PT - JOURNAL ARTICLE AU - van Rooyen, Cathrine AU - Brauer, Marieke AU - Swanepoel, Petri AU - van den Berg, Sylvia AU - van der Merwe, Cassandre AU - van der Merwe, Marischa AU - Green, Robin AU - Becker, Piet TI - Comparison of T-cell immune responses to SARS-CoV-2 spike (S) and nucleocapsid (N) protein using an in-house flow-cytometric assay in laboratory employees with and without previously confirmed COVID-19 in South Africa: nationwide cross-sectional study AID - 10.1136/jclinpath-2021-207556 DP - 2023 Jun 01 TA - Journal of Clinical Pathology PG - 384--390 VI - 76 IP - 6 4099 - http://jcp.bmj.com/content/76/6/384.short 4100 - http://jcp.bmj.com/content/76/6/384.full SO - J Clin Pathol2023 Jun 01; 76 AB - Aims To compare specific T-cell responses between laboratory employees in South Africa with and without previously diagnosed SARS-CoV-2 infection.Methods Employees at a private pathology laboratory in South Africa were invited to participate in a nationwide cross-sectional study. T-cell proliferation to SARS-CoV-2 nucleocapsid (N)-proteins and spike (S)-proteins was measured by flow cytometry and compared between participants.Results Based on classification according to SARS-CoV-2 reverse transcription (RT)-PCR results, a total of 81% (42/52) of positive participants demonstrated T-cell proliferation to SARS-CoV-2 N-proteins or S-proteins (95% CI 67.5% to 90.4%), while 62% (68/110) of negative participants also had detectable T-cell responses to SARS-CoV-2 proteins (95% CI 52.1% to 70.9%). When classified according to SARS-CoV-2 serology results, 92.6% (50/54) of positive participants demonstrated T-cell proliferation to SARS-CoV-2 proteins (95% CI 82.1 to 97,9 %), while 56% (60/108) of negative participants demonstrated T-cell proliferation (95% CI 45.7% to 65.1%). The magnitude of the T-cell responses as determined by a stimulation index, was significantly higher in the group previously infected by SARS-CoV-2 than in the negative group. A statistically significant difference in T-cell proliferation was noted between high risk and low risk groups for exposure to SARS-CoV-2 within the negative group, but no significant difference in magnitude of the response.Conclusions A significant proportion of South African laboratory employees who were not previously diagnosed with COVID-19 demonstrated T-cell reactivity to SARS-CoV-2 N-proteins and S-proteins. The pre-existing T-cell proliferation responses may be attributable to cross-reactive immune responses to other human coronaviruses, or possibly asymptomatic infection.All data relevant to the study are included in the article or uploaded as online supplemental information. Deidentified participant data available as online supplemental information.