DNA-MVA-protein vaccination of rhesus macaques induces HIV-specific immunity in mucosal-associated lymph nodes and functional antibodies

Successful future HIV vaccines are expected to generate an effective cellular and humoral response against the virus in both the peripheral blood and mucosal compartments. We previously reported the development of DNA-C and MVA-C vaccines based on HIV-1 subtype C and demonstrated their immunogenicity when given in a DNA prime-MVA boost combination in a nonhuman primate model. In the current study, rhesus macaques previously vaccinated with a DNA-C and MVA-C vaccine regimen were re-vaccinated 3.5 years later with MVA-C followed by a protein vaccine based on HIV-1 subtype C envelope formulated with MF59 adjuvant (gp140Env/MF59), and finally a concurrent boost with both vaccines. A single MVA-C re-vaccination elicited T cell responses in all animals similar to previous peak responses, with 4/7 demonstrating responses >1000 SFU/10⁶ PBMC. In contrast to an Env/MF59-only vaccine, concurrent boosting with MVA-C and Env/MF59 induced HIV-specific cellular responses in multiple mucosal associated lymph nodes in 6/7 animals, with high magnitude responses in some animals. Both vaccine regimens induced high titer Env-specific antibodies with ADCC activity, as well as neutralization of Tier 1 viruses and modest Tier 2 neutralization. These data demonstrate the feasibility of inducing HIV-specific immunity in the blood and mucosal sites of viral entry by means of DNA and poxvirus-vectored vaccines, in combination with a HIV envelope-based protein vaccine.     

Microparticles in MF59, a potent adjuvant combination for a recombinant protein vaccine against HIV-1

Novel adjuvant formulations involving PLG microparticles with entrapped recombinant protein antigens (env gp120 and p24 gag) from human immunodeficiency virus type-1 (HIV-1), dispersed in the emulsion adjuvant MF59 were evaluated as potential HIV-1 vaccine candidates in mice and baboons. In mice, the adjuvant combination induced significantly enhanced antibody responses in comparison to either adjuvant used alone. In addition, the polylactide co-glycolide polymer (PLG) microparticles and MF59 combination induced CTL activity against HIV-1 p24 gag. In baboons, the adjuvant combination induced significantly enhanced antibody titers after a single dose of gp120, but the responses were comparable to gp120 in MF59 alone after boosting. Both MF59+gp120 alone and PLG/gp120 in MF59 induced neutralizing antibodies against a T cell line-adapted (TCLA) strain and a primary isolate of HIV-1. In contrast to the observations with gp120, immunization in baboons with PLG/p24 in MF59 induced significantly enhanced antibody responses after boosting, in comparison to immunization with MF59 alone + p24.     

Candidate HIV-1 gp140DeltaV2, Gag and Tat vaccines protect against experimental HIV-1/MuLV challenge

Pre-clinical HIV-1 vaccine protocols, using multiple vaccine modalities and a potent adjuvant were assessed for vaccine efficacy in an experimental HIV-1 challenge model. C57Bl/6 mice were immunized with DNA plasmids encoding HIV-1 gp140, Gag and Tat alone or in combination with the corresponding recombinant proteins formulated in the adjuvant MF59. HIV-1 DNA alone or a DNA prime protein boost schedule resulted in complete protection against challenge with HIV-1/MuLV-infected murine cells. Although HIV-1 protein immunization in combination with MF59 resulted in partial protection, the DNA priming seemed to be crucial for obtaining full protection against the challenge. It is likely that the partial protection seen after immunization with protein alone is, to a certain extent, due to effects of the adjuvant since some animals that received the adjuvant MF59 alone were protected from the challenge. For the most part, antigen-specific cell-mediated immune responses as detected in the spleen (in contrast to responses detected in peripheral blood) of immunized animals appeared to be associated with protection in this study.     

