AIDS Vaccine Design Immunogenicity Efficacy
Ngu, L. N., N. N. Nji, G. Ambada, A. A. Ngoh, G. D. Njambe Priso, J. C. Tchadji, A. Lissom, S. H. Magagoum, C. N. Sake, T. F. Tchouangueu, G. O. Chukwuma, A. S. Okoli, B. Sagnia, R. Chukwuanukwu, D. M. Tebit, C. O. Esimone, A. B. Waffo, C. G. Park, K. Uberla and G. W. Nchinda (2017). “Dendritic cell targeted HIV-1 gag protein vaccine provides help to a recombinant Newcastle disease virus vectored vaccine including mobilization of protective CD8(+) T cells.” Immun Inflamm Dis.
INTRODUCTION: Recombinant Newcastle Disease virus (rNDV) vectored vaccines are safe mucosal applicable vaccines with intrinsic immune-modulatory properties for the induction of efficient immunity. Like all viral vectored vaccines repeated inoculation via mucosal routes invariably results to immunity against viral vaccine vectors. To obviate immunity against viral vaccine vectors and improve the ability of rNDV vectored vaccines in inducing T cell immunity in murine air way we have directed dendritic cell targeted HIV-1 gag protein (DEC-Gag) vaccine; for the induction of helper CD4(+) T cells to a Recombinant Newcastle disease virus expressing codon optimized HIV-1 Gag P55 (rNDV-L-Gag) vaccine. METHODS: We do so through successive administration of anti-DEC205-gagP24 protein plus polyICLC (DEC-Gag) vaccine and rNDV-L-Gag. First strong gag specific helper CD4(+) T cells are induced in mice by selected targeting of anti-DEC205-gagP24 protein vaccine to dendritic cells (DC) in situ together with polyICLC as adjuvant. This targeting helped T cell immunity develop to a subsequent rNDV-L-Gag vaccine and improved both systemic and mucosal gag specific immunity. RESULTS: This sequential DEC-Gag vaccine prime followed by an rNDV-L-gag boost results to improved viral vectored immunization in murine airway, including mobilization of protective CD8(+) T cells to a pathogenic virus infection site. CONCLUSION: Thus, complementary prime boost vaccination, in which prime and boost favor distinct types of T cell immunity, improves viral vectored immunization, including mobilization of protective CD8(+) T cells to a pathogenic virus infection site such as the murine airway.
AIDS Vaccine Envelope Design
Wang, Q., Y. Dai, Z. Sun, X. Su, Y. Yu, C. Hua, W. Xu, S. Jiang and L. Lu (2017). “HIV-1 Env DNA prime plus gp120 and gp70-V1V2 boosts induce high level of V1V2-specific IgG and ADCC responses and low level of Env-specific IgA response: implication for improving RV144 vaccine regimen.” Emerg Microbes Infect 6(11): e102.
Wang, H., X. Chen, D. Wang, C. Yao, Q. Wang, J. Xie, X. Shi, Y. Xiang, W. Liu and L. Zhang (2017). “Epitope-focused immunogens against the CD4-binding site of HIV-1 envelope protein induce neutralizing antibodies against auto- and heterologous viruses.” J Biol Chem.
Recent discoveries of broadly neutralizing antibodies (bnAbs) in HIV-1-infected individuals have led to the identification of several major ”vulnerable sites” on the HIV-1 envelope (Env) glycoprotein. These sites have provided precise targets for HIV-1 vaccine development, but identifying and utilizing many of these targets remains technically challenging. Using a yeast surface display-based approach, we sought to identify epitope-focused antigenic domains (EADs) containing one of the ”vulnerable sites”, the CD4-binding site (CD4bs), through screening and selection of a combinatorial antigen library of the HIV-1 Env glycoprotein with the CD4bs bnAb VRC01. We isolated multiple EADs and found that their trimeric forms have biochemical and structural features that preferentially bind and activate B cells that express VRC01 in vitro. More importantly, these EADs could induce detectable levels of neutralizing antibodies against genetically related autologous and heterologous subtype B viruses in guinea pigs. Our results demonstrate that an epitope-focused approach involving a screen of a combinatorial antigen library is feasible. The EADs identified here represent a promising collection of possible targets in the rational design of HIV-1 vaccines and lay the foundation for harnessing the specific antigenicity of CD4bs for protective immunogenicity in vivo.
Joyce, M. G., I. S. Georgiev, Y. Yang, A. Druz, H. Geng, G. Y. Chuang, Y. D. Kwon, M. Pancera, R. Rawi, M. Sastry, G. B. E. Stewart-Jones, A. Zheng, T. Zhou, M. Choe, J. G. Van Galen, R. E. Chen, C. R. Lees, S. Narpala, M. Chambers, Y. Tsybovsky, U. Baxa, A. B. McDermott, J. R. Mascola and P. D. Kwong (2017). “Soluble Prefusion Closed DS-SOSIP.664-Env Trimers of Diverse HIV-1 Strains.” Cell Rep 21(10): 2992-3002.
