Viral vector delivered immunogen focuses HIV-1 antibody specificity and increases durability of the circulating antibody recall response.

The modestly efficacious HIV-1 vaccine regimen (RV144) conferred 31% vaccine efficacy at 3 years following the four-shot immunization series, coupled with rapid waning of putative immune correlates of decreased infection risk. New strategies to increase magnitude and durability of protective immunity are critically needed. The RV305 HIV-1 clinical trial evaluated the immunological impact of a follow-up boost of HIV-1-uninfected RV144 recipients after 6-8 years with RV144 immunogens (ALVAC-HIV alone, AIDSVAX B/E gp120 alone, or ALVAC-HIV + AIDSVAX B/E gp120). Previous reports demonstrated that this regimen elicited higher binding, antibody Fc function, and cellular responses than the primary RV144 regimen. However, the impact of the canarypox viral vector in driving antibody specificity, breadth, durability and function is unknown. We performed a follow-up analysis of humoral responses elicited in RV305 to determine the impact of the different booster immunogens on HIV-1 epitope specificity, antibody subclass, isotype, and Fc effector functions. Importantly, we observed that the ALVAC vaccine component directly contributed to improved breadth, function, and durability of vaccine-elicited antibody responses. Extended boosts in RV305 increased circulating antibody concentration and coverage of heterologous HIV-1 strains by V1V2-specific antibodies above estimated protective levels observed in RV144. Antibody Fc effector functions, specifically antibody-dependent cellular cytotoxicity and phagocytosis, were boosted to higher levels than was achieved in RV144. V1V2 Env IgG3, a correlate of lower HIV-1 risk, was not increased; plasma Env IgA (specifically IgA1), a correlate of increased HIV-1 risk, was elevated. The quality of the circulating polyclonal antibody response changed with each booster immunization. Remarkably, the ALVAC-HIV booster immunogen induced antibody responses post-second boost, indicating that the viral vector immunogen can be utilized to selectively enhance immune correlates of decreased HIV-1 risk. These results reveal a complex dynamic of HIV-1 immunity post-vaccination that may require careful balancing to achieve protective immunity in the vaccinated population. Trial registration: RV305 clinical trial (ClinicalTrials.gov number, NCT01435135). ClinicalTrials.gov Identifier: NCT00223080.

Analysis of the HIV Vaccine Trials Network 702 Phase 2b-3 HIV-1 Vaccine Trial in South Africa Assessing RV144 Antibody and T-Cell Correlates of HIV-1 Acquisition Risk.

BACKGROUND: The ALVAC/gp120 + MF59 vaccines in the HIV Vaccine Trials Network (HVTN) 702 efficacy trial did not prevent human immunodeficiency virus-1 (HIV-1) acquisition. Vaccine-matched immunological endpoints that were correlates of HIV-1 acquisition risk in RV144 were measured in HVTN 702 and evaluated as correlates of HIV-1 acquisition. METHODS: Among 1893 HVTN 702 female vaccinees, 60 HIV-1-seropositive cases and 60 matched seronegative noncases were sampled. HIV-specific CD4+ T-cell and binding antibody responses were measured 2 weeks after fourth and fifth immunizations. Cox proportional hazards models assessed prespecified responses as predictors of HIV-1 acquisition. RESULTS: The HVTN 702 Env-specific CD4+ T-cell response rate was significantly higher than in RV144 (63% vs 40%, P = .03) with significantly lower IgG binding antibody response rate and magnitude to 1086.C V1V2 (67% vs 100%, P < .001; Pmag < .001). Although no significant univariate associations were observed between any T-cell or binding antibody response and HIV-1 acquisition, significant interactions were observed (multiplicity-adjusted P ≤.03). Among vaccinees with high IgG A244 V1V2 binding antibody responses, vaccine-matched CD4+ T-cell endpoints associated with decreased HIV-1 acquisition (estimated hazard ratios = 0.40-0.49 per 1-SD increase in CD4+ T-cell endpoint). CONCLUSIONS: HVTN 702 and RV144 had distinct immunogenicity profiles. However, both identified significant correlations (univariate or interaction) for IgG V1V2 and polyfunctional CD4+ T cells with HIV-1 acquisition. Clinical Trials Registration . NCT02968849.

