AIDS VACCINE DESIGN IMMUNOGENICITY EFFICACY
Bauer, A., L. Podola, P. Mann, M. Missanga, A. Haule, L. Sudi, C. Nilsson, B. Kaluwa, C. Lueer, M. Mwakatima, P. J. Munseri, L. Maboko, M. L. Robb, S. Tovanabutra, G. Kijak, M. Marovich, S. McCormack, S. Joseph, E. Lyamuya, B. Wahren, E. Sandstrom, G. Biberfeld, M. Hoelscher, M. Bakari, A. Kroidl and C. Geldmacher (2017). “Preferential Targeting of Conserved Gag Regions after Vaccination with a Heterologous DNA prime – Modified Vaccinia Ankara (MVA) boost HIV-1 vaccine regimen.” J Virol.
Prime-boost vaccination strategies against HIV-1 often include multiple variants for a given immunogen for better coverage of the extensive viral diversity. To study the immunologic effects of this approach, we characterized breadth, phenotype, function and specificity of Gag-specific T cells induced by a DNA-prime Modified Vaccinia Ankara (MVA)-boost vaccination strategy, which uses mismatched Gag immunogens in the TamoVac 01 phase IIa trial. Healthy Tanzanian volunteers received three injections of the DNA-SMI vaccine encoding for a subtype B and AB-recombinant Gagp37 and two vaccinations with MVA-CMDR encoding subtype A Gagp55 Gag-specific T-cell responses were studied in 42 vaccinees using fresh peripheral blood mononuclear cells. After the first MVA-CMDR boost, vaccine-induced IFN-gamma+ Gag-specific T cell responses were dominated by CD4+ T cells (compared to CD8+ T cells, p<0.001) that co-expressed IL-2 (66.4%) and/or TNFalpha (63.7%). A median of 3 antigenic regions were targeted with a higher median response magnitude to Gagp24 regions – more conserved between prime and boost – as compared to regions within Gagp15 (not primed) and Gagp17 (less conserved, both p<0.0001). Four regions within Gagp24 were each targeted by 45% to 74% of vaccinees upon restimulation with DNA-SMI-Gag matched peptides. The response rate to individual antigenic regions correlated with the sequence homology between the MVA and DNA Gag encoded immunogens (p=0.04, r2=0.47). In summary, after the first MVA-CMDR boost, the sequence-mismatched DNA-prime MVA-boost vaccine strategy induced a Gag-specific T cell response that was dominated by polyfunctional CD4+ T cells and that targeted multiple antigenic regions within the conserved Gagp24 Protein.IMPORTANCE Genetic diversity is a major challenge for the design of vaccines against variable viruses. While including multiple variants for a given immunogen in prime-boost vaccination strategies is one approach that aims to improve coverage for global virus variants, the immunologic consequences of this strategy have been poorly defined so far. It is unclear whether inclusion of multiple variants in prime-boost vaccination strategies improves recognition of variant viruses by T cells and by which mechanisms this would be achieved; either by improved cross-recogniton of multiple variants for a given antigenic region or rather through preferential targeting of antigenic regions more conserved between prime and boost. Engineering vaccines to induce adaptive immune responses that preferentially target conserved antigenic regions of viral vulnerability might facilitate better immune control after preventive and therapeutic vaccination for HIV and for other variable viruses.
Bogers, W., S. W. Barnett, H. Oostermeijer, I. G. Nieuwenhuis, N. Beenhakker, D. Mortier, P. Mooij, G. Koopman, E. Remarque, G. Martin, R. Pei-Jen 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 Responses to HIV-1 Envelope in Macaques Vaccinated with gp140 Occluded at the CD4 Receptor Binding Site.” J Virol.
Strategies are needed to improve the immunogenicity of HIV-1 envelope (Env) antigens for more long lived, efficacious HIV-1 vaccine induced B-cell responses. HIV-1 Env gp140 (native or un-cleaved 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 may result 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 3kD CD4 miniprotein mimetic serving to block ligation of gp140 on CD4+T-cells while preserving CD4 inducible (CDi) neutralizing and epitopes targeted by antibody dependent cellular cytotoxic (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 animals immunized with gp140. Of the cytokines examined, Ag-specific IL-4 T-helper ELISpots in the CD4bs-occluded group increased earlier (p=0.025) during the inductive phase. Importantly CD4bs-occluded gp140 antigen not only induced superior B-cell and ADCC responses, the elevated B-cell responses proved to be remarkably durable lasting more than 60 weeks post-immunization.IMPORTANCE Attempts to develop HIV vaccines capable of inducing potent and durable B-cell responses have until now been unsuccessful. 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 may in part be 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.
