ABSTRACT
Influenza vaccination is an effective public health measure to reduce the risk of influenza illness, particularly when the vaccine is well matched to circulating strains. Notwithstanding, the efficacy of influenza vaccination varies greatly among vaccinees due to largely unknown immunological determinants, thereby dampening population-wide protection. Here, we report that dietary fibre may play a significant role in humoral vaccine responses. We found dietary fibre intake and the abundance of fibre-fermenting intestinal bacteria to be positively correlated with humoral influenza vaccine-specific immune responses in human vaccinees, albeit without reaching statistical significance. Importantly, this correlation was largely driven by first-time vaccinees; prior influenza vaccination negatively correlated with vaccine immunogenicity. In support of these observations, dietary fibre consumption significantly enhanced humoral influenza vaccine responses in mice, where the effect was mechanistically linked to short-chain fatty acids, the bacterial fermentation product of dietary fibre. Overall, these findings may bear significant importance for emerging infectious agents, such as COVID-19, and associated de novo vaccinations.
Subject(s)
Dietary Fiber/pharmacology , Immunity, Humoral/drug effects , Influenza Vaccines/immunology , Influenza, Human/immunology , Adolescent , Adult , Animals , Dietary Fiber/metabolism , Fatty Acids, Volatile/metabolism , Fatty Acids, Volatile/pharmacology , Female , Fermentation , Gastrointestinal Microbiome/drug effects , Gastrointestinal Microbiome/immunology , Humans , Immunogenicity, Vaccine , Influenza, Human/microbiology , Influenza, Human/prevention & control , Male , Mice , Middle Aged , Orthomyxoviridae/immunology , Seasons , Vaccination , Young AdultABSTRACT
Bacteria that colonize the human gastrointestinal tract are essential for good health. The gut microbiota has a critical role in pulmonary immunity and host's defense against viral respiratory infections. The gut microbiota's composition and function can be profoundly affected in many disease settings, including acute infections, and these changes can aggravate the severity of the disease. Here, we discuss mechanisms by which the gut microbiota arms the lung to control viral respiratory infections. We summarize the impact of viral respiratory infections on the gut microbiota and discuss the potential mechanisms leading to alterations of gut microbiota's composition and functions. We also discuss the effects of gut microbial imbalance on disease outcomes, including gastrointestinal disorders and secondary bacterial infections. Lastly, we discuss the potential role of the lung-gut axis in coronavirus disease 2019.