Objective: The peculiarity of immune response during and after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is of special interest as this may contribute to the development of an efficient diagnostic approach. Data characterizing humoral or T-cell mediated immune responses after SARS-CoV-2 infection are available, although the same sample determination of both these biomarkers of immune response has not been performed yet.

Materials and Methods: We have determined the biomarkers related to humoral and T-cell-mediated immune response after SARS-CoV-2 infection by using the enzyme-linked immunosorbent assay (ELISA) method in blood samples of 49 patients who recovered from COVID-19 (35 females and 14 males; age range: 17-55 years) after paucisymptomatic disease that did not require hospitalization nor corticosteroid therapy. In all participants, SARS-CoV-2 infection was documented through clinical symptoms and polymerase chain reaction (PCR) test for SARS-CoV-2 performed through a nasopharyngeal swab.

Results: It has been revealed that: a) 28 (57.1%) participants were positive for biomarker of humoral immune response against SARS-CoV-2, and b) negative (16 cases; 32.7%) or equivocal (5 cases; 10.2%) for biomarker of humoral immune response against SARS-CoV-2. Patients with a negative status of immunoglobulin G (IgG) antibodies directed against SARS-CoV-2 nucleocapsid protein exhibited an increased expression of specific biomarkers of T-cell-mediated immune response (Ki67 and IL-2).

Conclusions: SARS-CoV-2 infection can induce both a humoral and a T-cell-mediated immune response. Yet, the regulatory mechanisms of this process should be further investigated. Future and larger case-control studies with additional biomarkers of SARS-CoV-2-specific immune response are warranted to confirm our preliminary findings.