Vaccinology in the post-COVID-19 era.

The COVID-19 pandemic is a shocking reminder of how our world would look in the absence of vaccination. Fortunately, new technologies, the pace of understanding new and existing pathogens, and the increased knowledge of the immune system allow us today to develop vaccines at an unprecedented speed. Some of the vaccine technologies that are fast-tracked by the urgency of COVID-19 may also be the answer for other health priorities, such as antimicrobial resistance, chronic infections, and cancer, that the post-COVID-19 world will urgently need to face. This perspective analyzes the way COVID-19 is transforming vaccinology and the opportunities for vaccines to have an increasingly important role in health and well-being.

TMQuery: a database of precomputed template modeling scores for assessment of protein structural similarity.

SUMMARY: Comparisons of protein structures are critical for developing novel protein designs, annotating protein functions and predicting protein structure. The template modeling score (TM-score) is a widely used but computationally expensive measure of protein similarity that is applicable to a wide variety of structural biology problems. We introduce TMQuery-a continuously updated database containing over eight billion pre-computed TM-score values for every pair of proteins in the Protein Data Bank, allowing researchers to quickly query and download TM-scores via a web interface. AVAILABILITY AND IMPLEMENTATION: Publicly available at https://tmquery.gsk.com/.

Antibody light-chain-restricted recognition of the site of immune pressure in the RV144 HIV-1 vaccine trial is phylogenetically conserved.

In HIV-1, the ability to mount antibody responses to conserved, neutralizing epitopes is critical for protection. Here we have studied the light chain usage of human and rhesus macaque antibodies targeted to a dominant region of the HIV-1 envelope second variable (V2) region involving lysine (K) 169, the site of immune pressure in the RV144 vaccine efficacy trial. We found that humans and rhesus macaques used orthologous lambda variable gene segments encoding a glutamic acid-aspartic acid (ED) motif for K169 recognition. Structure determination of an unmutated ancestor antibody demonstrated that the V2 binding site was preconfigured for ED motif-mediated recognition prior to maturation. Thus, light chain usage for recognition of the site of immune pressure in the RV144 trial is highly conserved across species. These data indicate that the HIV-1 K169-recognizing ED motif has persisted over the diversification between rhesus macaques and humans, suggesting an evolutionary advantage of this antibody recognition mode.

Correction: ALVAC-HIV B/C candidate HIV vaccine efficacy dependent on neutralization profile of challenge virus and adjuvant dose and type.

[This corrects the article DOI: 10.1371/journal.ppat.1008121.].

Boosting with AIDSVAX B/E Enhances Env Constant Region 1 and 2 Antibody-Dependent Cellular Cytotoxicity Breadth and Potency.

Induction of protective antibodies is a critical goal of HIV-1 vaccine development. One strategy is to induce nonneutralizing antibodies (NNAbs) that kill virus-infected cells, as these antibody specificities have been implicated in slowing HIV-1 disease progression and in protection. HIV-1 Env constant region 1 and 2 (C1C2) monoclonal antibodies (MAbs) frequently mediate potent antibody-dependent cellular cytotoxicity (ADCC), making them an important vaccine target. Here, we explore the effect of delayed and repetitive boosting of RV144 vaccine recipients with AIDSVAX B/E on the C1C2-specific MAb repertoire. It was found that boosting increased clonal lineage-specific ADCC breadth and potency. A ligand crystal structure of a vaccine-induced broad and potent ADCC-mediating C1C2-specific MAb showed that it bound a highly conserved Env gp120 epitope. Thus, boosting to affinity mature these types of IgG C1C2-specific antibody responses may be one method by which to make an improved HIV vaccine with higher efficacy than that seen in the RV144 trial.IMPORTANCE Over one million people become infected with HIV-1 each year, making the development of an efficacious HIV-1 vaccine an important unmet medical need. The RV144 human HIV-1 vaccine regimen is the only HIV-1 clinical trial to date to demonstrate vaccine efficacy. An area of focus has been on identifying ways by which to improve upon RV144 vaccine efficacy. The RV305 HIV-1 vaccine regimen was a follow-up boost of RV144 vaccine recipients that occurred 6 to 8 years after the conclusion of RV144. Our study focused on the effect of delayed boosting in humans on the vaccine-induced Env constant region 1 and 2 (C1C2)-specific antibody repertoire. It was found that boosting with an HIV-1 Env vaccine increased C1C2-specific antibody-dependent cellular cytotoxicity potency and breadth.

