Emerging COVID-19 Subvariant in China may Attack Brain

The COVID-19 subvariant surging in China may be evolving to attack the brain, feel researchers. The new study challenges previous assumptions that viruses usually evolve to become less dangerous.

New research on the Omicron subvariant of the coronavirus has suggested the pathogen could be changing how it attacks the human body - shifting from infecting respiratory systems to increasingly targeting the brain.

Coronavirus
Coronaviruses infect animals, humans, and birds. Human coronaviruses, such as SARS, MERS, and 2019-nCoV cause respiratory distress and even death. The S protein is the infectious agent of the virus.

‘The Omicron lineage of the COVID-19 virus is not evolving to reduce its effect on the human body, instead it increases the attack.’

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Researchers from Australia and France found BA.5 - the coronavirus subvariant driving what is now the world's biggest surge of infections in China - did much more severe damage to mouse brains and cultured human brain tissues than the previous BA.1 subvariant, leading to brain inflammation, weight loss, and death.

Compared with BA. 1, they found that a BA.5 isolate displayed increased pathogenicity in mice with rapid weight loss, brain infection and encephalitis, and mortality. In addition, BA.5 productively infected human brain organoids significantly better than BA. 1. The study findings have been uploaded in bioRxiv.

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These results suggest that the Omicron lineage is not evolving towards reduced pathogenicity. However, other experts have sounded a note of caution, noting that a major limitation of the study was the mouse model it used, which might not apply to human beings.

They showed that all the mice died from brain infections of BA. 5, which is very different from human infections.

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It was widely accepted that BA.5 did not cause more brain abnormalities in humans than previous subvariants, adding that the World Health Organization has said the pathogenicity of Omicron variants has not increased.

In a paper published in the journal Nature last month, a team of Japanese and US scientists reported that BA.5 seemed to have inherited the reduced pathogenicity of Omicron subvariants.

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Multiple studies have shown that BA.5 is more transmissible than other Omicron subvariants and can evade a human immune system with a previous vaccination or infection.

The strain has been detected in more than 100 nations and was the dominant strain in countries such as the United States and the United Kingdom a few months ago.

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But in China, the two major strains circulating are BA. 5.2 and BF. 7, both sub-lineages of BA.5. Together they accounted for more than 80 percent of the country's total COVID-19 infections. There was also well-documented evidence of brain abnormalities and infection among COVID-19 patients.

Hence, researchers feel more work was needed to better understand the neuroinvasive mechanism. However, even if the respiratory disease is less severe for Omicron variants as a whole, BA.5 may show an increased risk of acute and long-term neurological complications over previous Omicron variants.

Still, critics maintain there is a big gap between studies using the mouse model and those using humans.

Source-Medindia