CCMB study detects gene suppression in COVID-19 patients as reason for loss of taste and sense of smell

Published : September 27, 2021 13:44 IST

A health worker collecting a swab sample from a person to test for COVID-19, in Hyderabad. A file picture. Photo: The Hindu Archives

At the height of both waves of the COVID-19 pandemic, health care workers and scientists were keenly looking at two key clinical symptoms: a loss of the olfactory (smell) and gustation (taste) receptors. The loss of both receptors, and their associated pathways, were a major correlate of the COVID-19 infection.

Geneticists at the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad have now published a study on the reasons why some people infected with the SARS-CoV-2 virus tend to lose their sense of smell and taste. The researchers have indicated that genes associated with the olfactory and gustation functions become suppressed, causing COVID-19 positive patients to lose their ability to smell and taste. The study found that genes associated with crucial body functions, including those of the respiratory system, the heart, the endocrine system and the nervous system, were also suppressed or lowered.

The CCMB study, which was published on September 21 in the open access Wiley Online Library, revealed that the SARS-CoV-2 virus tended to react with genes leading to ‘downregulation’ or ‘upregulation’ of some of them. While downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus, upregulation is an increase in these components. Both downregulation and upregulation disrupt the functioning of the body. The study revealed that while upregulation was found in the immune response genes and resulted in an increase in the amount of inflammation, downregulation was witnessed in genes responsible for neurotransmission, neurological, cardiovascular, and muscular contraction.

The study involved investigating the genetic changes in 36 COVID-19 patients, ranging from those needing critical and intensive care intervention to those treated at the ward-level, during the pandemic’s first wave. Five COVID-19 negative samples were also analysed. Researchers of the study said that studies such as theirs were useful for scientists to not only compare host responses in the current and subsequent waves of the pandemic but also come up with therapeutic solutions.

Stated the researchers: “We also found robust activation of the innate immune response associated with a reduction in the gene expression profiles associated with cardiac, muscular, and neurological processes, as well as peripheral neurosensory markers.” They added: “In conclusion, we have documented significantly misregulated genes and associated pathways during the SARS-CoV-2 infection in Indian patients. Our results highlight a commonly upregulated network of innate immune response genes and an absence of hyper-inflammatory markers.”

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