The elicitation of autologous neutralizing responses by immunization with HIV-1 envelope (Env) trimers conformationally stabilized in a prefusion closed state has generated considerable interest in the HIV-1 vaccine field. However, soluble prefusion closed Env trimers have been produced from only a handful of HIV-1 strains, limiting their utility as vaccine antigens and B cell probes. Here, we report the engineering from 81 HIV-1 strains of soluble, fully cleaved, prefusion Env trimers with appropriate antigenicity. We used a 96-well expression-screening format to assess the ability of artificial disulfides and Ile559Pro substitution (DS-SOSIP) to produce soluble cleaved-Env trimers; from 180 Env strains, 20 yielded prefusion closed trimers. We also created chimeras, by utilizing structure-based design to incorporate select regions from the well-behaved BG505 strain; from 180 Env strains, 78 DS-SOSIP-stabilized chimeras, including 61 additional strains, yielded prefusion closed trimers. Structure-based design thus enables the production of prefusion closed HIV-1-Env trimers from dozens of diverse strains.
Piai, A., J. Dev, Q. Fu and J. J. Chou (2017). “Stability and Water Accessibility of the Trimeric Membrane Anchors of the HIV-1 Envelope Spikes.” J Am Chem Soc.
HIV-1 envelope spike (Env) is a type I membrane protein that mediates viral entry. Recent studies showed that its transmembrane domain (TMD) forms a trimer in lipid bilayer whose structure has several peculiar features that remain difficult to explain. One is the presence of an arginine R696 in the middle of the TM helix. Additionally, the N- and C-terminal halves of the TM helix form trimeric cores of opposite nature (hydrophobic and hydrophilic, respectively). Here we determined the membrane partition and solvent accessibility of the TMD in bicelles that mimic a lipid bilayer. Solvent paramagnetic relaxation enhancement analysis showed that the R696 is indeed positioned close to the center of the bilayer, but, surprisingly, can exchange rapidly with water as indicated by hydrogen-deuterium exchange measurements. The solvent accessibility of R696 is likely mediated by the hydrophilic core, which also showed fast water exchange. In contrast, the N-terminal hydrophobic core showed extremely slow solvent exchange, suggesting the trimer formed by this region is extraordinarily stable. Our data explain how R696 is accommodated in the middle of the membrane while reporting the overall stability of the Env TMD trimer in lipid bilayer.
Emerging Infectious Diseases
Eastwood, G., R. C. Sang, M. Guerbois, E. L. N. Taracha and S. C. Weaver (2017). “Enzootic Circulation of Chikungunya Virus in East Africa: Serological Evidence in Non-human Kenyan Primates.” Am J Trop Med Hyg 97(5): 1399-1404.
Chikungunya virus (CHIKV) is a globally emerging pathogen causing debilitating arthralgia and fever in humans. First identified in Tanzania (1953), this mosquito-borne alphavirus received little further attention until a 2004 re-emergence in Kenya from an unknown source. This outbreak subsequently spread to the Indian Ocean, with adaptation for transmission by a new urban vector. Under the hypothesis that sylvatic progenitor cycles of CHIKV exist in Kenya (as reported in West Africa, between non-human primates (NHPs) and arboreal Aedes spp. mosquitoes), we pursued evidence of enzootic transmission and human spillover events. We initially screened 252 archived NHP sera from Kenya using plaque reduction neutralization tests. Given an overall CHIKV seroprevalence of 13.1% (marginally higher in western Kenya), we sought more recent NHP samples during 2014 from sites in Kakamega County, sampling wild blue monkeys, olive baboons, and red-tailed monkeys (N = 33). We also sampled 34 yellow baboons near Kwale, coastal Kenya. Overall, CHIKV seropositivity in 2014 was 13.4% (9/67). Antibodies reactive against closely related o’nyong-nyong virus (ONNV) occurred; however, neutralization titers were too low to conclude ONNV exposure. Seroprevalence for the flavivirus dengue was also detected (28%), mostly near Kwale, suggesting possible spillback from humans to baboons. CHIKV antibodies in some juvenile and subadult NHPs suggested recent circulation. We conclude that CHIKV is circulating in western Kenya, despite the 2004 human outbreaks only being reported coastally. Further work to understand the enzootic ecology of CHIKV in east Africa is needed to identify sites of human spillover contact where urban transmission may be initiated.
Emerging Infectious Disease Vaccines
Graham, B. S. and N. J. Sullivan (2017). “Emerging viral diseases from a vaccinology perspective: preparing for the next pandemic.” Nat Immunol.
Emerging infectious diseases will continue to threaten public health and are sustained by global commerce, travel and disruption of ecological systems. Most pandemic threats are caused by viruses from either zoonotic sources or vector-borne sources. Developing better ways to anticipate and manage the ongoing microbial challenge will be critical for achieving the United Nations Sustainable Development Goals and, conversely, each such goal will affect the ability to control infectious diseases. Here we discuss how technology can be applied effectively to better prepare for and respond to new viral diseases with a focus on new paradigms for vaccine development.
Bergren, N. A., M. R. Miller, T. P. Monath and R. C. Kading (2017). “Assessment of the ability of V920 recombinant vesicular stomatitis-Zaire ebolavirus vaccine to replicate in relevant arthropod cell cultures and vector species.” Hum Vaccin Immunother: 0.
