Longevity and neutralisation activity of secretory IgA following SARS-CoV-2 infection

Abstract

The mucosal barrier is a primary defence against inhaled pathogens, comprising secretory antibodies which have the potential to block viral entry and neutralise infection. There is an ongoing need for greater understanding of the mucosal immunity to SARS-CoV-2 infection. In this study, we investigated mucosal IgA through non-invasive saliva sampling of healthcare workers. A total of 551 saliva samples were collected from staff at Great Ormond Street Children’s Hospital who previously tested positive for COVID-19. Participant metadata included age, gender, ethnicity and symptoms. IgA titres were measured by ELISA against viral antigens spike protein, nucleocapsid protein, and spike receptor-binding domain. SARS-CoV-2 neutralisation was measured using a VERO E6 cell culture infection assay. We found that approximately 30% of saliva samples contained detectable IgA specific for at least one of the SARS-CoV-2 antigens. IgA levels in saliva decreased with the time post-infection, and were largely undetectable after six months. IgA titres specific to SARS-CoV-2 were lowest in participants over 60 years old. Specific saliva samples were identified which effectively neutralised SARS-CoV-2 virus infection of epithelial cells. Our results suggest secretory IgA specific to SARS-CoV-2 can be detected in saliva following infection, an accessible sample type for testing, although titres decreased over time. Some saliva samples were able to neutralise SARS-CoV-2 infectivity against cultured epithelial cells. This data could be used to assess the risk of re-infection with SARS-CoV-2, as well as accelerate efforts to develop effective mucosal vaccination with longer lasting protection.

Extracellular Vimentin is a Damage-Associated Molecular Pattern Protein Serving as an Agonist of TLR4 in Human Neutrophils

“…Moreover, reported eVim concentration in COVID-19 patient saliva can reach up to 70 µg/mL (44). These findings underline the relevance and necessity of the diverse range of eVim and CitVim doses (0.1 -20 µg/mL) employed in our study, reflecting the complex and varying nature of eVim and CitVim levels in different disease states.…”

“…Notably, during inflammation, eVim and CitVim levels at the site often surpass peripheral blood levels, as evidenced by findings of higher CitVim concentrations in lung tissue and bronchoalveolar lavage fluid of IPF patients compared to their bloodstream (14). Moreover, reported eVim concentration in COVID-19 patient saliva can reach up to 70 µg/mL (44). These findings underline the relevance and necessity of the diverse range of eVim and CitVim doses (0.1 - 20 µg/mL) employed in our study, reflecting the complex and varying nature of eVim and CitVim levels in different disease states.…”