Chaipan, C., A. Pryszlak, H. Dean, P. Poignard, V. Benes, A. D. Griffiths and C. A. Merten (2017). “Single-Virus Droplet Microfluidics for High-Throughput Screening of Neutralizing Epitopes on HIV Particles.” Cell Chem Biol 24(6): 751-757 e753.
Analyzing surface epitopes of single HIV particles holds great potential for the development of vaccine candidates. However, existing technologies do not allow corresponding screens at high throughput. We present here a single-virus droplet-based microfluidics platform enabling sorting of millions of HIV-1 particles with >99% efficiency, based on the expression of epitopes recognized by broadly neutralizing antibodies. We show that virus particles displaying these epitopes can be identified, sorted, and analyzed by next-generation sequencing: an approximately 1,900-fold enrichment of viral particles displaying neutralizing epitopes could be obtained in a single sort, thus opening the way for screening diverse virus libraries with optimal antigenic features for HIV vaccine candidates.
Desrosiers, R. C. (2017). “Protection against HIV Acquisition in the RV144 Trial.” J Virol.
Differences of opinion regarding whether there may, or may not, have been protective efficacy in the RV144 vaccine trial have important societal implications.
Hinkula, J., S. Petkov, K. Ljungberg, D. Hallengard, A. Brave, M. Isaguliants, T. Falkeborn, S. Sharma, V. Liakina, M. Robb, M. Eller, B. Moss, G. Biberfeld, E. Sandstrom, C. Nilsson, K. Markland, P. Blomberg and B. Wahren (2017). “HIVIS-DNA or HIVISopt-DNA priming followed by CMDR vaccinia-based boosts induce both humoral and cellular murine immune responses to HIV.” Heliyon 3(6): e00339.
BACKGROUND: In order to develop a more effective prophylactic HIV-1 vaccine it is important optimize the components, improve Envelope glycoprotein immunogenicity as well as to explore prime-boost immunization schedules. It is also valuable to include several HIV-1 subtype antigens representing the world-wide epidemic. METHODS: HIVIS-DNA plasmids which include Env genes of subtypes A, B and C together with Gag subtypes A and B and RTmut/Rev of subtype B were modified as follows: the Envelope sequences were shortened, codon optimized, provided with an FT4 sequence and an immunodominant region mutated. The reverse transcriptase (RT) gene was shortened to contain the most immunogenic N-terminal fragment and fused with an inactivated viral protease vPR gene. HIVISopt-DNA thus contains fewer plasmids but additional PR epitopes compared to the native HIVIS-DNA. DNA components were delivered intradermally to young Balb/c mice once, using a needle-free Biojector(R) immediately followed by dermal electroporation. Vaccinia-based MVA-CMDR boosts including Env gene E and Gag-RT genes A were delivered intramuscularly by needle, once or twice. RESULTS: Both HIVIS-DNA and HIVISopt-DNA primed humoral and cell mediated responses well. When boosted with heterologous MVA-CMDR (subtypes A and E) virus inhibitory neutralizing antibodies were obtained to HIV-1 subtypes A, B, C and AE. Both plasmid compositions boosted with MVA-CMDR generated HIV-1 specific cellular responses directed against HIV-1 Env, Gag and Pol, as measured by IFNgamma ELISpot. It was shown that DNA priming augmented the vector MVA immunological boosting effects, the HIVISopt-DNA with a trend to improved (Env) neutralization, the HIVIS-DNA with a trend to better (Gag) cell mediated immune reponses. CONCLUSIONS: HIVIS-DNA was modified to obtain HIVISopt-DNA that had fewer plasmids, and additional epitopes. Even with one DNA prime followed by two MVA-CMDR boosts, humoral and cell-mediated immune responses were readily induced by priming with either DNA construct composition. Priming by HIV-DNA augmented neutralizing antibody responses revealed by boosting with the vaccinia-based heterologous sequences. Cellular and antibody responses covered selected strains representing HIV-1 subtypes A, B, C and CRF01_AE. We assume this is related to the inclusion of heterologous full genes in the vaccine schedule.
AIDS VACCINE ENVELOPE DESIGN
Forsell, M. N. E., L. Kvastad, S. K. Sedimbi, J. Andersson and M. C. I. Karlsson (2017). “Regulation of Subunit-Specific Germinal Center B Cell Responses to the HIV-1 Envelope Glycoproteins by Antibody-Mediated Feedback.” Front Immunol 8: 738.
