ABSTRACT
The immune response promoted by SARS-CoV-2 vaccination is relevant to develop novel vaccines and optimized prevention strategies. We analyzed the adaptive immunity in healthy donors (HD) and convalescent individuals (CD), before and after administering BNT162b2 vaccine. Our results revealed specific changes in CD4+ T cell reactivity profile in vaccinated HD and CD, with an increase in S1 and S2 positive individuals, proportionally higher for S2. On the contrary, NCAP reactivity observed in HD and CD patients was no longer detectable after vaccination. Despite the substantial antibody response in CD, MPro-derived peptides did not elicit CD4+ lymphocyte activation in our assay in either condition. HD presented an increment in anti-S and anti-RBD IgG after first dose vaccination, which increased after the second vaccination. Conversely, anti-S and anti-RBD IgG and IgA titers increased in already positive CD after first dose administration, remaining stable after second dose inoculation. Interestingly, we found a strong significant correlation between S1-induced CD4+ response and anti-S IgA pre-vaccination, which was lost after vaccine administration.
Subject(s)
BNT162 Vaccine/immunology , CD4-Positive T-Lymphocytes/immunology , COVID-19/immunology , SARS-CoV-2/physiology , Adult , Cells, Cultured , Convalescence , Female , Healthy Volunteers , Humans , Immunization, Secondary , Immunoglobulin A/metabolism , Immunoglobulin G/metabolism , Male , Middle Aged , Spike Glycoprotein, Coronavirus/immunology , T-Cell Antigen Receptor Specificity , VaccinationABSTRACT
Here, we describe a new, simple, highly multiplexed serological test that generates a more complete picture of seroconversion than single antigen-based assays. Flow cytometry is used to detect multiple Ig isotypes binding to four SARS-CoV-2 antigens: the Spike glycoprotein, its RBD fragment (the main target for neutralizing antibodies), the nucleocapsid protein, and the main cysteine-like protease in a single reaction. Until now, most diagnostic serological tests measured antibodies to only one antigen and in some laboratory-confirmed patients no SARS-CoV-2-specific antibodies could be detected. Our data reveal that while most patients respond against all the viral antigens tested, others show a marked bias to make antibodies against either proteins exposed on the viral particle or those released after cellular infection. With this assay, it was possible to discriminate between patients and healthy controls with 100% confidence. Analysing the response of multiple Ig isotypes to the four antigens in combination may also help to establish a correlation with the severity degree of disease. A more detailed description of the immune responses of different patients to SARS-CoV-2 virus might provide insight into the wide array of clinical presentations of COVID-19.