![]() ![]() ![]() It showed positive results only for the COVID-19 patients and not for any of those controls. Initial tests of four blood samples from three confirmed COVID-19 patients and from 59 serum samples banked before the start of the outbreak showed that the test worked, as antibodies to SARS-CoV-2 bound to the test's proteins. Those labmade molecules provided the basis for an ELISA test, in which antibodies in a sample of blood or plasma trigger a color change when they recognize a target protein-here an RBD or the spike protein. They then used cell lines to produce large quantities of the altered spike proteins and RBDs. They also isolated the short piece of the spike protein called the receptor-binding domain (RBD), which the virus uses to attach to cells it tries to invade. (The alterations made the protein more stable for use in the lab.) That protein helps the virus enter cells, and it is a key target in the immune reaction against the virus, as the body churns out antibodies that recognize the protein and tag the virus for destruction. To create the test, the researchers began by designing a slightly altered version of the "spike" protein on SARS-CoV-2's outer coat. Together with increased availability of commercial tests, that means some important answers about immunity to COVID-19, the disease caused by the novel coronavirus, may be available soon, he says. It's one of the first such detailed protocols to be widely distributed, and the procedure is simple enough, he says, that other labs could easily scale it up "to screen a few thousand people a day," and quickly amass more data on the accuracy and specificity of the test. Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai, and his colleagues posted a preprint yesterday describing a SARS-CoV-2 antibody test they have developed, and directions for replicating it. Scientists hope that will soon change as more tests become available.Ī new recipe could offer labs an alternative to waiting for or buying commercial tests. But so far, large-scale data from such tests-for example showing what fraction of people in the hard-hit city of Wuhan, China, might now be immune-is still lacking or at least not public. Labs and companies around the world have raced to develop antibody tests, and a few have been used in small studies and received commercial approval, including several from China. Such tests can detect active infections, too, but more importantly, they can tell whether a person has been infected in the past because the body retains antibodies against pathogens it has already overcome. ![]() But scientists also need to test a person's blood for antibodies to the new virus, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). They look for the presence of viral genes in a nose or throat swab, a sign of an active infection. But the answers won't come from the RNA-based diagnostic tests now being given by the tens of thousands. How many COVID-19 cases have gone undetected? And are those who had mild cases of the disease-perhaps so mild they dismissed it as a cold or allergies-immune to new infections? If so, they could slow the spread of the burgeoning pandemic.Īnswering those questions is crucial to managing the pandemic and forecasting its course. ![]()
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