Radiolabeled Antibody Saliva Test for Detecting SARS-CoV-2 Delivers Rapid, Accurate and High Volume Results

By LabMedica International staff writers
Posted on 28 Dec 2021

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Scientists are using radiolabeled antibodies to develop an accurate, inexpensive, portable, high volume, rapid and non-invasive saliva-based testing kit for the detection of SARS CoV-2.

International Isotopes Inc. (INIS; Idaho Falls, ID, USA) has entered into an exclusive licensing agreement with Memorial Sloan Kettering Cancer Center (MSK; Manhattan, NY, USA) for the commercialization of a radiolabled antibody test for detecting SARS CoV-2. In early 2021, INIS and MSK entered into a sponsored research agreement to further advance and develop research being conducted at MSK using radiolabeled antibodies to develop an accurate, inexpensive, portable, high volume, rapid and non-invasive saliva-based testing kit to detect SARS CoV-2.

The sponsored research effort was successful and after a series of in vitro assays to define the sensitivity, specificity, and automation of the testing kit, the testing procedure was further validated at John Hopkins University using live SARS-CoV-2 virions diluted at different plaque-forming unit (PFU) concentrations. The new testing procedure successfully detected SARS CoV-2 virions at a concentration as low as 19700 PFU/mL (corresponding to 2.04 X 108 copies/mL) and as high as 1970000 PFU/mL, confirming the efficacy of the new testing procedure. While the initial research focused on SARS-CoV-2 detection, INIS plans to support additional research and development to apply the new testing method to other viruses.

Briefly, a patient's saliva is diluted with a radiolabeled virus targeted antibody to form a solution. The solution is then placed in a centrifuge, and by using a filter, target bound antibody is size separated from unbound antibody. Detection of the radiochemical in the target bound antibody sample indicates virions. A very large number of samples could be placed into the centrifuge simultaneously, supporting efficient high-volume testing. In terms of accuracy, using an assay the radiolabeled antibody shows a normalized target binding fraction percentage of 1.73 at 2.5 nanograms (ng), confirming both the affinity of the radiolabeled antibody to bind to the Spike S1 on the virus surface and detection of Spike S1 at levels as low as 2.5 ng. The test requires a very small volume of approximately 1 ml of saliva. High volume sample analysis takes approximately 30 minutes and does not require a sterile environment or expensive equipment such that the new testing technology can be deployed to countries and locations with limited resources.

"We are pleased with the excellent results we have seen to date with this new methodology of viral detection and testing. The prospect of developing a quick, inexpensive, accurate, sensitive, non-invasive, saliva-based test for SARS CoV-2, its variants, and any future SARS type virus, is exciting," said Steve Laflin, CEO of INIS. "We are eager to begin testing on other viruses since the targeting capability and affinity of the radiolabeled antibody to bind to the Spike on the virus surface should be applicable to other viruses such as influenza or viral cancers. We are currently evaluating the cost benefit of pursuing FDA Emergency Use Authorization for COVID detection given the large number of tests currently on the market. We will keep shareholders appraised as the commercialization plan matures."