The remaining 22 HD, negative for SARS-CoV-2-specific PCR and/or serologic analyses, were recruited from the onset of the pandemic until December 2020. We recruited 45 individuals, 23 of which had a history of COVID-19 confirmed by PCR, and were enrolled during the first of the pandemic in Spain.
Conversely, we found a strong significant correlation between S1-induced CD4+ response and anti-S IgA in CD, which was lost after vaccination. Interestingly, we did not detect MPro-elicited CD4+ activation despite the overt humoral response against this protein in CD. Likewise, we detected an increment in anti-S and anti-RBD antibodies that peaked after first dose administration in CD. We provide evidence for specific changes in T cell reactivity profile, which include increased S1 and mainly S2 specific CD4+ lymphocytes, and a loss of reactivity against NCAP in vaccinated subjects. In the present study, we conducted a comprehensive characterization of CD4+T and B cell response in healthy donors (HD) and convalescents (CD) pre-and post-vaccination. Recent reports describe kinetics of humoral and cellular responses after vaccine administration ( 14– 17) however, there are no detailed analysis of immune profile changes in patients before and after vaccine administration. Officially approved COVID-19 mRNA vaccines include BNT162b2 and mRNA-1273, which require two doses administered 3-4 weeks apart. These lymphocytes could be responsible for heterologous immunity, conferring resistance to infection by SARS-CoV-2 or leading to milder COVID-19 symptoms, but no studies confirm this hypothesis. In most cases, these epitopes have a high degree of homology with sequences present in common cold coronaviruses. Numerous studies show the presence of T lymphocytes reactive against SARS-CoV-2 epitopes in a variable percentage of healthy individuals ( 3, 4, 10– 13). Similarly, specific CD4+ and CD8+ cells were found respectively in 89% and 50-74% of patients 6-9 months after infection ( 9). IgG against S protein was found in 90% of patients 6-8 months after infection ( 7, 8). Phenotypic characterization of T lymphocytes indicates they are mostly CD4+ Th1 ( 3, 4), with characteristics of effector (T EM) or central (T CM) memory cells ( 5, 6). SARS-CoV-2-reactive T lymphocytes predominantly recognize peptides belonging to spike (S) protein, followed by membrane protein (VME1) and nucleoprotein (NCAP), although reactivity against other viral proteins has been described. The development of humoral and cellular immunity against SARS-CoV-2, the causative agent of new coronavirus disease (COVID-19) ( 1), has been the subject of numerous studies, given its importance in the pathogenesis of the disease and its usefulness from a diagnostic and epidemiological perspective ( 2, 3). Interestingly, we found a strong significant correlation between S1-induced CD4+ response and anti-S IgA pre-vaccination, which was lost after vaccine administration. 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. HD presented an increment in anti-S and anti-RBD IgG after first dose vaccination, which increased after the second vaccination. Despite the substantial antibody response in CD, MPro-derived peptides did not elicit CD4+ lymphocyte activation in our assay in either condition. On the contrary, NCAP reactivity observed in HD and CD patients was no longer detectable after vaccination. 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. We analyzed the adaptive immunity in healthy donors (HD) and convalescent individuals (CD), before and after administering BNT162b2 vaccine. Cry it out for naps reddit.The immune response promoted by SARS-CoV-2 vaccination is relevant to develop novel vaccines and optimized prevention strategies.