Mucosal antibody and cytokine responses to SARS-CoV-2 variants of concerns

Background: A thorough understanding of the host immune response, especially at the mucosal level, is essential for effectively controlling SARS-CoV-2. However, the understanding of mucosal immune responses to COVID-19 is limited. Enhanced understanding of mucosal immune responses to SARS-CoV-2 infection is needed for the development of new-generation mucosal COVID-19 vaccines. Methods: Various antibody and cytokine responses in nasopharyngeal specimens of 30 healthy individuals, 30 Delta (B.1.617.2) COVID-19 patients, and 30 Omicron BA.1 (B.1.1.529) COVID-19 patients were investigated. Results: There was no significant difference in mucosal antibody responses between healthy vaccinated participants and infection groups except significant higher IgG level in the healthy vaccinated group compared to the Omicron BA.1 infected group. However, the mucosal cytokine patterns were different between the infected and healthy groups. Patients infected with the Delta variant exhibited a higher trend in cytokine responses, especially from interleukin (IL)-6, IL-8, and tumor necrosis factor alpha, when compared to those infected with the Omicron BA.1 variant. Conclusions: The Delta variant of SARS-CoV-2 triggered significantly stronger mucosal cytokine responses when compared to both the Omicron BA.1 variant and healthy groups. More studies regarding the mucosal immunity of COVID-19 are required to enhance further understanding of the pathophysiology of the disease and vaccine development.