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Summary The HIV-1-envelope glycoprotein (Env) is the main target of antigen design for antibody-based prophylactic vaccines. The generation of broadly neutralizing antibodies (bNAb) likely requires the appropriate presentation of stabilized trimers preventing exposure of non-neutralizing antibody (nNAb) epitopes. We designed a series of membrane-bound Envs with increased trimer stability through the introduction of key stabilization mutations. We derived a stabilized HIV-1 trimer, ConSOSL.UFO.750, which displays a dramatic reduction in nNAb binding while maintaining high quaternary and MPER-specific bNAb binding. Its soluble counterpart, ConSOSL.UFO.664, displays similar antigenicity, and its native-like Env structure is confirmed by negative stain-EM and glycosylation profiling of the soluble ConSOSL.UFO.664 trimer. A rabbit immunization study demonstrated that the ConSOSL.UFO.664 can induce autologous tier 2 neutralization. We have successfully designed a stabilized native-like Env trimer amenable to nucleic acid or viral vector-based vaccination strategies., Graphical Abstract, Highlights • DNA-expressed closed pre-fusion native-like Env with preserved MPER exposure • Env antigenicity varies across cell types and assays • Muscle cells present properly folded and glycosylated membrane-bound Envs • Fully glycosylated ConSOSL.UFO.664 induces autologous tier 2 neutralization, Aldon et al. developed membrane-bound and soluble stabilized HIV-1 Env trimer immunogens suitable for DNA/RNA or viral vector vaccines. The sequential iterative design and analysis in muscle cells have the potential to be used as a generalizable method for the expression of stabilized native-like trimers.

International audience; The female reproductive tract (FRT) is one of the major mucosal invasion sites for HIV-1. This site has been neglected in previous HIV-1 vaccine studies. Immune responses in the FRT after systemic vaccination remain to be characterized. Using a modified vaccinia virus Ankara (MVA) as a vaccine model, we characterized specific immune responses in all compartments of the FRT of nonhuman primates after systemic vaccination. Memory T cells were preferentially found in the lower tract (vagina and cervix), whereas APCs and innate lymphoid cells were mainly located in the upper tract (uterus and fallopian tubes). This compartmentalization of immune cells in the FRT was supported by transcriptomic analyses and a correlation network. Polyfunctional MVA-specific CD8+ T cells were detected in the blood, lymph nodes, vagina, cervix, uterus, and fallopian tubes. Anti-MVA IgG and IgA were detected in cervicovaginal fluid after a second vaccine dose. Thus, systemic vaccination with an MVA vector elicits cellular and Ab responses in the FRT

Although vaccines and antiretroviral (ARV) prevention have demonstrated partial success against human immunodeficiency virus (HIV) infection in clinical trials, their combined introduction could provide more potent protection. Furthermore, combination approaches could ameliorate the potential increased risk of infection following vaccination in the absence of protective immunity. We used a nonhuman primate model to determine potential interactions of combining a partially effective ARV microbicide with an envelope-based vaccine. The vaccine alone provided no protection from infection following 12 consecutive low-dose intravaginal challenges with simian-HIV strain SF162P3, with more animals infected compared to naive controls. The microbicide alone provided a 68% reduction in the risk of infection relative to that of the vaccine group and a 45% reduction relative to that of naive controls. The vaccine-microbicide combination provided an 88% reduction in the per-exposure risk of infection relative to the vaccine alone and a 79% reduction relative to that of the controls. Protected animals in the vaccine-microbicide group were challenged a further 12 times in the absence of microbicide and demonstrated a 98% reduction in the risk of infection. A total risk reduction of 91% was observed in this group over 24 exposures ( P = 0.004). These important findings suggest that combined implementation of new biomedical prevention strategies may provide significant gains in HIV prevention. IMPORTANCE There is a pressing need to maximize the impact of new biomedical prevention tools in the face of the 2 million HIV infections that occur each year. Combined implementation of complementary biomedical approaches could create additive or synergistic effects that drive improved reduction of HIV incidence. Therefore, we assessed a combination of an untested vaccine with an ARV-based microbicide in a nonhuman primate vaginal challenge model. The vaccine alone provided no protection (and may have increased susceptibility to a simian-HIV vaginal challenge), while the microbicide reduced the infection risk compared to that of vaccinated and naive animals. Importantly, the combined interventions provided the greatest level of protection, which was sustained following withdrawal of the microbicide. The data suggest that provision of ARV prophylaxis during vaccination reduces the potential for unexpected increased risks of infection following immunization and augments vaccine efficacy. These findings are important for the potential adoption of ARV prophylaxis as the baseline intervention for future HIV/AIDS vaccines.

International audience; Although vaccines and antiretroviral (ARV) prevention have demonstrated partial success against HIV infection in clinical trials, their combined introduction could provide more potent protection. Furthermore, combination approaches could ameliorate potential increased risk of infection following vaccination in the absence of protective immunity. We used a non-human primate model to determine potential interactions of combining a partially effective ARV microbicide with an envelope-based vaccine. The vaccine alone provided no protection from infection following 12 consecutive low dose intravaginal challenges with SHIVSF162P3, with more animals infected compared to naïve controls. The microbicide alone provided a 68% reduction in risk of infection relative to the vaccine group and a 45% reduction relative to naïve controls. The vaccine-microbicide combination provided an 88% reduction in per exposure risk of infection relative to vaccine alone, 79% reduction relative to controls. Protected animals in the vaccine-microbicide group were challenged a further 12 times in the absence of microbicide and demonstrated a 98% reduction in risk of infection. Taken together a total risk reduction of 91% was observed in this group over 24 exposures (P=0.004). These important findings suggest that combined implementation of new biomedical prevention strategies may provide significant gains in HIV prevention.