralization activity based on initial screening or to evaluate neutralization magnitude-breadth distributions of newly isolated antibodies. We identified these panels by downselection after hierarchical clustering of bnAb neutralization titers. The resulting panels represent the diversity of neutralization profiles throughout the range of virus sensitivities identified in the original panel of 200 viruses. A small 12-Env panel was chosen to screen sera from vaccine trials or natural-infection studies for neutralization responses. We considered panels selected by previously described methods but favored a computationally informed method that enabled selection of viruses representing diverse neutralization sensitivity patterns, given that we do not a priori know what the neutralization-response profile of vaccine sera will be relative to that of sera from infected individuals. The resulting 12-Env panel complements existing panels. Use of standardized panels enables direct comparisons of data from different trials and study sites testing HIV-1 clade C-specific products.IMPORTANCE HIV-1 group M includes nine clades and many recombinants. Clade C is the most common lineage, responsible for roughly half of current HIV-1 infections, and is a focus for vaccine design and testing. Standard reference reagents, particularly virus panels to study neutralization by antibodies, are crucial for developing cost-effective and yet rigorous and reproducible assays against diverse examples of this variable virus. We developed clade C-specific panels for use as standardized reagents to monitor complex polyclonal sera for neutralization activity and to characterize the potency and breadth of cross-reactive neutralization by monoclonal antibodies, whether engineered or isolated from infected individuals. We chose from 200 southern African, clade C envelope-pseudotyped viruses with neutralization titers against 16 broadly neutralizing antibodies and 30 sera from chronic clade C infections. We selected panels to represent the diversity of bnAb neutralization profiles and Env neutralization sensitivities. Use of standard virus panels can facilitate comparison of results across studies and sites.
Chen, Q., J. Nie, W. Huang, Y. Jiao, L. Li, T. Zhang, J. Zhao, H. Wu and Y. Wang (2017). “Development and optimization of a sensitive pseudovirus-based assay for HIV-1 neutralizing antibodies detection using A3R5 cells.” Hum Vaccin Immunother: 0.
Sensitive assays for HIV-1 neutralizing antibody detection are urgently needed for vaccine immunogen optimization and identification of protective immune response levels. In this study, we developed an easy-to-use HIV-1 pseudovirus neutralization assay based on a human CD4+ lymphoblastoid cell line A3R5 by employing a high efficient pseudovirus production system. Optimal conditions for cell counts, infection time, virus dose and concentration of DEAE-dextran were tested and identified. For T-cell line-adapted tier 1 virus strains, significantly higher inhibitory efficiency was observed for both monoclonal neutralizing antibody (4 fold) and plasma (2 fold) samples in A3R5 than those in TZM-bl assay. For circulating tier 2 strains, the A3R5 pseudovirus assay showed even much higher sensitivity for both neutralizing antibody (10 fold) and plasma (9 fold) samples. When sequential neutralizing antibody seroconverting samples were tested in both A3R5 and TZM-bl assays, the seroconverting points could be detected earlier for tier 1 (15.7 weeks) and tier 2 (68.3 weeks) strains in A3R5 assay respectively. The high sensitive pseudovirus assay using more physiological target cells could serve as an alternative to the TZM-bl assay for evaluation of vaccine-induced neutralizing antibodies and identification of the correlates of protection.
HIV – Cures & Treatments
Tumiotto, C., L. Riviere, P. Bellecave, P. Recordon-Pinson, A. Vilain-Parce, G. L. Guidicelli and H. Fleury (2017). “Sanger and Next-Generation Sequencing data for characterization of CTL epitopes in archived HIV-1 proviral DNA.” PLoS One 12(9): e0185211.
One of the strategies for curing viral HIV-1 is a therapeutic vaccine involving the stimulation of cytotoxic CD8-positive T cells (CTL) that are Human Leucocyte Antigen (HLA)-restricted. The lack of efficiency of previous vaccination strategies may have been due to the immunogenic peptides used, which could be different from a patient’s virus epitopes and lead to a poor CTL response. To counteract this lack of specificity, conserved epitopes must be targeted. One alternative is to gather as many data as possible from a large number of patients on their HIV-1 proviral archived epitope variants, taking into account their genetic background to select the best presented CTL epitopes. In order to process big data generated by Next-Generation Sequencing (NGS) of the DNA of HIV-infected patients, we have developed a software package called TutuGenetics. This tool combines an alignment derived either from Sanger or NGS files, HLA typing, target gene and a CTL epitope list as input files. It allows automatic translation after correction of the alignment obtained between the HxB2 reference and the reads, followed by automatic calculation of the MHC IC50 value for each epitope variant and the HLA allele of the patient by using NetMHCpan 3.0, resulting in a csv file as output result. We validated this new tool by comparing Sanger and NGS (454, Roche) sequences obtained from the proviral DNA of patients at success of ART included in the Provir Latitude 45 study and showed a 90% correlation between the quantitative results of NGS and Sanger. This automated analysis combined with complementary samples should yield more data regarding the archived CTL epitopes according to the patients’ HLA alleles and will be useful for screening epitopes that in theory are presented efficiently to the HLA groove, thus constituting promising immunogenic peptides for a therapeutic vaccine.
Carrillo, M. A., A. Zhen, J. A. Zack and S. G. Kitchen (2017). “New approaches for the enhancement of chimeric antigen receptors for the treatment of HIV.” Transl Res 187: 83-92.
