%0 Journal Article
%T Salivary IgA and vimentin differentiate in vitro SARS-CoV-2 infection: A study of 290 convalescent COVID-19 patients.
%A Ellis S
%A Way R
%A Nel M
%A Burleigh A
%A Doykov I
%A Kembou-Ringert J
%A Woodall M
%A Masonou T
%A Case KM
%A Ortez AT
%A McHugh TD
%A Casal A
%A McCoy LE
%A Murdan S
%A Hynds RE
%A Gilmour KC
%A Grandjean L
%A Cortina-Borja M
%A Heywood WE
%A Mills K
%A Smith CM
%J Mucosal Immunol
%V 17
%N 1
%D 2024 Feb 24
%M 38007005
%F 8.701
%R 10.1016/j.mucimm.2023.11.007
%X SARS-CoV-2 initially infects cells in the nasopharynx and oral cavity. The immune system at these mucosal sites plays a crucial role in minimizing viral transmission and infection. To develop new strategies for preventing SARS-CoV-2 infection, this study aimed to identify proteins that protect against viral infection in saliva. We collected 551 saliva samples from 290 healthcare workers who had tested positive for COVID-19, before vaccination, between June and December 2020. The samples were categorized based on their ability to block or enhance infection using in vitro assays. Mass spectrometry and enzyme-linked immunosorbent assay experiments were used to identify and measure the abundance of proteins that specifically bind to SARS-CoV-2 antigens. Immunoglobulin (Ig)A specific to SARS-CoV-2 antigens was detectable in over 83% of the convalescent saliva samples. We found that concentrations of anti-receptor-binding domain IgA >500 pg/µg total protein in saliva correlate with reduced viral infectivity in vitro. However, there is a dissociation between the salivary IgA response to SARS-CoV-2, and systemic IgG titers in convalescent COVID-19 patients. Then, using an innovative technique known as spike-baited mass spectrometry, we identified novel spike-binding proteins in saliva, most notably vimentin, which correlated with increased viral infectivity in vitro and could serve as a therapeutic target against COVID-19.