Optimal priming of poxvirus vector (NYVAC)-based HIV vaccine regimens for T cell responses requires three DNA injections. Results of the randomized multicentre EV03/ANRS VAC20 Phase I/II Trial.

DNA vectors have been widely used as a priming of poxvirus vaccine in prime/boost regimens. Whether the number of DNA impacts qualitatively or quantitatively the immune response is not fully explored. With the aim to reinforce T-cell responses by optimizing the prime-boost regimen, the multicentric EV03/ANRS VAC20 phase I/II trial, randomized 147 HIV-negative volunteers to either 3xDNA plus 1xNYVAC (weeks 0, 4, 8 plus 24; n = 74) or to 2xDNA plus 2xNYVAC (weeks 0, 4 plus 20, 24; n = 73) groups. T-cell responses (IFN-γ ELISPOT) to at least one peptide pool were higher in the 3xDNA than the 2xDNA groups (91% and 80% of vaccinees) (P = 0.049). In the 3xDNA arm, 26 (37%) recipients developed a broader T-cell response (Env plus at least to one of the Gag, Pol, Nef pools) than in the 2xDNA (15; 22%) arms (primary endpoint; P = 0.047) with a higher magnitude against Env (at week 26) (P<0.001). In both groups, vaccine regimens induced HIV-specific polyfunctional CD4 and CD8 T cells and the production of Th1, Th2 and Th17/IL-21 cytokines. Antibody responses were also elicited in up to 81% of vaccines. A higher percentage of IgG responders was noted in the 2xDNA arm compared to the 3xDNA arm, while the 3xDNA group tended to elicit a higher magnitude of IgG3 response against specific Env antigens. We show here that the modulation of the prime strategy, without modifying the route or the dose of administration, or the combination of vectors, may influence the quality of the responses.

Antibody and cellular responses to HIV vaccine regimens with DNA plasmid as compared with ALVAC priming: An analysis of two randomized controlled trials.

BACKGROUND: DNA plasmids promise a pragmatic alternative to viral vectors for prime-boost HIV-1 vaccines. We evaluated DNA plasmid versus canarypox virus (ALVAC) primes in 2 randomized, double-blind, placebo-controlled trials in southern Africa with harmonized trial designs. HIV Vaccine Trials Network (HVTN) 111 tested DNA plasmid prime by needle or needleless injection device (Biojector) and DNA plasmid plus gp120 protein plus MF59 adjuvant boost. HVTN 100 tested ALVAC prime and ALVAC plus gp120 protein plus MF59 adjuvant boost (same protein/adjuvant as HVTN 111) by needle. METHODS AND FINDINGS: The primary endpoints for this analysis were binding antibody (bAb) responses to HIV antigens (gp120 from strains ZM96, 1086, and TV1; variable 1 and 2 [V1V2] regions of gp120 from strains TV1, 1086, and B.CaseA, as 1086 V1V2 and B.CaseA were correlates of risk in the RV144 efficacy trial), neutralizing antibody (nAb) responses to pseudoviruses TV1c8.2 and MW925.26, and cellular responses to vaccine-matched antigens (envelope [Env] from strains ZM96, 1086, and TV1; and Gag from strains LAI and ZM96) at month 6.5, two weeks after the fourth vaccination. Per-protocol cohorts included vaccine recipients from HVTN 100 (n = 186, 60% male, median age 23 years) enrolled between February 9, 2015, and May 26, 2015 and from HVTN 111 (n = 56, 48% male, median age 24 years) enrolled between June 21, 2016, and July 13, 2017. IgG bAb response rates were 100% to 3 Env gp120 antigens in both trials. Response rates to V1V2 were lower and similar in both trials except to vaccine-matched 1086 V1V2, with rates significantly higher for the DNA-primed regimen than the ALVAC-primed regimen: 96.6% versus 72.7% (difference = 23.9%, 95% CI 15.6%-32.2%, p < 0.001). Among positive responders, bAb net mean fluorescence intensity (MFI) was significantly higher with the DNA-primed regimen than ALVAC-primed for 1086 V1V2 (geometric mean [GM] 2,833.3 versus 1,200.9; ratio = 2.36, 95% CI 1.42-3.92, p < 0.001) and B.CaseA V1V2 (GM 2314.0 versus 744.6, ratio = 3.11, 95% CI 1.51-6.38, p = 0.002). nAb response rates were >98% in both trials, with significantly higher 50% inhibitory dilution (ID50) among DNA-primed positive responders (n = 53) versus ALVAC-primed (n = 182) to tier 1A MW965.26 (GM 577.7 versus 265.7, ratio = 2.17, 95% CI 1.67-2.83, p < 0.001) and to TV1c8.2 (GM 187.3 versus 100.4, ratio = 1.87, 95% CI 1.48-2.35, p < 0.001). CD4+ T-cell response rates were significantly higher with DNA plasmid prime via Biojector than ALVAC prime (91.4% versus 52.8%, difference = 38.6%, 95% CI 20.5%-56.6%, p < 0.001 for ZM96.C; 88.0% versus 43.1%, difference = 44.9%, 95% CI 26.7%-63.1%, p < 0.001 for 1086.C; 55.5% versus 2.2%, difference = 53.3%, 95% CI 23.9%-82.7%, p < 0.001 for Gag LAI/ZM96). The study's main limitations include the nonrandomized comparison of vaccines from 2 different trials, the lack of data on immune responses to other non-vaccine-matched antigens, and the uncertain clinical significance of the observed immunological effects. CONCLUSIONS: In this study, we found that further investigation of DNA/protein regimens is warranted given enhanced immunogenicity to the V1V2 correlates of decreased HIV-1 acquisition risk identified in RV144, the only HIV vaccine trial to date to show any efficacy.

