Volunteers
Peripheral venous blood was collected from 88 volunteers enrolled in
this observational cross-sectional study classified according to a
previous COVID-19 diagnosis determined by PCR test for SARS-CoV-2 or
household contact persons to PCR-tested persons which were not tested
despite exposure from a previously published cohort of the first
pandemic wave in spring 2020 by Wuhan type SARS-CoV-2 (Sonnleitner,
Prelog et al. 2021). Blood samples were obtained between July 2020 and
December 2020 6 to 9 months post infection or contacts in the area of
East Tyrol, Austria, and the city area of Wuerzburg, Bavaria, Germany.
Eight were PCR negative (PCR-), 51 were PCR positive (PCR+), and 29 were
not PCR-tested (NT) who had household contact with SARS-CoV-2 infected
PCR+ persons (Table 1). Symptomatic persons reported at least one
symptom of the infection including headache, cough, temperature
>38.5°C, fatigue or anosmia. All participants gave their
written informed consent according to the principles of the declaration
of Helsinski 2013 and ethical approval of the committee at the
University of Wuerzburg (Protocol number 20201105_01).
Peripheral mononuclear blood cells (PBMCs) were isolated by density
centrifugation (FicoLite-H, Linaris, Wertheim, Germany) according to
standardized laboratory procedures and preserved in liquid nitrogen,
while serum samples were preserved at -20°C until use.