How Bacteria Could Help Us Fight Off Viruses

This pandemic has taught many of us that vaccines don't completely prevent infection. But as research intensifies, that may be set to change.


The global response to the COVID-19 pandemic has spurred intensive research into improving the effectiveness of vaccines not only against the SARS-CoV-2 virus, but also against other pathogens. While much attention has been given to mRNA vaccines due to their potency in reducing mortality risk, there is a critical need for vaccines that prevent infections altogether.

Working together with a team of researchers, Dr. Mansour Haeryfar — a professor in the Department of Immunology at Western University — has discovered a novel compound with the potential to greatly enhance vaccine efficacy against various viral pathogens. The findings of this research were published in PLOS Pathogens.

Adjuvants help enhance the immune response to vaccines, which is particularly important when dealing with viruses that might not trigger a robust response on their own. In this case, the adjuvant known as 5-OP-RU is derived from vitamin B2 and is synthesized by bacteria. Mucosa-Associated Invariant T (MAIT) cells recognize bacterial compounds that are presented to them by the MR1 protein. By binding to the MR1 protein and subsequently stimulating MAIT cells, 5-OP-RU triggers a robust immune response.

These MAIT cells are particularly abundant in mucosal tissues, including the respiratory system, where viruses like SARS-CoV-2 often first enter the body. Their rapid response to infections and their role in signalling the immune system to eliminate infected cells make them a prime target for strategies aimed at improving vaccine efficacy.

Through a comprehensive research approach involving both pre-clinical mouse models and human cell cultures, Haeryfar’s team explored the impact of 5-OP-RU on a range of antiviral vaccines, including those against influenza, SARS-CoV-2, and smallpox. In each case, the molecule demonstrated a dual mechanism of action: expanding the population of MAIT cells and reprogramming them to recruit other essential immune cells required for virus-specific responses.

Additionally, MAIT cells exhibit antibacterial and tissue repair properties, which adds another layer of significance to their activation. Given that viral infections can often lead to secondary bacterial infections and tissue damage, the activation of MAIT cells holds promise not only for combating the primary infection, but also for mitigating the aftermath of viral infections.

The discovery of 5-OP-RU and its ability to enhance vaccine efficacy by targeting MAIT cells represents a significant leap forward in the quest to develop more potent and effective vaccines against a range of viral pathogens. Haeryfar’s research exemplifies the innovative and collaborative spirit of scientific inquiry that has been invigorated by the challenges posed by the COVID-19 pandemic.

As further research unfolds, this breakthrough could potentially revolutionize vaccine development strategies and contribute to a more resilient global defense against viral outbreaks.

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Sumayya Abdul Qadir is a PhD student in the Department of Molecular Genetics at the University of Toronto where she also earned her Bsc in Molecular Genetics and Immunology. Sumayya’s passion for science communication is driven by the desire to bridge the gap between complex scientific concepts and the general public, fostering understanding, curiosity, and engagement with the wonders of the scientific world.