RESUMO
The knowledge of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) shedding is highly relevant to the diagnosis, treatment and follow-up of patients with COVID-19 (coronavirus disease 2019). Deep nasopharyngeal swabs repeatedly collected from a cohort of one hundred patients with COVID-19 were tested for SARS-CoV-2 RNA using RT-PCR (real-time polymerase chain reaction). The median period of viral genome detectability was 15 days. Furthermore, the authors tested the hypothesis on the relationship between the severity of COVID-19 and the period in which the viral genome is detectable. They did not find any statistically significant difference in the duration of viral clearance between patients with asymptomatic to mild disease or severe disease.
Assuntos
Betacoronavirus , Infecções por Coronavirus , Pandemias , Pneumonia Viral , COVID-19 , Humanos , RNA Viral , SARS-CoV-2Assuntos
Subpopulações de Linfócitos B/imunologia , Memória Imunológica , Animais , Células Cultivadas , Eritrócitos/imunologia , Imunização , Imunoglobulina G/biossíntese , Imunoglobulina M/biossíntese , Camundongos , Camundongos Endogâmicos BALB C , Camundongos SCID , Ovinos/sangue , Transdução de Sinais/efeitos dos fármacosRESUMO
The conditions for induction of memory cells (B-MC) and evocation of the secondary antibody (Ab) response in tissue cultures (TC) were estimated. (1) In vivo primed B-MC cells were isolated 6-150 d after priming and stimulated in TC with different doses of sheep red blood cell (SRBC) antigen. The Ab response has a strict time and dose dependence: only small doses (10(5)) evoke a secondary response, high doses (10(8), 10(9)) a state of immediate tolerance. (2) Antigen added to TC directly with B-MC rescued their Ab production for a long period. Addition of the antigen 1 or 2 d after setting the TC, follows the Ab-response decay, comparable with virgin cells (B-ICC). (3) Primed B-MC stimulated in TC responded preferentially with an IgM secondary response; the same cell suspension adoptively transferred into isologous recipients switched into IgG cells. (4) Virgin, immunocompetent, B-ICC were primarily stimulated in TC with a small dose of antigen (10(5) SRBC); after 7 d of cultivation the cells were transferred into isologous recipients, SCID mice and into TC. In all cases, the secondary response of IgM was determined, 10 times higher than in the primary controls.