V920, rVSVDeltaG-ZEBOV-GP, is a recombinant vesicular stomatitis-Zaire ebolavirus vaccine which has shown an acceptable safety profile and provides a protective immune response against Ebola virus disease (EVD) induced by Zaire ebolavirus in humans. The purpose of this study was to determine whether the V920 vaccine is capable of replicating in arthropod cell cultures of relevant vector species and of replicating in live mosquitoes. While the V920 vaccine replicated well in Vero cells, no replication was observed in Anopheles or Aedes mosquito, Culicoides biting midge, or Lutzomyia sand fly cells, nor in live Culex or Aedes mosquitoes following exposure through intrathoracic inoculation or feeding on a high-titer infectious blood meal. The insect taxa selected for use in this study represent actual and potential epidemic vectors of VSV. V920 vaccine inoculated into Cx. quinquefasciatus and Ae. aegypti mosquitoes demonstrated persistence of replication-competent virus following inoculation, consistent with the recognized biological stability of the vaccine, but no evidence for active virus replication in live mosquitoes was observed. Following administration of an infectious blood meal to Ae. aegypti and Cx. quinquefasciatus mosquitoes at a titer several log10 PFU more concentrated than would be observed in vaccinated individuals, no infection or dissemination of V920 was observed in either mosquito species. In vitro and in vivo data gathered during this study support minimal risk of the vector-borne potential of the V920 vaccine.
Wong, G. and X. Qiu (2017). “Funding vaccines for emerging infectious diseases.” Hum Vaccin Immunother: 0.
Immunization has played a large role in substantially reducing the infected and death tolls from infectious diseases. In the case of emerging diseases, the identity of the pathogen responsible, as well as the time and location for the next outbreak, cannot be accurately predicted using current means. Coupled with disjointed efforts towards the development of vaccines and a lack of funds and desire to advance promising products against known emerging pathogens to clinical trials, there has been a shortage of approved products ready for emergency use. Recent outbreaks have exposed these weaknesses, and the Coalition for Epidemic Preparedness Innovations (CEPI) was created in 2016 to address these issues. In this commentary, we discuss the establishment of such a global vaccine fund, and provide some additional points to consider for stimulating further discussion on this comprehensive, ambitious initiative.
Moodie, Z., M. Juraska, Y. Huang, Y. Zhuang, Y. Fong, L. N. Carpp, S. G. Self, L. Chambonneau, R. Small, N. Jackson, F. Noriega and P. B. Gilbert (2017). “Neutralizing Antibody Correlates Analysis of Tetravalent Dengue Vaccine Efficacy Trials in Asia and Latin America.” J Infect Dis.
Background: In the CYD14 and CYD15 Phase 3 trials of the CYD-TDV dengue vaccine, estimated vaccine efficacy (VE) against symptomatic, virologically-confirmed dengue (VCD) occurring between Months 13 and 25 was 56.5% and 60.8%, respectively. Methods: Neutralizing antibody titers to the four dengue serotypes in the CYD-TDV vaccine insert were measured at Month 13 in a randomly sampled immunogenicity sub-cohort and in all VCD cases through Month 25 (2848 vaccine, 1574 placebo) and studied for their association with VCD and with the level of VE to prevent VCD. Results: For each trial and serotype, vaccinees with higher Month 13 titer to the serotype had significantly lower risk of VCD with that serotype (hazard ratios 0.19-0.43 per 10-fold increase). Moreover, for each trial vaccinees with higher Month 13 average titer to the four serotypes had significantly higher VE against VCD of any serotype (P values < 0.001). Conclusions: Neutralizing antibody titers post-dose three correlate with CYD-TDV VE to prevent dengue. High titers associate with high VE for all serotypes, baseline serostatus groups, age groups, and both trials. However, lowest titers do not fully correspond to zero VE, indicating that other factors influence VE.
Modjarrad, K., L. Lin, S. L. George, K. E. Stephenson, K. H. Eckels, R. A. De La Barrera, R. G. Jarman, E. Sondergaard, J. Tennant, J. L. Ansel, K. Mills, M. Koren, M. L. Robb, J. Barrett, J. Thompson, A. E. Kosel, P. Dawson, A. Hale, C. S. Tan, S. R. Walsh, K. E. Meyer, J. Brien, T. A. Crowell, A. Blazevic, K. Mosby, R. A. Larocca, P. Abbink, M. Boyd, C. A. Bricault, M. S. Seaman, A. Basil, M. Walsh, V. Tonwe, D. F. Hoft, S. J. Thomas, D. H. Barouch and N. L. Michael (2017). “Preliminary aggregate safety and immunogenicity results from three trials of a purified inactivated Zika virus vaccine candidate: phase 1, randomised, double-blind, placebo-controlled clinical trials.” The Lancet.
Background: A safe, effective, and rapidly scalable vaccine against Zika virus infection is needed. We developed a purified formalin-inactivated Zika virus vaccine (ZPIV) candidate that showed protection in mice and non-human primates against viraemia after Zika virus challenge. Here we present the preliminary results in human beings.
HIV – Africa
Ortblad, K., D. Kibuuka Musoke, T. Ngabirano, A. Nakitende, J. Magoola, P. Kayiira, G. Taasi, L. G. Barresi, J. E. Haberer, M. A. McConnell, C. E. Oldenburg and T. Bärnighausen (2017). “Direct provision versus facility collection of HIV self-tests among female sex workers in Uganda: A cluster-randomized controlled health systems trial.” PLOS Medicine 14(11): e1002458.
