Study Reveals Why COVID-19 Can Infect Sensory Neurons, Explaining Loss Of Smell and Taste

When COVID-19 emerged in 2020, it quickly became apparent that the virus could cause a wide range of symptoms, including the loss of smell and taste. While early evidence suggested that the virus didn't readily infect neurons, a recent study conducted by researchers at the Whitehead Institute for Biomedical Research in the US has shed new light on this aspect.

The study, published in the journal iScience, focused on the peripheral nervous system, which plays a crucial role in our sensory perception. It was previously unclear how SARS-CoV-2 triggered symptoms related to the peripheral nervous system, particularly the loss of smell and taste.

However, the researchers discovered that SARS-CoV-2 can indeed infect sensory neurons, which are responsible for our senses of smell and taste. This infection leads to changes in the genetic expression of these neurons.

Understanding that the virus can infect and potentially alter the function of sensory neurons provides valuable insights into the causes of COVID-19 symptoms related to the peripheral nervous system. This knowledge could serve as a foundation for the development of effective treatments.

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To arrive at these findings, the research team cultivated induced pluripotent stem cells in a lab environment, differentiating them into human sensory neurons. They confirmed the success of this process by ensuring that these neurons expressed specific genes characteristic of sensory neurons.

Next, they examined whether these sensory neurons expressed ACE2, the gene responsible for the protein that SARS-CoV-2 uses to enter human cells. The study showed that sensory neurons did express ACE2, indicating their susceptibility to infection by the virus.

The researchers exposed these sensory neurons to three different strains of SARS-CoV-2, including the original strain, as well as the Delta and Omicron variants. They found that all three strains infected a portion of the sensory neurons, with Omicron displaying a slower infection rate, potentially explaining its reduced impact on the loss of smell and taste.

Further research is required to solidify the link between Omicron's slower infection and milder sensory symptoms. Nevertheless, these findings provide critical insights into how the virus affects the peripheral nervous system, advancing our understanding of COVID-19's varied symptoms.