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).

Rare Detection of Antiviral Functions of Polyclonal IgA Isolated from Plasma and Breast Milk Compartments in Women Chronically Infected with HIV-1.

The humoral response to invading mucosal pathogens comprises multiple antibody isotypes derived from systemic and mucosal compartments. To understand the contribution of each antibody isotype/source to the mucosal humoral response, parallel investigation of the specificities and functions of antibodies within and across isotypes and compartments is required. The role of IgA against HIV-1 is complex, with studies supporting a protective role as well as a role for serum IgA in blocking effector functions. Thus, we explored the fine specificity and function of IgA in both plasma and mucosal secretions important to infant HIV-1 infection, i.e., breast milk. IgA and IgG were isolated from milk and plasma from 20 HIV-1-infected lactating Malawian women. HIV-1 binding specificities, neutralization potency, inhibition of virus-epithelial cell binding, and antibody-mediated phagocytosis were measured. Fine-specificity mapping showed IgA and IgG responses to multiple HIV-1 Env epitopes, including conformational V1/V2 and linear V2, V3, and constant region 5 (C5). Env IgA was heterogeneous between the milk and systemic compartments (Env IgA, τ = 0.00 to 0.63, P = 0.0046 to 1.00). Furthermore, IgA and IgG appeared compartmentalized as there was a lack of correlation between the specificities of Env-specific IgA and IgG (in milk, τ = -0.07 to 0.26, P = 0.35 to 0.83). IgA and IgG also differed in functions: while neutralization and phagocytosis were consistently mediated by milk and plasma IgG, they were rarely detected in IgA from both milk and plasma. Understanding the ontogeny of the divergent IgG and IgA antigen specificity repertoires and their effects on antibody function will inform vaccination approaches targeted toward mucosal pathogens.IMPORTANCE Antibodies within the mucosa are part of the first line of defense against mucosal pathogens. Evaluating mucosal antibody isotypes, specificities, and antiviral functions in relationship to the systemic antibody profile can provide insights into whether the antibody response is coordinated in response to mucosal pathogens. In a natural immunity cohort of HIV-infected lactating women, we mapped the fine specificity and function of IgA in breast milk and plasma and compared these with the autologous IgG responses. Antigen specificities and functions differed between IgG and IgA, with antiviral functions (neutralization and phagocytosis) predominantly mediated by the IgG fraction in both milk and plasma. Furthermore, the specificity of milk IgA differed from that of systemic IgA. Our data suggest that milk IgA and systemic IgA should be separately examined as potential correlates of risk. Preventive vaccines may need to employ different strategies to elicit functional antiviral immunity by both antibody isotypes in the mucosa.