In a cluster-randomized trial, Katrina Ortblad and colleagues study the provision of HIV self-tests for female sex workers in Uganda.
Vandormael, A., T. Barnighausen, J. Herbeck, A. Tomita, A. Phillips, D. Pillay, T. de Oliveira and F. Tanser (2017). “Longitudinal trends in the prevalence of detectable HIV viremia: Population-based evidence from rural KwaZulu-Natal, South Africa.” Clin Infect Dis.
Background: The prevalence of detectable viremia has previously been used to infer the potential for ongoing HIV transmission. To date, no study has evaluated the longitudinal change in the prevalence of detectable viremia within the HIV-positive community (PDV+) and the entire population (PDVP) using data from a sub-Saharan African setting. Methods: In 2011, 2013, and 2014, we obtained 6,752 HIV-positive and 15,415 HIV-negative test results from a population-based surveillance system in the KwaZulu-Natal province of South Africa. We quantified the PDV+ as the proportion of the 6,752 HIV-positive results with a viral load >1,550 copies/mL and the PDVP as the proportion of the 6,752 HIV-positive and 15,415 HIV-negative results with a viral load >1,550 copies/mL. Results: Between 2011 and 2014, the PDV+ decreased by 16.5 percentage points (pp) for women (from 71.8% to 55.3%) and 10.6 pp for men (from 77.8% to 67.2%). However, a steady rise in the overall HIV prevalence, from 26.7% to 32.4%, offset the declines in the PDV+ for both sexes. For woman, the PDVP decreased by only 2.1 pp, from 21.3% to 19.2%; but for men, the PDVP actually increased by 1.6 pp, from 14.6% to 16.2%, over the survey period. Discussion: The PDV+, which is currently being tracked under the UNAID 90-90-90 targets, may not be accurate indicator of the potential for ongoing HIV transmission. There is a critical need for countries to monitor and report the prevalence of detectable viremia among all adults (PDVP), irrespective of HIV status.
HIV – Cures & Treatments
Cummins, N. W., S. Rizza, M. R. Litzow, S. Hua, G. Q. Lee, K. Einkauf, T.-W. Chun, F. Rhame, J. V. Baker, M. P. Busch, N. Chomont, P. G. Dean, R. Fromentin, A. T. Haase, D. Hampton, S. M. Keating, S. M. Lada, T.-H. Lee, S. Natesampillai, D. D. Richman, T. W. Schacker, S. Wietgrefe, X. G. Yu, J. D. Yao, J. Zeuli, M. Lichterfeld and A. D. Badley (2017). “Extensive virologic and immunologic characterization in an HIV-infected individual following allogeneic stem cell transplant and analytic cessation of antiretroviral therapy: A case study.” PLOS Medicine 14(11): e1002461.
Andrew Badley and colleagues study the viral reservoir in an individual with HIV infection after allogeneic stem cell transplantation.
Deeks, S. G., S. R. Lewin and L. G. Bekker (2017). “The end of HIV: Still a very long way to go, but progress continues.” PLoS Med 14(11): e1002466.
In an Editorial accompanying PLOS Medicine’s Special Issue on Advances in Prevention, Treatment and Cure of HIV/AIDS, Guest Editors Steven Deeks, Sharon Lewin, and Linda-Gail Bekker discuss priorities in the field and the content of the issue.
Lederman, M. M. and E. Pike (2017). “Ten Years HIV Free: An Interview with “The Berlin Patient,” Timothy Ray Brown.” Pathog Immun 2(3): 422-430.
Okee, M., A. Bayiyana, C. Musubika, M. Joloba, F. Ashaba-Katabazi, B. S. Bagaya and M. Wayengera (2017). “In-vitro Transduction and Target-Mutagenesis Efficiency of HIV-1 po gene targeting ZFN and CRISPER/Cas9 delivered by various plasmids and or vectors: Towards an HIV cure..” AIDS Res Hum Retroviruses.
Efficiency of artificial restriction enzymes (AREs) towards curing HIV has only been separately examined, using differing delivery vehicles. We compared the in-vitro transduction and target-mutagenesis efficiency of consortium-plasmid and adenoviral vector delivered HIV-1<i> pol </i>gene targeting ZFN with CRISPER/Cas. Custom-ZFN, CRISPER-Cas-9, plasmids and vectors (murCTSD_pZFN, pGS-U-gRNA, pCMV-Cas-D01A, Ad5-RGD); cell-lines (TZM-bl and ACH-2/J-Lat cells); and the latency reversing agents Prostatin, SAHA, and PMA were used. Cell-lines were grown in either Dulbecco Modified Eagle Medium (DMEM) or Roswell Park Memorial Institute (RPMI) with the antibiotics Kanamycin, Zeocin and effavirenz. Efficiency was assayed by GFP/Luciferase activity; and or validated by yeast MEL-1 reporter assay, CEL1 restriction fragment assay and qRT-PCR. Ad5-RGD vectors had better transduction efficiency than murCTSD and pGS-U-gRNA/ pCMV-Cas-D01A plasmids. CRISPER/Cas-9 exhibited better target mutagenesis efficiency relative to ZFN (delivered by either plasmid or Ad5 vector) based on gel-electrophoresis of <i>pol</i> gene amplicons within ACH-2 and JLat cells. Ad-5-RGD vectors enhanced target-mutagenesis of ZFN relative to murCTSD_pZFN plasmids to levels of CRISPER/Cas9 plasmids. Similar reduction of luciferase activity among TZM-bl treated with Ad5-ZFN vectors relative to CRISPER/Cas9 and murCTSD_pZFN plasmids were observed on challenge with HIV-1. qRT-PCR of HIV-1 <i>pol</i> gene transcripts affirmed Ad5 (RGD) vectors enhanced target mutagenesis of ZFN. Whereas CRISPER/Cas9 may possess inherent superior target-mutagenesis efficiency; the efficiency of ZFN (off-target toxicity withstanding), can be enhanced by altering delivery vehicle from plasmid to Ad5 (RGD) vectors.