The regulation of germinal center (GC) B cell responses to single epitopes is well investigated. How monoclonal B cells are regulated within the polyclonal B cell response to protein antigens is less so. Here, we investigate the primary GC B cell response after injection of mice with HIV-1 envelope glycoproteins. We demonstrate that single GCs are seeded by a diverse number of B cell clones shortly after a single immunization and that the presence of Env-specific antibodies can inhibit the development of early GC B cells. Importantly, the suppression was dependent on the GC B cells and the infused antibodies to target the same subunit of the injected HIV-1 envelope glycoproteins. An affinity-dependent antibody feedback has previously been shown to regulate GC B cell development. Here, we propose that this antibody-based feedback acts on GC B cells only if they target the same or overlapping epitopes. This study provides important basic information of GC B cell regulation, and for future vaccine designs with aim to elicit neutralizing antibodies against HIV-1.
HIV – AFRICA
Sawers, L. and A. Isaac (2017). “Partnership duration, concurrency, and HIV in sub-Saharan Africa.” Afr J AIDS Res: 1-10.
A widely accepted explanation for the exceptionally high HIV prevalence in sub-Saharan Africa is the practice of long-term overlapping heterosexual partnering. This article shows that long-duration concurrent partnering can be protective against HIV transmission rather than promoting it. Monogamous partnering prevents sexual transmission to anyone outside the partnership and, in an initially concordant-seronegative partnership, prevents sexual acquisition of HIV by either partner. Those protections against transmission and acquisition last as long as the partnership persists without new outside partnerships. Correspondingly, these two protective effects characterise polygynous partnerships, whether or not the polygyny is formal or informal, until a partner initiates a new partnership. Stable and exclusive unions of any size protect against HIV transmission, and more durable unions provide a longer protective effect. Survey research provides little information on partnership duration in sub-Saharan Africa and sheds no light on the interaction of duration, concurrency, and HIV. This article shows how assumptions about partnership duration in individual-based sexual-network models affect the contours of simulated HIV epidemics. Longer mean partnership duration slows the pace at which simulated epidemics grow. With plausible assumptions about partnership duration and at levels of concurrency found in the region, simulated HIV epidemics grow slowly or not at all. Those results are consistent with the hypothesis that long-duration partnering is protective against HIV and inconsistent with the hypothesis that long-term concurrency drives the HIV epidemics in sub-Saharan Africa.
HIV – CURES & TREATMENTS
Brezar, V., L. Hani, M. Surenaud, A. Hubert, C. Lacabaratz, J. D. Lelievre, Y. Levy and N. Seddiki (2017). “Negative modulation of suppressive HIV-specific regulatory T cells by IL-2 adjuvanted therapeutic vaccine.” PLoS Pathog 13(7): e1006489.
The potential benefit in using IL-2 in immunotherapy for cancer and autoimmunity has been linked to the modulation of immune responses, which partly relies on a direct effect on Tregs populations. Here, we revisited the role of IL-2 in HIV infection and investigated whether its use as an adjuvant with therapeutic vaccination, impacts on HIV-specific responses. Antiretroviral therapy treated-patients were randomized to receive 4 boosts of vaccination (ALVACHIV/Lipo-6T, weeks 0/4/8/12) followed by 3 cycles of IL-2 (weeks 16/24/32) before treatment interruption (TI) at week40. IL-2 administration increased significantly HIV-specific CD4+CD25+CD134+ T-cell responses, which inversely correlated with viral load after TI (r = -0.7, p <0.007) in the vaccine/IL-2 group. IL-2 increased global CD25+CD127lowFoxP3+Tregs (p <0.05) while it decreased HIV- but not CMV- specific CD39+FoxP3+CD25+CD134+Tregs (p <0.05). HIV-specific Tregs were inversely correlated with IFN-gamma producing specific-effectors (p = 0.03) and positively correlated with viral load (r = 0.7, p = 0.01), revealing their undesired presence during chronic infection. Global Tregs, but not HIV-specific Tregs, inversely correlated with a decrease in exhausted PD1+CD95+ T-cells (p = 0.001).Altogether, our results underline the negative impact of HIV-specific Tregs on HIV-specific effectors and reveal the beneficial use of IL-2 as an adjuvant as its administration increases global Tregs that impact on T-cell exhaustion and decreases HIV-specific CD39+Tregs by shifting the balance towards effectors.
HIV- ELITE CONTROLLERS AND EXPOSED SERONEGATIVE
Madhavi, V., B. D. Wines, J. Amin, S. Emery, E. Lopez, A. Kelleher, R. J. Center, P. M. Hogarth, A. W. Chung, S. J. Kent and I. Stratov (2017). “HIV-1 Env- and Vpu-specific antibody-dependent cellular cytotoxicity responses associated with elite control of HIV.” J Virol.
