Amidst a nationwide shortage of antibody tests for the novel coronavirus, a test developed and validated by Einstein scientists and Montefiore clinical pathologists was submitted on May 4 to the New York State Department of Health (NYSDOH) for approval as a laboratory developed test (LDT).
By detecting antibodies in serum, the test indicates that a person has been exposed to the virus and has mounted an immune response to it. “Thanks to Montefiore’s convalescent plasma trial, we were able to obtain the de-identified [anonymous] plasma samples we needed to validate this new assay,” said Amy Fox, M.D., M.S., professor of pathology and of pediatrics at Einstein and director of the virology lab at Montefiore.
That multicenter randomized placebo-controlled trial, which began in late April at Montefiore, is evaluating whether serum from recovered patients can effectively treat patients ill with COVID-19, the disease caused by the coronavirus. Liise-anne Pirofski, M.D., professor of medicine and of microbiology & immunology and chief of infectious diseases, is directing the Montefiore portion of that trial, which will involve 150 COVID-19 patients.
Creating A Comprehensive Test
The LDT submission allows the antibody test to be used in clinical labs at Montefiore to test patients and healthcare workers, even before it receives NYSDOH approval. In principle, tests approved as LDTs are then granted emergency use authorization from the U.S. Food and Drug Administration, allowing their use anywhere in the country.
The antibody test was created in the laboratories of Einstein’s Kartik Chandran, Ph.D., and Jonathan Lai, Ph.D. Their expertise in developing monoclonal antibody therapeutics against Ebola virus and other viral pathogens enabled them to respond to Montefiore’s urgent need for a coronavirus antibody test. Dr. Chandran is professor of microbiology and immunology and the Harold and Muriel Block Faculty Scholar in Virology. Dr. Lai is professor of biochemistry.
Tests for coronavirus antibodies look specifically for those made against the coronavirus’ spike proteins, which protrude from the viral surface and enable the virus to infect human cells. “Our test detects and measures levels of two types of antibodies: IgG, the primary target of commercial antibody tests, as well as IgA—an advantage compared with antibody assays that measure just one type,” said Michael Prystowsky, M.D., Ph.D., professor and chair of pathology.
IgA antibodies form early in the course of infection, can be detected a week or two after a person becomes infected, and can persist for weeks or months. IgG antibodies typically appear a week or so later than IgA antibodies but last much longer. Assessing both types of antibodies provides a more complete picture of a person’s immunologic response to infection.
“Being able to detect those early IgA antibodies is especially helpful for a respiratory pathogen like this one, which an asymptomatic person can so easily and unknowingly transmit with a cough or even an exhalation,” said Dr. Chandran. The test has already proven its sensitivity when used on sera found negative for IgG but positive for IgA, he noted.
The test’s submission to New York State resulted from a rigorous and ultimately successful effort to validate it. During that process, members of Dr. Chandran’s team ran the test on hundreds of serum samples. Many of those samples were obtained from the sera of Montefiore patients with COVID-19 that was confirmed by nasal swab testing.
“Unfortunately, Montefiore was at the epicenter of the epicenter of the pandemic in the United States,” said Dr. Chandran. “But as a result, Montefiore was able to give us a plentiful supply of the sera we needed to validate our test.”
Montefiore also provided serum samples from before 2019—which should not have contained antibodies to the novel coronavirus. “We needed our test to detect only antibodies made against the novel coronavirus,” said Dr. Chandran. “Other coronaviruses, including several that cause the common cold, also circulate in humans, so we had to make sure that antibodies against those other coronaviruses would not produce false positive results with our test.”
Developing and deploying the antibody test required generating large amounts of high-quality coronavirus spike protein—a process spearheaded by Dr. Lai’s group with support from the laboratories of Dr. Chandran and Steven Almo, Ph.D., professor and chair of biochemistry and of physiology & biophysics, and the Wollowick Family Foundation Chair in Multiple Sclerosis and Immunology.
“The spike protein is an antigen that our test uses like bait, to fish out the antibodies from a patient’s serum,” said Dr. Lai.
In Montefiore’s Immunodiagnostics lab, James Faix, M.D., and Sean Campbell, Ph.D., translated the test into a clinical test and validated it once again: It gave very few false-negative results (i.e., it accurately detected the anti-coronavirus antibodies in serum samples from patients known to have COVID-19) as well as very few false positives. Dr. Faix is director of clinical chemistry and immunology at Montefiore, and Dr. Campbell is an instructor in the pathology department.
The final step—applying to New York State to have the test approved as an LDT—was handled by Dr. Fox and Louis Weiss, M.D., M.P.H., professor of pathology and of medicine at Einstein. The application contained information about the antibody test itself, the clinical timeline of de-identified patients whose sera it was tested against, and how well the test performed.
“The antibody test will be really useful here in the Bronx, where so many people are being affected by COVID-19,” said Dr. Chandran. “Its development was a joint effort between Einstein and Montefiore, and it is a great example of the synergy that can result when our institutions work closely together.”
Posted on: Monday, May 11, 2020