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.

HIV-1 Envelope Glycoproteins from Diverse Clades Differentiate Antibody Responses and Durability among Vaccinees.

Induction of broadly cross-reactive antiviral humoral responses with the capacity to target globally diverse circulating strains is a key goal for HIV-1 immunogen design. A major gap in the field is the identification of diverse HIV-1 envelope antigens to evaluate vaccine regimens for binding antibody breadth. In this study, we define unique antigen panels to map HIV-1 vaccine-elicited antibody breadth and durability. Diverse HIV-1 envelope glycoproteins were selected based on genetic and geographic diversity to cover the global epidemic, with a focus on sexually acquired transmitted/founder viruses with a tier 2 neutralization phenotype. Unique antigenicity was determined by nonredundancy (Spearman correlation), and antigens were clustered using partitioning around medoids (PAM) to identify antigen diversity. Cross-validation demonstrated that the PAM method was better than selection by reactivity and random selection. Analysis of vaccine-elicited V1V2 binding antibody in longitudinal samples from the RV144 clinical trial revealed the striking heterogeneity among individual vaccinees in maintaining durable responses. These data support the idea that a major goal for vaccine development is to improve antibody levels, breadth, and durability at the population level. Elucidating the level and durability of vaccine-elicited binding antibody breadth needed for protection is critical for the development of a globally efficacious HIV vaccine.IMPORTANCE The path toward an efficacious HIV-1 vaccine will require characterization of vaccine-induced immunity that can recognize and target the highly genetically diverse virus envelope glycoproteins. Antibodies that target the envelope glycoproteins, including diverse sequences within the first and second hypervariable regions (V1V2) of gp120, were identified as correlates of risk for the one partially efficacious HIV-1 vaccine. To build upon this discovery, we experimentally and computationally evaluated humoral responses to define envelope glycoproteins representative of the antigenic diversity of HIV globally. These diverse envelope antigens distinguished binding antibody breadth and durability among vaccine candidates, thus providing insights for advancing the most promising HIV-1 vaccine candidates.

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.

Cross-Linking of a CD4-Mimetic Miniprotein with HIV-1 Env gp140 Alters Kinetics and Specificities of Antibody Responses against HIV-1 Env in Macaques.

Evaluation of the epitope specificities, locations (systemic or mucosal), and effector functions of antibodies elicited by novel HIV-1 immunogens engineered to improve exposure of specific epitopes is critical for HIV-1 vaccine development. Utilizing an array of humoral assays, we evaluated the magnitudes, epitope specificities, avidities, and functions of systemic and mucosal immune responses elicited by a vaccine regimen containing Env cross-linked to a CD4-mimetic miniprotein (gp140-M64U1) in rhesus macaques. Cross-linking of gp140 Env to M64U1 resulted in earlier increases of both the magnitude and avidity of the IgG binding response than those with Env protein alone. Notably, IgG binding responses at an early time point correlated with antibody-dependent cellular cytotoxicity (ADCC) function at the peak immunity time point, which was higher for the cross-linked Env group than for the Env group. In addition, the cross-linked Env group developed higher IgG responses against a linear epitope in the gp120 C1 region of the HIV-1 envelope glycoprotein. These data demonstrate that structural modification of the HIV-1 envelope immunogen by cross-linking of gp140 with the CD4-mimetic M64U1 elicited an earlier increase of binding antibody responses and altered the specificity of the IgG responses, correlating with the rise of subsequent antibody-mediated antiviral functions.IMPORTANCE The development of an efficacious HIV-1 vaccine remains a global priority to prevent new cases of HIV-1 infection. Of the six HIV-1 efficacy trials to date, only one has demonstrated partial efficacy, and immune correlate analysis of that trial revealed a role for binding antibodies and antibody Fc-mediated effector functions. New HIV-1 envelope immunogens are being engineered to selectively expose the most vulnerable and conserved sites on the HIV-1 envelope, with the goal of eliciting antiviral antibodies. Evaluation of the humoral responses elicited by these novel immunogen designs in nonhuman primates is critical for understanding how to improve upon immunogen design to inform further testing in human clinical trials. Our results demonstrate that structural modifications of Env that aim to mimic the CD4-bound conformation can result in earlier antibody elicitation, altered epitope specificity, and increased antiviral function postimmunization.

