Study takes us a step closer to a universal antibody test for COVID-19

September 10, 2020

HOUSTON - A new study released by Houston Methodist takes researchers a significant step closer to developing a uniform, universal COVID-19 antibody test. The multicenter collaboration tested alternative ways to measure COVID-19 antibody levels that is faster and easier and can inexpensively be used on a larger scale to accurately identify potential donors with the best chance of helping patients infected with the SARS-CoV-2 virus with convalescent plasma therapy.

The findings will also have applications beyond determining who the best plasma donors are. The consensus among the study authors is that, following donor identification, it will most likely next be used in practice to establish target levels of COVID-19 antibodies individuals will need to be considered candidates for vaccines and passive immune therapies.

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's 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.

In assessing the correlation between VN antibody levels and anti-RBD and anti-ECD ELISA protein titer data, the researchers found that the ELISA tests had an 80% probability or greater of comparable antibody level to VN titers at or above the FDA-recommended levels for COVID-19 convalescent plasma. These results affirm that all three types of tests could potentially serve as a quantitative target for therapeutic and prophylactic treatments.

They also found that convalescent donors maintain high levels of immunity over the course of many weeks and that frequent plasma donations did not cause a significant decrease in antibody or virus neutralization levels.

Perhaps most surprising is that they also identified 27 individuals from the surveillance cohort with high enough antibody titers across all three tests to indicate that some asymptomatic individuals may have plasma suitable for therapeutic use and may have a degree of relative immunity against SARS-CoV-2.

Ultimately, the study successfully concluded that anti-RBD or anti-ECD IgG antibody titers can serve as a surrogate for VN titers to identify suitable plasma donors and that these alternate ELISA tests may provide critical information about COVID-19 immunity.
-end-
The findings are described in a paper titled "Convalescent plasma anti-SARS-CoV-2 spike protein ectodomain and receptor binding domain IgG correlate with virus neutralization," appearing online Sept. 10 in the Journal of Clinical Investigation. Musser, M.D., Ph.D., who is chair of the Department of Pathology and Genomic Medicine at Houston Methodist, is the corresponding author on the study. Eric Salazar, M.D., Ph.D., assistant professor of pathology and genomic medicine with the Houston Methodist Research Institute, is the principal investigator who led the project to treat critically ill COVID-19 patients with convalescent plasma. Houston Methodist became the first academic medical center in the nation to transfuse plasma from recovered individuals into COVID-19 patients.

Other collaborators working with Musser and Salazar on this study were Suresh V. Kuchipudi, Paul A. Christensen, Todd N. Eagar, Xin Yi, Picheng Zhao, Zhicheng Jin, S. Wesley Long, Randall J. Olsen, Jian Chen, Brian Castillo, Christopher Leveque, Dalton M. Towers, Jason Lavinder, Jimmy D. Gollihar, Jose Cardona, Gregory C. Ippolito, Ruth H. Nissly, Ian M. Bird, Denver Greenawalt, Randall M. Rossi, Abinhay Gontu, Sreenidhi Srinivasan, Indira B. Poojary, Isabella M. Cattadori, Peter J. Hudson, Nicole Joselyn, Laura Prugar, Kathleen Huie, Andrew Herbert, David W. Bernard, John Dye and Vivek Kapur.

This study was supported by funding from the National Institutes of Health (grants AI146771-01 and AI139369-01), the Fondren Foundation, the National Institute of Allergy and Infectious Diseases (Contract Number 75N93019C00050), the Army Research Office (Cooperative Agreement W911NF-12-1-0390), Houston Methodist Hospital, Houston Methodist Infectious Diseases Research Fund, Houston Methodist Research Institute and seed funding from the Huck Institutes of the Life Sciences for the studies at Penn State, together with the Huck Distinguished Chair in Global Health award. Funding was also provided through the CARES Act with programmatic oversight from the Military Infectious Diseases Research Program.

For more information: Convalescent plasma anti-SARS-CoV-2 spike protein ectodomain and receptor binding domain IgG correlate with virus neutralization. Journal of Clinical Investigation. (online Sept. 10, 2020) E. Salazar, S.V. Kuchipudi, P.A. Christensen, T.N. Eagar, X. Yi, P. Zhao, Z. Jin, S.W. Long, R.J. Olsen, J. Chen, B. Castillo, C. Leveque, D.M. Towers, J. Lavinder, J.D. Gollihar, J. Cardona, G.C. Ippolito, R.H. Nissly, I.M. Bird, D. Greenawalt, R.M. Rossi, A. Gontu, S. Srinivasan, I.B. Poojary, I.M. Cattadori, P.J. Hudson, N. Joselyn, L. Prugar, K. Huie, A. Herbert, D.W. Bernard, J. Dye, V. Kapur and J.M. Musser. DOI: https://doi.org/10.1172/JCI141206

Houston Methodist

Related Antibodies Articles from Brightsurf:

Scientist develops new way to test for COVID-19 antibodies
New research details how a cell-free test rapidly detects COVID-19 neutralizing antibodies and could aid in vaccine testing and drug discovery efforts.

Mussels connect antibodies to treat cancer
POSTECH research team develops innovative local anticancer immunotherapy technology using mussel protein.

For an effective COVID vaccine, look beyond antibodies to T-cells
Most vaccine developers are aiming solely for a robust antibody response against the SARS-CoV-2 virus, despite evidence that antibodies are not the body's primary protective response to infection by coronaviruses, says Marc Hellerstein of UC Berkeley.

Children can have COVID-19 antibodies and virus in their system simultaneously
With many questions remaining around how children spread COVID-19, Children's National Hospital researchers set out to improve the understanding of how long it takes pediatric patients with the virus to clear it from their systems, and at what point they start to make antibodies that work against the coronavirus.

The behavior of therapeutic antibodies in immunotherapy
Since the late 1990s, immunotherapy has been the frontline treatment against lymphomas where synthetic antibodies are used to stop the proliferation of cancerous white blood cells.

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity

Seroprevalence of antibodies to SARS-CoV-2 in 10 US sites
This study estimates how common SARS-CoV-2 antibodies are in convenience samples from 10 geographic sites in the United States.

Neutralizing antibodies in the battle against COVID-19
An important line of defense against SARS-CoV-2 is the formation of neutralizing antibodies.

Three new studies identify neutralizing antibodies against SARS-CoV-2
A trio of papers describes several newly discovered human antibodies that target the SARS-CoV-2 virus, isolated from survivors of SARS-CoV-2 and SARS-CoV infection.

More effective human antibodies possible with chicken cells
Antibodies for potential use as medicines can be made rapidly in chicken cells grown in laboratories.

Read More: Antibodies News and Antibodies Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.