Characterization of immune responses elicited in mice by intranasal co-immunization with HIV-1 Tat, gp140 DeltaV2Env and/or SIV Gag proteins and the nontoxicogenic heat-labile Escherichia coli enterotoxin

The development of a vaccine against HIV/AIDS capable of inducing broad humoral and cellular responses at both systemic and mucosal sites, able to stop or reduce viral infection at the portal of entry, represents the only realistic way to control the infection caused by HIV world-wide. The promising results obtained with the HIV-1 Tat-based vaccines in preclinical and clinical settings, the evidence that a broad immunity against HIV correlates with reduced viral load or virus control, as well as the availability of novel gp140 V2-loop deleted HIV-1 Env (DeltaV2Env) immunogens capable of inducing cross-reactive neutralizing antibodies, have led to the design of new vaccine strategies based on the combination of non-structural and structural proteins. In this study, we demonstrate that immunization with a biologically active HIV-1 Tat protein in combination with the oligomeric HIV-1 gp140 DeltaV2Env and/or SIV Gag proteins, delivered intranasally with the detoxified LTK63 mucosal adjuvant, whose safety has been recently shown in humans, elicits long-lasting local and systemic antibody and cellular immune responses against the co-administered antigens in a fashion similar to immune responses induced by vaccination with Tat, DeltaV2Env and Gag proteins alone. The results indicate lack of antigen interference implying that HIV-1 Tat is an optimal co-antigen for combined vaccine strategies employing DeltaV2Env and/or Gag proteins.     

Antibody responses after intravaginal immunisation with trimeric HIV-1 CN54 clade C gp140 in Carbopol gel are augmented by systemic priming or boosting with an adjuvanted formulation

Optimum strategies to elicit and maintain antibodies at mucosal portals of virus entry are critical for the development of vaccines against human immunodeficiency virus (HIV). Here we show in non-human primates that a novel regimen of repeated intravaginal delivery of a non-adjuvanted, soluble recombinant trimeric HIV-1_CN54 clade C envelope glycoprotein (gp140) administered in Carbopol gel can prime for B-cell responses even in the absence of seroconversion. Following 3 cycles of repeated intravaginal administration, throughout each intermenses interval, 3 of 4 macaques produced or boosted systemic and mucosally-detected antibodies upon intramuscular immunisation with gp140 formulated in AS01 adjuvant. Reciprocally, a single intramuscular immunisation primed 3 of 4 macaques for antibody boosting after a single cycle of intravaginal immunisation. Virus neutralising activity was detected against clade C and clade B HIV-1 envelopes but was restricted to highly neutralisation sensitive pseudoviruses.     

HIV-1 Envgp140 trimers elicit neutralizing antibodies without efficient induction of conformational antibodies

Currently, no vaccine for human immunodeficiency virus (HIV-1) provides protection from virus infection. One reason for these disappointing results has been the difficulty of current vaccine candidates to elicit high-titer, broadly reactive immunity to a large number of viral proteins. Recently, our laboratory demonstrated that the coupling of C3d to a soluble trimerized HIV-1 envelope (Env(gp140(FT))) elicited higher titers of neutralizing antibodies than monomers of Env(gp120) coupled to C3d [Bower JF, Yang X, Sodroski J, Ross TM. Elicitation of neutralizing antibodies with DNA vaccines expressing soluble stabilized human immunodeficiency virus type 1 envelope glycoprotein trimers conjugated to C3d. J Virol 2004;78(9):4710-9]. To determine if the induction of conformational antibodies correlated with neutralization, mice (BALB/c) were primed (2x) with DNA plasmids expressing monomeric Env(gp120) or trimeric Env(gp140) alone or fused to mC3d(3) at one of two doses (2.0microg or 0.2microg), followed by a boost of recombinant uncleaved, trimeric Env(gp140). Regardless of the priming dose of DNA, all mice had high-titer anti-Env IgG antibodies. Interestingly, Env(gp140) trimers did not elicit higher titers of antibodies that recognized conformational Env epitopes compared to monomers of Env(gp120). Therefore, additional parameters were examined for correlation with neutralization. For neutralization-resistant HIV-1 isolates, ADA and YU-2, neutralization correlated with high-titer, high avidity antibodies, with Env(gp140) eliciting slightly higher neutralization titers than Env(gp120). In contrast, none of the measured parameters correlated with neutralization for the more neutralization-sensitive isolates, MN or 89.6. Therefore, even though soluble, uncleaved Env(gp140) trimers may be marginally more effective at eliciting neutralizing antibodies than Env(gp120), neutralization does not appear to correlate with the elicitation of conformationally dependent antibodies.     

