Virus World

Highly efficacious vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed. However, the emergence of viral variants that are more infectious than the earlier SARS-CoV-2 strains is concerning. Several of these viral variants have the potential to partially escape neutralizing antibody responses warranting continued immune-monitoring. Here, we tested a number of currently circulating viral variants of concern/interest, including B.1.526 (Iota), B.1.1.7+E484K (Alpha), B.1.351 (Beta), B.1.617.2 (Delta) and C.37 (Lambda) in neutralization assays using a panel of post-mRNA vaccination sera. The assays were performed with authentic SARS-CoV-2 clinical isolates in an assay that mimics physiological conditions.

We found only small decreases in neutralization against B.1.526 and an intermediate phenotype for B.617.2. The reduction was stronger against a sub-variant of C.37, followed by B.1.351 and B.1.1.7+E484K. C.37 is currently circulating in parts of Latin America and was detected in Germany, the US and Israel. Of note, reduction in a binding assay that also included P.1, B.1.617.1 (Kappa) and A.23.1 was negligible. Taken together, these findings suggest that mRNA SARS-CoV-2 vaccines may remain effective against these viral variants of concern/interest and that spike binding antibody tests likely retain specificity in the face of evolving SARS-CoV-2 diversity.

Preprint Available in medRxiV (July 23, 2021):

https://doi.org/10.1101/2021.07.21.21260961 

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. Answering those questions is crucial to managing the pandemic and forecasting its course. But the answers won’t come from the RNA-based diagnostic tests now being given by the tens of thousands. They look for the presence of viral genes in a nose or throat swab, a sign of an active infection. But scientists also need to test a person’s blood for antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 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.

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. 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. Scientists hope that will soon change as more tests become available. A new recipe could offer labs an alternative to waiting for or buying commercial tests. 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. 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. 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.

To create the test, the researchers began by designing a slightly altered version of the “spike” protein on SARS-CoV-2’s outer coat. (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. 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. They then used cell lines to produce large quantities of the altered spike proteins and RBDs....

Preprint Published in medRxiv (March 18, 2020):

https://doi.org/10.1101/2020.03.17.20037713

SARS-CoV-2 has caused a global pandemic with millions infected and numerous fatalities. Questions regarding the robustness, functionality and longevity of the antibody response to the virus remain unanswered. Here we report that the vast majority of infected individuals with mild-to-moderate COVID-19 experience robust IgG antibody responses against the viral spike protein, based on a dataset of 19,860 individuals screened at Mount Sinai Health System in New York City.

We also show that titers are stable for at least a period approximating three months, and that anti-spike binding titers significantly correlate with neutralization of authentic SARS-CoV-2. Our data suggests that more than 90% of seroconverters make detectible neutralizing antibody responses and that these titers are stable for at least the near-term future...

Preprint available at medRxiv (July 17, 2020):

 https://doi.org/10.1101/2020.07.14.20151126