# Potential antiviral effects of the marine probiotic Paraliobacillus zengyii on the respiratory syncytial virus

## TL;DR

A marine probiotic called Paraliobacillus zengyii shows potential to fight respiratory syncytial virus by boosting the body's immune response.

## Contribution

P. zengyii is a novel marine probiotic that inhibits RSV and enhances antiviral immunity, with unique halophilic traits and low-temperature growth.

## Key findings

- P. zengyii inhibits RSV infection by enhancing interferon responses in vitro and in vivo.
- The probiotic increases phosphorylation of TBK1 and IRF3 and upregulates IFITM1 and IFITM3 expression.
- P. zengyii promotes IFN-β production in response to RSV, SeV, or poly(I:C) stimulation.

## Abstract

Probiotics can reduce the incidence of respiratory syncytial virus (RSV) disease in premature infants; this approach is resource‐intensive and less expensive than other strategies and easier to implement than most current methods worldwide. Traditional lactic acid‐producing bacteria are the main probiotics that have been studied for RSV treatment. Marine probiotics promote the survival, immunity, and disease resistance of aquatic plants and animals. However, relatively little research has been conducted on viral infections in humans. Here, we report a slightly halophilic and extremely halotolerant marine bacterium, Paraliobacillus zengyii, which has antiviral activity and grows at a relatively low temperature (28°C). We found that P. zengyii inhibited RSV infection by regulating the interferon (IFN) response both in vitro and in vivo. P. zengyii significantly increased the RSV‐induced phosphorylation of TBK1 and IRF3 and the expression of antiviral factors interferon‐induced transmembrane protein 1 (IFITM1) and interferon‐induced transmembrane protein 3 (IFITM3). Furthermore, P. zengyii upregulated Sendai virus (SeV)‐ and poly(I:C)‐induced IFN‐β expression. These results indicate that the marine bacterium P. zengyii inhibits RSV infection and increases IFN‐β production in response to RSV, SeV infection, or poly(I:C) stimulation. Consequently, P. zengyii has potential as a broad‐spectrum anti‐RNA virus probiotic.

Marine probiotics are an underexplored bioactive resource, and to date, few studies have investigated their antiviral effects. Here, we show that the marine probiotic Paraliobacillus zengyii inhibits respiratory syncytial virus (RSV) infection in vitro and in vivo. In addition, P. zengyii promotes the host innate immune response to RNA viruses and double‐stranded RNA (dsRNA) mimics. Therefore, P. zengyii can exert broad‐spectrum anti‐RNA virus effects, and it is a unique potential probiotic because it is slightly halophilic and extremely halotolerant. This is the only known probiotic with antiviral potential that can be grown at low temperatures, which may have advantages under certain conditions. Notably, P. zengyii is a natural microbial dweller of marine ecosystems isolated from animal feces.