ALVAC-HIV B/C candidate HIV vaccine efficacy dependent on neutralization profile of challenge virus and adjuvant dose and type.

The ALVAC-HIV clade B/AE and equivalent SIV-based/gp120 + Alum vaccines successfully decreased the risk of virus acquisition in humans and macaques. Here, we tested the efficacy of HIV clade B/C ALVAC/gp120 vaccine candidates + MF59 or different doses of Aluminum hydroxide (Alum) against SHIV-Cs of varying neutralization sensitivity in macaques. Low doses of Alum induced higher mucosal V2-specific IgA that increased the risk of Tier 2 SHIV-C acquisition. High Alum dosage, in contrast, elicited serum IgG to V2 that correlated with a decreased risk of Tier 1 SHIV-C acquisition. MF59 induced negligible mucosal antibodies to V2 and an inflammatory profile with blood C-reactive Protein (CRP) levels correlating with neutralizing antibody titers. MF59 decreased the risk of Tier 1 SHIV-C acquisition. The relationship between vaccine efficacy and the neutralization profile of the challenge virus appear to be linked to the different immunological spaces created by MF59 and Alum via CXCL10 and IL-1ß, respectively.

Safety and immune responses after a 12-month booster in healthy HIV-uninfected adults in HVTN 100 in South Africa: A randomized double-blind placebo-controlled trial of ALVAC-HIV (vCP2438) and bivalent subtype C gp120/MF59 vaccines.

BACKGROUND: HVTN 100 evaluated the safety and immunogenicity of an HIV subtype C pox-protein vaccine regimen, investigating a 12-month booster to extend vaccine-induced immune responses. METHODS AND FINDINGS: A phase 1-2 randomized double-blind placebo-controlled trial enrolled 252 participants (210 vaccine/42 placebo; median age 23 years; 43% female) between 9 February 2015 and 26 May 2015. Vaccine recipients received ALVAC-HIV (vCP2438) alone at months 0 and 1 and with bivalent subtype C gp120/MF59 at months 3, 6, and 12. Antibody (IgG, IgG3 binding, and neutralizing) and CD4+ T-cell (expressing interferon-gamma, interleukin-2, and CD40 ligand) responses were evaluated at month 6.5 for all participants and at months 12, 12.5, and 18 for a randomly selected subset. The primary analysis compared IgG binding antibody (bAb) responses and CD4+ T-cell responses to 3 vaccine-matched antigens at peak (month 6.5 versus 12.5) and durability (month 12 versus 18) timepoints; IgG responses to CaseA2_gp70_V1V2.B, a primary correlate of risk in RV144, were also compared at these same timepoints. Secondary and exploratory analyses compared IgG3 bAb responses, IgG bAb breadth scores, neutralizing antibody (nAb) responses, antibody-dependent cellular phagocytosis, CD4+ polyfunctionality responses, and CD4+ memory sub-population responses at the same timepoints. Vaccines were generally safe and well tolerated. During the study, there were 2 deaths (both in the vaccine group and both unrelated to study products). Ten participants became HIV-infected during the trial, 7% (3/42) of placebo recipients and 3% (7/210) of vaccine recipients. All 8 serious adverse events were unrelated to study products. Less waning of immune responses was seen after the fifth vaccination than after the fourth, with higher antibody and cellular response rates at month 18 than at month 12: IgG bAb response rates to 1086.C V1V2, 21.0% versus 9.7% (difference = 11.3%, 95% CI = 0.6%-22.0%, P = 0.039), and ZM96.C V1V2, 21.0% versus 6.5% (difference = 14.5%, 95% CI = 4.1%-24.9%, P = 0.004). IgG bAb response rates to all 4 primary V1V2 antigens were higher 2 weeks after the fifth vaccination than 2 weeks after the fourth vaccination: 87.7% versus 75.4% (difference = 12.3%, 95% CI = 1.7%-22.9%, P = 0.022) for 1086.C V1V2, 86.0% versus 63.2% (difference = 22.8%, 95% CI = 9.1%-36.5%, P = 0.001) for TV1c8.2.C V1V2, 67.7% versus 44.6% (difference = 23.1%, 95% CI = 10.4%-35.7%, P < 0.001) for ZM96.C V1V2, and 81.5% versus 60.0% (difference = 21.5%, 95% CI = 7.6%-35.5%, P = 0.002) for CaseA2_gp70_V1V2.B. IgG bAb response rates to the 3 primary vaccine-matched gp120 antigens were all above 90% at both peak timepoints, with no significant differences seen, except a higher response rate to ZM96.C gp120 at month 18 versus month 12: 64.5% versus 1.6% (difference = 62.9%, 95% CI = 49.3%-76.5%, P < 0.001). CD4+ T-cell response rates were higher at month 18 than month 12 for all 3 primary vaccine-matched antigens: 47.3% versus 29.1% (difference = 18.2%, 95% CI = 2.9%-33.4%, P = 0.021) for 1086.C, 61.8% versus 38.2% (difference = 23.6%, 95% CI = 9.5%-37.8%, P = 0.001) for TV1.C, and 63.6% versus 41.8% (difference = 21.8%, 95% CI = 5.1%-38.5%, P = 0.007) for ZM96.C, with no significant differences seen at the peak timepoints. Limitations were that higher doses of gp120 were not evaluated, this study was not designed to investigate HIV prevention efficacy, and the clinical significance of the observed immunological effects is uncertain. CONCLUSIONS: In this study, a 12-month booster of subtype C pox-protein vaccines restored immune responses, and slowed response decay compared to the 6-month vaccination. TRIAL REGISTRATION: ClinicalTrials.gov NCT02404311. South African National Clinical Trials Registry (SANCTR number: DOH--27-0215-4796).

