Cross-reactive neutralization of SARS-CoV-2 by serum antibodies from recovered SARS patients and immunized animals

The current COVID-19 pandemic, caused by a novel coronavirus SARS-CoV-2, poses serious threats to public health and social stability, calling for urgent need for vaccines and therapeutics. SARS-CoV-2 is genetically close to SARS-CoV, thus it is important to define the between antigenic cross-reactivity and neutralization. In this study, we firstly analyzed 20 convalescent serum samples collected from SARS-CoV infected individuals during the 2003 SARS outbreak. All patient sera reacted strongly with the S1 subunit and receptor-binding domain (RBD) of SARS-CoV, cross-reacted with the S ectodomain, S1, RBD, and S2 proteins of SARS-CoV-2, and neutralized both SARS-CoV and SARS-CoV-2 S protein-driven infections. Multiple panels of antisera from mice and rabbits immunized with a full-length S and RBD immunogens of SARS-CoV were also characterized, verifying the cross-reactive neutralization against SARS-CoV-2. Interestingly, we found that a palm civet SARS-CoV-derived RBD elicited more potent cross-neutralizing responses in immunized animals than the RBD from a human SARS-CoV strain, informing a strategy to develop a universe vaccine against emerging CoVs. SummarySerum antibodies from SARS-CoV infected patients and immunized animals cross-neutralize SARS-CoV-2 suggests strategies for universe vaccines against emerging CoVs.

Design of potent membrane fusion inhibitors against SARS-CoV-2, an emerging coronavirus with high fusogenic activity

The coronavirus disease COVID-19, caused by emerging SARS-CoV-2, has posed serious threats to global public health, economic and social stabilities, calling for the prompt development of therapeutics and prophylactics. In this study, we firstly verified that SARS-CoV-2 uses human ACE2 as a cell receptor and its spike (S) protein mediates high membrane fusion activity. Comparing to that of SARS-CoV, the heptad repeat 1 (HR1) sequence in the S2 fusion protein of SARS-CoV-2 possesses markedly increased -helicity and thermostability, as well as a higher binding affinity with its corresponding heptad repeat 2 (HR1) site. Then, we designed a HR2 sequence-based lipopeptide fusion inhibitor, termed IPB02, which showed highly poent activities in inibibiting the SARS-CoV-2 S protein-mediated cell-cell fusion and pseudovirus infection. IPB02 also inhibited the SARS-CoV pseudovirus efficiently. Moreover, the strcuture and activity relationship (SAR) of IPB02 were characterzized with a panel of truncated lipopeptides, revealing the amino acid motifs critical for its binding and antiviral capacities. Therefore, the presented results have provided important information for understanding the entry pathway of SARS-CoV-2 and the design of antivirals that target the membrane fusion step.

Comparison of the Immunogenicities of HIV-1 Mutants Based on Structural Modification of env / 中国病毒学·英文版

Eleven env mutants were designed and generated by site-directed mutagenesis of the regions around Nab epitopes and deletions of variable regions in env.The immunogenicities of the generated mutants were evaluated using single-cycle infection neutralization assays with two pseudoviruses and IFN-γELISPOT.Overall,five mutants(dWt,M2,M5-2,M5-1 and dM7)induced highed neutralization activities for both pseudoviruses than plasmid Wt,while only two of the mutants(dWt and M5-2)showed significant differences(P<0.05).Two mutants(M2 and dM2)induced more Env-specific T cells than plasmid Wt.Statistically however,significance was only reached for mutant M2.Thus,properly modified HIV-1 Env may have the potential to induce potent cellular and humoral immune responses.

Establishment and primary application of pseudovirus-based neutralization assay for HIV-1 / 中华微生物学和免疫学杂志

Objective To establish a pseudovirus-based neutralization assay. Methods The functional gp160 genes were amplified from plasmids containing HIV-1 gene. The products were ligased into pcDNA3.1 plasmid and positive clones were screened by digestion with restriction enzymes. The pseudoviruses were harvested by co-transfection of the positive clone and pSG3△env plasmid. The neutralizing activities of monoclonal antibodies and HIV-1 antibody positive plasma were measured by these pseudoviruses. Results The four strains of psedoviruses (CHB01, CHB02, CHBC03 and CHAE04) had been successfully obtained. Monoclonal antibody 4E10 could neutralize all of 4 pseudoviruses while 2G12 could not neutralize any pesudoviruses. Monoclonal antibody 2F5 could neutralize pseudovirus CHB01, CHB02 and CHAE04 but not CHBC03, while IgG1b12 could neutralize pseudovirus CHB01, CHB02 and CHBC03 but not CHAE04. The neutralizing activities of 43 of HIV-1 antibody positive plasma against different subtypes of pseudovirus were significant differences and the cross-neutralization effects for some samples exist. Conclusion The harvested pseudoviruses could be used in the neutralization assay. However, the neutralizing characteristics of different pseudoviruses may be different.

The impact of site-directed deglycosylation of the HIV-1 envelope (Env) on its immunogenicity and assembly of functional pseudovirus / 中华微生物学和免疫学杂志

Objective To study the influence of site-directed deglycosylation of the HIV-1 envelope (Env) on its immunogenicity and assembly of functional pseudovirus. Methods Site-directed deglycosylation were performed using cycling mutagenesis and selection of mutants with DpnⅠ. Single-cycle infection assay was employed to analyze the effect of the mutations on the ability of functional pseudovirus assembly. The influence of deglycosylations on the immunodeficiency of Env was evaluated using pseudovirusbased neutralization assay and ELISPOT assay. Results Mutant N197Q induced higher neutralization activities for both pseudoviruses, but lower Env-specific T-cell response. And N197Q rendered the Env to lose the ability of functional pseudovirus assembly. Mutant G2 induced higher neutralization activities for pseudovirus 74-2 but lower for pseudovirus Wt, and had almost no influence on Env-specific T-cell response and functional pseudovirus forming. Conclusion The site-directed deglycosylation of the HIV-1 Env affects the pseudovirus forming and its immunogenicity.