Protein microarray-based profiling of salivary IgA antibodies against human proteins in COVID-19 patients with depressive symptoms

To understand the pathophysiology and etiology of COVID-19 patients with depressive symptoms, we investigated the presence of autoantibodies associated with neurological sequelae using salivary IgA antibody profiling in COVID-19 patients with depressive symptoms. We used a human protein microarray system to comprehensively measure IgA antibodies against human proteins in the saliva of three groups of participants: those who developed moderate or severe depressive symptoms 2–14 months after SARS-CoV-2 infection (the ‘COVID-19 group’), those with no infection history who showed no depressive symptoms or only mild depressive symptoms (the ‘healthy control group’), and those with no infection history who were diagnosed with depression. As a result, 65 types of IgA antibodies recognizing human proteins were identified, all of which were present only in the COVID-19 group and not in the healthy control group. Several antigens recognized by these antibodies are associated with depressive symptoms. These findings suggest that distinctive salivary IgA antibody profiles may be associated with depressive symptoms following SARS-CoV-2 infection and could serve as candidate biomarkers for further investigation.