Study Finds Certain Nasal Bacteria May Increase COVID-19 Infection Risk

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Recent research conducted by scientists at George Washington University suggests that certain nasal bacteria may play a significant role in determining an individual’s susceptibility to COVID-19. This study, published in EBioMedicine, reveals that specific types of bacteria present in the nose can influence the levels of two crucial proteins that the virus requires to gain entry into human cells. This finding sheds light on the disparities in COVID-19 vulnerability among different individuals.

“While it’s established that the SARS-CoV-2 virus primarily infects the body via the respiratory system, particularly through the nose, the discovery that nasal bacteria can modify the expression of infection-related proteins is both novel and intriguing,” noted Cindy Liu, associate professor at the GW Milken Institute School of Public Health.

Higher Gene Expression of Viral Entry Proteins Increases COVID-19 Infection Risk

The research team, led by Liu, analyzed nasal swabs from over 450 individuals, including those who subsequently tested positive for COVID-19. They found elevated levels of gene expression for two proteins, ACE2 and TMPRSS2, in those who became infected. ACE2 facilitates the entry of the virus into nasal cells, while TMPRSS2 plays a role in activating the virus by cleaving its spike protein.

Participants exhibiting high levels of these proteins were over three times more likely to test positive for COVID-19 compared to those with normal levels. Furthermore, individuals with moderate expression levels had double the likelihood of infection. The study also highlighted the fluctuating gene expression patterns in those who tested positive, particularly noting sharp increases in expression prior to diagnosis, suggesting that rising protein levels may signal increased risk.

Interestingly, the study found that women generally exhibited heightened gene expression of these proteins, aligning with previous research indicating higher COVID-19 infection rates among women. However, for men, elevated levels of these proteins were more strongly correlated with increased risk of infection, indicating gender differences in susceptibility related to protein expression.

Nasal Bacteria May Play a Role in COVID-19 Risk

To further investigate what factors might influence the expression of the viral entry proteins, the researchers examined the nasal microbiome—the varied array of bacteria residing in the nasal cavity. Their research uncovered that specific bacteria could modulate the expression levels of ACE2 and TMPRSS2, thereby influencing the risk of COVID-19.

Three types of common nasal bacteria—Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis/nonliquefaciens—were linked to increased expression of ACE2 and TMPRSS2, heightening the risk of COVID-19. In contrast, Dolosigranulum pigrum was associated with lower protein levels, suggesting a potential protective effect against the virus.

“Certain bacteria present in the nasal cavity could either facilitate or hinder the entry of viruses like SARS-CoV-2,” remarked Daniel Park, the study’s lead author and senior research scientist at GW.

While some of the more harmful bacteria were less prevalent, about 20% of participants harbored sufficient amounts of S. aureus to nearly double their risk for exhibiting elevated ACE2 and TMPRSS2 levels, marking it as a significant risk factor in the nasal microbiome in relation to COVID-19 infection.

Why This Matters

The implications of this research are significant for both predicting and preventing COVID-19 infections. Monitoring the expression levels of ACE2 and TMPRSS2 could provide a means to identify individuals who are at greater risk. Additionally, this study opens avenues for exploring how manipulating the nasal microbiome could serve as a preventive strategy against viral infections.