Potential role of aberrant mucosal immune response to SARS-CoV-2 in pathogenesis of IgA Nephropathy

Aberrant mucosal immunity has been suggested to play a pivotal role in pathogenesis of IgA nephropathy (IgAN), the most common form of glomerulonephritis worldwide. The outbreak of severe acute respiratory syndrome coronavirus (SARS-CoV-2), the causal pathogen of coronavirus disease 2019 (COVID-19), has become a global concern. However, whether the mucosal immune response caused by SARS-CoV-2 influences the clinical manifestations of IgAN patients remains unknown. Here we tracked the SARS-CoV-2 anti-receptor binding domain (RBD) antibody levels in a cohort of 88 COVID-19 patients. We found that 52.3% of the COVID-19 patients produced more SARS-CoV-2 anti-RBD IgA than IgG or IgM, and the levels of the IgA were stable during 4-41 days of infection. Among these IgA-dominated COVID-19 patients, we found a severe COVID-19 patient concurrent with IgAN. The renal function of the patient declined presenting with increased serum creatinine during the infection and till 7 months post infection. This patient predominantly produced anti-RBD IgA as well as total IgA in the serum compared to that of healthy controls. The analysis of the IgA-coated microbiota as well as proinflammatory cytokine IL-18, which was mainly produced in the intestine, reveals intestinal inflammation, although no obvious gastrointestinal symptom was reported. The mucosal immune responses in the lung are not evaluated due to the lack of samples from respiratory tract. Collectively, our work highlights the potential adverse effect of the mucosal immune response towards SARS-CoV-2, and additional care should be taken for COVID-19 patients with chronic diseases like IgAN.