Replication-Competent NYVAC-KC Yields Improved Immunogenicity to HIV-1 Antigens in Rhesus Macaques Compared to Nonreplicating NYVAC.

As part of the continuing effort to develop an effective HIV vaccine, we generated a poxviral vaccine vector (previously described) designed to improve on the results of the RV144 phase III clinical trial. The construct, NYVAC-KC, is a replication-competent, attenuated recombinant of the vaccinia virus strain NYVAC. NYVAC is a vector that has been used in many previous clinical studies but is replication deficient. Here, we report a side-by-side comparison of replication-restricted NYVAC and replication-competent NYVAC-KC in a nonhuman primate study, which utilized a prime-boost regimen similar to that of RV144. NYVAC-C and NYVAC-C-KC express the HIV-1 antigens gp140, and Gag/Gag-Pol-Nef-derived virus-like particles (VLPs) from clade C and were used as the prime, with recombinant virus plus envelope protein used as the boost. In nearly every T and B cell immune assay against HIV-1, including neutralization and antibody binding, NYVAC-C-KC induced a greater immune response than NYVAC-C, indicating that replication competence in a poxvirus may improve upon the modestly successful regimen used in the RV144 clinical trial.IMPORTANCE Though the RV144 phase III clinical trial showed promise that an effective vaccine against HIV-1 is possible, a successful vaccine will require improvement over the vaccine candidate (ALVAC) used in the RV144 study. With that goal in mind, we have tested in nonhuman primates an attenuated but replication-competent vector, NYVAC-KC, in direct comparison to its parental vector, NYVAC, which is replication restricted in human cells, similar to the ALVAC vector used in RV144. We have utilized a prime-boost regimen for administration of the vaccine candidate that is similar to the one used in the RV144 study. The results of this study indicate that a replication-competent poxvirus vector may improve upon the effectiveness of the RV144 clinical trial vaccine candidate.

Priming with a Potent HIV-1 DNA Vaccine Frames the Quality of Immune Responses prior to a Poxvirus and Protein Boost.

The use of heterologous immunization regimens and improved vector systems has led to increases in immunogenicity of HIV-1 vaccine candidates in nonhuman primates. In order to resolve interrelations between different delivery modalities, three different poxvirus boost regimens were compared. Three groups of rhesus macaques were each primed with the same DNA vaccine encoding Gag, Pol, Nef, and gp140. The groups were then boosted with either the vaccinia virus strain NYVAC or a variant with improved replication competence in human cells, termed NYVAC-KC. The latter was administered either by scarification or intramuscularly. Finally, macaques were boosted with adjuvanted gp120 protein to enhance humoral responses. The regimen elicited very potent CD4+ and CD8+ T cell responses in a well-balanced manner, peaking 2 weeks after the boost. T cells were broadly reactive and polyfunctional. All animals exhibited antigen-specific humoral responses already after the poxvirus boost, which further increased following protein administration. Polyclonal reactivity of IgG antibodies was highest against HIV-1 clade C Env proteins, with considerable cross-reactivity to other clades. Substantial effector functional activities (antibody-dependent cell-mediated cytotoxicity and antibody-dependent cell-mediated virus inhibition) were observed in serum obtained after the last protein boost. Notably, major differences between the groups were absent, indicating that the potent priming induced by the DNA vaccine initially framed the immune responses in such a way that the subsequent boosts with NYVAC and protein led only to an increase in the response magnitudes without skewing the quality. This study highlights the importance of selecting the best combination of vector systems in heterologous prime-boost vaccination regimens.IMPORTANCE The evaluation of HIV vaccine efficacy trials indicates that protection would most likely correlate with a polyfunctional immune response involving several effector functions from all arms of the immune system. Heterologous prime-boost regimens have been shown to elicit vigorous T cell and antibody responses in nonhuman primates that, however, qualitatively and quantitatively differ depending on the respective vector systems used. The present study evaluated a DNA prime and poxvirus and protein boost regimen and compared how two poxvirus vectors with various degrees of replication capacity and two different delivery modalities-conventional intramuscular delivery and percutaneous delivery by scarification-impact several immune effectors. It was found that despite the different poxvirus boosts, the overall immune responses in the three groups were similar, suggesting the potent DNA priming as the major determining factor of immune responses. These findings emphasize the importance of selecting optimal priming agents in heterologous prime-boost vaccination settings.

