Persistent immune and clotting dysfunction detected in saliva and blood plasma after COVID-19

A growing number of studies indicate that coronavirus disease 2019 (COVID-19) is associated with inflammatory sequelae, but molecular signatures governing the normal versus pathologic convalescence process have not been well-delineated. Here, we characterized global immune and proteome responses in matched plasma and saliva samples obtained from COVID-19 patients collected between 20 and 90 days after initial clinical symptoms resolved. Convalescent subjects showed robust total IgA and IgG responses and positive antibody correlations in saliva and plasma samples. Shotgun proteomics revealed persistent inflammatory patterns in convalescent samples including dysfunction of salivary innate immune cells, such as neutrophil markers (e.g., myeloperoxidase), and clotting factors in plasma (e.g., fibrinogen), with positive correlations to acute COVID-19 disease severity. Saliva samples were characterized by higher concentrations of IgA, and proteomics showed altered myeloid-derived pathways that correlated positively with SARSCoV-2 IgA levels. Beyond plasma, our study positions saliva as a viable fluid to monitor normal and aberrant immune responses including vascular, inflammatory, and coagulation-related sequelae.

Automated summary

An increasing number of studies have shown that COVID-19 is associated with inflammatory sequelae, and this study characterized the immune and proteome responses in plasma and saliva samples from convalescent COVID-19 patients. The results showed robust antibody responses in both saliva and plasma samples, and persistent inflammatory patterns were observed in convalescent samples. This study also suggests that saliva could be a viable fluid for monitoring immune responses and related sequelae.