Structural and immunogenicity studies of a cleaved,stabilized envelope trimer derived from subtype A HIV-1

SOSIP gp140 trimers represent a soluble, stabilized, proteolytically cleaved form of the HIV-1 envelope (Env) glycoproteins. SOSIP gp140 derived from a subtype A HIV-1 isolate, KNH1144, forms exceptionally stable trimers that resemble virion-associated Env in antigenicity and topology. Here, we used electron microscopy to demonstrate that KNH1144 SOSIP gp140 trimers bound three soluble CD4 molecules in a symmetrical orientation similar to that seen for native Env. We compared the immunogenicities of KNH1144 SOSIP gp140 trimers and gp120 monomers in rabbits and found that the trimers were superior at eliciting neutralizing antibodies (NAbs) to homologous virus as well as neutralization-sensitive subtype B and C viruses. The NAb specificities for SOSIP antisera mapped in part to the CD4 binding site on gp120. We also observed adjuvant-dependent induction of antibodies to the residual levels of host cell proteins (HCPs) contained in the purified Env preparations. When present, HCP antibodies enhanced pseudovirus infection. Our findings are relevant for the further development of Env-based vaccines for HIV-1.     

Purified complexes of HIV-1 envelope glycoproteins with CD4 and CCR5(CXCR4): production, characterization and immunogenicity

The ability to readily elicit broadly neutralizing antibodies to HIV-1 remains elusive. We and others have hypothesized that interaction of the viral envelope glycoprotein (Env, gp120-gp41) with its receptor molecules could enhance the exposure of conserved epitopes that may facilitate the elicitation of broadly neutralizing antibodies. The Env-CD4-coreceptor complexes mediate HIV-1 entry into cells and serve as a major target for inhibitors of this process. To begin to evaluate their potential also as vaccine immunogens we produced relatively large amounts of complexes of purified recombinant soluble truncated Env, gp140(89.6) or gp120(89.6), with CD4 and CCR5 or CXCR4. We found that gp140(gp120)-CD4-CCR5 complexes are stable and immunogenic in mice transgenic for human CD4 and CCR5. They elicited anti-gp120 and anti-gp140 antibodies that inhibited an heterologous primary HIV-1 isolate (JR-FL) with two- to threefold higher neutralizing activity than those elicited by gp120 and gp140. The antibodies elicited by the complexes competed better with the antibodies X5 and CG10 but not with b12 for binding to gp120 and gp120-CD4 complexes compared to those elicited with gp140(120) alone. These findings suggest that stable purified Env-CD4-CCR5(CXCR4) complexes can be produced in relatively large amount sufficient for their further characterization that may help in the development of novel vaccines candidates.     

Envelope proteins of two HIV-1 clades induced different epitope-specific antibody response

Using HIV-1 envelope protein (Env)-based immunogens that closely mimic the conformation of functional HIV-1 Envs and represent the isolates prevalent in relevant geographical region is considered a rational approach towards developing HIV vaccine. We recently reported that like clade B Env, JRFL, membrane bound Indian clade C Env, 4-2.J41 is also efficiently cleaved and displays desirable antigenic properties for plasmid DNA immunization. Here, we evaluated the immune response in rabbit by injecting the animals with plasmid expressing membrane bound efficiently cleaved 4-2.J41 Env followed by its gp140-foldon (gp140-fd) protein boost. The purified 4-2.J41-gp140-fd protein is recognized by a wide panel of broadly neutralizing antibodies (bNAbs) including the quaternary conformation-dependent antibody, PGT145 with high affinity. We have also evaluated and compared the quality of antibody response elicited in rabbits after immunizing with plasmid DNA expressing the membrane bound efficiently cleaved Env followed by gp140-fd proteins boost with either of clade C Env, 4-2.J41 or clade B Env, JRFL or in combination. In comparison to JRFL group, 4-2.J41 group elicited autologous as well as limited low level cross clade neutralizing antibody response. Preliminary epitope-mapping of sera from animals show that in contrast to JRFL group, no reactivity to either linear peptides or V3-loop is detected in 4-2.J41 group. Furthermore, the presence of conformation-specific antibody in sera from animals immunized with 4-2.J41 Env is observed. However, unlike JRFL group, in 4-2.J41 group of animals, CD4-binding site-directed antibodies cannot be detected. Additionally, we have demonstrated that the quality of antibody response in combination group is guided by JRFL Env-based immunogen suggesting that the selection and the quality of Envs in multicade candidate vaccine are important factors to elicit desirable response.     