HIV- Elite Controllers and Exposed Seronegative
Santos, J. S., S. M. Almeida, G. F. Silveira, J. Bordignon, S. L. Teixeira, A. Lima and S. M. Raboni (2017). “Host factors predictors in long-term nonprogressors HIV-1 infected with distinct viral clades.” Curr HIV Res.
BACKGROUND: HIV-1+ long-term non-progressors (LTNPs) maintain natural control of viral infection. This study sought to identify and characterize HIV- LTNPs series case, regarding the presence of possible host factors that may be associated with this status. METHODS: We evaluated the plasma levels of IP-10/IL-8 chemokines, HLA-B alleles, and IL28B rs12979860 polymorphism in 24 LTNPs who presented with infection by different clades of HIV-1. RESULTS: IL-8 chemokine was significantly higher in progressors than in LTNPs, but there was no difference between the LTNP subgroups. There was a negative correlation in CD4+ T cell (TC) count and IL-8 dosage, and a positive correlation with CD8+ TC. IP-10 chemokine levels were associated with viremia, and the elite controller (EC) subgroup showed nearly the same level than healthy individuals and progressors with viral load suppressed. Furthermore, the CD4+ TC count, percentage of CD4+ TC, and CD4/CD8 ratio were negatively correlated with IP-10. No association was found in plasma levels of IL-8 and IP-10 chemokines and HIV-1 clades. In the EC/viremic controller subgroup, 80% presented with at least one HLA-B allele previously considered as potentially protective for AIDS progression. No association was observed between the HLA-B alleles and HIV-1 clades. The IL28B CC genotype was identified in 87.5% of LTNPs. CONCLUSION: In this LTNP series case we observed different host factors that may be contributing to their nonprogressor status, and the association of these factors with the control of infection progression may be critically important for future therapeutic and prophylactic options in HIV-1 infection.
HIV – HLA
Holzemer, A., W. F. Garcia-Beltran and M. Altfeld (2017). “Natural Killer Cell Interactions with Classical and Non-Classical Human Leukocyte Antigen Class I in HIV-1 Infection.” Front Immunol 8: 1496.
Natural killer (NK) cells are effector lymphocytes of the innate immune system that are able to mount a multifaceted antiviral response within hours following infection. This is achieved through an array of cell surface receptors surveilling host cells for alterations in human leukocyte antigen class I (HLA-I) expression and other ligands as signs of viral infection, malignant transformation, and cellular stress. This interaction between HLA-I ligands and NK-cell receptor is not only important for recognition of diseased cells but also mediates tuning of NK-cell-effector functions. HIV-1 alters the expression of HLA-I ligands on infected cells, rendering them susceptible to NK cell-mediated killing. However, over the past years, various HIV-1 evasion strategies have been discovered to target NK-cell-receptor ligands and allow the virus to escape from NK cell-mediated immunity. While studies have been mainly focusing on the role of polymorphic HLA-A, -B, and -C molecules, less is known about how HIV-1 affects the more conserved, non-classical HLA-I molecules HLA-E, -G, and -F. In this review, we will focus on the recent progress in understanding the role of non-classical HLA-I ligands in NK cell-mediated recognition of HIV-1-infected cells.
Du, Y., T. H. Zhang, L. Dai, X. Zheng, A. M. Gorin, J. Oishi, T. T. Wu, J. M. Yoshizawa, X. Li, O. O. Yang, O. Martinez-Maza, R. Detels and R. Sun (2017). “Effects of Mutations on Replicative Fitness and Major Histocompatibility Complex Class I Binding Affinity Are Among the Determinants Underlying Cytotoxic-T-Lymphocyte Escape of HIV-1 Gag Epitopes.” MBio 8(6).