HIV infection continues to be a life-long chronic disease in spite of the success of antiretroviral therapy (ART) in controlling viral replication and preventing disease progression. However, because of the high cost of treatment, severe side effects, and inefficiency in curing the disease with ART, there is a call for alternative therapies that will provide a functional cure for HIV. Cytotoxic T lymphocytes (CTLs) are vital in the control and clearance of viral infections and therefore immune-based therapies have attempted to engineer HIV-specific CTLs that would be able to clear the infection from the body. The development of chimeric antigen receptors (CARs) provides an opportunity to engineer superior HIV-specific CTLs that will be independent of the major histocompatibility complex for target recognition. A CD4-based CAR has been previously tested in clinical trials to test the antiviral efficacy of peripheral T cells armed with this CD4-based CAR. The results from these clinical trials showed the safety and feasibility of CAR T cell therapy for HIV infection; however, minimal antiviral efficacy was seen. In this review, we will discuss the various strategies being developed to enhance the therapeutic potency of anti-HIV CARs with the goal of generating superior antiviral responses that will lead to life-long HIV immunity and clearance of the virus from the body.
Marsden, M. D., B. A. Loy, X. Wu, C. M. Ramirez, A. J. Schrier, D. Murray, A. Shimizu, S. M. Ryckbosch, K. E. Near, T. W. Chun, P. A. Wender and J. A. Zack (2017). “In vivo activation of latent HIV with a synthetic bryostatin analog effects both latent cell “kick” and “kill” in strategy for virus eradication.” PLoS Pathog 13(9): e1006575.
The ability of HIV to establish a long-lived latent infection within resting CD4+ T cells leads to persistence and episodic resupply of the virus in patients treated with antiretroviral therapy (ART), thereby preventing eradication of the disease. Protein kinase C (PKC) modulators such as bryostatin 1 can activate these latently infected cells, potentially leading to their elimination by virus-mediated cytopathic effects, the host’s immune response and/or therapeutic strategies targeting cells actively expressing virus. While research in this area has focused heavily on naturally-occurring PKC modulators, their study has been hampered by their limited and variable availability, and equally significantly by sub-optimal activity and in vivo tolerability. Here we show that a designed, synthetically-accessible analog of bryostatin 1 is better-tolerated in vivo when compared with the naturally-occurring product and potently induces HIV expression from latency in humanized BLT mice, a proven and important model for studying HIV persistence and pathogenesis in vivo. Importantly, this induction of virus expression causes some of the newly HIV-expressing cells to die. Thus, designed, synthetically-accessible, tunable, and efficacious bryostatin analogs can mediate both a “kick” and “kill” response in latently-infected cells and exhibit improved tolerability, therefore showing unique promise as clinical adjuvants for HIV eradication.
Rosas-Umbert, M., B. Mothe, M. Noguera-Julian, R. Bellido, M. C. Puertas, J. Carrillo, C. Rodriguez, N. Perez-Alvarez, P. Cobarsi, C. E. Gomez, M. Esteban, J. L. Jimenez, F. Garcia, J. Blanco, J. Martinez-Picado, R. Paredes and C. Brander (2017). “Virological and immunological outcome of treatment interruption in HIV-1-infected subjects vaccinated with MVA-B.” PLoS One 12(9): e0184929.
The most relevant endpoint in therapeutic HIV vaccination is the assessment of time to viral rebound or duration of sustained control of low-level viremia upon cART treatment cessation. Structured treatment interruptions (STI) are however not without risk to the patient and reliable predictors of viral rebound/control after therapeutic HIV-1 vaccination are urgently needed to ensure patient safety and guide therapeutic vaccine development. Here, we integrated immunological and virological parameters together with viral rebound dynamics after STI in a phase I therapeutic vaccine trial of a polyvalent MVA-B vaccine candidate to define predictors of viral control. Clinical parameters, proviral DNA, host HLA genetics and measures of humoral and cellular immunity were evaluated. A sieve effect analysis was conducted comparing pre-treatment viral sequences to breakthrough viruses after STI. Our results show that a reduced proviral HIV-1 DNA at study entry was independently associated with two virological parameters, delayed HIV-1 RNA rebound (p = 0.029) and lower peak viremia after treatment cessation (p = 0.019). Reduced peak viremia was also positively correlated with a decreased number of HLA class I allele associated polymorphisms in Gag sequences in the rebounding virus population (p = 0.012). Our findings suggest that proviral DNA levels and the number of HLA-associated Gag polymorphisms may have an impact on the clinical outcome of STI. Incorporation of these parameters in future therapeutic vaccine trials may guide refined immunogen design and help conduct safer STI approaches.
HIV – Immune Activation
Brocca-Cofano, E., D. Kuhrt, B. Siewe, C. Xu, G. S. Haret-Richter, J. Craigo, C. Labranche, D. C. Montefiori, A. Landay, C. Apetrei and I. Pandrea (2017). “Pathogenic Correlates of the Simian Immunodeficiency Virus (SIV)-Associated B Cell Dysfunction.” J Virol.
We compared and contrasted pathogenic (pigtailed macaques-PTMs) and nonpathogenic (African green monkeys-AGMs) SIVsab infections to assess the significance of the B-cell dysfunction observed in SIV/HIV infection. We report that the loss of B cells is specifically associated with the pathogenic SIV infection, while in the nonpathogenic natural hosts B cells rapidly increase in both LNs and intestine. SIV-associated B-cell dysfunction associated to the pathogenic SIV infection is characterized by loss of naive B cells; loss of resting memory B cells due to their redistribution to the gut; increases of the activated B cells and circulating tissue-like memory B cells and expansion of the B regulatory cells. While circulating B cells are virtually restored to preinfection levels during the chronic pathogenic SIV infection, restoration is mainly due to an expansion of the “exhausted”, virus-specific B cells, i.e., activated memory cells and tissue-like memory B cells. Despite of the B-cell dysfunction, SIV-specific Ab production was higher in the PTMs than in AGMs, with the caveat that rapid disease progression in PTMs was strongly associated with lack of anti-SIV Ab. Neutralization titers, the avidity and maturation of immune responses did not differ between pathogenic and nonpathogenic infections, with the exception of the conformational epitope recognition, which evolved from low to high conformations in the nonpathogenic host. The patterns of humoral immune responses in the natural host are therefore more similar to those observed in HIV-infected subjects, suggesting that natural hosts may be more appropriate for modeling the immunization strategies aimed at preventing HIV disease progression. The numerous differences between the pathogenic and nonpathogenic infections with regard to dynamics of the memory B-cell subsets point to their role in the pathogenesis of HIV/SIV infections, and suggest that monitoring B cells may be a reliable approach for assessing disease progression.IMPORTANCE We report here that the HIV/SIV-associated B cell dysfunction (defined by loss of total and memory B cells, increased Breg counts and B cell activation and apoptosis) is specifically associated to pathogenic SIV infection and absent during the course of nonpathogenic SIV infection in natural NHP hosts. Alterations of the B cell population are not correlated with production of neutralizing antibodies, which is similar in both species. Rapid progressive infections associate a severe impairment in SIV-specific antibody production. While we did not find major differences in avidity and maturation between the pathogenic and nonpathogenic SIV infection, we identified a major difference in conformational epitope recognition, with the nonpathogenic infection being characterized by an evolution from low to high conformations. B cell dysfunction should be considered in designing immunization strategies aimed at preventing HIV disease progression.
