New study sheds light on why Delta variant was the deadliest

Study was taken up by scientists of CCMB

A COVID-19 patient from Andhra Pradesh on oxygen support in an ambulance waits for medical attention outside a private hospital in Hyderabad in May 2021 when the Delta (second) wave was at its peak. File | Photo Credit: The Hindu Photo Library

Several SARS-CoV-2 variants have spread across the world since the outbreak of COVID-19 in late 2019, but the Delta variant was inarguably the deadliest. This has been confirmed once again in a study taken up by scientists of CSIR-Centre for Cellular and Molecular Biology.

The team found that the human body’s immune system could not produce defence molecules against Delta variant as effectively as the other variants. While infection due to the other four earlier variants alerted the immune system quickly, the Delta variant could silently replicate in the host cells.

“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. The study hints at why the Delta variant could spread more easily,” said lead investigator Krishnan Harshan.

His team did the study in collaboration with fellow scientist Divya Tej Sowpati’s team where they tried to understand if the humans infected by the virus, reacted differently to the different SARS-CoV-2 variants like Alpha, Delta, and three others.

Upon viral infection, the first line of attack by the host’s immune system is by producing certain defence chemicals that break down the viruses with researchers studying how their production responds to these five variants.

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

“We navigated through the hundreds of immune pathways known to us using high throughput sequencing and analysis,” said Nitesh Kumar Singh, who worked on the project with Sowpati. The study has been published in ‘Microbiology Spectrum’ journal and “helps us understand how viruses evolve with changing effects on human hosts,” added Harshan, in an official release on Monday.