A Randomized, Double-Blinded, Placebo-Controlled, Phase 1 Study of a Replication-Defective Herpes Simplex Virus (HSV) Type 2 Vaccine, HSV529, in Adults With or Without HSV Infection.

BACKGROUND: Herpes simplex virus 2 (HSV2) causes genital herpes in >400 million persons worldwide. METHODS: We conducted a randomized, double-blinded, placebo-controlled trial of a replication-defective HSV2 vaccine, HSV529. Twenty adults were enrolled in each of 3 serogroups of individuals: those negative for both HSV1 and HSV2 (HSV1-/HSV2-), those positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+), and those positive for HSV1 and negative for HSV2 (HSV1+/HSV2-). Sixty participants received vaccine or placebo at 0, 1, and 6 months. The primary end point was the frequency of solicited local and systemic reactions to vaccination. RESULTS: Eighty-nine percent of vaccinees experienced mild-to-moderate solicited injection site reactions, compared with 47% of placebo recipients (95% confidence interval [CI], 12.9%-67.6%; P = .006). Sixty-four percent of vaccinees experienced systemic reactions, compared with 53% of placebo recipients (95% CI, -17.9% to 40.2%; P = .44). Seventy-eight percent of HSV1-/HSV2- vaccine recipients had a ≥4-fold increase in neutralizing antibody titer after 3 doses of vaccine, whereas none of the participants in the other serogroups had such responses. HSV2-specific CD4+ T-cell responses were detected in 36%, 46%, and 27% of HSV1-/HSV2-, HSV1±/HSV2+, and HSV1+/HSV2- participants, respectively, 1 month after the third dose of vaccine, and CD8+ T-cell responses were detected in 14%, 8%, and 18% of participants, respectively. CONCLUSIONS: HSV529 vaccine was safe and elicited neutralizing antibody and modest CD4+ T-cell responses in HSV-seronegative vaccinees. CLINICAL TRIALS REGISTRATION: NCT01915212.

Immunogenicity of NYVAC Prime-Protein Boost Human Immunodeficiency Virus Type 1 Envelope Vaccination and Simian-Human Immunodeficiency Virus Challenge of Nonhuman Primates.

A preventive human immunodeficiency virus type 1 (HIV-1) vaccine is an essential part of the strategy to eradicate AIDS. A critical question is whether antibodies that do not neutralize primary isolate (tier 2) HIV-1 strains can protect from infection. In this study, we investigated the ability of an attenuated poxvirus vector (NYVAC) prime-envelope gp120 boost to elicit potentially protective antibody responses in a rhesus macaque model of mucosal simian-human immunodeficiency virus (SHIV) infection. NYVAC vector delivery of a group M consensus envelope, trivalent mosaic envelopes, or a natural clade B isolate B.1059 envelope elicited antibodies that mediated neutralization of tier 1 viruses, cellular cytotoxicity, and phagocytosis. None of the macaques made neutralizing antibodies against the tier 2 SHIV SF162P3 used for mucosal challenge. Significant protection from infection was not observed for the three groups of vaccinated macaques compared to unvaccinated macaques, although binding antibody to HIV-1 Env correlated with decreased viremia after challenge. Thus, NYVAC Env prime-gp120 boost vaccination elicited polyfunctional, nonneutralizing antibody responses with minimal protective activity against tier 2 SHIV mucosal challenge.IMPORTANCE The antibody responses that confer protection against HIV-1 infection remain unknown. Polyfunctional antibody responses correlated with time to infection in previous macaque studies. Determining the ability of vaccines to induce these types of responses is critical for understanding how to improve upon the one efficacious human HIV-1 vaccine trial completed thus far. We characterized the antibody responses induced by a NYVAC-protein vaccine and determined the protective capacity of polyfunctional antibody responses in an R5, tier 2 mucosal SHIV infection model.

