Sequentially immune-induced antibodies could cross-neutralize SARS-CoV-2 variants

Background:The Omicron(B.1.1.529)SARS-COV-2 variant has raised serious concerns because of its unprecedented rapid rate of spreading and the fact that there are 36 mutations in the spike protein.Since the vaccine-induced neutralizing antibody targets are the spike protein,this may lead to the possibility of vaccine-induced hu-moral immunity escape.Methods:We measured the neutralizing activity in vitro for Omicron and compared this with wild type(WH-09)and Delta variants in human and monkey sera from different types of immunity.The monkey sera samples were collected at 1 and 3 months post three-dose inactivated(PiCoVacc)and recombinant protein(ZF2001)vaccination.Human sera were collected from 1 month post three-dose inactivated vaccination.Results:In inactivated vaccine sera,at 1/3 months post three-dose,geometric mean titers(GMTs)of neutralization antibody(NAb)against the Omicron variant were 4.9/5.2-fold lower than those of the wild type.In recombinant protein vaccine sera,GMTs of NAb against Omicron were 15.7/8.9-fold lower than those of the wild type.In human sera,at 1 month post three-dose inactivated vaccination,GMTs of NAb against Omicron were 3.1-fold lower than those of the wild type.Conclusion:This study demonstrated that despite a reduction in neutralization titers,cross-neutralizing activity against Omicron and Delta variants was still observed after three doses of inactivated and recombinant protein vaccination.

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.