Comparison of multiple adjuvants on the stability and immunogenicity of a clade C HIV-1 gp140 trimer

Immunogens based on the human immunodeficiency virus type-1 (HIV-1) Envelope (Env) glycoprotein have to date failed to elicit potent and broadly neutralizing antibodies against diverse HIV-1 strains. An understudied area in the development of HIV-1 Env-based vaccines is the impact of various adjuvants on the stability of the Env immunogen and the magnitude of the induced humoral immune response. We hypothesize that optimal adjuvants for HIV-1 gp140 Env trimers will be those with high potency but also those that preserve structural integrity of the immunogen and those that have a straightforward path to clinical testing. In this report, we systematically evaluate the impact of 12 adjuvants on the stability and immunogenicity of a clade C (CZA97.012) HIV-1 gp140 trimer in guinea pigs and a subset in non-human primates. Oil-in-water emulsions (GLA-emulsion, Ribi, Emulsigen) resulted in partial aggregation and loss of structural integrity of the gp140 trimer. In contrast, alum (GLA-alum, Adju-Phos, Alhydrogel), TLR (GLA-aqueous, CpG, MPLA), ISCOM (Matrix M) and liposomal (GLA-liposomes, virosomes) adjuvants appeared to preserve trimer integrity as measured by size exclusion chromatography. However, multiple classes of adjuvants similarly augmented Env-specific binding and neutralizing antibody responses in guinea pigs and non-human primates.     

Improvement of antibody responses by HIV envelope DNA and protein co-immunization

Background

Developing HIV envelope (Env) vaccine components that elicit durable and protective antibody responses is an urgent priority, given the results from the RV144 trial. Optimization of both the immunogens and vaccination strategies will be needed to generate potent, durable antibodies. Due to the diversity of HIV, an effective Env-based vaccine will most likely require an extensive coverage of antigenic variants. A vaccine co-delivering Env immunogens as DNA and protein components could provide such coverage. Here, we examine a DNA and protein co-immunization strategy by characterizing the antibody responses and evaluating the relative contribution of each vaccine component.

Method

We co-immunized rabbits with representative subtype A or B HIV gp160 plasmid DNA plus Env gp140 trimeric glycoprotein and compared the responses to those obtained with either glycoprotein alone or glycoprotein in combination with empty vector.

Results

DNA and glycoprotein co-immunization was superior to immunization with glycoprotein alone by enhancing antibody kinetics, magnitude, avidity, and neutralizing potency. Importantly, the empty DNA vector did not contribute to these responses. Humoral responses elicited by mismatched DNA and protein components were comparable or higher than the responses produced by the matched vaccines.

Conclusion

Our data show that co-delivering DNA and protein can augment antibodies to Env. The rate and magnitude of immune responses suggest that this approach has the potential to streamline vaccine regimens by inducing higher antibody responses using fewer vaccinations, an advantage for a successful HIV vaccine design.     

