Additional uses coming later that are likely to have the biggest societal impact, the researchers say, are to assess relative immunity in those previously infected by the SARS-CoV-2 virus and identifying asymptomatic individuals with high levels of neutralizing antibodies against SARS-CoV-2.
It was also found that donors who experienced shortness of breath (or dyspnea) while infected with COVID-19 and those who were hospitalized or had severe disease were more likely to have a robust immune response and, thus, had higher levels of neutralizing antibodies in all the tests. In the absence of available testing, identifying such donor characteristics may be used as a contingency plan to determine which patients have developed higher antibody levels and inform efforts to recruit plasma donors for therapeutic purposes.
In collaboration with Penn State, University of Texas at Austin and U.S. Army Medical Research Institute of Infectious Diseases, study authors James M. Musser, M.D., Ph.D., and Eric Salazar, M.D., Ph.D., physician scientists at Houston Methodist, sought to find alternatives to measuring virus neutralization (VN) titers, which is the gold standard of COVID-19 antibody testing, as VN antibodies in the blood correlate with immunity. This kind of antibody testing, however, is not widely available, because it is technically complex, requires days to set up, run and interpret, and needs to be performed in a biosafety level 3 laboratory. This leads to most donor plasma virus antibody levels remaining unknown prior to transfusions, so an easier, more readily available method is needed to identify more suitable convalescent plasma donors.
The research team, therefore, looked to another type of test, called ELISA assays, which can be implemented and performed with relative ease in a high-throughput fashion and are widely available and extensively used in clinical labs across the world. The ELISA tests, or enzyme-linked immunosorbent assays, look at whether antibodies against the SARS-CoV-2 proteins are present and produce a quantitative measure of those antibodies. The UT Austin research team developed the ELISA antibody test for SARS-CoV-2 and provided the viral antigens for this study.
Specifically, scientists looked at the relationship of anti-spike ectodomain (ECD) and anti-receptor binding domain (RBD) IgG bloodstream antibody titers. The spike ECD and RBD proteins are physiological parts of the much-talked-about spike protein made by SARS-CoV-2 and critical to how the virus finds its way into the body, spreads and causes COVID-19 disease, so they are prime targets for antibody testing and vaccine development. The blood samples for the study were identified during an institutional surveillance program involving 2,814 Houston Methodist employees.
The goal of the study was to test the hypothesis that anti-ECD and anti-RBD IgG bloodstream antibody titers are correlated with VN titer, making these more accessible, easier-to-perform ELISA tests a surrogate marker to identify plasma donors with titers above the recommended U.S. Food and Drug Administration threshold for convalescent plasma donation.
MEDICA-tradefair.com; Source: Houston Methodist