Certain “protective” major histocompatibility complex class I (MHC-I) alleles, such as B*57 and B*27, are associated with long-term control of HIV-1 in vivo mediated by the CD8(+) cytotoxic-T-lymphocyte (CTL) response. However, the mechanism of such superior protection is not fully understood. Here we combined high-throughput fitness profiling of mutations in HIV-1 Gag, in silico prediction of MHC-peptide binding affinity, and analysis of intraperson virus evolution to systematically compare differences with respect to CTL escape mutations between epitopes targeted by protective MHC-I alleles and those targeted by nonprotective MHC-I alleles. We observed that the effects of mutations on both viral replication and MHC-I binding affinity are among the determinants of CTL escape. Mutations in Gag epitopes presented by protective MHC-I alleles are associated with significantly higher fitness cost and lower reductions in binding affinity with respect to MHC-I. A linear regression model accounting for the effect of mutations on both viral replicative capacity and MHC-I binding can explain the protective efficacy of MHC-I alleles. Finally, we found a consistent pattern in the evolution of Gag epitopes in long-term nonprogressors versus progressors. Overall, our results suggest that certain protective MHC-I alleles allow superior control of HIV-1 by targeting epitopes where mutations typically incur high fitness costs and small reductions in MHC-I binding affinity.IMPORTANCE Understanding the mechanism of viral control achieved in long-term nonprogressors with protective HLA alleles provides insights for developing functional cure of HIV infection. Through the characterization of CTL escape mutations in infected persons, previous researchers hypothesized that protective alleles target epitopes where escape mutations significantly reduce viral replicative capacity. However, these studies were usually limited to a few mutations observed in vivo Here we utilized our recently developed high-throughput fitness profiling method to quantitatively measure the fitness of mutations across the entirety of HIV-1 Gag. The data enabled us to integrate the results with in silico prediction of MHC-peptide binding affinity and analysis of intraperson virus evolution to systematically determine the differences in CTL escape mutations between epitopes targeted by protective HLA alleles and those targeted by nonprotective HLA alleles. We observed that the effects of Gag epitope mutations on HIV replicative fitness and MHC-I binding affinity are among the major determinants of CTL escape.
HIV – Models
Masse-Ranson, G., H. Mouquet and J. P. Di Santo (2017). “Humanized mouse models to study pathophysiology and treatment of HIV infection.” Curr Opin HIV AIDS.
PURPOSE OF REVIEW: Immunodeficient mice that lack all lymphocyte subsets and have phagocytic cells that are tolerant of human cells can be stably xenografted with human hematopoietic stem cell as well as other human tissues (fetal liver and thymus) creating ‘human immune system’ (HIS) mice. HIS mice develop all major human lymphocyte classes (B, T, natural killer, and innate lymphoid cell) and their specialized subsets as well as a variety of myeloid cells (dendritic cell, monocytes, and macrophages) thereby providing a small animal model in which to interrogate human immune responses to infection. RECENT FINDINGS: HIS mouse models have been successfully used to study several aspects of HIV-1 biology, including viral life cycle (entry, restriction, replication, and spread) as well as virus-induced immunopathology (CD4 T-cell depletion, immune activation, and mucosal inflammation). Recent work has shown that HIV reservoirs can be established in HIV-infected HIS mice after treatment with combinations of antiretroviral drugs thereby providing a model to test new approaches to eliminate latently infected cells. SUMMARY: HIS mice provide cost-effective preclinical platform to assess combination immunotherapies that can target HIV reservoirs. Therapeutic strategies validated in HIS mice should be considered in designing the roadmap toward HIV ‘cure’.
HIV – NEUTRALIZING ANTIBODIES
Kumar, S., R. Kumar, L. Khan, M. A. Makhdoomi, R. Thiruvengadam, M. Mohata, M. Agarwal, R. Lodha, S. K. Kabra, S. Sinha and K. Luthra (2017). “CD4-Binding Site Directed Cross-Neutralizing scFv Monoclonals from HIV-1 Subtype C Infected Indian Children.” Front Immunol 8: 1568.
Progression of human immunodeficiency virus type-1 (HIV-1) infection in children is faster than adults. HIV-1 subtype C is responsible for more than 50% of the infections globally and more than 90% infections in India. To date, there is no effective vaccine against HIV-1. Recent animal studies and human Phase I trials showed promising results of the protective effect of anti-HIV-1 broadly neutralizing antibodies (bnAbs). Interaction between CD4 binding site (CD4bs) on the HIV-1 envelope glycoprotein and CD4 receptor on the host immune cells is the primary event leading to HIV-1 infection. The CD4bs is a highly conserved region, comprised of a conformational epitope, and is a potential target of bnAbs such as VRC01 that is presently under human clinical trials. Recombinant scFvs can access masked epitopes due to their small size and have shown the potential to inhibit viral replication and neutralize a broad range of viruses. Pediatric viruses are resistant to many of the existing bnAbs isolated from adults. Therefore, in this study, pooled peripheral blood mononuclear cells from 9 chronically HIV-1 subtype C infected pediatric cross-neutralizers whose plasma antibodies exhibited potent and cross-neutralizing activity were used to construct a human anti-HIV-1 scFv phage library of 9 x 10(8) individual clones. Plasma mapping using CD4bs-specific probes identified the presence of CD4bs directed antibodies in 4 of these children. By extensive biopanning of the library with CD4bs-specific antigen RSC3 core protein, we identified two cross-neutralizing scFv monoclonals 2B10 and 2E4 demonstrating a neutralizing breadth and GMT of 77%, 17.9 microg/ml and 32%, 51.2 microg/ml, respectively, against a panel of 49 tier 1, 2 and 3 viruses. Both scFvs competed with anti-CD4bs bnAb VRC01 confirming their CD4bs epitope specificity. The 2B10 scFv was effective in neutralizing the 7 subtype C and subtype A pediatric viruses tested. Somatic hypermutations in the VH gene of scFvs (10.1-11.1%) is comparable with that of the adult antibodies. These cross-neutralizing CD4bs-directed scFvs can serve as potential reagents for passive immunotherapy. A combination of cross-neutralizing scFvs of diverse specificities with antiretroviral drugs may be effective in suppressing viremia at an early stage of HIV-1 infection and prevent disease progression.
