U.S. NIH Study Finds That SARS-CoV-2 Infection of the Salivary Glands Causes Weakening of Antifungal Defenses
Nikhil Prasad Fact checked by:Thailand Medical News Team Dec 14, 2024 6 hours, 43 minutes ago
Medical News: Researchers have uncovered critical insights into how SARS-CoV-2, the virus responsible for COVID-19, affects oral health. Conducted by teams from the National Institutes of Health (NIH)-USA and the University of Maryland-USA, this groundbreaking study highlights how SARS-CoV-2 infection compromises salivary gland functions, leading to a decrease in an important antifungal protein called histatin-5. This protein plays a crucial role in maintaining oral health by preventing infections caused by Candida albicans, a fungus that can lead to oral candidiasis, commonly known as thrush.
U.S. NIH Study Finds That SARS-CoV-2 Infection of the Salivary Glands Causes Weakening of Antifungal Defenses
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Saliva and Its Role in Oral Health
Saliva, a substance many take for granted, is vital for maintaining oral health. Beyond aiding digestion and keeping the mouth moist, it is enriched with antimicrobial peptides like histatin-5, which protect against pathogens. Histatin-5 is particularly effective against Candida albicans, a fungus usually present in the mouth without causing harm. However, if the immune system is weakened or saliva production is disrupted, this fungus can grow uncontrollably, leading to painful infections.
This
Medical News report sheds light on how SARS-CoV-2 affects the production of this essential antifungal protein and increases the risk of fungal infections in COVID-19 patients.
Key Study Findings
The researchers conducted multiple experiments using tissue samples, saliva analysis, and advanced imaging techniques. They found that SARS-CoV-2 infects the salivary glands, particularly the acinar cells, which are responsible for producing histatin-5. The infection caused a significant drop in histatin-5 levels, leaving the mouth vulnerable to fungal overgrowth. Bulk RNA sequencing of the salivary glands from deceased COVID-19 patients revealed that genes responsible for producing histatin-5 and other critical proteins like amylase were significantly downregulated.
Additionally, the team confirmed these findings through in situ hybridization and immunofluorescence imaging, which showed minimal or no presence of histatin-5 in the glands of infected individuals. The virus directly disrupts the normal production of these proteins, weakening oral defenses.
Clinical Evidence
The study also involved analyzing saliva samples from both COVID-19 patients and healthy individuals. Results showed that histatin-5 levels were markedly lower in COVID-19 patients. For instance, hospitalized patients had histatin-5 levels averaging just 10.4 μg/ml compared to 21.3 μg/ml in healthy controls. The decreased levels of this antifungal protein coincided with a significant increase in Candida albicans colonization, with nearly half of the COVID-19 patients testing positive for this fungus.
Interestingly, the study also followed patients over time, showing that histatin-5 levels gradually recovered du
ring the post-acute phase of COVID-19 in mild cases. However, for severe cases, the damage to salivary glands might be long-lasting, potentially leading to chronic oral health issues.
The Role of Inflammation
The research revealed another important connection: the activation of the Th17 inflammatory pathway during SARS-CoV-2 infection. This immune response plays a dual role. While it attempts to fight off the virus, it also disrupts the normal balance in the salivary glands, reducing the production of histatin-5. The interplay between inflammation and decreased antifungal proteins creates a perfect environment for Candida albicans to thrive.
Testing Saliva in the Lab
To understand the clinical implications further, researchers tested saliva samples in the lab. When Candida albicans was introduced to saliva with low histatin-5 levels from COVID-19 patients, the fungus proliferated rapidly. In contrast, saliva from recovered patients with restored histatin-5 levels inhibited fungal growth. This finding underscores the critical role of histatin-5 in maintaining oral health and preventing infections.
Broader Implications for Oral Health
The findings from this study go beyond just understanding the impact of SARS-CoV-2 on salivary glands. They highlight the vulnerability of the oral cavity during systemic infections and the long-term consequences of viral infections on oral health. For individuals recovering from COVID-19, especially those with severe symptoms, maintaining good oral hygiene and monitoring for signs of oral candidiasis is crucial.
Conclusion and Future Directions
The study provides compelling evidence that SARS-CoV-2 directly infects salivary glands, impairing their ability to produce histatin-5 and other vital proteins. This disruption not only weakens oral defenses but also increases the risk of opportunistic infections like oral candidiasis. While histatin-5 levels may recover in mild cases, the potential for long-term damage in severe cases raises concerns about chronic oral health issues in COVID-19 survivors.
Moving forward, these findings pave the way for further research into targeted treatments to restore salivary gland function and enhance oral immunity in affected individuals. Developing therapies to boost histatin-5 levels or counteract the inflammatory effects of the virus could significantly improve oral health outcomes for COVID-19 patients.
The study findings were published in the peer-reviewed journal: PLOS Pathogens.
https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1012375
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