Rife Magalis, B., D. J. Nolan, P. Autissier, T. H. Burdo, K. C. Williams and M. Salemi (2017). “Insights into the impact of CD8+ immune modulation on HIV evolutionary dynamics in distinct anatomical compartments using SIV-infected macaque models of AIDS progression.” J Virol.
A thorough understanding of the role of HIV intra-host evolution in AIDS pathogenesis has been limited by the need for longitudinally sampled viral sequences from the vast target space within the host, which are often difficult to obtain from human subjects. CD8+ lymphocyte-depleted macaques infected with simian immunodeficiency virus (SIV) provide an increasingly utilized model of pathogenesis due to similar clinical manifestations as HIV-1 infection and AIDS progression, as well as characteristic rapid disease onset. Comparison of this model with SIV-infected non-CD8+ lymphocyte-depleted macaques also provides a unique opportunity to investigate the role of CD8+ cells in viral evolution and population dynamics throughout the duration of infection. Using several different phylogenetic methods, we analyzed viral gp120 sequences obtained from extensive longitudinal sampling of multiple tissues and enriched leukocyte populations from SIVmac251-infected macaques, with or without CD8+ lymphocyte depletion. SIV evolutionary and selection patterns in non-CD8+ lymphocyte-depleted animals were characterized by sequential population turnover and continual viral adaptation, a scenario readily comparable to intra-host evolutionary patterns during human HIV infection in the absence of antiretroviral therapy. Alternatively, animals that were CD8+ lymphocyte depleted exhibited greater variation in population dynamics among tissues and cell populations over the course of infection. Our findings highlight the major role for CD8+ lymphocytes in prolonging disease progression through continual control of SIV sub-populations from varying anatomical compartments and the potential for greater independent viral evolutionary behavior among these compartments in response to immune modulation.IMPORTANCE Although developments in combined antiretroviral therapy (cART) strategies have successfully prolonged AIDS onset in HIV-1-infected individuals, a functional cure has yet to be found. Improvement of drug interventions for a virus that is able to infect a wide range of tissues and cell types requires a thorough understanding of viral adaptation and infection dynamics within this target milieu. Although difficult to accomplish in the human host, longitudinal sampling of multiple anatomical locations is readily accessible in the SIV-infected macaque models of neuroAIDS. The significance of our research is in identifying the impact of immune modulation, through differing immune selective pressure, on viral evolutionary behavior in a multitude of anatomical compartments. The results provide evidence encouraging the development of a more sophisticated model that considers a network of individual viral subpopulations within the host with differing infection and transmission dynamics, which is necessary for more effective treatment strategies.
HIV – Microbicides
Coutinho, C., B. Sarmento and J. das Neves (2017). “Targeted microbicides for preventing sexual HIV transmission.” J Control Release.
Sexual transmission remains one of the most significant hurdles in the fight against HIV infection. The use of vaginal or rectal microbicides has been proposed for topical pre-exposure prophylaxis but available results from clinical trials of candidate products have been, at best, less than optimal. While waiting for the first product to get regulatory approval, novel approaches are being explored in order to enhance efficacy, as well as to assure safety. Strategies involving specific delivery of antiviral agents to key players involved in the early steps of sexual transmission have the potential to help achieving such purposes. Engineering systems that allow targeting cells, tissues or other biological structures of interest may provide a way to modulate local pharmacokinetics of promising microbicide molecules and, thus, maximize protection. This concise review discusses the identification and use of potential targets for such purpose, while detailing on several examples of targeted systems engineered as potential microbicide candidates. Furthermore, remaining challenges and hints for future work in the field of targeted microbicides are addressed.
HIV – Neutralizing Antibodies
Julg, B., P. T. Liu, K. Wagh, W. M. Fischer, P. Abbink, N. B. Mercado, J. B. Whitney, J. P. Nkolola, K. McMahan, L. J. Tartaglia, E. N. Borducchi, S. Khatiwada, M. Kamath, J. A. LeSuer, M. S. Seaman, S. D. Schmidt, J. R. Mascola, D. R. Burton, B. T. Korber and D. H. Barouch (2017). “Protection against a mixed SHIV challenge by a broadly neutralizing antibody cocktail.” Sci Transl Med 9(408).