Studying HIV-infected individuals who control HIV replication (elite controllers, ECs) enable exploration of effective anti-HIV immunity. HIV Env- and non-Env-specific antibody-dependent cellular cytotoxicity (ADCC) may contribute to protection from progressive HIV infection but the evidence is limited. We recruited 22 ECs and matched them with 44 viremic subjects. HIV Env- and Vpu-specific ADCC responses were studied in sera using a novel ELISA-based dimeric recombinant soluble (rs) FcgammaRIIIa-binding assay, surface plasmon resonance, antibody-dependent natural killer (NK) cell activation assays and ADCC-mediated killing assays. ECs had higher levels of HIV Env-specific antibodies capable of binding FcgammaRIIIa, activating NK cells and mediating Granzyme B activity (all p<0.01) compared to viremic subjects. ECs also had higher levels of antibodies against a C-terminal 13-mer Vpu peptide capable of mediating FcgammaRIIIa-binding and NK cell-activation compared to viremic subjects (both p<0.05). Our data associate Env-specific and Vpu epitope-specific ADCC in effective immune responses against HIV among ECs. Our findings have implications for understanding the role of ADCC in HIV control. IMPORTANCE Understanding immune responses associated with elite control of HIV may aid the development of immunotherapeutic and vaccine strategies for controlling HIV infection. Env is a major HIV protein target of functional antibody responses that are heightened in ECs. Interestingly, EC antibodies also target Vpu, an accessory protein crucial to HIV, which degrades CD4 and antagonizes tetherin. Antibodies specific to Vpu are a common feature of the immune response of ECs that may prove of functional importance to the design of improved ADCC-based immunotherapy and preventative HIV vaccines.
Westrop, S. J., A. T. H. Cocker, A. Boasso, A. K. Sullivan, M. R. Nelson and N. Imami (2017). “Enrichment of HLA Types and Single-Nucleotide Polymorphism Associated With Non-progression in a Strictly Defined Cohort of HIV-1 Controllers.” Front Immunol 8: 746.
HIV-1 controllers (HIC) are extremely rare patients with the ability to control viral replication, maintain unchanging CD4 T-cell count, and evade disease progression for extensive periods of time, in the absence of antiretroviral therapy. In order to establish the representation of key genetic correlates of atypical disease progression within a cohort of HIV-1+ individuals who control viral replication, we examine four-digit resolution HLA type and single-nucleotide polymorphisms (SNP) previously identified to be correlated to non-progressive infection, in strictly defined HIC. Clinical histories were examined to identify patients exhibiting HIC status. Genomic DNA was extracted, and high definition HLA typing and genome-wide SNP analysis was performed. Data were compared with frequencies of SNP in European long-term non-progressors (LTNP) and primary infection cohorts. HLA-B alleles associated with atypical disease progression were at very high frequencies in the group of five HIC studied. All four HIC of European ancestry were HLA-B*57+ and half were also HLA-B*27+. All HIC, including one of self-reported African ethnicity, had the HLA-Cw*0602 allele, and the HLA-DQ9 allele was present only in HIC of European ancestry. A median 95% of the top 19 SNP known to be associated with LTNP status was observed in European HIC (range 78-100%); 17/19 of the SNP considered mapped to chromosome 6 in the HLA region, whereas 2/19 mapped to chromosome 8. The HIC investigated here demonstrated high enrichment of HLA types and SNP previously associated with long-term non-progression. These findings suggest that the extreme non-progressive phenotype considered here is associated with a genetic signature characterized by a single-genetic unit centered around the HLA-B*57 haplotype and the possible additive effect of HLA-B*27.
HIV – NEUTRALIZING ANTIBODIES
Lucar, O., B. Su, V. Potard, A. Samri, B. Autran, C. Moog, P. Debre and V. Vieillard (2017). “Neutralizing Antibodies Against a Specific Human Immunodeficiency Virus gp41 Epitope are Associated With Long-term Non-progressor Status.” EBioMedicine.
Antibodies (Abs) play a central role in human immunodeficiency virus (HIV) protection due to their multiple functional inhibitory activities. W614A-3S Abs recognize a specific form of a highly conserved motif of the gp41 envelope protein and can elicit viral neutralization to protect CD4+ T cells. Here, we describe in detail the neutralizing profile of W614A-3S Abs in untreated long-term non-progressor (LTNP) HIV-infected patients. W614A-3S Abs were detected in 23.5% (16/68) of untreated LTNP patients compared with <5% (5/104) of HIV-1 progressor patients. The W614A-3S Abs had efficient neutralizing activity that inhibited transmitted founder primary viruses and exhibited Fc-mediated inhibitory functions at low concentrations in primary monocyte-derived macrophages. The neutralizing capacity of W614A-3S Abs was inversely correlated with viral load (r=-0.9013; p<0.0001), viral DNA (r=-0.7696; p=0.0005) and was associated the preservation of high CD4+ T-cell counts and T-cell responses. This study demonstrates that W614A-3S neutralizing Abs may confer a crucial advantage to LTNP patients. These results provide insights for both pathophysiological research and the development of vaccine strategies.
