CCMB study shows Delta variant better capable of evading human immune response

A CSIR-Centre for Cellular and Molecular Biology study proved that the Delta variant of Covid-19 is better capable of evading the human immune system than other variants.

Molecular mechanisms regulating the host immune response have not been as potent against the Delta variant of SARS-CoV-2, said the research findings published in Microbiology Spectrum journal recently.

In the last two and half years, many Coronavirus variants have spread across the world. However, their outcomes have varied greatly, with the Delta variant recognized as the deadliest.

Researchers at the Hyderabad-based CCMB attempted to understand how differently humans infected by the virus reacted to different SARS-CoV-2 variants.

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Five different SARS-CoV-2 variants - Alpha, Delta, and three more that emerged before the Alpha were selected and the human immune system response in each case was examined.

Upon viral infection, the first line of attack by the host's immune system is the production of certain defence chemicals that break down the viruses. The researchers studied how this production varied in the five cases.

“We infected the human cells in a cell culture system and monitored the production of known immune defence molecules and the activation of signalling pathways associated with them in each case,” said Dixit Tandel, first author of the study.

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While infection due to the other four variants alerted the immune system quickly, the Delta variant could silently replicate in the host cells, researchers found.

“We have identified that molecular mechanisms regulating the host immune response have not been as potent against the Delta variant of SARS-CoV-2. This also includes the production of interferons, immune molecules often used for antiviral therapies. Our study hints at why the Delta variant could spread more easily," said Dr Krishnan Harshan, the study's lead investigator.

Dr Harshan says their study also helps understand how viruses evolve with changing effects on human hosts.