HIV-1 gp120 and Modified Vaccinia Virus Ankara (MVA) gp140 Boost Immunogens Increase Immunogenicity of a DNA/MVA HIV-1 Vaccine.

An important goal of human immunodeficiency virus (HIV) vaccine design is identification of strategies that elicit effective antiviral humoral immunity. One novel approach comprises priming with DNA and boosting with modified vaccinia virus Ankara (MVA) expressing HIV-1 Env on virus-like particles. In this study, we evaluated whether the addition of a gp120 protein in alum or MVA-expressed secreted gp140 (MVAgp140) could improve immunogenicity of a DNA prime-MVA boost vaccine. Five rhesus macaques per group received two DNA primes at weeks 0 and 8 followed by three MVA boosts (with or without additional protein or MVAgp140) at weeks 18, 26, and 40. Both boost immunogens enhanced the breadth of HIV-1 gp120 and V1V2 responses, antibody-dependent cellular cytotoxicity (ADCC), and low-titer tier 1B and tier 2 neutralizing antibody responses. However, there were differences in antibody kinetics, linear epitope specificity, and CD4 T cell responses between the groups. The gp120 protein boost elicited earlier and higher peak responses, whereas the MVAgp140 boost resulted in improved antibody durability and comparable peak responses after the final immunization. Linear V3 specific IgG responses were particularly enhanced by the gp120 boost, whereas the MVAgp140 boost also enhanced responses to linear C5 and C2.2 epitopes. Interestingly, gp120, but not the MVAgp140 boost, increased peak CD4+ T cell responses. Thus, both gp120 and MVAgp140 can augment potential protection of a DNA/MVA vaccine by enhancing gp120 and V1/V2 antibody responses, whereas potential protection by gp120, but not MVAgp140 boosts, may be further impacted by increased CD4+ T cell responses.IMPORTANCE Prior immune correlate analyses with humans and nonhuman primates revealed the importance of antibody responses in preventing HIV-1 infection. A DNA prime-modified vaccinia virus Ankara (MVA) boost vaccine has proven to be potent in eliciting antibody responses. Here we explore the ability of boosts with recombinant gp120 protein or MVA-expressed gp140 to enhance antibody responses elicited by the GOVX-B11 DNA prime-MVA boost vaccine. We found that both types of immunogen boosts enhanced potentially protective antibody responses, whereas the gp120 protein boosts also increased CD4+ T cell responses. Our data provide important information for HIV vaccine designs that aim for effective and balanced humoral and T cell responses.

Superiority in Rhesus Macaques of Targeting HIV-1 Env gp140 to CD40 versus LOX-1 in Combination with Replication-Competent NYVAC-KC for Induction of Env-Specific Antibody and T Cell Responses.