Verrier, B., S. Paul, C. Terrat, L. Bastide, A. Ensinas, C. Phelip, B. Chanut, L. Bulens-Grassigny, F. Jospin and C. Guillon (2017). “Exploiting Natural Cross-reactivity between Human Immunodeficiency Virus (HIV)-1 p17 Protein and Anti-gp41 2F5 Antibody to Induce HIV-1 Neutralizing Responses In Vivo.” Front Immunol 8: 770.
Anti-p17 antibodies are able to neutralize human immunodeficiency virus (HIV) entry in a mouse model. In this study, we identified a region of sequence similarity between the epitopes of anti-p17 neutralizing antibodies and anti-gp41 neutralizing 2F5 antibody and verified cross-reactivity between p17 and 2F5 in vitro. The p17 sequence was modified to increase sequence identity between the p17 and 2F5 epitopes, which resulted in enhanced cross-reactivity in vitro. Immunogenicity of wild-type and modified p17 was characterized in a rabbit model. Both wild-type and mutated p17 induced anti-gp41 responses in rabbits; sera from these animals reacted with gp41 from different HIV clades. Moreover, introduction of the 2F5 sequence in p17 resulted in induction of antibodies with partially neutralizing activity. Based upon these data, we suggest that the natural cross-reactivity between HIV-1 p17 protein and 2F5 antibody can be exploited to induce antibodies with neutralizing activity in an animal model.
HIV – PREVENTION ADHERENCE
Stalter, R. M., J. Tharaldson, D. H. Owen, E. Okumu, T. Moench, N. Mack, E. E. Tolley and K. M. MacQueen (2017). “Attitudes and perceptions towards novel objective measures of ARV-based vaginal ring use: Results from a global stakeholder survey.” PLoS One 12(7): e0180963.
Results of recent microbicide and pre-exposure prophylaxis clinical trials have shown adherence to be a significant challenge with new HIV prevention technologies. As the vaginal ring containing dapivirine moves into two open label follow-on studies (HOPE/MTN-025 and DREAM) and other antiretroviral-based and multi-purpose prevention technology ring products advance through the development pipeline, there is a need for more accurate and reliable measures of adherence to microbicide ring products. We previously conducted a comprehensive landscape analysis to identify new technologies that could be applied to adherence measurement of vaginal rings containing antiretrovirals. To explore attitudes and perceptions towards the approaches that we identified, we conducted a survey of stakeholders with experience and expertise in microbicide and HIV prevention clinical trials. From May to July 2015 an electronic survey was distributed via email to 894 stakeholders; a total of 206 eligible individuals responded to at least one question and were included in the data analysis. Survey respondents were presented with various objective measures and asked about their perceived acceptability to trial participants, feasibility of implementation by study staff, usefulness for measuring adherence and ethical concerns. Methods that require no additional input from the participant and require no modifications to the existing ring product (i.e., measurement of residual drug or excipient, or a vaginal analyte that enters the ring) were viewed as being more acceptable to trial participants and more feasible to implement in the field. Respondents saw value in using objective measures to provide real-time feedback on adherence. However, approaches that involve unannounced home visits for sample collection or spot checks of ring use, which could provide significant value to adherence feedback efforts, were met with skepticism. Additional research on the acceptability of these methods to potential trial participants and trial staff is recommended.
Vaccine Design Adjuvants
Thompson, E. A. and K. Lore (2017). “Non-human primates as a model for understanding the mechanism of action of toll-like receptor-based vaccine adjuvants.” Curr Opin Immunol 47: 1-7.
While transgenic mouse models are powerful for understanding how the immune system is manipulated by vaccines, they cannot fully recapitulate the characteristics of the innate immune responses leading to adaptive immunity after vaccination in humans. Outbred non-human primates are far more representative models of human vaccine responses as there is high degree of similarities in immune cell subset distributions, receptor expression (including toll-like receptors; TLRs), and immune cell functions, in addition to modeling doses and injection sites more accurately. Vaccine adjuvants targeting TLRs have shown great promise in their ability to enhance responses to non-live vaccines. As TLR ligands are molecularly defined, studies of the mechanisms by which they interact with the immune system are facilitated. In this brief review, we focus on the use of TLR3, 4, 7/8 and 9 stimulating adjuvants in NHPs by evaluating similarities between the specified TLRs in human and NHPs and highlighting recent work studying the mode of action or efficacy of TLR based adjuvants in NHPs.
VACCINE DESIGN IMMUNOGENICITY EFFICACY
Kostova, E. B. and G. A. Poland (2017). “Vaccinology in the 21st century-The 10th Annual Vaccine Congress.” Vaccine.