Lee, W. S. and S. J. Kent (2017). “Anti-HIV-1 antibody-dependent cellular cytotoxicity: is there more to antibodies than neutralization?” Curr Opin HIV AIDS.
PURPOSE OF REVIEW: An increasing body of evidence suggests that nonneutralizing Fc effector functions including antibody-dependent cellular cytotoxicity (ADCC) contribute to protection against HIV-1 acquisition. We discuss recent advances in anti-HIV-1 ADCC research with a particular focus on ADCC mediated by Env-specific antibodies in vitro and in vivo, the curative potential of HIV-1-specific ADCC antibodies and the mechanisms of HIV-1 resistance to ADCC. RECENT FINDINGS: ADCC activities of broadly neutralizing and nonneutralizing monoclonal antibody panels were recently characterized in vitro against several lab-adapted and primary isolates of HIV-1. ADCC activity of these monoclonal antibodies generally correlated with binding to infected cells and were greater against the lab-adapted strains compared with primary HIV-1 isolates. Several recent studies in mouse and macaque models of HIV-1 infection suggest Fc-mediated effector functions contribute to the protective efficacy of broadly neutralizing antibodies and exert immune pressure on HIV-1 in vivo. SUMMARY: An increasing body of evidence suggests that ADCC-mediating antibodies, particularly when combined with neutralizing functions, can facilitate prevention and control of HIV-1. The precise mechanisms of partial protection conferred by nonneutralizing antibodies in vivo remain unclear and will need to be fully investigated in order to realize their full potential for HIV-1 vaccines.
Mayr, L. M., B. Su and C. Moog (2017). “Non-Neutralizing Antibodies Directed against HIV and Their Functions.” Front Immunol 8: 1590.
B cells produce a plethora of anti-HIV antibodies (Abs) but only few of them exhibit neutralizing activity. This was long considered a profound limitation for the enforcement of humoral immune responses against HIV-1 infection, especially since these neutralizing Abs (nAbs) are extremely difficult to induce. However, increasing evidence shows that additional non-neutralizing Abs play a significant role in decreasing the viral load, leading to partial and sometimes even total protection. Mechanisms suspected to participate in protection are numerous. They involve the Fc domain of Abs as well as their Fab part, and consequently the induced Ab isotype will be determinant for their functions, as well as the quantity and quality of the Fc-receptors (FcRs) expressed on immune cells. Fc-mediated inhibitory functions, such as Ab-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, aggregation, and even immune activation have been proposed. However, as for nAbs, the non-neutralizing activities are limited to a subset of anti-HIV Abs. An improved in-depth characterization of the Abs displaying these functional responses is required for the development of new vaccination strategies, which aim to selectively trigger the B cells able to induce the right functional Ab combinations both at the right place and at the right time. This review summarizes our current knowledge on non-neutralizing functional inhibitory Abs and discusses the potential benefit of inducing them via vaccination. We also provide new insight into the roles of the FcgammaR-mediated Ab therapeutics in clinical trials for HIV diseases.
Haks, M. C., B. Bottazzi, V. Cecchinato, C. De Gregorio, G. Del Giudice, S. H. E. Kaufmann, A. Lanzavecchia, D. J. M. Lewis, J. Maertzdorf, A. Mantovani, F. Sallusto, M. Sironi, M. Uguccioni and T. H. M. Ottenhoff (2017). “Molecular Signatures of Immunity and Immunogenicity in Infection and Vaccination.” Front Immunol 8: 1563.
Vaccinology aims to understand what factors drive vaccine-induced immunity and protection. For many vaccines, however, the mechanisms underlying immunity and protection remain incompletely characterized at best, and except for neutralizing antibodies induced by viral vaccines, few correlates of protection exist. Recent omics and systems biology big data platforms have yielded valuable insights in these areas, particularly for viral vaccines, but in the case of more complex vaccines against bacterial infectious diseases, understanding is fragmented and limited. To fill this gap, the EC supported ADITEC project (http://www.aditecproject.eu/; http://stm.sciencemag.org/content/4/128/128cm4.full) featured a work package on “Molecular signatures of immunity and immunogenicity,” aimed to identify key molecular mechanisms of innate and adaptive immunity during effector and memory stages of immune responses following vaccination. Specifically, technologies were developed to assess the human immune response to vaccination and infection at the level of the transcriptomic and proteomic response, T-cell and B-cell memory formation, cellular trafficking, and key molecular pathways of innate immunity, with emphasis on underlying mechanisms of protective immunity. This work intersected with other efforts in the ADITEC project. This review summarizes the main achievements of the work package.
Corridoni, D. and A. Simmons (2017). “Innate immune receptors for cross-presentation: The expanding role of NLRs.” Mol Immunol.
