Serological responders are able to develop positive cellular
reactivity towards SARS-CoV-2 spike molecule
Serological non-responders with IgG concentrations below the detection
limit of the ELISA system (NR) were analyzed separately (Table 2). No
significant difference was found between NR and serological responders
regarding age and sex distribution or the number of asymptomatic or
symptomatic infections.
In serological responders, 1 of 4 (25.0%) of PCR- individuals, in 8 of
33 (24.2%) of PCR+ and in 1 of 6 (16.7%) NT had SFU <20
(Figure 3A, C). In serological responders, 3 (75.0%) of PCR-, 25
(75.8%) of PCR+ and 5 (83.3%) of NT developed positive SFU, whereas in
the NR group positive SFU were found in 3 of 4 (75.0%) of PCR-, in 7 of
18 (38.9%) of PCR+ and in 6 of 23 (26.1%) of NT.
In serological responders, the SI was negative in 1 (25.0%) of PCR-, in
7 (21.2%) of PCR+ and in 1 (16.7%) NT (Figure 3B). A positive SI was
developed in 3 (75.0%) of PCR-, in 26 (78.8%) of PCR+ and in 5
(83.3%) of NT. In the NR group, 1 of 4 (25.0%) of PCR- (not
significant compared to serological responders), 6 of 18 (33.3%) of
PCR+ (p<0.001) and 6 of 23 (26.1%) of NT developed positive
SI (p<0.001).
Significantly higher SI were found in PCR+ responders compared to PCR+
NR, as well as in NT responders compared to NT NR (Figure 3A, B). No
correlation could be found between IgG concentrations and cellular
reactivity. No correlation was seen between age and parameters of
humoral or cellular immune responses.