The pathogenesis of SARS‐CoV‐2 infection, causative pathogen of the known COVID‐19 pandemic is not well clarified. In this regard oxidative stress is one of the topics that need to be investigated. Therefore, the present research was performed to explore the relationship between the oxidant/antioxidant system and COVID‐19 exacerbation. Sera were collected from 120 patients with COVID‐19 infection and 60 healthy volunteers as the control group. The patient group consisted of 60 cases with mild disease and 60 severely ill patients. Serum levels of total antioxidant capacity (TAC) and nitric oxide (NO) as well as serum activities of the two main antioxidant defense enzymes, superoxide dismutase (SOD) and catalase (CAT), were measured. TAC levels were considerably lower in patients compared with healthy individuals (p < 0.05) and also between patients with mild and severe diseases (p < 0.05). A rather decreasing trend was also found in NO concentration as well as SOD and CAT activity, though, the observed differences were not statistically significant (p > 0.05). These findings suggest that COVID‐19 patients may be susceptible to depleted total antioxidant capacity. Moreover, showing such variations in blood samples of infected individuals could be considered as a predictive marker of COVID‐19 severity.

Background The present study aimed to compare serum total IgA levels between severe and mild COVID-19 patients’ groups and the control group. Methods In this cross-sectional study, 216 definite severe COVID-19 patients (as the inpatient group), 183 subjects with positive specific COVID-19 IgG with mild or no symptoms as the (outpatient group), and 203 healthy subjects with negative specific serology, as the control group were investigated. The cases’ laboratory data were collected, and thereafter, statistical tests, including independent samples t test, ANOVA test, and post hoc test, were performed using SPSS software version 22. Result The mean ± SD of IgA in all the included subjects was 2.23 ± 0.78 (g/L). According to the obtained results, there were statistically significant changes in IgA among the three study groups ( P value < 0.05). This difference was significant between both outpatient and inpatient groups ( P value < 0.05). The mean ± SD of serum IgG in all the subjects was calculated as 15.83 ± 5.73 (g/L). A strong statistically significant change was also seen in IgG among all three groups ( P value < 0.001). Of note, there was a significant negative correlation between IgG and IgA total titers of the outpatient group ( P value = 0.011* r =  − 0.188). Conclusion It was shown that the total serum IgA and IgG levels are significantly associated with the severity of COVID-19 infection. As well, we found that total serum IgA and IgG are associated with the severity of illness. Since a low level of IgA is asymptomatic and high frequent in Iran and other countries, we suggest the evaluation of serum IgA levels in high-risk people and strengthening immune system in subjects with a low level of IgA, in order to reduce the rate of death. In this regard, oral or nasal mucosal vaccines in combination with parenteral vaccination are recommended due to increasing immunity versus COVID-19 by further secretion of the IgA antibody and preventing virus transmission.

Purpose: The global pandemic of COVID-19 and high mortality rates, necessitate the development of diagnostic and prognostic tools and expansion of testing capacity. The existing approaches to identification and characterization of SARS-COV-II infection are usually based on viral genome detection or measuring COVID-19-specific antibody levels. Despite being valuable, these methods are unable to anticipate disease outcomes in patients. Given the point that the innate immune cells, particularly NK cells, ‌contribute significantly to anti-viral defense, this research aimed to determine the prognostic value of serum secretory MHC class I polypeptide–related sequence A (sMICA) levels as an important ligand for NKG2D receptor, the master regulator of NK cell development and responsiveness.Methods: Serum levels of MICA were measured by ELISA assay. Sera (n = 60) were collected from SARS-CoV-2 positive patients and disease severity was assessed by clinical criteria. The patient group consisted of 30 cases with mild disease and 30 severely ill patients examined versus 30 controls. Results: Our data revealed that serum levels of MICA were considerably higher in patients compared with controls, particularly in cases with severe complications (P<0.0001). Conclusion: Higher serum levels of MICA may be associated with respiratory failure in COVID-19 and can serve as a marker of clinical severity for patients with SARS-CoV-2 infection in particular whenever the clinical manifestations are not sufficient to make a confident prediction.