Boosting of HIV envelope CD4 binding site antibodies with long variable heavy third complementarity determining region in the randomized double blind RV305 HIV-1 vaccine trial.

The canary pox vector and gp120 vaccine (ALVAC-HIV and AIDSVAX B/E gp120) in the RV144 HIV-1 vaccine trial conferred an estimated 31% vaccine efficacy. Although the vaccine Env AE.A244 gp120 is antigenic for the unmutated common ancestor of V1V2 broadly neutralizing antibody (bnAbs), no plasma bnAb activity was induced. The RV305 (NCT01435135) HIV-1 clinical trial was a placebo-controlled randomized double-blinded study that assessed the safety and efficacy of vaccine boosting on B cell repertoires. HIV-1-uninfected RV144 vaccine recipients were reimmunized 6-8 years later with AIDSVAX B/E gp120 alone, ALVAC-HIV alone, or a combination of ALVAC-HIV and AIDSVAX B/E gp120 in the RV305 trial. Env-specific post-RV144 and RV305 boost memory B cell VH mutation frequencies increased from 2.9% post-RV144 to 6.7% post-RV305. The vaccine was well tolerated with no adverse events reports. While post-boost plasma did not have bnAb activity, the vaccine boosts expanded a pool of envelope CD4 binding site (bs)-reactive memory B cells with long third heavy chain complementarity determining regions (HCDR3) whose germline precursors and affinity matured B cell clonal lineage members neutralized the HIV-1 CRF01 AE tier 2 (difficult to neutralize) primary isolate, CNE8. Electron microscopy of two of these antibodies bound with near-native gp140 trimers showed that they recognized an open conformation of the Env trimer. Although late boosting of RV144 vaccinees expanded a novel pool of neutralizing B cell clonal lineages, we hypothesize that boosts with stably closed trimers would be necessary to elicit antibodies with greater breadth of tier 2 HIV-1 strains. TRIAL REGISTRATION: ClinicalTrials.gov NCT01435135.

HIV/AIDS Vaccine Candidates Based on Replication-Competent Recombinant Poxvirus NYVAC-C-KC Expressing Trimeric gp140 and Gag-Derived Virus-Like Particles or Lacking the Viral Molecule B19 That Inhibits Type I Interferon Activate Relevant HIV-1-Specific B and T Cell Immune Functions in Nonhuman Primates.

The nonreplicating attenuated poxvirus vector NYVAC expressing clade C(CN54) HIV-1 Env(gp120) and Gag-Pol-Nef antigens (NYVAC-C) showed limited immunogenicity in phase I clinical trials. To enhance the capacity of the NYVAC vector to trigger broad humoral responses and a more balanced activation of CD4+ and CD8+ T cells, here we compared the HIV-1-specific immunogenicity elicited in nonhuman primates immunized with two replicating NYVAC vectors that have been modified by the insertion of the K1L and C7L vaccinia virus host range genes and express the clade C(ZM96) trimeric HIV-1 gp140 protein or a Gag(ZM96)-Pol-Nef(CN54) polyprotein as Gag-derived virus-like particles (termed NYVAC-C-KC). Additionally, one NYVAC-C-KC vector was generated by deleting the viral gene B19R, an inhibitor of the type I interferon response (NYVAC-C-KC-ΔB19R). An immunization protocol mimicking that of the RV144 phase III clinical trial was used. Two groups of macaques received two doses of the corresponding NYVAC-C-KC vectors (weeks 0 and 4) and booster doses with NYVAC-C-KC vectors plus the clade C HIV-1 gp120 protein (weeks 12 and 24). The two replicating NYVAC-C-KC vectors induced enhanced and similar HIV-1-specific CD4+ and CD8+ T cell responses, similar levels of binding IgG antibodies, low levels of IgA antibodies, and high levels of antibody-dependent cellular cytotoxicity responses and HIV-1-neutralizing antibodies. Small differences within the NYVAC-C-KC-ΔB19R group were seen in the magnitude of CD4+ and CD8+ T cells, the induction of some cytokines, and the neutralization of some HIV-1 isolates. Thus, replication-competent NYVAC-C-KC vectors acquired relevant immunological properties as vaccine candidates against HIV/AIDS, and the viral B19 molecule exerts some control of immune functions.IMPORTANCE It is of special importance to find a safe and effective HIV/AIDS vaccine that can induce strong and broad T cell and humoral immune responses correlating with HIV-1 protection. Here we developed novel replicating poxvirus NYVAC-based HIV/AIDS vaccine candidates expressing clade C HIV-1 antigens, with one of them lacking the vaccinia virus B19 protein, an inhibitor of the type I interferon response. Immunization of nonhuman primates with these novel NYVAC-C-KC vectors and the protein component gp120 elicited high levels of T cell and humoral immune responses, with the vector containing a deletion in B19R inducing a trend toward a higher magnitude of CD4+ and CD8+ T cell responses and neutralization of some HIV-1 strains. These poxvirus vectors could be considered HIV/AIDS vaccine candidates based on their activation of potential immune correlates of protection.

