Memory T-cell response persists for up to 8 months after SARS-CoV-2 symptom onset, according to results of a study published in the Journal of Infectious Diseases.
Investigators analyzed peripheral blood mononuclear cells (PBMCs) of patients who had laboratory-confirmed COVID-19 with severe (n=8), mild (n=9), or asymptomatic (n=7) disease. PBMCs were collected at 2, 5, and 8 months after symptom onset. The investigators then compared PBMCs from SARS-CoV-2-negative healthy controls (n=6) and controls who had been infected with Middle East respiratory syndrome coronavirus (MERS-CoV; n=7) 5 years previously with SARS-CoV-2 symptomatic patients.
The median age of patients with severe, mild, or asymptomatic SARS-CoV-2 were 63 (range, 39-76), 48 (range, 24-69), and 25 (range, 20-28) years (P =.001), respectively. The median age was 35 (range, 28-47) years for healthy controls and 60 (range, 38-64) years for the MERS-CoV cohort.
At 8 months, OX40+CD137+ SARS-CoV-2-specific CD4+ T-cells were elevated among the COVID-19 cohort, especially in those who had severe disease. The response of the Ag-specific memory CD4+ T-cells was elevated among the symptomatic COVID-19 cohort compared with controls. The OX69+CD137+ SARS-CoV-2-specific CD8+ T-cells were elevated among the COVID-19 cohort but did not differ on the basis of symptoms.
Over time, the frequency of the SARS-CoV-2-specific CD4+ and CD8+ T-cells exhibited a nonsignificant decline among the COVID-19 cohort.
At 8 months, cytokine production by CD137+ memory CD4+ T-cells was higher among the patients with mild (mean, 213±76; P =.0261) or severe disease (mean, 293±75; P =.0648) than that from the healthy control group (mean, 23±9). Production by Ag-specific memory CD4+ T-cells was significantly increased among patients with severe disease compared with patients who were asymptomatic at 2 months and declined over time.
This study was limited by its small sample size and cohort age imbalances.
The study authors concluded the frequency and function of memory T-cell persisted up to 8 months after COVID-19 symptom onset. Additional follow-up is needed to determine how long the T-cell response to SARS-CoV-2 persists.
Kang C K, Kim M, Lee S, et al. Longitudinal Analysis of Human Memory T-Cell Response according to the Severity of Illness up to 8 Months after SARS-CoV-2 Infection. J Infect Dis. 2021;jiab159. doi:10.1093/infdis/jiab159