A study revealed that severe COVID-19 patients develop detectable T-cell mediated responses about 3 months after the onset of symptoms and the levels of IgG-specific anti-SARS-CoV-2 antibodies decline over time. The current study was designed to evaluate the specificity and durability of anti- SARS-CoV-2 immune responses in 58 COVID-19 recovered patients who had been hospitalized because of severe COVID-19-related complications.
The patients enrolled in the study had a severe form of COVID-19 with bilateral pneumonia. About 60% of all patients had comorbidities. About 10% and 29% of enrolled COVID-19 recovered patients showed detectable levels of SARS-CoV-2 spike/membrane protein-reactive CD8+ and CD4+ T-cells, respectively, on an average 84 days after the onset of symptoms. The serum samples obtained from 35 patients were analyzed for IgG-specific antibodies developed against the RBD of the viral spike protein. Of these patients, about 60% exhibited detectable levels of SARS-CoV-2-specific antibodies on an average 118 days after the onset of symptoms.
However, the levels of SARS-CoV-2-specific antibodies were found to decline over time in all COVID-19 recovered patients. The T cell responses become undetectable after 130 days of COVID-19 diagnosis. Interestingly, the presence of comorbidities is found to influence the T cell response but not the antibody response; whereas, disease severity is found to influence the antibody response but not the T cell response. The antibody response showed a declining trend over time.
Ref link: https://www.medrxiv.org/content/10.1101/2021.01.05.20249027v1