Health

COVID-19: Do Indians have higher immunity to novel coronavirus

Indians have some genetic advantage, but these are still early days to come to any conclusion

 
By Vibha Varshney
Last Updated: Thursday 09 April 2020
Indians are constantly exposed to microbes that keep the immune system primed Photo: Flickr/McKay Savage

The fewer-than-expected cases positive to the novel coronavirus (SARS-CoV-2) in India have spawned several theories, one of them being, Indians being immune to the virus.

It is theoretically possible as Indians are constantly exposed to microbes that keep the immune system primed, destroying pathogens attempting to attack. This is why children in very clean environments fall sick at the slightest exposure to a pathogen — a concept known as the hygiene hypothesis.

Indians have some genetic advantage as well: They have evolved to gain more genes that protect against viral infections, according to Rajalingam Raja, director of Immunogenetics and Transplantation Laboratory at the University of California in San Francisco, US. He said:

These genes enable natural killer (NK) cells, a type of white blood cells in our body that provide a first line of defense against viral infections

Two families of genes — KIR genes and HLA genes — play a part in this protective function. Indians have more KIR genes than the Chinese and caucasians. This could make Indians more immune to the virus, according to Raja.

A similar mechanism protects bats from viruses like Ebola and SARS. “Bats are immune since they have expanded gene families that enhance NK cell function,” said Raja, who first wrote about NK cells in 2008 in journal Genes and Immunity.

This alone is, however, not enough to guide India’s strategy to fight the disease or even suggest that strict measures are not needed. A team of researchers from India and the US studied umbilical cord blood of children in the two countries and found differences. The findings were published in journal PLoS One in 2018.

“We interpreted our study to suggest that Indian babies could be more susceptible to early-life infections if they had lower frequencies of certain immune cells,” said Holden Maecker, director of the Human Immune Monitoring Center at Stanford University School of Medicine.

Persistent pathogen assault — especially early in life — is almost certainly detrimental. This is seen in the phenomenon of environmental enteropathy, where kids with poor sanitation and high enteric pathogen loads develop malnutrition and stunting, Maecker said. But he agreed exposure to pathogens could equip the immune system better to fight new assaults like Zika or coronavirus, to an extent.

This was similar to the protective effect provided by latent tuberculosis. It was certainly possible that there was increasing resistance — if not specific immunity — to COVID-19 in certain genetic groups. It is difficult, however, to extrapolate this to all Indians who are a diverse collection of ethnic groups.

“It is a balance and my guess is that it’s too soon to say where Indians as a whole will fall on this balance in terms of their sensitivity to COVID-19,” he said.

Arguments about the Indian immune systems are mostly speculative, according to Satyajit Rath of the National Institute of Immunology. He co-authored the 2018 study with Maecker.

“I am yet to see any indication that COVID-19 will, in fact, turn out to be less prevalent and/or milder in India, since the epidemic is still in its early stages in the subcontinent,” he said.

There are no publications, as of now, on the differential prevalence or outcome of COVID-19 among Indians and those of other ancestries worldwide.

Good nutrition, exercise and sleep can improve the immune system.

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