HIV-1 sequence diversity presents a major challenge for the clinical development of broadly neutralizing antibodies (bNAbs) for both therapy and prevention. Sequence variation in critical bNAb epitopes has been observed in most HIV-1-infected individuals and can lead to viral escape after bNAb monotherapy in humans. We show that viral sequence diversity can limit both the therapeutic and prophylactic efficacy of bNAbs in rhesus monkeys. We first demonstrate that monotherapy with the V3 glycan-dependent antibody 10-1074, but not PGT121, results in rapid selection of preexisting viral variants containing N332/S334 escape mutations and loss of therapeutic efficacy in simian-HIV (SHIV)-SF162P3-infected rhesus monkeys. We then show that the V3 glycan-dependent antibody PGT121 alone and the V2 glycan-dependent antibody PGDM1400 alone both fail to protect against a mixed challenge with SHIV-SF162P3 and SHIV-325c. In contrast, the combination of both bNAbs provides 100% protection against this mixed SHIV challenge. These data reveal that single bNAbs efficiently select resistant viruses from a diverse challenge swarm to establish infection, demonstrating the importance of bNAb cocktails for HIV-1 prevention.
Soldemo, M. and G. B. Karlsson Hedestam (2017). “Env-Specific Antibodies in Chronic Infection versus in Vaccination.” Front Immunol 8: 1057.
Antibodies are central in vaccine-mediated protection. For HIV-1, a pathogen that displays extreme antigenic variability, B cell responses against conserved determinants of the envelope glycoproteins (Env) are likely required to achieve broadly protective vaccine-induced responses. To understand antibodies in chronic infection, where broad serum neutralizing activity is observed in a subset of individuals, monoclonal antibodies mediating this activity have been isolated. Studies of their maturation pathways reveal that years of co-evolution between the virus and the adaptive immune response are required for such responses to arise. Furthermore, they do so in subjects who display alterations of their B cell subsets caused by the chronic infection, conditions that are distinctly different from those in healthy hosts. So far, broadly neutralizing antibody responses were not induced by vaccination in primates or small animals with natural B cell repertoires. An increased focus on the development vaccine-induced responses in healthy subjects is therefore needed to delineate how the immune system recognizes different forms of HIV-1 Env and to optimize approaches to stimulate antibody responses against relevant neutralizing antibody epitopes. In this review, we describe aspects of Env-directed antibody responses that differ between chronic HIV-1 infection and subunit vaccination for an increased appreciation of these differences; and we highlight the need for an improved understanding of vaccine-induced B cell responses to complex glycoproteins such as Env, in healthy subjects.
Tanaka, K., T. Kuwata, M. Alam, G. Kaplan, S. Takahama, K. P. R. Valdez, A. Roitburd-Berman, J. M. Gershoni and S. Matsushita (2017). “Unique binding modes for the broad neutralizing activity of single-chain variable fragments (scFv) targeting CD4-induced epitopes.” Retrovirology 14(1): 44.
BACKGROUND: The CD4-induced (CD4i) epitopes in gp120 includes the co-receptor binding site, which are formed and exposed after interaction with CD4. Monoclonal antibodies (mAbs) to the CD4i epitopes exhibit limited neutralizing activity because of restricted access to their epitopes. However, small fragment counterparts such as single-chain variable fragments (scFvs) have been reported to neutralize a broad range of viruses compared with the full-size IgG molecule. To identify the CD4i epitope site responsible for this broad neutralization we constructed three scFvs of anti-CD4i mAbs from a human immunodeficiency virus type 1 (HIV-1)-infected elite controller, and investigated the neutralization coverage and precise binding site in the CD4i epitopes. RESULTS: We constructed scFvs from the anti-CD4i mAbs, 916B2, 4E9C, and 25C4b and tested their neutralization activity against a panel of 66 viruses of multi-subtype. Coverage of neutralization by the scFvs against this panel of pseudoviruses was 89% (59/66) for 4E9C, 95% (63/66) for 25C4b and 100% (66/66) for 916B2. Analysis using a series of envelope glycoprotein mutants revealed that individual anti-CD4i mAbs showed various dependencies on the hairpin 1 (H1) and V3 base. The binding profiles of 25C4b were similar to those of 17b, and 25C4b bound the region spanning multiple domains of H1 and hairpin 2 (H2) of the bridging sheet and V3 base. For 4E9C, the V3-base dependent binding was apparent from no binding to mutants containing the DeltaV3 truncation. In contrast, binding of 916B2 was dependent on the H1 region, which is composed of beta2 and beta3 strands, because mutants containing the H1 truncation did not show any reactivity to 916B2. Although the H1 region structure is affected by CD4 engagement, the results indicate the unique nature of the 916B2 epitope, which may be structurally conserved before and after conformational changes of gp120. CONCLUSIONS: Identification of a unique structure of the H1 region that can be targeted by 916B2 may have an important implication in the development of small molecules to inhibit infection by a broad range of HIV-1 for the purpose of HIV treatment and prevention.
Lloyd, S. B., K. P. Niven, B. R. Kiefel, D. C. Montefiori, A. Reynaldi, M. P. Davenport, S. J. Kent and W. R. Winnall (2017). “Exploration of broadly neutralizing antibody fragments produced in bacteria for the control of HIV.” Hum Vaccin Immunother: 0.
While broadly neutralizing antibodies (bnAbs) are a promising preventative and therapeutic tool for HIV infection, production is difficult and expensive. Production of antibody-like fragments in bacterial cytoplasm provides a cheaper alternative. This work explored the transplantation of the complementarity determining regions of the anti-HIV bnAbs PGT121 and 10E8 onto a single-chain variable fragment (scFv) scaffold, previously discovered through a novel screening platform. The scaffolded 10E8 scFv, but not the scaffolded PGT121 scFv, was soluble in bacterial cytoplasm, enabling efficient production in bacteria. Three additional multimeric constructs employing the scaffolded 10E8 scFv were also generated and soluble versions produced in bacteria. However, the constructs were found to have substantially lost anti-HIV binding function and had completely abrogated neutralizing activity. Overall, while this study provides a proof-of-concept for anti-HIV bnAb construct production in bacterial cytoplasm, future refinement of these technologies will be required to realize the goal of producing inexpensive and effective bnAb-like tools for the control of HIV.
