Current #antibody tests for #coronavirus are conducted using samples of blood. Relatively little research has been done into the presence of any antibody responses in #saliva. These tests are crucial to determining whether we have had the virus already and even more importantly, if and for how long we may be protected from contracting it again. Researchers from the University of Toronto have just had their study published in Science Immunology (October 2020) which compared the antibody levels from both blood and saliva samples from #COVID-19 patients for three months after initial symptoms.
A disadvantage of using saliva as a #biofluid is its relatively low concentration of antibodies, so it was imperative that the study optimised a sensitive level of detection. To assess if this had accurately been achieved, they needed to view a correlation between the antibody levels to the #SARS-CoV-2 spike and the receptor binding domain (#RBD) in both the saliva and serum data. A significant positive correlation was found in their results. The study comprised of data from 402 University of Toronto COVID-19 patients whose antibody responses were recorded from day 3 to day 115 after the onset of symptoms. These were then compared with responses from 339 pre-pandemic control patients. They found that levels of immunoglobin A and M (#IgA and #IgM) rapidly decayed but that immunoglobin G (#IgG) remained elevated and relatively stable for up to 115 days after first symptoms, representing the longest time interval measured. With saliva samples clearly easier to collect than blood this study indicates a significant breakthrough for future testing.