Broad strategies for neutralizing SARS-CoV-2 and other human coronaviruses with monoclonal antibodies

Antibody therapeutics and vaccines for coronavirus disease 2019(COVID-19)have been approved in many countries,with most being developed based on the original strain of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).SARS-CoV-2 has an exceptional ability to mutate under the pressure of host immunity,especially the immune-dominant spike protein of the virus,which is the target of both antibody drugs and vaccines.Given the continuous evolution of the virus and the identification of critical mutation sites,the World Health Organization(WHO)has named 5 variants of concern(VOCs):4 are previously circulating VOCs,and 1 is currently circulating(Omicron).Due to multiple mutations in the spike protein,the recently emerged Omicron and descendent lineages have been shown to have the strongest ability to evade the neutralizing antibody(NAb)effects of current antibody drugs and vaccines.The development and characterization of broadly neutralizing antibodies(bNAbs)will provide broad strategies for the control of the sophisticated virus SARS-CoV-2.In this review,we describe how the virus evolves to escape NAbs and the potential neutralization mechanisms that associated with bNAbs.We also summarize progress in the development of bNAbs against SARS-CoV-2,human coronaviruses(CoVs)and other emerging pathogens and highlight their scientific and clinical significance.

Two antibodies show broad,synergistic neutralization against SARS-CoV-2 variants by inducing conformational change within the RBD

Continual evolution of the severe acute respiratory syndrome coronavirus(SARS-CoV-2)virus has allowed for its gradual evasion of neutralizing antibodies(nAbs)produced in response to natural infection or vaccination.The rapid nature of these changes has incited a need for the development of superior broad nAbs(bnAbs)and/or the rational design of an antibody cocktail that can protect against the mutated virus strain.Here,we report two angiotensin-converting enzyme 2 competing nAbs—8H12 and 3E2—with synergistic neutralization but evaded by some Omicron subvariants.Cryo-electron microscopy reveals the two nAbs synergistic neutralizing virus through a rigorous pairing permitted by rearrangement of the 472-489 loop in the receptor-binding domain to avoid steric clashing.Bispecific antibodies based on these two nAbs tremendously extend the neutralizing breadth and restore neutralization against recent variants including currently dominant XBB.1.5.Together,these findings expand our understanding of the potential strategies for the neutralization of SARS-CoV-2 variants toward the design of broad-acting antibody therapeutics and vaccines.

Mutational escape prevention by combination of four neutralizing antibodies that target RBD conserved regions and stem helix

New variants of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) appear rapidly every few months.They have showed powerful adaptive ability to circumvent the immune system. To further understand SARS-CoV-2’s adaptability so as to seek for strategies to mitigate the emergence of new variants, herein we investigated the viral adaptation in the presence of broadly neutralizing antibodies and their combinations. First, we selected four broadly neutralizing antibodies, including pan-sarbecovirus and pan-betacoronavirus neutralizing antibodies that recognize distinct conserved regions on receptor-binding domain(RBD) or conserved stem-helix region on S2 subunit.Through binding competition analysis, we demonstrated that they were capable of simultaneously binding.Thereafter, a replication-competent vesicular stomatitis virus pseudotyped with SARS-CoV-2 spike protein was employed to study the viral adaptation. Twenty consecutive passages of the virus under the selective pressure of individual antibodies or their combinations were performed. It was found that it was not hard for the virus to adapt to broadly neutralizing antibodies, even for pan-sarbecovirus and pan-betacoronavirus antibodies. The virus was more and more difficult to escape the combinations of two/three/four antibodies. In addition, mutations in the viral population revealed by high-throughput sequencing showed that under the selective pressure of three/four combinational antibodies, viral mutations were not prone to present in the highly conserved region across betacoronaviruses(stem-helix region), while this was not true under the selective pressure of single/two antibodies.Importantly, combining neutralizing antibodies targeting RBD conserved regions and stem helix synergistically prevented the emergence of escape mutations. These studies will guide future vaccine and therapeutic development efforts and provide a rationale for the design of RBD-stem helix tandem vaccine, which may help to impede the generation of novel variants.

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.