ElSherif, M. S., C. Brown, D. MacKinnon-Cameron, L. Li, T. Racine, J. Alimonti, T. L. Rudge, C. Sabourin, P. Silvera, J. W. Hooper, S. A. Kwilas, N. Kilgore, C. Badorrek, W. J. Ramsey, D. G. Heppner, T. Kemp, T. P. Monath, T. Nowak, S. A. McNeil, J. M. Langley and S. A. Halperin (2017). “Assessing the safety and immunogenicity of recombinant vesicular stomatitis virus Ebola vaccine in healthy adults: a randomized clinical trial.” Cmaj 189(24): E819-e827.
BACKGROUND: The 2013-2016 Ebola virus outbreak in West Africa was the most widespread in history. In response, alive attenuated recombinant vesicular stomatitis virus (rVSV) vaccine expressing Zaire Ebolavirus glycoprotein (rVSVDeltaG-ZEBOV-GP) was evaluated in humans. METHODS: In a phase 1, randomized, dose-ranging, observer-blind, placebo-controlled trial, healthy adults aged 18-65 years were randomized into 4 groups of 10 to receive one of 3 vaccine doses or placebo. Follow-up visits spanned 180 days postvaccination for safety monitoring, immunogenicity testing and any rVSV virus shedding. RESULTS: Forty participants were injected with rVSVDeltaG-ZEBOV-GP vaccine (n = 30) or saline placebo (n = 10). No serious adverse events related to the vaccine or participant withdrawals were reported. Solicited adverse events during the 14-day follow-up period were mild to moderate and self-limited, with the exception of injection-site pain and headache. Viremia following vaccination was transient and no longer detectable after study day 3, with no virus shedding in saliva or urine. All vaccinated participants developed serum immunoglobulin G (IgG), as measured by Ebola virus envelope glycoprotein-based enzyme-linked immunosorbent assay (ELISA). Immunogenicity was comparable across all dose groups, and sustained IgG titers were detectable through to the last visit, at study day 180. INTERPRETATION: In this phase 1 study, there were no safety concerns after a single dose of rVSVDeltaG-ZEBOV-GP vaccine. IgG ELISA showed persistent high titers at 180 days postimmunization. There was a period of reactogenicity, but in general, the vaccine was well tolerated. This study provides evidence of the safety and immunogenicity of rVSVDeltaG-ZEBOV-GP vaccine and importance of its further investigation. Trial registration: Clinical-Trials.gov no., NCT02374385.
Magnani, D. M., C. G. T. Silveira, B. C. Rosen, M. J. Ricciardi, N. Pedreno-Lopez, M. J. Gutman, V. K. Bailey, H. S. Maxwell, A. Domingues, L. Gonzalez-Nieto, V. I. Avelino-Silva, M. Trindade, J. Nogueira, C. S. Oliveira, A. Maestri, A. C. Felix, J. E. Levi, M. L. Nogueira, M. A. Martins, J. M. Martinez-Navio, S. P. Fuchs, S. S. Whitehead, D. R. Burton, R. C. Desrosiers, E. G. Kallas and D. I. Watkins (2017). “A human inferred germline antibody binds to an immunodominant epitope and neutralizes Zika virus.” PLoS Negl Trop Dis 11(6): e0005655.
The isolation of neutralizing monoclonal antibodies (nmAbs) against the Zika virus (ZIKV) might lead to novel preventative strategies for infections in at-risk individuals, primarily pregnant women. Here we describe the characterization of human mAbs from the plasmablasts of an acutely infected patient. One of the 18 mAbs had the unusual feature of binding to and neutralizing ZIKV despite not appearing to have been diversified by affinity maturation. This mAb neutralized ZIKV (Neut50 ~ 2 mug/ml) but did not react with any of the four dengue virus serotypes. Except for the expected junctional diversity created by the joining of the V-(D)-J genes, there was no deviation from immunoglobulin germline genes. This is a rare example of a human mAb with neutralizing activity in the absence of detectable somatic hypermutation. Importantly, binding of this mAb to ZIKV was specifically inhibited by human plasma from ZIKV-exposed individuals, suggesting that it may be of value in a diagnostic setting.
Richner, J. M., B. W. Jagger, C. Shan, C. R. Fontes, K. A. Dowd, B. Cao, S. Himansu, E. A. Caine, B. T. D. Nunes, D. B. A. Medeiros, A. E. Muruato, B. M. Foreman, H. Luo, T. Wang, A. D. Barrett, S. C. Weaver, P. F. C. Vasconcelos, S. L. Rossi, G. Ciaramella, I. U. Mysorekar, T. C. Pierson, P. Y. Shi and M. S. Diamond (2017). “Vaccine Mediated Protection Against Zika Virus-Induced Congenital Disease.” Cell 170(2): 273-283 e212.
