We compare immunogenicity and protective efficacy of an HIV vaccine comprised of env and gag DNA and Env (Envelope) proteins by co-administration of the vaccine components in the same muscles or by separate administration of DNA + protein in contralateral sites in female rhesus macaques. The 6-valent vaccine includes gp145 Env DNAs, representing six sequentially isolated Envs from the HIV-infected individual CH505, and matching GLA-SE-adjuvanted gp120 Env proteins. Interestingly, only macaques in the co-administration vaccine group are protected against SHIV CH505 acquisition after repeated low-dose intravaginal challenge and show 67% risk reduction per exposure. Macaques in the co-administration group develop higher Env-specific humoral and cellular immune responses. Non-neutralizing Env antibodies, ADCC, and antibodies binding to FcγRIIIa are associated with decreased transmission risk. These data suggest that simultaneous recognition, processing, and presentation of DNA + Env protein in the same draining lymph nodes play a critical role in the development of protective immunity.

Background The gut mucosal homing integrin receptor a4b7 present on activated CD4+ T-cells interacts with the HIV-1 gp120 second variable loop (V2). Case control analysis of the RV144 phase III vaccine trial showed that antibodies induced by the vaccine bound to a MuLV-gp70 scaffolded V1V2 loop of gp120 (V1V2-gp70) and correlated inversely with infection. These, and other data, generate the hypothesis that the vaccine-elicited antibodies may have been involved in limiting HIV-1 acquisition. We have developed a high-throughput assay to evaluate antibodies that block a4b7 binding. We have named this the RAP assay.

Background The canarypox vector ALVAC-HIV, together with the HIV gp120 envelope, has protected 31.2% of Thai heterosexual individuals from HIV acquisition in the RV144 HIV vaccine trial. This outcome was unexpected, given the limited ability of the ALVAC-HIV vaccine component to induce CD8+T-cell responses, and of the HIVgp120 envelope to elicit broad neutralizing antibodies. Methods We vaccinated macaques with an immunization regimen that mimics the RV144 trial and exposed them to a mucosal dose of SIVmac251 that transmits few virus variants, similar to HIV transmission to humans. Results

Background HIV-1 envelope protein gp41 is a very attractive vaccine target as its epitopes are recognized by three broadly neutralizing antibodies. However, the extreme hydrophobicity and very transient exposure of neutralizing epitopes during infection has hampered its usage in HIV-1 vaccine development. Our goal is to design a soluble trimeric gp41 vaccine stabilized as a pre-hairpin intermediate.

Background The goal of this study was to design structural mimics of HIV-1 epitopes that have the potential to induce broadly neutralizing antibodies (bnAbs). The structure of the gp41 membrane proximal external region (MPER), targeted by three bnAbs, requires further definition. Experiments were designed to select epitopes with enhanced binding to MPER bnAbs, to identify neutralization-competent MPER structures, and to determine if selected MPER epitopes can broaden the immune response as potential vaccines. Methods

Background Development of vaccine formulations that induce cross clade neutralizing antibodies to the membrane proximal external region (MPER) of gp41 similar to 4E10 and 2F5 have been extensively investigated. We previously demonstrated that immunization with liposomes containing MPER and lipid A as an adjuvant could induce antibodies to the MPER and IgM monoclonal antibodies obtained from the mice bound to both lipids and MPER and neutralized HIV-1 (Matyas et al., 2009 AIDS 23, 2069-77). We now report a new IgG monoclonal antibody WR324 obtained from mice immunized with a similar vaccine formulation that binds to MPER and can neutralize multiple clades of HIV-1. Methods Mice were immunized with liposomes containing phosphatidyl inositol-4-phosphate and MPER with lipid A as an adjuvant. The peptide, LELDKWASLWNWFDITNWLWYIK (aa 661-684) was derived from gp41 (HXB2 stain). Spleen cells were fused with SP2/O cells and cloned. WR324 was purified and the binding specificities were assessed by ELISA. HIV-1 neutralization was assessed in PBMC using replication competent, Renila reniformis luciferase (LucR)-expressing HIV-1 reporter viruses (LucRIMC) and in a human monocyte derived macrophage (MDM) assay with purified viruses. Results WR324 is an IgG2b with a kappa light chain and it bound to the MPER peptide, but not to lipids or recombinant gp41. WR324 neutralized clade B, BaL and SF162, clade CRF01_AE, CM235, and clade C, GS 014 IMC viruses in the PBMC assay using two different donors. It also neutralized primary viruses, US-1 ,B aL, and clade CRF01_AE, M066 in the MDM assay using 3 different donors. WR324 did not bind to the surface of MDM cells, but binding to HIV-1 was observed by electron microscopy with immuno-gold labeling. Conclusion

Background Eliciting broadly reactive neutralizing antibodies remains a challenge in HIV-1 vaccine development, complicated by variations in envelope (Env) subtype and structure, and by the assays used for product down-selection. Since a majority of new HIV-1 infections are subtype C and considering the novel properties of C Envs, a C Env (CO6980v0c22) from an acutely infected Tanzanian was developed as a candidate HIV vaccine.