Challenges on Induction of Broadly Neutralizing Antibodies for Optimization of HIV Vaccines Development and Vectored Immunoprophylaxis

Despite extensive research efforts, a preventive human immunodeficiency virus (HIV) vaccine remains one of the major challenges in the field of AIDS research. Experimental strategies which have been proven successful for other viral vaccines are not enough to tackle HIV-1 and new approaches to design effective preventive AIDS vaccines are of utmost importance. Due to enormous diversity among global circulating HIV strains, an effective HIV vaccine must elicit broadly protective antibodies based responses;therefore discovering new broadly neutralizing antibodies (bNAbs) against HIV has become major focus in HIV vaccine research. However further understanding of the viral targets of such antibodies and mechanisms of action of bNAbs is required for advancement of HIV vaccine research. This technical note discusses our current knowledge on the bNAbs and immunoprophylaxis using viral vectors with their relevance in designing of new candidates to HIV-1 vaccines.

Exploration of a Sequential Gp140-Gp145 Immunization Regimen with Heterologous Envs to Induce a Protective Cross-Reactive HIV Neutralizing Antibody Response In Non-human Primates

Raising a heterologous tier 2 neutralizing antibody(nAb)response remains a daunting task for HIV vaccine development.In this study,we explored the utility of diverse HIV-1 envelope(Env)immunogens in a sequential immunization scheme as a solution to this task.This exploration stemmed from the rationale that gp145,a membrane-bound truncation form of HIV Env,may facilitate the focusing of induced antibody response on neutralizing epitopes when sequentially combined with the soluble gp140 form as immunogens in a prime-boost mode.We first showed that gp140 DNA prime-gp145 Tiantan vaccinia(TV)boost likely represents a general format for inducing potent nAb response in mice.However,when examined in rhesus macaque,this modality showed little effectiveness.To improve the efficacy,we extended the original modality by adding a strong protein boost,namely native-like SOSIP.664 trimer displayed on ferritin-based nanoparticle(NP),which was generated by a newly developed click approach.The resulting three-immunization regimen succeeded in eliciting tier-2 nAb response with substantial breadth when implemented in rhesus macaque over a short 8-week schedule.Importantly,the elicited nAb response was able to effectively contain viremia upon a heterologous SHIV challenge.Collectively,our studies highlighted that diversification of Env immunogens,in both types and formulations,under the framework of a sequential immunization scheme might open new opportunity toward HIV vaccine development.