We compared the HIV-1-specific immune responses generated by targeting HIV-1 envelope protein (Env gp140) to either CD40 or LOX-1, two endocytic receptors on dendritic cells (DCs), in rhesus macaques primed with a poxvirus vector (NYVAC-KC) expressing Env gp140. The DC-targeting vaccines, humanized recombinant monoclonal antibodies fused to Env gp140, were administered as a boost with poly-ICLC adjuvant either alone or coadministered with the NYVAC-KC vector. All the DC-targeting vaccine administrations with poly-ICLC increased the low-level serum anti-Env IgG responses elicited by NYVAC-KC priming significantly more (up to a P value of 0.01) than in a group without poly-ICLC. The responses were robust and cross-reactive and contained antibodies specific to multiple epitopes within gp140, including the C1, C2, V1, V2, and V3, C4, C5, and gp41 immunodominant regions. The DC-targeting vaccines also elicited modest serum Env-specific IgA responses. All groups gave serum neutralization activity limited to tier 1 viruses and antibody-dependent cytotoxicity responses (ADCC) after DC-targeting boosts. Furthermore, CD4+ and CD8+ T cell responses specific to multiple Env epitopes were strongly boosted by the DC-targeting vaccines plus poly-ICLC. Together, these results indicate that prime-boost immunization via NYVAC-KC and either anti-CD40.Env gp140/poly-ICLC or anti-LOX-1.Env gp140/poly-ICLC induced balanced antibody and T cell responses against HIV-1 Env. Coadministration of NYVAC-KC with the DC-targeting vaccines increased T cell responses but had minimal effects on antibody responses except for suppressing serum IgA responses. Overall, targeting Env to CD40 gave more robust T cell and serum antibody responses with broader epitope representation and greater durability than with LOX-1.IMPORTANCE An effective vaccine to prevent HIV-1 infection does not yet exist. An approach to elicit strong protective antibody development is to direct virus protein antigens specifically to dendritic cells, which are now known to be the key cell type for controlling immunity. In this study, we have tested in nonhuman primates two prototype vaccines engineered to direct the HIV-1 coat protein Env to dendritic cells. These vaccines bind to either CD40 or LOX-1, two dendritic cell surface receptors with different functions and tissue distributions. We tested the vaccines described above in combination with attenuated virus vectors that express Env. Both vaccines, but especially that delivered via CD40, raised robust immunity against HIV-1 as measured by monitoring potentially protective antibody and T cell responses in the blood. The safety and efficacy of the CD40-targeted vaccine justify further development for future human clinical trials.

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.

Induction of Heterologous Tier 2 HIV-1-Neutralizing and Cross-Reactive V1/V2-Specific Antibodies in Rabbits by Prime-Boost Immunization.

UNLABELLED: Poxvirus prime-protein boost used in the RV144 trial remains the only immunization strategy shown to elicit a modest level of protection against HIV-1 acquisition in humans. Although neutralizing antibodies (NAb) were generated, they were against sensitive viruses, not the more resistant "tier 2" isolates that dominate circulating strains. Instead, risk reduction correlated with antibodies recognizing epitopes in the V1/V2 region of HIV-1 envelope glycoprotein (Env). Here, we examined whether tier 2 virus NAb and V1/V2-specific non-NAb could be elicited by a poxvirus prime-gp120 boost strategy in a rabbit model. We studied two clade B Envs that differ in multiple parameters, including tissue origin, neutralization sensitivity, and presence of the N197 (N7) glycan that was previously shown to modulate the exposure of conserved epitopes on Env. We demonstrate that immunized rabbits generated cross-reactive neutralizing activities against >50% of the tier 2 global HIV-1 isolates tested. Some of these activities were directed against the CD4 binding site (CD4bs). These rabbits also generated antibodies that recognized protein scaffolds bearing V1/V2 sequences from diverse HIV-1 isolates and mediated antibody-dependent cellular cytotoxicity. However, there are subtle differences in the specificities and the response rates of V1/V2-specific antibodies between animals immunized with different Envs, with or without the N7 glycan. These findings demonstrate that antibody responses that have been correlated with protection against HIV-1 acquisition in humans can be elicited in a preclinical model by a poxvirus prime-gp120 boost strategy and that improvements may be achievable by optimizing the nature of the priming and boosting immunogens. IMPORTANCE: The only vaccine approach shown to elicit any protective efficacy against HIV-1 acquisition is based on a poxvirus prime-protein boost regimen (RV144 Thai trial). Reduction of risk was associated with nonneutralizing antibodies targeting the V1/V2 loops of the envelope protein gp120. However, the modest efficacy (31.2%) achieved in this trial highlights the need to examine approaches and factors that may improve vaccine-induced responses, including cross-reactive neutralizing activities. We show here that rabbits immunized with a novel recombinant vaccinia virus prime-gp120 protein boost regimen generated antibodies that recognize protein scaffolds bearing V1/V2 sequences from diverse HIV-1 isolates and mediated antibody-dependent cellular cytotoxicity. Importantly, immunized rabbits also showed neutralizing activities against heterologous tier 2 HIV-1 isolates. These findings may inform the design of prime-boost immunization approaches and help improve the protective efficacy of candidate HIV-1 vaccines.