Lin, T. Y. and J. R. Lai (2017). “Interrogation of side chain biases for oligomannose recognition by antibody 2G12 via structure-guided phage display libraries.” Bioorg Med Chem.
Monoclonal antibodies (mAbs) are essential reagents for deciphering gene or protein function and have been a fruitful source of therapeutic and diagnostic agents. However, developing anticarbohydrate antibodies to target glycans for those purposes has been less successful because the molecular basis for glycan-mAb interactions is poorly understood relative to protein- or peptide-binding mAbs. Here, we report our investigation on glycan-mAb interactions by using the unique architectural scaffold of 2G12, an antibody that targets oligomannoses on the HIV-1 glycoprotein gp120, as the template for engineering highly specific mAbs to target glycans. We first analyzed 24 different X-ray structures of antiglycan mAbs from the Protein Data Bank to determine side chain amino acid distributions in of glycan-mAb interactions. We identified Tyr, Arg, Asn, Ser, Asp, and His as the six most prevalent residues in the glycan-mAb contacts. We then utilized this information to construct two phage display libraries (“Lib1” and “Lib2”) in which positions on the heavy chain variable domains of 2G12 were allowed to vary in restricted manner among Tyr, Asp, Ser, His, Asn, Thr, Ala and Pro to interrogate the minimal physicochemical requirements for oligomannose recognition. We analyzed the sequences of 39 variants from Lib1 and 14 variants from Lib2 following selection against gp120, the results showed that there is a high degree of malleability within the 2G12 for glycan recognitions. We further characterized five unique phage clones from both libraries that exhibited a gp120-specific binding profile. Expression of two of these variants as soluble mAbs indicated that, while specificity of gp120-binding was retained, the affinity of these mutants was significantly reduced relative to WT 2G12. Nonetheless, the results indicate these is some malleability in the identity of contact residues and provide a novel insight into the nature of glycan-antibody interactions and how they may differ from protein-antibody binding interactions.
HIV and Schistosomiasis
Downs, J. A., K. M. Dupnik, G. J. van Dam, M. Urassa, P. Lutonja, D. Kornelis, C. J. de Dood, P. Hoekstra, C. Kanjala, R. Isingo, R. N. Peck, M. H. Lee, P. Corstjens, J. Todd, J. M. Changalucha, W. D. Johnson, Jr. and D. W. Fitzgerald (2017). “Effects of schistosomiasis on susceptibility to HIV-1 infection and HIV-1 viral load at HIV-1 seroconversion: A nested case-control study.” PLoS Negl Trop Dis 11(9): e0005968.
BACKGROUND: Schistosomiasis affects 218 million people worldwide, with most infections in Africa. Prevalence studies suggest that people with chronic schistosomiasis may have higher risk of HIV-1 acquisition and impaired ability to control HIV-1 replication once infected. We hypothesized that: (1) pre-existing schistosome infection may increase the odds of HIV-1 acquisition and that the effects may differ between men and women, and (2) individuals with active schistosome infection at the time of HIV-1 acquisition may have impaired immune control of HIV-1, resulting in higher HIV-1 viral loads at HIV-1 seroconversion. METHOLOGY/PRINCIPAL FINDINGS: We conducted a nested case-control study within a large population-based survey of HIV-1 transmission in Tanzania. A population of adults from seven villages was tested for HIV in 2007, 2010, and 2013 and dried blood spots were archived for future studies with participants’ consent. Approximately 40% of this population has Schistosoma mansoni infection, and 2% has S. haematobium. We tested for schistosome antigens in the pre- and post-HIV-1-seroconversion blood spots of people who acquired HIV-1. We also tested blood spots of matched controls who did not acquire HIV-1 and calculated the odds that a person with schistosomiasis would become HIV-1-infected compared to these matched controls. Analysis was stratified by gender. We compared 73 HIV-1 seroconverters with 265 controls. Women with schistosome infections had a higher odds of HIV-1 acquisition than those without (adjusted OR = 2.8 [1.2-6.6], p = 0.019). Schistosome-infected men did not have an increased odds of HIV-1 acquisition (adjusted OR = 0.7 [0.3-1.8], p = 0.42). We additionally compared HIV-1 RNA levels in the post-seroconversion blood spots in HIV-1 seroconverters with schistosomiasis versus those without who became HIV-infected in 2010, before antiretroviral therapy was widely available in the region. The median whole blood HIV-1 RNA level in the 15 HIV-1 seroconverters with schistosome infection was significantly higher than in the 22 without schistosomiasis: 4.4 [3.9-4.6] log10 copies/mL versus 3.7 [3.2-4.3], p = 0.017. CONCLUSIONS/SIGNIFICANCE: We confirm, in an area with endemic S. mansoni, that pre-existing schistosome infection increases odds of HIV-1 acquisition in women and raises HIV-1 viral load at the time of HIV-1 seroconversion. This is the first study to demonstrate the effect of schistosome infection on HIV-1 susceptibility and viral control, and to differentiate effects by gender. Validation studies will be needed at additional sites.
Douglas, A. O., D. R. Martinez and S. R. Permar (2017). “The Role of Maternal HIV Envelope-Specific Antibodies and Mother-to-Child Transmission Risk.” Front Immunol 8: 1091.