Dense display of HIV-1 envelope spikes on the lambda phage scaffold does not result in the generation of improved antibody responses to HIV-1 Env

The generation of strong, virus-neutralizing antibody responses to the HIV-1 envelope spike (Env) is a major goal in HIV-1 vaccine research. To try to enhance the Env-specific response, we displayed oligomeric gp140 on a virus-like scaffold provided by the lambda phage capsid. To do this, an in vitro complementation system was used to “decorate” phage particles with glycosylated, mammalian cell-derived envelope oligomers. We compared the immune response to lambda phage particles displaying HIV-1 Env to that elicited by soluble oligomeric gp140 in rabbits. Env-binding antibody titers were higher in animals that received oligomeric gp140 as compared to Env decorated phage particles, as were virus neutralizing antibody responses. The Env decorated phage particles were, however, able to efficiently boost a protein-primed humoral response to levels equivalent to those elicited by high-dose adjuvanted Env oligomers. These results show that display of HIV-1 envelope spikes on the bacteriophage lambda capsid does not result in an improved, Env-specific humoral immune response.     

Trimeric HIV-1 gp140 fused with APRIL,BAFF, and CD40L on the mucosal gp140-specific antibody responses in mice

HIV-1 envelope (Env)-specific antibody present at mucosal surfaces can block entry of HIV-1 into these portals and thus should be elicited by an HIV-1 preventive vaccine. Since three molecules of tumor necrosis factor superfamily (TNFSF), APRIL, BAFF, and CD40L, could promote mucosal antibody responses, we made fusion constructs of them with an HIV-1 gp140 trimer and tested the mucosal gp140-specific antibody elicited by the fusion constructs in mice using a DNA prime-protein boost vaccination regimen. The fusion constructs formed trimers and displayed both broadly neutralizing antibody epitopes and non-broadly neutralizing antibody epitopes. Compared with the control construct, trimeric gp140, trimeric gp140-APRIL and gp140-BAFF fusion proteins mildly promoted B cell proliferation in vitro, enhanced HIV-1 gp140-binding IgG responses in vaginal lavage or fecal pellets, respectively, and decreased HIV-1 gp140-binding IgA in sera. Gp140-APRIL also augmented HIV-1 gp140-binding IgG in sera. Surprisingly, gp140-CD40L did not promote B cell proliferation in vitro and inhibited mucosal and systemic HIV-1 gp140-binding IgG or IgA. These results suggest that APRIL and BAFF should be further explored as molecular adjuvants for HIV-1 vaccines to enhance mucosal antibody responses, but covalent fusion of TNFSFs to gp140 may hinder their adjuvancy due to steric interactions.     

Comparison of immunogenicity between codon optimized HIV-1 Thailand subtype B gp140 and gp145 vaccines

HIV-1 pandemic posed an unprecedented challenge to the global health and it is believed that an effective vaccine will be the final solution against HIV-1. HIV-1 envelope is the primary immunogen in developing neutralization antibody based HIV vaccine. To define the suitable Env derived immunogen, we systemically compared the immunogenicity of gp140 and gp145 in a DNA vaccination alone and a prime-boost modalities. Two DNA vaccines and two recombinant Tiantan vaccinia vaccines (rTTV) were constructed for vaccination of female Balb/c mice. Elispot assay was used to read out the T cell immunity and ELISA assay was used to quantify antibody immunity. PLL (poly-L-leucine)-ELISA assay was used in linear antibody epitope mapping. Mice primed with gp145 tended to elicit more Env-specific T cells responses than those primed with gp140, significant difference was observed in DNA immunization alone. The ultimate T cell responses in prime-boost regimen tend to be determined mainly by the priming efficacy. Linear antibody epitope mapping displayed that sera raised by gp145 priming were vigorously reactive to more peptides than that by gp140. Our data demonstrated HIV-1 Thailand B-derived gp145 may raise higher T-cell responses and broader linear peptide-specific antibody responses than gp140 does. However, it remains to be determined that how these observations are relevant to the neutralization of antibody activities.     