The emergence of Zika virus (ZIKV) and its association with congenital malformations has prompted the rapid development of vaccines. Although efficacy with multiple viral vaccine platforms has been established in animals, no study has addressed protection during pregnancy. We tested in mice two vaccine platforms, a lipid nanoparticle-encapsulated modified mRNA vaccine encoding ZIKV prM and E genes and a live-attenuated ZIKV strain encoding an NS1 protein without glycosylation, for their ability to protect against transmission to the fetus. Vaccinated dams challenged with a heterologous ZIKV strain at embryo day 6 (E6) and evaluated at E13 showed markedly diminished levels of viral RNA in maternal, placental, and fetal tissues, which resulted in protection against placental damage and fetal demise. As modified mRNA and live-attenuated vaccine platforms can restrict in utero transmission of ZIKV in mice, their further development in humans to prevent congenital ZIKV syndrome is warranted.
Sarathy, V. V., T. J. Pitcher, G. D. Gromowski, J. T. Roehrig and A. D. T. Barrett (2017). “A DENV-2-type-specific monoclonal antibody binds to the DENV-complex-reactive antigenic site on envelope protein domain 3.” J Gen Virol 98(6): 1299-1304.
The Dengue virus (DENV) envelope (E) protein is the major component of the viral surface and is structurally subdivided into three domains, ED1, ED2 and ED3. ED3 elicits potent neutralizing antibodies and contains two major antigenic sites: the DENV-type-specific and DENV-complex-reactive antigenic sites. Each site is composed of a limited subset of residues that are required for monoclonal antibody (mAb) binding. Here we show that DENV-2-type-specific mAb 9A3D-8 utilizes the functionally critical residues K307, V308, K310, I312, P332, L387, L389 and N390 for ED3 binding. Surprisingly, this DENV-type-specific epitope is predicted to overlap with the ED3 DENV-complex-reactive antigenic site on the viral surface. Further, this unique binding site enables mAb 9A3D-8 to neutralize virus infectivity at relatively low occupancy of virions compared to other ED3 mAbs identified to date. Together, the data in this study indicate that this is a new DENV-2-type-specific antigenic site on ED3.
Wu, L., Z. Zhang, H. Gao, Y. Li, L. Hou, H. Yao, S. Wu, J. Liu, L. Wang, Y. Zhai, H. Ou, M. Lin, X. Wu, J. Liu, G. Lang, Q. Xin, G. Wu, L. Luo, P. Liu, J. Shentu, N. Wu, J. Sheng, Y. Qiu, W. Chen and L. Li (2017). “Open-Label Phase I Clinical Trial of Ad5-EBOV in Africans in China.” Hum Vaccin Immunother: 0.
BACKGROUND: To determine the safety and immunogenicity of a novel recombinant adenovirus type 5 vector based Ebola virus disease vaccine (Ad5-EBOV) in Africans in China. METHODS: A phase 1, dose-escalation, open-label trial was conducted. 61 healthy Africans were sequentially enrolled, with 31 participants receiving one shot intramuscular injection and 30 participants receiving a double-shot regimen. Primary and secondary end points related to safety and immunogenicity were assessed within 28 days after vaccination. This study was registered with ClinicalTrials.gov (NCT02401373). RESULTS: Ad5-EBOV is well tolerated and no adverse reaction of grade 3 or above was observed. 53 (86.89%) participants reported at least one adverse reaction within 28 days of vaccination. The most common reaction was fever and the mild pain at injection site, and there were no significant difference between these two groups. Ebola glycoprotein-specific antibodies appeared in all 61 participants and antibodies titers peaked after 28 days of vaccination. The geometric mean titres (GMTs) were similar between these two groups (1919.01 vs 1684.70 P = 0.5562). The glycoprotein-specific T-cell responses rapidly peaked after 14 days of vaccination and then decreased, however, the percentage of subjects with responses were much higher in the high-dose group (60.00% vs 9.68%, P = 0.0014). Pre-existing Ad5 neutralizing antibodies could significantly dampen the specific humoral immune response and cellular response to the vaccine. CONCLUSION: The application of Ad5-EBOV demonstrated safe in Africans in China and a specific GP antibody and T-cell response could occur 14 days after the first immunization. This acceptable safety profile provides a reliable basis to proceed with trials in Africa.
Walker, R. and P. Dull (2017). “Combination vaccine strategies to prevent enteric infections.” Vaccine.
New vaccine candidates entering the current routine immunization schedule can best be accommodated as combination vaccines. A combined Shigella and enterotoxigenic E. coli (ETEC) vaccine could greatly benefit children in disease-endemic areas. New candidates are getting closer to being able to meet these needs, but they raise numerous strategic questions related to presentation, formulation, and regulatory approach. The “Combination Vaccine Strategies to Prevent Enteric Infections” workshop at the 2016 Vaccines Against Shigella and ETEC (VASE) Conference examined some of the considerations for developing such vaccines against enteric pathogens.