Despite the wide availability of antiretroviral therapy (ART) prophylaxis during pregnancy, >150,000 infants become infected through mother-to-child transmission (MTCT) of HIV worldwide. It is likely that additional intervention strategies, such as a maternal HIV vaccine, will be required to eliminate pediatric HIV infections. A deeper understanding of the fine specificity and function of maternal HIV envelope (Env)-specific responses that provide partial protection against MTCT will be critical to inform the design of immunologic strategies to curb the pediatric HIV epidemic. Recent studies have underlined a role of maternal HIV Env-specific neutralizing and non-neutralizing responses in reducing risk of MTCT of HIV and in prolonging survival rates in HIV-infected infants. However, critical gaps in our knowledge include (A) the specific role of maternal autologous-virus IgG-neutralizing responses in driving the selection of infant transmitted founder (T/F) viruses and (B) Env mechanisms of escape from maternal autologous virus-neutralizing antibodies (NAbs). A more refined understanding of the fine specificities of maternal autologous virus NAbs and ways that maternal circulating viruses escape from these antibodies will be crucial to inform maternal vaccination strategies that can block MTCT to help achieve an HIV-free generation.
Shuper, P. A., N. Joharchi, P. M. Monti, M. Loutfy and J. Rehm (2017). “Acute Alcohol Consumption Directly Increases HIV Transmission Risk: A Randomized Controlled Experiment.” J Acquir Immune Defic Syndr.
BACKGROUND: Alcohol consumption has frequently been purported as a driver of condomless sex and HIV transmission, but to date, experimental evidence for the causal risk-taking impact of alcohol among HIV-positive populations is lacking. The present experiment sought to determine whether acute alcohol consumption has a direct causal impact on condomless sex intentions among HIV-positive men-who-have-sex-with-men (MSM), and to assess whether alcohol’s impact differs between MSM who are HIV-positive versus HIV-negative. METHODS: In a randomized controlled alcohol administration experiment, HIV-positive and HIV-negative MSM were brought into a specialized barroom laboratory and randomly assigned to beverage consumption condition: alcohol (target BAC=.080%), placebo alcohol (target BAC=.000%), or water (control). Participants then underwent a video-based sexual arousal manipulation (sexually aroused/non-aroused) and indicated their intentions to engage in condom-protected and condomless sexual acts in a standardized paradigm. The primary outcome entailed intentions to engage in condomless receptive and condomless insertive anal sex. RESULTS: A total of 282 MSM (141 HIV-positive; 141 HIV-negative) completed experimental procedures. MSM who received alcohol reported significantly stronger intentions to engage in condomless sex than those who received placebo alcohol or water (F(1,274)=9.43, p=0.002). The impact of alcohol did not differ between HIV-positive and HIV-negative MSM (F(1,274)=1.86, p=0.174). CONCLUSIONS: The present investigation entailed the first risk-focused alcohol administration experiment to involve an HIV-positive sample, and results demonstrated that consuming alcohol had an independent, causal impact on intentions to engage in sexual behaviors that can result in HIV transmission. Findings strongly suggest that alcohol-focused initiatives should be incorporated into HIV prevention efforts.
Ortiz, K., R. S. Sampathkumar, A. A. Ansari and S. N. Byrareddy (2017). “Preliminary studies on the use of pertussis toxin for the modulation of intravaginal SIV transmission in rhesus macaques.”J Med Primatol.
BACKGROUND: Pertussis toxin (PTX) blocks GPCR signaling resulting in the inhibition of chemotaxis/cell adhesion. It was reasoned that inhibition of cell trafficking may be an approach to prevent HIV/SIV transmission. METHODS: In this study, PTX in HEC gel was applied to the vaginal wall of monkeys that were then challenged intravaginally with SIVmac251. RESULTS: Results of these studies showed that 2 of 4 animals were resistant to infection. Furthermore, infection was correlated with a marked increase in the plasma and cervicovaginal lavage levels of select chemokines and cytokines. CONCLUSIONS: Results from this preliminary feasibility study dictate that further studies that include a larger number of animals are required to optimize this protocol and establish the efficacy of this approach. In addition, such future studies will provide important information on the role of specific chemokines that play a role in lymphocyte trafficking within the genital tract and serve as additional therapeutic targets.
Sandfort, T. G. M., J. R. Knox, C. Alcala, N. El-Bassel, I. Kuo and L. R. Smith (2017). “Substance Use and HIV Risk Among Men Who Have Sex With Men in Africa: A Systematic Review.” J Acquir Immune Defic Syndr 76(2): e34-e46.
BACKGROUND: Substance use and its relation to HIV risk among men who have sex in Africa, a population at high risk for HIV, has received little attention. METHODS: This systematic review summarizes and discusses findings from 68 empirical studies, published between 1980 and 2016 that included data about substance use in men who have sex with men (MSM) in Africa. RESULTS: Substance use has rarely been the primary focus of studies in African MSM. In general, measurement of substance use was suboptimal. Whereas prevalence of alcohol use varied across studies, partly resulting from variety in assessment strategies, it seemed higher than in the general male population across countries. Alcohol use was associated with sexual risk practices, but not with HIV infection. The most frequently reported drug used by African MSM was cannabis. The use of other drugs, such as cocaine and heroin seemed relatively rare, although injection drug use was exceptionally high in a few studies. As alcohol, drugs were regularly used in conjunction with sex. Both alcohol and drug use were often associated with other risk factors for HIV infection, including violence and transactional sex. No interventions were found addressing substance use among African MSM. CONCLUSIONS: Given high HIV risk and prevalence in this population, substance use should be studied more in-depth, taking into account the specific social and cultural context. Assessment of substance use practices in this population has to be improved. The available information suggests, though, that there is an urgent need for interventions addressing substance use tailored to the needs of this critical population.
Vaccine Design Immunogenicity Efficacy
Abbasi, J. (2017). “Flu Vaccine Patch in Development.” Jama 318(6): 510.
Broecker, F. and P. H. Seeberger (2017). “Identification and Design of Synthetic B Cell Epitopes for Carbohydrate-Based Vaccines.” Methods Enzymol 597: 311-334.