Motif-optimized subtype A HIV envelope-based DNA vaccines rapidly elicit neutralizing antibodies when delivered sequentially

HIV-1 infection results in the development of a diverging quasispecies unique to each infected individual. Envelope (Env)-specific neutralizing antibodies (NAbs) typically develop over months to years after infection and initially are limited to the infecting virus. In some subjects, antibody responses develop that neutralize heterologous isolates (HNAbs), a phenomenon termed broadening of the NAb response. Studies of co-crystalized antibodies and proteins have facilitated the identification of some targets of broadly neutralizing monoclonal antibodies (NmAbs) capable of neutralizing many or most heterologous viruses; however, the ontogeny of these antibodies in vivo remains elusive. We hypothesize that Env protein escape variants stimulate broad NAb development in vivo and could generate such NAbs when used as immunogens. Here we test this hypothesis in rabbits using HIV Env vaccines featuring: (1) use of individual quasispecies env variants derived from an HIV-1 subtype A-infected subject exhibiting high levels of NAbs within the first year of infection that increased and broadened with time; (2) motif optimization of envs to enhance in vivo expression of DNA formulated as vaccines; and (3) a combined DNA plus protein boosting regimen. Vaccines consisted of multiple env variants delivered sequentially and a simpler regimen that utilized only the least and most divergent clones. The simpler regimen was as effective as the more complex approach in generating modest HNAbs and was more efficient when modified, motif-optimized DNA was used in combination with trimeric gp140 protein. This is a rationally designed strategy that facilitates future vaccine design by addressing the difficult problem of generating HNAbs to HIV by empirically testing the immunogenicity of naturally occurring quasispecies env variants.     

Antigenicity and immunogenicity of HIV-1 gp140 with different combinations of glycan mutation and V1/V2 region or V3 crown deletion

The carbohydrate moieties on HIV-1 envelope glycoprotein (Env) act as shields to mask conserved neutralizing epitopes, while the hyperimmunogenic variable regions are immunodominant in inducing non-neutralizing antibodies, representing the major challenge for using Env as a vaccine candidate to induce broadly neutralizing antibodies (bNAbs). In this study, we designed a series of HIV-1 gp140 constructs with the removal of N276/N463 glycans, deletion of the V1/V2 region and the V3 crown, alone or in combination. We first demonstrated that all the constructs had a comparable level of expression and were mainly expressed as trimers. Following purification of gp140s from mammalian cells, we measured their binding to bNAbs and non-NAbs in vitro and capability in inducing bNAbs in vivo. Antibody binding assay showed that removal of N276/N463 glycans together with the deletion of V1/V2 region enhanced the binding of gp140s to CD4-binding site-targeting bNAbs VRC01 and 3BNC117, and CD4-induced epitopes-targeting non-NAbs A32, 17b and F425 A1g8, whereas further deletion of V3 crown in the gp140 mutants demonstrated slightly compromised binding capability to these Abs. Immunogenicity study showed that the above mutations did not lead to the induction of a higher Env-specific IgG response via either DNA-DNA or DNA-protein prime-boost strategies in mice, while neutralization assay did not show an apparent difference between wild type and mutated gp140s. Taken together, our results indicate that removal of glycans at N276/N463 and deletion of the V1/V2 region can expose the CD4-binding site and CD4-induced epitopes, but such exposure alone appears incapable of enhancing the induction of bNAbs in mice, informing that additional modification or/and immunization strategies are needed. In addition, the strategies which we established for producing gp140 proteins and for analyzing the antigenicity and immunogenicity of gp140 provide useful means for further vaccine design and assessment.     

Long-term memory B-cell responses in recipients of candidate human immunodeficiency virus type 1 vaccines

The efficacy and practical application of human immunodeficiency virus type 1 (HIV-1) vaccines may depend in part on the longevity of the immune responses generated, particularly those in the memory compartment. Candidate vaccines based on the HIV-1 envelope glycoproteins generate binding and neutralizing antibodies in humans but there have been no prior studies on the long-term persistence and recall of those responses. We evaluated six healthy, HIV non-infected adults who had received a combination of recombinant canarypox HIV-1 vaccines boosted by gp120 and who had achieved a high serum titer of neutralizing antibody to HIV-1 MN. These individuals were administered a gp160 boost 4-5 years after their last vaccination. Four volunteers had detectable binding and neutralizing antibodies at the time of boosting and all six volunteers exhibited a recall binding and neutralizing antibody response. The antibodies neutralized multiple T cell line-adapted (TCLA) strains of virus, including the vaccine strain, but not primary isolates. These results demonstrate that memory B-cell responses can last for many years following HIV-1 envelope glycoprotein immunization. In principle, similar long-term memory may be possible with improved immunogens that generate broadly cross-reactive neutralizing antibodies.     

