Probiotics study shows nasal microbiota may affect host response to viral respiratory infection

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Nasal microbiota may have an influence on immune response, inflammation, viral load, and cold symptoms, according to a collaborative clinical study¹ between DuPont Nutrition & Health (Madison, WI), the University of Virginia, and contract research firm 4Pharma Ltd. In the randomized, double-blind, placebo-controlled trial, 152 healthy young adults were inoculated with a form rhinovirus (the common cold) after having samples taken of their nasal passages. They then had periodic nasal swabs were taken to determine the content of the nasal microbiota and 52 subjects in the intervention group were supplemented with the probiotic strain Bifidobacterium animalis subsp. lactis Bl-04.

Subjects’ baseline nasal microbiota samples were divided into six clusters named after the predominant bacterial genera: 1) Staphylococcus, 2) Corynebacterium/Alloiococcus, 3) Moraxella, 4) Haemophilus, 5) Pseudomonadaceae/Mixed, and 6) Mixed. In comparing cold symptoms in subjects in the Staphylococcus, Corynebacterium/Alloiococcus, Moraxella, and Pseudomonadaceae/Mixed clusters through a Wisconsin Upper Respiratory Symptom Score, scores for total cold symptoms were lower in the Corynebacterium/Alloiococcus cluster. On scores of individual symptoms, the Corynebacterium/Alloiococcus cluster had lower scores in nasal obstruction, sneezing, and cough.

Change in inflammatory response between clusters was also found. Concentrations of inflammatory mediators were higher in the Moraxella and Pseudomonadaceae/Mixed clusters, although only the latter group had a lower viral load. According to researchers, this indicates that inflammatory response wasn’t associated with lower viral load, nor was there a correlation with symptom severity.

The intervention with Bifidobacterium animalis subsp. lactis Bl-04 in 52 of the subjects following infection of rhinovirus did not produce any significant change in nasal microbiota, nor did the viral infection itself. This means that the differences in the way subjects reacted to the virus could not be correlated with the probiotic intervention and the microbiota remained stable despite viral infection. To explain why that may be, the researchers write, “The lack of a detectable effect of Bl-04 on the nasal microbiota suggests that the inflammatory and viral shedding effects are not mediated through significant changes in the nasal or fecal microbiota, but perhaps rather driven by direct contact of the probiotic with the mucosal immune system,” wrote the researchers. So, while they cannot attribute the differences in reaction to the virus to the probiotic strain’s influence on the nasal microbiota, there may be some kind of influence at play. More research is required.

While the intervention of probiotics did not produce an effect, it is apparent that the microbiota content did influence how the subjects’ bodies reacted to and fought the rhinovirus. Further research is required to better understand the role of nasal microbiota in response to the common cold, the researchers said.

References:

1. Lehtinen MJ et al. “Nasal microbiota clusters associate with inflammatory response, viral load, and symptom severity in experimental rhinovirus challenge.” Scientific Reports. Published online ahead of print July 30, 2018.