Wang, K., G. D. Tomaras, S. Jegaskanda, M. A. Moody, H. X. Liao, K. 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 ADCC, and Protect Mice from Ocular Challenge with HSV-1.” J Virol.
The RV144 HIV vaccine trial included a recombinant HIV glycoprotein 120 (gp120) construct fused to a small portion of herpes simplex virus (HSV-1) glycoprotein D (gD), such 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 HSV1 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 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 (a) neutralized HSV-1 infection in a cell receptor-specific manner, (b) mediated ADCC, and (c) reduced ocular disease in virus-infected mice.IMPORTANCE Herpes simplex virus 1 (HSV-1) causes cold sores, neonatal herpes, and is a leading cause of blindness. Despite many trials, no HSV vaccine is 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.
Petousis-Harris, H., J. Paynter, J. Morgan, P. Saxton, B. McArdle, F. Goodyear-Smith and S. Black (2017). “Effectiveness of a group B outer membrane vesicle meningococcal vaccine against gonorrhoea in New Zealand: a retrospective case-control study.” Lancet.
BACKGROUND: Gonorrhoea is a major global public health problem that is exacerbated by drug resistance. Effective vaccine development has been unsuccessful, but surveillance data suggest that outer membrane vesicle meningococcal group B vaccines affect the incidence of gonorrhoea. We assessed vaccine effectiveness of the outer membrane vesicle meningococcal B vaccine (MeNZB) against gonorrhoea in young adults aged 15-30 years in New Zealand. METHODS: We did a retrospective case-control study of patients at sexual health clinics aged 15-30 years who were born between Jan 1, 1984, and Dec 31, 1998, eligible to receive MeNZB, and diagnosed with gonorrhoea or chlamydia, or both. Demographic data, sexual health clinic data, and National Immunisation Register data were linked via patients’ unique personal identifier. For primary analysis, cases were confirmed by laboratory isolation or detection of Neisseria gonorrhoeae only from a clinical specimen, and controls were individuals with a positive chlamydia test only. We estimated odds ratios (ORs) comparing disease outcomes in vaccinated versus unvaccinated participants via multivariable logistic regression. Vaccine effectiveness was calculated as 100x(1-OR). FINDINGS: 11 of 24 clinics nationally provided records. There were 14 730 cases and controls for analyses: 1241 incidences of gonorrhoea, 12 487 incidences of chlamydia, and 1002 incidences of co-infection. Vaccinated individuals were significantly less likely to be cases than controls (511 [41%] vs 6424 [51%]; adjusted OR 0.69 [95% CI 0.61-0.79]; p<0.0001). Estimate vaccine effectiveness of MeNZB against gonorrhoea after adjustment for ethnicity, deprivation, geographical area, and sex was 31% (95% CI 21-39). INTERPRETATION: Exposure to MeNZB was associated with reduced rates of gonorrhoea diagnosis, the first time a vaccine has shown any protection against gonorrhoea. These results provide a proof of principle that can inform prospective vaccine development not only for gonorrhoea but also for meningococcal vaccines. FUNDING: GSK Vaccines.
VACCINE DESIGN - Vectors
Zhang, W. and A. Ehrhardt (2017). “Getting genetic access to natural adenovirus genomes to explore vector diversity.” Virus Genes.
Recombinant vectors based on the human adenovirus type 5 (HAdV5) have been developed and extensively used in preclinical and clinical studies for over 30 years. However, certain restrictions of HAdV5-based vectors have limited their clinical applications because they are rather inefficient in specifically transducing cells of therapeutic interest that lack the coxsackievirus and adenovirus receptor (CAR). Moreover, enhanced vector-associated toxicity and widespread preexisting immunity have been shown to significantly hamper the effectiveness of HAdV-5-mediated gene transfer. However, evolution of adenoviruses in the natural host is driving the generation of novel types with altered virulence, enhanced transmission, and altered tissue tropism. As a consequence, an increasing number of alternative adenovirus types were identified, which may represent a valuable resource for the development of novel vector types. Thus, researchers are focusing on the other naturally occurring adenovirus types, which are structurally similar but functionally different from HAdV5. To this end, several strategies have been devised for getting genetic access to adenovirus genomes, resulting in a new panel of adenoviral vectors. Importantly, these vectors were shown to have a host range different from HAdV5 and to escape the anti-HAdV5 immune response, thus underlining the great potential of this approach. In summary, this review provides a state-of-the-art overview of one essential step in adenoviral vector development.