Synthetic oligosaccharide-based vaccines are promising alternatives to conventional antibacterial carbohydrate vaccines prepared with isolated polysaccharides. Unlike polysaccharides, synthetic glycans are well defined, contaminant-free, and accessible even for pathogens that cannot be fermented or show limited carbohydrate biosynthesis in vitro. However, identifying synthetic glycan B cell epitopes that induce protective immunity has traditionally been a time-consuming trial-and-error process, as predicting the immunogenicity of an oligosaccharide by means of structure alone is not straightforward. We here describe how synthetic oligosaccharide epitopes for candidate vaccines can be rationally identified prior to preclinical immunogenicity studies. Epitopes are selected on the basis of their recognition by antibodies associated with protection from disease in humans or small animals. In addition, we show how murine antibody responses to a large oligosaccharide can inform the identification of a minimal B cell epitope that may help designing easy to synthesize vaccine candidates. The procedures, exemplified with a surface carbohydrate of Clostridium difficile, may serve as a guideline for selecting protective oligosaccharide epitopes for vaccines against infectious and malignant diseases.
Griesenauer, R. H. and M. S. Kinch (2017). “An overview of FDA-approved vaccines & their innovators.” Expert Rev Vaccines: 1-14.
INTRODUCTION: A survey of FDA-approved biologicals focused upon the development of immunotherapies over time to gain insight on the challenges and trends of vaccine development today. Areas covered: A total of 135 different immune-based therapies were broadly divided into passive or active immunotherapies. Whereas just over half of passive immunotherapies targeted infectious diseases, the vast majority of active immunotherapy products (vaccines) were directed against a handful of viral and bacterial pathogens. We also analyze changes in vaccine strategy, including the use of viable antigens and subunit approaches. Expert commentary: An analysis of vaccine innovators revealed an ever-increasing presence of the private sector and a relatively diminishing role for the public sector . Whereas North American companies have contributed to the approval of two-thirds of vaccines, European companies have regained parity in terms of hosting innovators of vaccine research and development.
Lakshminarayanan, A., B. Vijayakrishnan, H. Bayley and B. G. Davis (2017). “Strategies in the Design and Use of Synthetic “Internal Glycan” Vaccines.” Methods Enzymol 597: 335-357.
The relative structural conservation of “internal glycans” in the cell walls of pathogens suggests that they might as target epitopes less prone to variation and hence with greater potential universality as vaccine targets. Examples of such glycans include the inner core sugars of lipopolysaccharides in Gram-negative bacteria. However, due to the buried nature of such internal epitopes, this approach has been rarely adopted. Here we briefly review and compare strategic approaches and outline practical methods associated with evaluating one synergistic strategy that combines (i) blocking of the display of “external glycans” with (ii) vaccination targeted at “internal glycans.”
Venkatraman, N., N. Anagnostou, C. Bliss, G. Bowyer, D. Wright, K. Lovgren-Bengtsson, R. Roberts, I. Poulton, A. Lawrie, K. Ewer and V. S. H. A (2017). “Safety and immunogenicity of heterologous prime-boost immunization with viral-vectored malaria vaccines adjuvanted with Matrix-M.”Vaccine.
The use of viral vectors in heterologous prime-boost regimens to induce potent T cell responses in addition to humoral immunity is a promising vaccination strategy in the fight against malaria. We conducted an open-label, first-in-human, controlled Phase I study evaluating the safety and immunogenicity of Matrix-M adjuvanted vaccination with a chimpanzee adenovirus serotype 63 (ChAd63) prime followed by a modified vaccinia Ankara (MVA) boost eight weeks later, both encoding the malaria ME-TRAP antigenic sequence (a multiple epitope string fused to thrombospondin-related adhesion protein). Twenty-two healthy adults were vaccinated intramuscularly with either ChAd63-MVA ME-TRAP alone (n=6) or adjuvanted with 25mug (n=8) or 50mug (n=8) Matrix-M. Vaccinations appeared to be safe and generally well tolerated, with the majority of local and systemic adverse events being mild in nature. The addition of Matrix-M to the vaccine did not increase local reactogenicity; however, systemic adverse events were reported more frequently by volunteers who received adjuvanted vaccine in comparison to the control group. T cell ELISpot responses peaked at 7-days post boost vaccination with MVA ME-TRAP in all three groups. TRAP-specific IgG responses were highest at 28-days post boost with MVA ME-TRAP in all three groups. There were no differences in cellular and humoral immunogenicity at any of the time points between the control group and the adjuvanted groups. We demonstrate that Matrix-M can be safely used in combination with ChAd63-MVA ME-TRAP heterologous prime-boost immunization without any reduction in cellular or humoral immunogenicity. Clinical Trials Registration NCT01669512.
Valguarnera, E. and M. F. Feldman (2017). “Glycoengineered Outer Membrane Vesicles as a Platform for Vaccine Development.” Methods Enzymol 597: 285-310.
As we enter into the postantibiotic era, vaccines to prevent bacterial infections previously treatable with antibiotics are urgently needed. Most successful antibacterial vaccines are glycoconjugates, composed of cell surface carbohydrates chemically attached to a carrier protein. Glycoconjugate vaccines provide a safe and consistent strategy against polysaccharide-encapsulated pathogens. The best examples are the conjugate vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis, all based on capsular polysaccharides. Although these types of vaccines are effective, their current manufacturing process presents multiple drawbacks, such as biosafety risks and batch-to-batch variability. Furthermore, inclusion of additional serotypes is extremely slow, mainly due to the intricate chemical methods of conjugation. Thus, novel platforms for antibacterial vaccines are required. Gram-negative bacteria are able to produce outer membrane vesicles (OMVs). OMVs are mainly composed of lipopolysaccharide (LPS), outer membrane and periplasmic proteins, and phospholipids. Although their biogenesis is poorly understood, it is known that OMVs are formed by blebbing of the outer membrane. OMVs are attractive candidates for novel vaccine delivery platforms due to their immunogenic properties, self-adjuvanticity, and capacity for enhancement by recombinant engineering. We have shown that OMVs can be engineered to display surface glycans from different bacteria and that these glycoengineered OMVs (geOMVs) are effective in diverse animal models of infection. Here we provide a detailed method for the design and preparation of geOMV displaying the O-antigen from a prominent uropathogenic Escherichia coli (UPEC) serotype, O25b, as a proof of concept for the use of geOMVs as vaccine candidates.
