Anti-Influenza virus effects of Enterococcus faecalis KH2 and Lactobacillus plantarum SNK12 RNA.

Bacterial RNA has recently emerged as an immune-stimulating factor during viral infection. The immune response in an organism is directly related to the progression of virus infections. Lactic acid bacteria in particular have anticancer, bioprotective, and antiallergic effects by modulating immunity. Here, we aimed to demonstrate the effect of bacterial RNA on in vitro production of IL-12, a proinflammatory cytokine, and on in vivo activity against influenza A virus (IFV) infection. Oral administration of heat-killed Enterococcus faecalis KH2 (KH2) or Lactobacillus plantarum SNK12 (SNK) in IFV-infected mice suppressed viral replication and stimulated production of virus-specific antibodies. However, ribonuclease-treated KH2 or SNK abrogated the effect, reducing IL-12 production in vitro and anti-IFV effects in vivo. Taken together, KH2 or SNK showed antiviral effects in vivo when administered orally, and the RNAs of KH2 and SNK play a part in these effects, despite the phylogenetic differences between the bacteria.