Boosting of ALVAC-SIV Vaccine-Primed Macaques with the CD4-SIVgp120 Fusion Protein Elicits Antibodies to V2 Associated with a Decreased Risk of SIVmac251 Acquisition.

The recombinant ALVAC vaccine coupled with the monomeric gp120/alum protein have decreased the risk of HIV and SIV acquisition. Ab responses to the V1/V2 regions have correlated with a decreased risk of virus acquisition in both humans and macaques. We hypothesized that the breadth and functional profile of Abs induced by an ALVAC/envelope protein regimen could be improved by substituting the monomeric gp120 boost, with the full-length single-chain (FLSC) protein. FLSC is a CD4-gp120 fusion immunogen that exposes cryptic gp120 epitopes to the immune system. We compared the immunogenicity and relative efficiency of an ALVAC-SIV vaccine boosted either with bivalent FLSC proteins or with monomeric gp120 in alum. FLSC was superior to monomeric gp120 in directing Abs to the C3 α2 helix, the V5 loop, and the V3 region that contains the putative CCR5 binding site. In addition, FLSC boosting elicited significantly higher binding Abs to V2 and increased both the Ab-dependent cellular cytotoxicity activity and the breadth of neutralizing Abs. However, the FLSC vaccine regimen demonstrated only a trend in vaccine efficacy, whereas the monomeric gp120 regimen significantly decreased the risk of SIVmac251 acquisition. In both vaccine regimens, anti-V2 Abs correlated with a decreased risk of virus acquisition but differed with regard to systemic or mucosal origin. In the FLSC regimen, serum Abs to V2 correlated, whereas in the monomeric gp120 regimen, V2 Abs in rectal secretions, the site of viral challenge, were associated with efficacy.

Randomized, Double-Blind Evaluation of Late Boost Strategies for HIV-Uninfected Vaccine Recipients in the RV144 HIV Vaccine Efficacy Trial.

Background: The RV144 ALVAC-HIV prime, AIDSVAX B/E boost afforded 60% efficacy against human immunodeficiency virus (HIV) acquisition at 1 year, waning to 31.2% after 3.5 years. We hypothesized that additional vaccinations might augment immune correlates of protection. Methods: In a randomized placebo-controlled double-blind study of 162 HIV-negative RV144 vaccine recipients, we evaluated 2 additional boosts, given 6-8 years since RV144 vaccination, for safety and immunogenicity, at weeks 0 and 24. Study groups 1-3 received ALVAC-HIV+AIDSVAX B/E, AIDSVAX B/E, and ALVAC-HIV, respectively, or placebo. Results: Vaccines were well tolerated. For groups 1 and 2, plasma immunoglobulin (Ig) G, IgA, and neutralizing antibody responses at week 2 were all significantly higher than 2 weeks after the last RV144 vaccination. IgG titers against glycoprotein (gp) 70V1V2 92TH023 increased 14-fold compared with 2 weeks after the last RV144 vaccination (14069 vs 999; P < .001). Groups 1 and 2 did not differ significantly from each other, whereas group 3 was similar to placebo recipients. Responses in groups 1 and 2 declined by week 24 but were boosted by the second vaccination, albeit at lower magnitude than for week 2. Conclusions: In RV144 vaccinees, AIDSVAX B/E with or without ALVAC-HIV 6-8 years after initial vaccination generated higher humoral responses than after RV144, but these responses were short-lived, and their magnitude did not increase with subsequent boost. Clinical Trials Registration: NCT01435135.

