Bout of common cold may give immunity

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

nNEW DELHI: 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.