Objectives Cytokine dysregulation has been proposed as one of the main culprits for severe COVID-19 and poor prognosis. We examined the parallel presence of lymphopoietic, proinflammatory, Th1, Th2, regulatory cytokines, and chemokines in the serum of 47 patients with mild, moderate, and severe COVID-19 and evaluated the association between cytokine concentrations and disease severity. Methods A multiplex quantitative cytokine analysis ProcartaPlex™ immunoassay was applied, using the LuminexTM 200X detection system (Invitrogen). Results The concentrations of twelve cytokines: IL-18, IFN-gamma, TNF-alpha; IL-21; IL-1alpha, IL-1beta, IL-6, IL-22; IL-10, IL-1RA; IL-7 and IFN-alpha were consistently elevated in the studied serum samples. All examined chemokines—Eotaxin, GRO-alpha, IL-8, IP-10, MCP-1, MIP-1alpha, MIP-1beta, SDF-1alpha, and RANTES, were detectable in all studied groups, confirming their importance in mediating the adaptive immune response regardless of disease severity. The serum concentrations of six mediators: IL-1beta, IL-6, IL-18, IL-10, IL-8, and IP-10, showed statistically significant differences among the groups with different disease severity. IL-6, IL-1beta, and IL-10 were more significantly elevated in severe cases while milder symptoms were associated with lower levels of IL-8 and IP-10. Conclusion Overall, the studied chemokines demonstrated an associated production in acute COVID-19 infection. A strong correlation was observed between the Th1 mediators IL-18 and IL-10 and the proinflammatory IL-6 in the severe COVID-19 group. Our results indicated that severe COVID-19 was characterized by a dysregulated cytokine pattern whereby the Th1 immune response is outweighed by the immunoregulatory response, while inhibitory signals cannot balance the hyperinflammatory response.

Background: In the response to the current COVID-19 pandemic caused by the novel SARS-CoV-2, one of the groups at higher risk were healthcare workers (HCWs), especially those who worked on the frontline. The presence of SARS-CoV-2 specific IgG antibodies (seropositivity) in certain populations provides better understanding of virus circulation and transmission. Our aim was to study the seroprevalence rates of anti-SARS-CoV-2 antibodies among a group of healthcare workers before and after vaccination/COVID-19 infection. Material and Methods: We determined the presence of SARS-CoV-2 specific IgG and IgA antibodies against S-antigen of by ELISA method. In this study, we enrolled 74 healthcare workers and three months later, 48 of the participants were followed up. At the baseline, none of the participants was vaccinated or had suffered COVID-19.  Results: SARS-Cov-2 specific IgG antibodies were found in 32.4% of the participants. Higher prevalence of class IgA antibodies – 44.6% was detected. All samples that were IgG seropositive were also positive or borderline for IgA antibodies. Overall, virus-specific antibodies were not detected in 40.6% of HCWs in the group. During the follow-up (after vaccination and/or COVID-19 infection) high rates of both IgG and IgA seroprevalence were established. SARS-C0V-2 specific IgG antibodies were detected in 95.8% of the participants. Statistically significant difference was found in the levels of IgG and IgA antibodies both before and after vaccination, p<0.0001. Conclusions: Based on detection of anti-SARS-CoV-2 IgG antibodies, seroprevalence of 32.4% was established in an unvaccinated group of HCWs. Our survey demonstrated that asymptomatic COVID-19 infection may induce weaker humoral immune response, with production of IgA but not of IgG antibodies.