Bout of common cold may give immunity

Having had a bout of common cold may have prepared some people to better fight off the coronavirus disease (Covid-19), according to a new study by American researchers who analysed the way some immune cells react to the pathogen.

The findings are part of rapidly evolving understanding of the Sars-Cov-2 (which causes Covid-19), which has presented a near-unprecedented challenge to scientists by manifesting itself in a plethora of ways including unpredictably serious progression and unexplained recoveries.

The latest research now shows a specific type of immune cells – called helper T cells – that can recognise and act on Sars-Cov-2 existed in some people who did not have Covid-19. Analysis was drawn from bioinformatics tools comparing how immune cells in blood samples from 40 people (20 of them who had Covid-19) responded to being exposed to Sars-Cov-2. “Importantly, we detected SARS-CoV-2−reactive CD4+ T cells in ~40-60% of unexposed individuals, suggesting cross-reactive T cell recognition between circulating ‘common cold’ coronaviruses and SARSCoV-2,” said the report published in journal, Cell, late Thursday.

CD4+ T cells refer to what are known as helper T cells, a component of body’s immune system that helps recognise a pathogen.

This suggests immune cells that responded to a common cold previously could recognise SarsCov-2. “Detecting SARS2-reactive T cells in ~50% of unexposed people suggests cross-reactive T cell recognition between circulating ‘common cold’ coronaviruses and SARS-CoV-2. This might influence susceptibility to Covid-19 disease,” one of the authors, Shane Crotty of the La Jolla Institute for Immunology, said in a series of tweets. “Whether this immunity is relevant in influencing clinical outcomes is unknown, but it is tempting to speculate the crossreactive CD4+ T cells may be of value in protective immunity, based on SARS and flu data,” he added.

Coronaviruses, the type that is Sars-Cov-2, are common in nature and some are known to cause common cold, along with other types known as rhinoviruses and adenoviruses.

The other aspect of report dealt with how T cells – helper T cells as well as another type known as CD8 or ‘killer’ T cells -- were present in blood of people who recovered from Covid-19, a finding that helps current vaccine research attempts that focus on simulating an immune reaction among people to give them protection over a longer period .

“In our study, 100% of COVID-19 cases made antibodies. 100% of COVID-19 cases made CD4 T cells. 70% of COVID-19 cases made measurable CD8 T cells. We believe these findings are good news, and consistent with normal antiviral immunity,” Crotty added.

The findings are similar to another reported last month, though yet to be peer-reviewed, on medRxiv, by immunologists of Charité University Hospital in Berlin. They analysed blood from 68 uninfected people and found 34% hosted helper T cells that recognised SARS-CoV-2.

WHETHER THIS

IMMUNITY IS RELEVANT IN CLINICAL OUTCOMES IS UNKNOWN, BUT IT IS TEMPTING TO

SPECULATE THE CELLS MAY BE OF VALUE, SAID ONE OF THE AUTHORS