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

5 March — T cells might provide rescue from rampant COVID variants

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

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 

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.

A worker wearing a protective suit and carrying an umbrella walks past the graves of COVID-19 victims, Brazil
The graves of people killed by COVID-19 surround a worker at a cemetery in Manaus, Brazil.Credit: Michael Dantas/AFP/Getty

4 March — A new viral variant hits a COVID-ravaged city

A coronavirus variant detected in the Brazilian city of Manaus might be driving reinfections and the city’s second wave of COVID-19.

During the first wave of the pandemic, Manaus experienced one of the world’s highest infection rates: an estimated two-thirds of residents were infected by October 2020, leading some researchers to predict that population-wide immunity might cause new infections to tail off. But in January 2021, researchers identified a novel coronavirus variant, called P.1, during a period of rising hospitalizations in the city and linked the variant to a few cases of reinfection.

To characterize the variant further, Nuno Faria, at Imperial College London, and his colleagues analysed viral genomes collected from 184 human samples in Manaus between November and December (N. R. Faria et al. Preprint at 2021). The variant harbours 17 mutations that alter SARS-CoV-2 proteins. Among the alterations are changes in the SARS-CoV-2 spike protein that have been previously linked to increased transmission and immune evasion.

By modelling the spread of P.1 and its possible effects during Manaus’ second wave, the researchers estimated that the variant was 1.4–2.2 times more transmissible than other lineages and that it was able to evade some of the immunity conferred by previous infections. The findings have not yet been peer reviewed.

Students work on their laptop computers
Students attend class at St. Joseph Catholic School in La Puente, California.Credit: Frederic J. Brown/AFP/Getty

3 March — Kids in the classroom could mean COVID at home

Living with children who are attending school in person raises an adult’s risk of developing COVID-19 symptoms, but only if schools don’t implement appropriate control measures, according to a large online survey in the United States.

Justin Lessler at Johns Hopkins University in Baltimore, Maryland, and his colleagues analysed responses to a Facebook survey completed in late 2020 and early 2021 by more than half a million people living with school-aged children; half of these respondents had children attending school in person, either full-time or part-time (J. Lessler et al. Preprint at medRxiv; https://doi.org/fxv6; 2021).

The researchers found that adults living with kids — especially high-school students — who went into school were more likely to report COVID-19 symptoms or test positive for SARS-CoV-2. But the researchers also found that schools could eliminate that risk entirely by implementing at least seven mitigation measures from a list that included requiring students and teachers to wear masks, preventing parents from entering schools and increasing the spacing between desks. The findings have not yet been peer reviewed.

A close up of syringe containing the Pfizer-BioNTech vaccine as it is administered to a man
A dose of the Pfizer-BioNTech vaccine is administered in Cwmbran, Wales.Credit: Matthew Horwood/Getty

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.