Evaluation of IgM and IgG in COVID-19 Recovered Patients in Iraq

Severe acute respiratory syndrome coronavirus-2 is a major threat to health care worldwide with high morbidity and mortality. Therefore, understanding the role of immune mechanisms and humoral response is vital in this disease. The present study aimed to investigate the relationship between Immunoglobulins (IgM, IgG) in COVID-19 recovered patients with age, gender, and severity of the disease. The duration of effect of antibody levels and protection against re-infection has also been evaluated in the patients. Three groups participated in this study; group 1: 0-14 days after recovery, group 2: 2 months after recovery, group 3: 3 months after recovery, group 4: 4-6 months after recovery, group 5: more than 6 months. The nasopharyngeal swab was used to confirm recovery by Real-Time Polymerase Chain Reaction (RT-PCR) technique. IgM and IgG antibody levels were evaluated using Enzyme-Linked Immuno Fluorescent Assay (ELIFA) technique. The results indicated that the IgM levels increased for one month during the seven days after infection and then decreased in most patients (P≤0.05). The mean of IgG in group 1 increased compared to those of other studied groups. A significant decrease was observed in group 2 compared to group 1, as well as in group 3 compared to groups 1, and 2. Also, a significant difference existed between group 4 compared to groups 1, 2, and 3. Finally, significant differences were noticed between group 5 compared to groups 1, 2, 3, and 4 (P≤0.05). No significant differences were observed in antibodies level between male, and female COVID-19 recovered patients in groups 1, 2, 3, 4, and 5 (P≤0.05). Finally, highly significant differences in IgG levels between mild, moderate, and severe subgroups in groups 1 and 2. The present study demonstrated that IgM and IgG against SARS-CoV-2 appeared in the early stages of the disease and decreased after 1 month and failed to maintain high levels during the 6-month observation.