The peptides were synthesized by GL Biochem (Shanghai, China)

The peptides were synthesized by GL Biochem (Shanghai, China). Open in a separate window Figure?1 Proteome microarray and neutralization inhibition rate (%inhibition) of serum samples. We observed large amounts of pre-existing cross-reactive antibodies in the conserved regions among sCoVs, especially the S2 subunit. Excep t for a few peptides, the IgG and IgM fluorescence intensities against S, M and N peptides did not differ significantly between pre-vaccination and post-vaccination sera of vaccinees who developed a neutralization inhibition rate (%inhibition) <40 and %inhibition 40 after two doses of the COVID-19 vaccine. Participants with strong and poor pre-existing cross-reactive antibodies (strong pre-CRA; poor pre-CRA) had comparable %inhibition pre-vaccination (10.9% 2.9% 12.0% 2.2%, 44.6% 21.5%, peptide stimulation and crystal structure analysis showed T cell-mediated cross-recognition to circulating CoV (OC43 and HKU1) (9). Additionally, T cell-mediated anti-SARS-CoV-2 responses were found in unexposed human, indicating a cross-reaction between human CoVs and SARS-CoV-2 (10C14). Accumulating evidence suggests that pre-existing humoral immunity to sCoVs may play a role in the specific anti-SARS-CoV-2 antibody responses (15), but this possibility is usually controversial (16, 17). Some studies showed that elevated levels of pre-existing antibodies against sCoVs, specifically OC43 and HKU1, were associated with a less severe course of COVID-19, suggesting a protective effect of prior exposure to sCoVs (18C20). In contrast, laboratory evidence indicates possible antibody-dependent enhancement (ADE) of SARS-CoV-2 contamination by previous sCoV immunity (21, 22). Concerns about the ADE or initial antigenic sin (OAS) effect induced by pre-existing antibody responses mainly come from the past evidence in dengue computer AZD8329 virus and influenza computer virus (23, 24). Although several studies have been carried out, there is currently no conclusive evidence that pre-existing immune responses to sCoVs induce neutralization or enhancement of SARS-CoV-2 antibodies. During the current outbreak, COVID-19 vaccination is usually a critical prevention measure to help end the COVID-19 pandemic by achieving sufficient populace immunity. As COVID-19 vaccines have been administered across the world, it is necessary to understand the factors that affect the effectiveness or safety of these vaccines. This exacerbates the urgent need for laboratory data to determine the relationship AZD8329 between pre-existing immunity to sCoVs and the effectiveness of COVID-19 vaccines against SARS-CoV-2. In this study, we collected paired serum samples from ACTN1 36 healthy volunteers before and after immunization with AZD8329 inactivated whole-virion SARS-CoV-2 vaccines and analyzed the distribution and intensity of pre-existing antibody responses at the epitope level pre-vaccination as well as the relationship between pre-existing sCoV immunity and vaccine-induced neutralization. Methods and Materials Serum Specimens Serum specimens were collected from 36 healthy volunteers who received inactivated SARS-CoV-2 vaccines (Sinopharm, China) between 16 December, 2020 and 10 February, 2021. Before vaccination, all volunteers gave informed consent for participation. All participants reported not having a prior history of COVID-19 disease. All participants were unfavorable both for SARS-CoV-2 nucleic acid on nasopharyngeal swab specimens by reverse transcriptase polymerase chain reaction (RT-PCR) assays and specific IgG/IgM antibody assessments of serum samples by commercial enzyme-linked immunosorbent assay (ELISA) kits (BGI PathoGenesis Pharmaceutical Tech, China). The volunteers received two doses of inactivated SARS-CoV-2 vaccine with a 28Cday interval. Serum specimens were collected before vaccination (n=36) and 2C4 weeks after the second injection (n=36) from the same volunteers by healthcare professionals of the Futian District Center for Disease Control and Prevention, Shenzhen, China. Microarray Fabrication The procedure for microarray fabrication is usually illustrated in Physique?1A . The epitope information for SARS-CoV-2 was collected from the Immune Epitope Database (IEDB; http://www.iedb.org/) in January 2021. The sequences were clustered using the Epitope Cluster Analysis tool (http://tools.iedb.org/) with a minimum sequence identity of 70%. Finally, a peptide library, which contained 243 peptides representing SARS-CoV-2, was prepared. The synthetic peptides were designed to cover almost the entire S (coverage 97.6%), N (coverage 95.0%) and M (coverage 94.2%) proteins. The peptide library was based on the proteome sequence of the computer virus isolate Wuhan-Hu-1,.