Serologic and Molecular Studies of human anti-hCoV antibody cross-immunity and protective responses among endemic HCoVs and SARS-CoV2

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Project Summary The emergence of the novel human betacoronavirus SARS-CoV2 in Wuhan, China in 2019 has rapidly evolved into a worldwide pandemic. Over a 100 million people have been infected and there have been several million deaths. There is also great disparity in the manner in which COVID-19 illness presents, from asymptomatic infection to death. COVID-19 illness in children is overall more mild or asymptomatic compared to adults. One hypothesis that may explain this disparity is that children have cross-immunity to SARS-CoV2 due to frequent early exposure to globally circulating human coronaviruses (HCoVs) that cause a milder respiratory illness. Whether there is some level of cross-immunity between the endemic HCoVs and SARS-CoV2 that carries into adulthood and can provide some level of protection from COVID-19 disease is the subject of this R01 application. Our primary goal is to provide serologic and molecular evidence of anti-HCoV/SARS-CoV2 spike (S) cross- reactive and neutralizing antibodies that can provide protection against SARS-CoV2 in vivo. We have an IRB- approved protocol to collect blood samples on 250 COVID-19 individuals. Our COVID cohort is comprised of 5 groups that includes adult and pediatric cancer patients, adult and pediatric healthcare providers and adults without COVID patient contact. In addition, we will study our pre-pandemic seasonal influenza cohort for evidence of pre-existing anti-SARS-CoV2 S Abs. In Aim 1 we will quantify the present of anti-S HCoV antibodies and quantitate their cross-reactivity to SARS-CoV2 S. The studies in subaim 1A will include FACS staining of S expressing cells and ELISAs of S subdomains for epitope mapping. In subaim 1B, selected plasma samples within each study group will be used for affinity column purification of plasma IgGs that will be passaged over and eluted from one of 4 HCoV or SARS-CoV2 spike columns and tested for cross-binding, cross-Fc effector activity and cross-neutralization activity. In subaim 1C, these purified IgGs will be tested in vivo in hACE2 mice for cross-protection against SARS-CoV2 challenge. In Aim 2 we will establish the molecular basis by which bi- directional immunity to among CoVs could provide cross immunity to HCoVs and SARS-CoV2 through common spike epitope recognition. In subaim 2A, we will perform memory B (mB) cell screening for presence of S cross- binding. Single mB cells that bind at least one hCoV S protein and SARS-CoV2 S will be isolated by FACS, their cognate VH/VL genes cloned, expressed as whole IgG1 mAbs and tested for cross-binding, virus neutralization and Fc effector activity against the different HoCoVs, SARS and SARS-CoV2. In subaim 2B, mAbs with cross- CoV activity will be tested in mouse and hamster models for protection against SARS-CoV2 challenge. In subaim 2C, we will adapt the novel LibraSeq technique to capture the single or multi-spike binding specificity, BCR repertoires and transcriptomes of selected Bm cells to study the potential different evolutionary origins that may exist between mono-spike and multi-spike binding cells. This R01 grant will provide proof-of-principle molecular studies of HCoV/SARS-CoV2 Ab cross-immunity that may aid in COVID-19 vaccine design.