Broad HIV-1 neutralizing antibody response induced by heterologous gp140/gp145 DNA prime-vaccinia boost immunization

Objective

To develop an effective HIV vaccine strategy that can induce cross-reactive neutralizing antibody.

Methods

Codon-optimized gp140 and gp145 env genes derived from HIV-1_cn54, a CRF07 B′/C recombinant strain, were constructed as DNA and recombinant Tiantan vaccinia (rTV) vaccines. The effect of heterologous immunization with gp140 and gp145 was tested in mice and guinea pigs. T cell responses were detected using the IFN-γ ELISPOT assay. A panel of primary isolates of clade B′ and B′/C HIV-1 and TZM-bl cells was used to determine the neutralizing activity of immunized sera.

Results

The neutralizing antibodies (NAbs) induced by the heterologous immunogen immunization neutralized all HIV-1 B′ and B′/C primary isolates in the guinea pig model. Gp145 and gp140 heterologous prime-boost induced the best neutralizing antibody response with a broad neutralizing spectrum and the highest titer of 1:270 at 6 weeks after the last inoculation. However, the T cell response to HIV-1 peptides was significantly weaker than the gp145 + gp145 homologous prime-boost.

Conclusions

This heterologous prime-boost immunization strategy could be used to design immunogen-generating broad neutralizing antibodies against genetic variance pathogens.     

Comparison of the patterns of antibody recall responses to HIV-1 gp120 and hepatitis B surface antigen in immunized mice

To date, we still lack an ideal strategy for designing envelope glycoprotein (Env) vaccines to elicit potent protective antibodies against HIV-1 infection. Since the human hepatitis B virus surface antigen (HBsAg) is representative of effective vaccines that can induce ideal humoral immune responses, knowledge of how it elicits antibody responses and T helper cells would be an useful reference for HIV vaccine development. We compared the characteristics of the HIV-1 Env gp120 trimer and HBsAg in antibody elicitation and induction of T follicular helper (Tfh) and memory B cells in immunized Balb/c mice. Using the strategy of protein prime-protein boost, we found that HIV-1 gp120 induced slower recall antibody responses but redundant non-specific IgG responses at early time after boosting compared to HBsAg. The higher frequency of PD-1^hiCD4⁺ T cells and Tfh cells that appeared at the early time point after gp120 boosting is likely to limit the development of memory B cells, memory T cells, and specific antibody recall responses. These findings regarding the different features of HIV envelope and HBsAg in T helper cell responses may provide a direction to improve HIV envelope immunogenicity.     

A randomized, controlled study in adults of the immunogenicity of a novel hepatitis B vaccine containing MF59 adjuvant.

The safety and immunogenicity of a novel hepatitis B virus (HBV) vaccine containing recombinant PreS2 and S antigens combined with MF59 adjuvant (HBV/MF59) was evaluated in healthy adults (N=230) who were randomized to receive 2 or 3 immunizations of either the study vaccine or a licensed control vaccine (Recombivax HB). After a single immunization, 105 of 118 (89%) recipients of HBV/MF59 achieved protective serum levels of anti-HBs antibody (> 10 mIU/ml), compared with 13 of 110 (12%) recipients of licensed vaccine (P < 0.001). The geometric mean titer (GMT) after 2 doses of HBV/MF59 given 2 months apart (13,422 mIU/ml) was more than 5-fold higher than that following 3 doses of licensed vaccine given over 6 months (2,346 mIU/ml; P < 0.001). The GMT following 3 injections of HBV/MF59 (249,917 mIU/ml) was 100-fold higher than licensed vaccine (P < 0.001). Anti-PreS2 antibodies were elicited in over 90% of the subset of HBV/MF59 recipients tested. Both vaccines were well tolerated; transient, mild-to-moderate local inflammation was the major postinjection reaction.