Wang, K., G. D. Tomaras, S. Jegaskanda, M. A. Moody, H. X. Liao, K. N. Goodman, P. W. Berman, S. Rerks-Ngarm, P. Pitisuttithum, S. Nitayapan, J. Kaewkungwal, B. F. Haynes and J. I. Cohen (2017). “Monoclonal Antibodies, Derived from Humans Vaccinated with the RV144 HIV Vaccine Containing the HVEM Binding Domain of Herpes Simplex Virus (HSV) Glycoprotein D, Neutralize HSV Infection, Mediate Antibody-Dependent Cellular Cytotoxicity, and Protect Mice from Ocular Challenge with HSV-1.” J Virol 91(19).
The RV144 HIV vaccine trial included a recombinant HIV glycoprotein 120 (gp120) construct fused to a small portion of herpes simplex virus 1 (HSV-1) glycoprotein D (gD) so that the first 40 amino acids of gp120 were replaced by the signal sequence and the first 27 amino acids of the mature form of gD. This region of gD contains most of the binding site for HVEM, an HSV receptor important for virus infection of epithelial cells and lymphocytes. RV144 induced antibodies to HIV that were partially protective against infection, as well as antibodies to HSV. We derived monoclonal antibodies (MAbs) from peripheral blood B cells of recipients of the RV144 HIV vaccine and showed that these antibodies neutralized HSV-1 infection in cells expressing HVEM, but not the other major virus receptor, nectin-1. The MAbs mediated antibody-dependent cellular cytotoxicity (ADCC), and mice that received the MAbs and were then challenged by corneal inoculation with HSV-1 had reduced eye disease, shedding, and latent infection. To our knowledge, this is the first description of MAbs derived from human recipients of a vaccine that specifically target the HVEM binding site of gD. In summary, we found that monoclonal antibodies derived from humans vaccinated with the HVEM binding domain of HSV-1 gD (i) neutralized HSV-1 infection in a cell receptor-specific manner, (ii) mediated ADCC, and (iii) reduced ocular disease in virus-infected mice.IMPORTANCE Herpes simplex virus 1 (HSV-1) causes cold sores and neonatal herpes and is a leading cause of blindness. Despite many trials, no HSV vaccine has been approved. Nectin-1 and HVEM are the two major cellular receptors for HSV. These receptors are expressed at different levels in various tissues, and the role of each receptor in HSV pathogenesis is not well understood. We derived human monoclonal antibodies from persons who received the HIV RV144 vaccine that contained the HVEM binding domain of HSV-1 gD fused to HIV gp120. These antibodies were able to specifically neutralize HSV-1 infection in vitro via HVEM. Furthermore, we showed for the first time that HVEM-specific HSV-1 neutralizing antibodies protect mice from HSV-1 eye disease, indicating the critical role of HVEM in HSV-1 ocular infection.
Vaccine Design – Vectors
Sharon, D. and A. Kamen (2017). “Advancements in the design and scalable production of viral gene transfer vectors.” Biotechnol Bioeng.
The last 10 years have seen a rapid expansion in the use of viral gene transfer vectors, with approved therapies and late stage clinical trials underway for the treatment of genetic disorders, and multiple forms of cancer, as well as prevention of infectious diseases through vaccination. With this increased interest and widespread adoption of viral vectors by clinicians and biopharmaceutical industries, there is an imperative to engineer safer and more efficacious vectors, and develop robust, scalable and cost-effective production platforms for industrialization. This review will focus on major innovations in viral vector design and production systems for three of the most widely used viral vectors: Adenovirus, Adeno-Associated Virus, and Lentivirus. This article is protected by copyright. All rights reserved.
Liu, F., Q. Niu, X. Fan, C. Liu, J. Zhang, Z. Wei, W. Hou, T. D. Kanneganti, M. L. Robb, J. H. Kim, N. L. Michael, J. Sun, L. Soong and H. Hu (2017). “Priming and Activation of Inflammasome by Canarypox Virus Vector ALVAC via the cGAS/IFI16-STING-Type I IFN Pathway and AIM2 Sensor.” J Immunol.
Viral vectors derived from different virus families, including poxvirus (canarypox virus vector ALVAC) and adenovirus (human Ad5 vector), have been widely used in vaccine development for a range of human diseases including HIV/AIDS. Less is known about the mechanisms underlying the host innate response to these vectors. Increasing evidence from clinical vaccine trials testing different viral vectors has suggested the importance of understanding basic elements of host-viral vector interactions. In this study, we investigated the innate interactions of APCs with two commonly used HIV vaccine vectors, ALVAC and Ad5, and identified AIM2 as an innate sensor for ALVAC, triggering strong inflammasome activation in both human and mouse APCs. Microarray and comprehensive gene-knockout analyses (CRISPR/Cas9) identified that ALVAC stimulated the cGAS/IFI16-STING-type I IFN pathway to prime AIM2, which was functionally required for ALVAC-induced inflammasome activation. We also provided evidence that, in contrast to ALVAC, the Ad5 vector itself was unable to induce inflammasome activation, which was related to its inability to stimulate the STING-type I IFN pathway and to provide inflammasome-priming signals. In preconditioned APCs, the Ad5 vector could stimulate inflammasome activation through an AIM2-independent mechanism. Therefore, our study identifies the AIM2 inflammasome and cGAS/IFI16-STING-type I IFN pathway as a novel mechanism for host innate immunity to the ALVAC vaccine vector.