Potential To Streamline Heterologous DNA Prime and NYVAC/Protein Boost HIV Vaccine Regimens in Rhesus Macaques by Employing Improved Antigens.

UNLABELLED: In a follow-up to the modest efficacy observed in the RV144 trial, researchers in the HIV vaccine field seek to substantiate and extend the results by evaluating other poxvirus vectors and combinations with DNA and protein vaccines. Earlier clinical trials (EuroVacc trials 01 to 03) evaluated the immunogenicity of HIV-1 clade C GagPolNef and gp120 antigens delivered via the poxviral vector NYVAC. These showed that a vaccination regimen including DNA-C priming prior to a NYVAC-C boost considerably enhanced vaccine-elicited immune responses compared to those with NYVAC-C alone. Moreover, responses were improved by using three as opposed to two DNA-C primes. In the present study, we assessed in nonhuman primates whether such vaccination regimens can be streamlined further by using fewer and accelerated immunizations and employing a novel generation of improved DNA-C and NYVAC-C vaccine candidates designed for higher expression levels and more balanced immune responses. Three different DNA-C prime/NYVAC-C+ protein boost vaccination regimens were tested in rhesus macaques. All regimens elicited vigorous and well-balanced CD8(+)and CD4(+)T cell responses that were broad and polyfunctional. Very high IgG binding titers, substantial antibody-dependent cellular cytotoxicity (ADCC), and modest antibody-dependent cell-mediated virus inhibition (ADCVI), but very low neutralization activity, were measured after the final immunizations. Overall, immune responses elicited in all three groups were very similar and of greater magnitude, breadth, and quality than those of earlier EuroVacc vaccines. In conclusion, these findings indicate that vaccination schemes can be simplified by using improved antigens and regimens. This may offer a more practical and affordable means to elicit potentially protective immune responses upon vaccination, especially in resource-constrained settings. IMPORTANCE: Within the EuroVacc clinical trials, we previously assessed the immunogenicity of HIV clade C antigens delivered in a DNA prime/NYVAC boost regimen. The trials showed that the DNA prime crucially improved the responses, and three DNA primes with a NYVAC boost appeared to be optimal. Nevertheless, T cell responses were primarily directed toward Env, and humoral responses were modest. The aim of this study was to assess improved antigens for the capacity to elicit more potent and balanced responses in rhesus macaques, even with various simpler immunization regimens. Our results showed that the novel antigens in fact elicited larger numbers of T cells with a polyfunctional profile and a good Env-GagPolNef balance, as well as high-titer and Fc-functional antibody responses. Finally, comparison of the different schedules indicates that a simpler regimen of only two DNA primes and one NYVAC boost in combination with protein may be very efficient, thus showing that the novel antigens allow for easier immunization protocols.

Broad neutralization coverage of HIV by multiple highly potent antibodies.

Broadly neutralizing antibodies against highly variable viral pathogens are much sought after to treat or protect against global circulating viruses. Here we probed the neutralizing antibody repertoires of four human immunodeficiency virus (HIV)-infected donors with remarkably broad and potent neutralizing responses and rescued 17 new monoclonal antibodies that neutralize broadly across clades. Many of the new monoclonal antibodies are almost tenfold more potent than the recently described PG9, PG16 and VRC01 broadly neutralizing monoclonal antibodies and 100-fold more potent than the original prototype HIV broadly neutralizing monoclonal antibodies. The monoclonal antibodies largely recapitulate the neutralization breadth found in the corresponding donor serum and many recognize novel epitopes on envelope (Env) glycoprotein gp120, illuminating new targets for vaccine design. Analysis of neutralization by the full complement of anti-HIV broadly neutralizing monoclonal antibodies now available reveals that certain combinations of antibodies should offer markedly more favourable coverage of the enormous diversity of global circulating viruses than others and these combinations might be sought in active or passive immunization regimes. Overall, the isolation of multiple HIV broadly neutralizing monoclonal antibodies from several donors that, in aggregate, provide broad coverage at low concentrations is a highly positive indicator for the eventual design of an effective antibody-based HIV vaccine.

Structure of HIV-1 gp120 V1/V2 domain with broadly neutralizing antibody PG9.

