COVID research updates: T cells might provide rescue from rampant COVID variants

Nature

Nature wades through the literature on the coronavirus — and summarizes key papers as they appear”

5 March – Emerging coronavirus variants do not seem to elude important immune-system players called T cells, laboratory studies suggest.

Most of the volunteers’ T cells recognized all four variants, thanks to viral protein snippets that were unaffected by the variants’ mutations. The results suggest that T cells could target these variants.

Some recently discovered SARS-CoV-2 variants can partially evade antibodies generated in response to vaccination and previous infection,raising fears that vaccines will be less effective against the variants than against the original strain of the virus. Alessandro Sette and Alba Grifoni at the La Jolla Institute for Immunology in California and their colleagues looked at whether these variants’ mutations might also help them to evade T cells — a component of the immune system that is particularly important for reducing the severity of infectious diseases (A. Tarke et al. Preprint at bioRxiv https://doi.org/gh6tkp; 2021).

The team collected T cells from volunteers who had either recovered from infection with the ancestral SARS-CoV-2 strain or had received an mRNA coronavirus vaccine. The researchers then tested the cells’ ability to recognize protein snippets from four emerging variants, including the B.1.351 variant first identified in South Africa.

Most of the volunteers’ T cells recognized all four variants, thanks to viral protein snippets that were unaffected by the variants’ mutations. The results suggest that T cells could target these variants.

2 March — Just one dose of vaccine protects against silent COVID infection

Asymptomatic coronavirus infections were four times less frequent in health-care workers who had received a single dose of a prominent COVID-19 vaccine than in their unvaccinated counterparts.

Michael Weekes at the University of Cambridge, UK, and his colleagues analysed the results of almost 8,900 SARS-CoV-2 tests taken by UK health-care workers without symptoms of COVID-19 (M. Weekes et al. Preprint at Authorea https://doi.org/fxkd; 2021). Study participants who were tested at least 12 days after receiving one dose of the vaccine developed by Pfizer of New York City and BioNTech of Mainz, Germany, had an infection rate of only 0.2%. By contrast, unvaccinated participants had an infection rate of 0.8%.

The team also noted that participants who showed evidence of SARS-CoV-2 infection well after vaccination tended to have lower levels of the coronavirus in their bodies than did those who were infected and unvaccinated, although the result did not reach statistical significance. If corroborated, this would suggest that the few vaccinated health-care workers who do have an asymptomatic infection are less likely to infect other people than are unvaccinated workers who become infected.

The findings have not yet been peer reviewed.

23 February — Viral variant is less susceptible to a COVID vaccine’s effects

Coronaviruses engineered to contain mutations from a worrisome variant partially blunt the immune protection offered by a prominent vaccine.

In recent months, studies have raised the possibility that the potent antibodies summoned by vaccines could be less effective against emerging SARS-CoV-2 variants than against older versions of the virus. Most of this work stems from experiments not on SARS-CoV-2, but on viruses such as HIV that have been modified to contain SARS-CoV-2’s signature spike protein.

Pei-Yong Shi at the University of Texas Medical Branch in Galveston and his colleagues engineered several variants of SARS-CoV-2, including one containing the same spike-protein mutations as a troubling variant called B.1.351 (also known as 501Y.V2) that was first identified in South Africa (Y. Liu et al. N. Engl. J. Med. https://doi.org/fwsc; 2021).

The team pitted the B.1.351-like virus against blood serum from people who had received two doses of the vaccine made by Pfizer and BioNTech in Mainz, Germany. Antibodies elicited by the vaccine neutralized the virus only one-third as effectively as they did a strain lacking those mutations.

The researchers traced most of the virus’s evasive ability to a trio of mutations in the portion of the spike protein that SARS-CoV-2 uses to adhere to host cells. However, it is not clear whether these changes make the vaccine less effective at preventing COVID-19.

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