Viruses Targeting Gut Bacteria May Be Players in Parkinson’s Disease, Study Suggests

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by Alice Melão |

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Viruses that infect bacteria, known as bacteriophages, may contribute to the onset and progression of Parkinson’s disease by unsettling the variety and number of the gut’s microbiota, a study reports.

These findings, in the study “Bacteriophages: are They An Overlooked Driver of Parkinson’S Disease?”, were recently presented at ASM Microbe 2018, the annual meeting of the American Society for Microbiology that took place in Atlanta, Georgia.

The microbiota of the human intestinal tract — its microbe population — consists of bacteria, fungi, and viruses, including bacteriophages. Growing evidence suggests that alterations to the gut microbiota can trigger diseases associated with increased intestinal permeability and chronic inflammation. (Intestinal permeability refers to degree to which material from the gastrointestinal tract “passes” into the body through the gut wall.)

Researchers led by George Tetz, with the Human Microbiology Institute in New York, showed in previous work in a rat model that bacteriophages could change the levels of various bacteria that reside in the gut.

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Now, working with Parkinson’s patients, the team analyzed the composition of bacterial and bacteriophage communities found in fecal samples collected from 32 patients  and 28 healthy controls.

Compared to controls, people with Parkinson’s had reduced levels of certain strains of bacteria that are known to be an important source of microbiota-derived neurochemicals, such as dopamine, and to regulate gut permeability (the passing of material from the gastrointestinal tract into the body through the gut wall).

Each of the events found in the patients have been implicated in Parkinson’s onset and progression.

In particular, researchers recorded a 10-fold reduction in the neurotransmitter-producing bacteria called Lactococcus, suggesting a possible role of bacteriophages in neurodegeneration. Significant decreases in Streptococcus and Lactobacillus amounts in Parkinson’s patients were also observed.

Of note, the lower-than-usual levels of Lactococci observed in patients was due to the appearance of virulent lactococcal phages that are frequently isolated from dairy products.

Based on these findings, the researchers considered it necessary “to pay attention to bacteriophages (including environmental phages) in human health” as they may be “previously overlooked” disease-causing microorganisms.

“To our knowledge, this is the first study to suggest a link between bacteriophages and Parkinson’s disease,” researchers wrote.

Additional studies are necessary to further evaluate how these bacterial viruses affect Parkinson’s, and to understand their potential as diagnostic and therapeutic targets.