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.

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.

Infant HIV type 1 gp120 vaccination elicits robust and durable anti-V1V2 immunoglobulin G responses and only rare envelope-specific immunoglobulin A responses.

BACKGROUND: Infant responses to vaccines can be impeded by maternal antibodies and immune system immaturity. It is therefore unclear whether human immunodeficiency virus type 1 (HIV-1) vaccination would elicit similar responses in adults and infants. METHOD: HIV-1 Env-specific antibody responses were evaluated in 2 completed pediatric vaccine trials. In the Pediatric AIDS Clinical Trials Group (PACTG) 230 protocol, infants were vaccinated with 4 doses of Chiron rgp120 with MF59 (n=48), VaxGen rgp120 with aluminum hydroxide (alum; n=49), or placebo (n=19) between 0 and 20 weeks of age. In PACTG 326, infants received 4 doses of ALVAC-HIV-1/AIDSVAX B/B with alum (n=9) or placebo (n=13) between 0 and 12 weeks of age. RESULTS: By 52 weeks of age, the majority of maternally acquired antibodies had waned and vaccine Env-specific immunoglobulin G (IgG) responses in vaccinees were higher than in placebo recipients. Chiron vaccine recipients had higher and more-durable IgG responses than VaxGen vaccine recipients or ALVAC/AIDSVAX vaccinees, with vaccine-elicited IgG responses still detectable in 56% of recipients at 2 years of age. Remarkably, at peak immunogenicity, the concentration of anti-V1V2 IgG, a response associated with a reduced risk of HIV-1 acquisition in the RV144 adult vaccine trial, was 22-fold higher in Chiron vaccine recipients, compared with RV144 vaccinees. CONCLUSION: As exemplified by the Chiron vaccine regimen, vaccination of infants against HIV-1 can induce robust, durable Env-specific IgG responses, including anti-V1V2 IgG.

Immune-correlates analysis of an HIV-1 vaccine efficacy trial.

BACKGROUND: In the RV144 trial, the estimated efficacy of a vaccine regimen against human immunodeficiency virus type 1 (HIV-1) was 31.2%. We performed a case-control analysis to identify antibody and cellular immune correlates of infection risk. METHODS: In pilot studies conducted with RV144 blood samples, 17 antibody or cellular assays met prespecified criteria, of which 6 were chosen for primary analysis to determine the roles of T-cell, IgG antibody, and IgA antibody responses in the modulation of infection risk. Assays were performed on samples from 41 vaccinees who became infected and 205 uninfected vaccinees, obtained 2 weeks after final immunization, to evaluate whether immune-response variables predicted HIV-1 infection through 42 months of follow-up. RESULTS: Of six primary variables, two correlated significantly with infection risk: the binding of IgG antibodies to variable regions 1 and 2 (V1V2) of HIV-1 envelope proteins (Env) correlated inversely with the rate of HIV-1 infection (estimated odds ratio, 0.57 per 1-SD increase; P=0.02; q=0.08), and the binding of plasma IgA antibodies to Env correlated directly with the rate of infection (estimated odds ratio, 1.54 per 1-SD increase; P=0.03; q=0.08). Neither low levels of V1V2 antibodies nor high levels of Env-specific IgA antibodies were associated with higher rates of infection than were found in the placebo group. Secondary analyses suggested that Env-specific IgA antibodies may mitigate the effects of potentially protective antibodies. CONCLUSIONS: This immune-correlates study generated the hypotheses that V1V2 antibodies may have contributed to protection against HIV-1 infection, whereas high levels of Env-specific IgA antibodies may have mitigated the effects of protective antibodies. Vaccines that are designed to induce higher levels of V1V2 antibodies and lower levels of Env-specific IgA antibodies than are induced by the RV144 vaccine may have improved efficacy against HIV-1 infection.