A critical role of pattern recognition receptors (PRRs) is to influence adaptive immune responses by regulating antigen presentation. Engagement of PRRs in dendritic cells (DCs) increases MHC class I antigen presentation and CD8(+) T-cell activation by cross-presented peptides but the molecular mechanisms underlying these effects are not completely understood. Studies looking at the role of PRRs in cross-presentation have been largely limited to TLRs but the role of other PRRs such as cytosolic nucleotide-binding oligomerization domain-like (NOD-like) receptors remains particularly enigmatic. Here we discuss recent evidence of the role of PRRs on cross-presentation and consider how cytosolic NLR-associated pathways, such as NOD2, may integrate these signals resulting in effective adaptive CD8(+) T cells responses.
Vaccine Design Immunogenicity Efficacy
van der Lee, S., E. A. M. Sanders, G. A. M. Berbers and A. M. Buisman (2017). “Whole-cell or acellular pertussis vaccination in infancy determines IgG subclass profiles to DTaP booster vaccination.” Vaccine.
INTRODUCTION: Duration of protection against pertussis is shorter in adolescents who have been immunized with acellular pertussis (aP) in infancy compared with adolescents who received whole-cell pertussis (wP) vaccines in infancy, which is related to immune responses elicited by these priming vaccines. To better understand differences in vaccine induced immunity, we determined pertussis, diphtheria, and tetanus (DTaP) vaccine antigen-specific IgG subclass responses in wP- and aP-primed children before and after two successive DTaP booster vaccinations. METHODS: Blood samples were collected in a cross-sectional study from wP- or aP-primed children before and 1month after the pre-school DTaP booster vaccination at age 4years. Blood samples were collected from two different wP- and aP-primed groups of children before, 1month and 1year after an additional pre-adolescent Tdap booster at age 9years. IgG subclass levels against the antigens included in the DTaP vaccine have been determined with fluorescent-bead-based multiplex immunoassays. RESULTS: At 4years of age, the IgG4 proportion and concentration for pertussis, diphtheria and tetanus vaccine antigens were significantly higher in aP-primed children compared with wP-primed children. IgG4 concentrations further increased upon the two successive booster vaccinations at 4 and 9years of age in both wP- and aP-primed children, but remained significantly higher in aP-primed children. CONCLUSIONS: The pertussis vaccinations administered in the primary series at infancy determine the vaccine antigen-specific IgG subclass profiles, not only against the pertussis vaccine antigens, but also against the co-administered diphtheria and tetanus vaccine antigens. These profiles did not change after DTaP booster vaccinations later in childhood. The different immune response with high proportions of specific IgG4 in some aP-primed children may contribute to a reduced protection against pertussis. ISRCTN65428640; ISRCTN64117538; NTR4089.
Scherer, E. M., R. A. Smith, J. J. Carter, G. C. Wipf, D. F. Gallego, M. Stern, A. Wald and D. A. Galloway (2017). “Analysis of memory B cell responses reveals suboptimal dosing schedule of a licensed vaccine.” J Infect Dis.
Current guidance recommends adolescents receive a two-dose HPV vaccine, whereas young adults and immunocompromised persons receive three doses. We examined secondary responses of vaccine-elicited memory B cells in naive women receiving three doses of the quadrivalent HPV vaccine to understand the quality of B cell memory generated by this highly effective vaccine. Unexpectedly, we observed a lower Bmem response rate and magnitude of Bmem responses to the third dose than to a booster dose administered at month 24. Moreover, high titers of antigen-specific serum antibody at vaccination inversely correlated with Bmem responses. As the purpose of additional doses/boosters is to stimulate Bmem to rapidly boost Ab levels, these results indicate the timing of the third dose is suboptimal and lend support to a two-dose HPV vaccine for young adults. Our findings also indicate more broadly that multi-dose vaccine schedules should be rationally determined on the basis of Bmem response rates. (150 words).
VACCINE DESIGN – VECTORS
Aponte-Ubillus, J. J., D. Barajas, J. Peltier, C. Bardliving, P. Shamlou and D. Gold (2017). “Molecular design for recombinant adeno-associated virus (rAAV) vector production.” Appl Microbiol Biotechnol.
Recombinant adeno-associated virus (rAAV) vectors are increasingly popular tools for gene therapy applications. Their non-pathogenic status, low inflammatory potential, availability of viral serotypes with different tissue tropisms, and prospective long-lasting gene expression are important attributes that make rAAVs safe and efficient therapeutic options. Over the last three decades, several groups have engineered recombinant AAV-producing platforms, yielding high titers of transducing vector particles. Current specific productivity yields from different platforms range from 10(3) to 10(5) vector genomes (vg) per cell, and there is an ongoing effort to improve vector yields in order to satisfy high product demands required for clinical trials and future commercialization.Crucial aspects of vector production include the molecular design of the rAAV-producing host cell line along with the design of AAV genes, promoters, and regulatory elements. Appropriately, configuring and balancing the expression of these elements not only contributes toward high productivity, it also improves process robustness and product quality. In this mini-review, the rational design of rAAV-producing expression systems is discussed, with special attention to molecular strategies that contribute to high-yielding, biomanufacturing-amenable rAAV production processes. Details on molecular optimization from four rAAV expression systems are covered: adenovirus, herpesvirus, and baculovirus complementation systems, as well as a recently explored yeast expression system.