Variable regions 1 and 2 (V1/V2) of human immunodeficiency virus-1 (HIV-1) gp120 envelope glycoprotein are critical for viral evasion of antibody neutralization, and are themselves protected by extraordinary sequence diversity and N-linked glycosylation. Human antibodies such as PG9 nonetheless engage V1/V2 and neutralize 80% of HIV-1 isolates. Here we report the structure of V1/V2 in complex with PG9. V1/V2 forms a four-stranded ß-sheet domain, in which sequence diversity and glycosylation are largely segregated to strand-connecting loops. PG9 recognition involves electrostatic, sequence-independent and glycan interactions: the latter account for over half the interactive surface but are of sufficiently weak affinity to avoid autoreactivity. The structures of V1/V2-directed antibodies CH04 and PGT145 indicate that they share a common mode of glycan penetration by extended anionic loops. In addition to structurally defining V1/V2, the results thus identify a paradigm of antibody recognition for highly glycosylated antigens, which-with PG9-involves a site of vulnerability comprising just two glycans and a strand.

Vaccine-Induced Linear Epitope-Specific Antibodies to Simian Immunodeficiency Virus SIVmac239 Envelope Are Distinct from Those Induced to the Human Immunodeficiency Virus Type 1 Envelope in Nonhuman Primates.

To evaluate antibody specificities induced by simian immunodeficiency virus (SIV) versus human immunodeficiency virus type 1 (HIV-1) envelope antigens in nonhuman primate (NHP), we profiled binding antibody responses to linear epitopes in NHP studies with HIV-1 or SIV immunogens. We found that, overall, HIV-1 Env IgG responses were dominated by V3, with the notable exception of the responses to the vaccine strain A244 Env that were dominated by V2, whereas the anti-SIVmac239 Env responses were dominated by V2 regardless of the vaccine regimen.

Head-to-Head Comparison of Poxvirus NYVAC and ALVAC Vectors Expressing Identical HIV-1 Clade C Immunogens in Prime-Boost Combination with Env Protein in Nonhuman Primates.

UNLABELLED: We compared the HIV-1-specific cellular and humoral immune responses elicited in rhesus macaques immunized with two poxvirus vectors (NYVAC and ALVAC) expressing the same HIV-1 antigens from clade C, Env gp140 as a trimeric cell-released protein and a Gag-Pol-Nef polyprotein as Gag-induced virus-like particles (VLPs) (referred to as NYVAC-C and ALVAC-C). The immunization protocol consisted of two doses of the corresponding poxvirus vector plus two doses of a combination of the poxvirus vector and a purified HIV-1 gp120 protein from clade C. This immunogenicity profile was also compared to that elicited by vaccine regimens consisting of two doses of the ALVAC vector expressing HIV-1 antigens from clades B/E (ALVAC-vCP1521) plus two doses of a combination of ALVAC-vCP1521 and HIV-1 gp120 protein from clades B/E (similar to the RV144 trial regimen) or clade C. The results showed that immunization of macaques with NYVAC-C stimulated at different times more potent HIV-1-specific CD4(+) T-cell responses and induced a trend toward higher-magnitude HIV-1-specific CD8(+) T-cell immune responses than did ALVAC-C. Furthermore, NYVAC-C induced a trend toward higher levels of binding IgG antibodies against clade C HIV-1 gp140, gp120, or murine leukemia virus (MuLV) gp70-scaffolded V1/V2 and toward best cross-clade-binding IgG responses against HIV-1 gp140 from clades A, B, and group M consensus, than did ALVAC-C. Of the linear binding IgG responses, most were directed against the V3 loop in all immunization groups. Additionally, NYVAC-C and ALVAC-C also induced similar levels of HIV-1-neutralizing antibodies and antibody-dependent cellular cytotoxicity (ADCC) responses. Interestingly, binding IgA antibody levels against HIV-1 gp120 or MuLV gp70-scaffolded V1/V2 were absent or very low in all immunization groups. Overall, these results provide a comprehensive survey of the immunogenicity of NYVAC versus ALVAC expressing HIV-1 antigens in nonhuman primates and indicate that NYVAC may represent an alternative candidate to ALVAC in the development of a future HIV-1 vaccine. IMPORTANCE: The finding of a safe and effective HIV/AIDS vaccine immunogen is one of the main research priorities. Here, we generated two poxvirus-based HIV vaccine candidates (NYVAC and ALVAC vectors) expressing the same clade C HIV-1 antigens in separate vectors, and we analyzed in nonhuman primates their immunogenicity profiles. The results showed that immunization with NYVAC-C induced a trend toward higher HIV-1-specific cellular and humoral immune responses than did ALVAC-C, indicating that this new NYVAC vector could be a novel optimized HIV/AIDS vaccine candidate for human clinical trials.