# The Gut Microbiota of the Greater Horseshoe Bat Confers Rapidly Corresponding Immune Cells in Mice

## TL;DR

This study shows that the gut microbiota of the Greater Horseshoe Bat can rapidly influence immune cells in mice, offering new insights into bat immunity.

## Contribution

The study introduces a novel approach using fecal microbiota transplantation to investigate bat gut microbiota's impact on immunity in mice.

## Key findings

- The gut microbiota of the Greater Horseshoe Bat altered immune cell composition in mice spleens and mesenteric lymph nodes.
- The bat microbiota conferred a faster and higher proportion of natural killer cell activation in mice.
- The transplanted microbiota exhibited characteristics similar to the original bat gut microbiota.

## Abstract

Bats are natural hosts for numerous pathogens, and the study of bats that carry pathogens without developing disease helps deepen our understanding of the relationship between immunity and infectious disease. Bat-specific habits and the lack of specific reagents have limited bat immunity-related studies, while existing bat immunity studies have neglected the role of gut microbiota in modulating immunity. In this study, we first treated specific pathogen-free (SPF) C57BL/6 mice with a complex antibiotic solution for 7 consecutive days to obtain pseudo-sterile mice and then transplanted the gut microbiota of bats into the mice through fecal microbiota transplantation (FMT), thereby bypassing the dilemma of studying the gut microbiota of wildlife. The results showed that on days 7 and 14 after FMT, the gut microbiota of the Greater Horseshoe bat, a widely distributed insectivorous bat, could regulate immune cells in mice, which exhibited a rapid innate immune response. This result improves our understanding of the unique immune system of bats and emphasizes the importance of bat gut microbiota in immunity.

Background: Emerging infectious diseases threaten human and animal health, with most pathogens originating from wildlife. Bats are natural hosts for many infectious agents. Previous studies have demonstrated that changes in some specific genes in bats may contribute to resistance to viral infections, but they have mostly overlooked the immune function of the bat gut microbiota. Aims: In this study, we used fecal transplants to transfer the gut microbiota from the Greater Horseshoe Bat (Rhinolophus ferrumequinum) into mice treated with antibiotics. The gut microbiota changes in mice were detected using 16S rRNA high-throughput sequencing technology. Flow cytometry was used to detect changes in associated immune cells in the spleen and mesenteric lymph nodes of the mice. Results: The results showed that the gut microbiota of mice showed characteristics of some bat gut microbiota. The Greater Horseshoe Bat’s gut microbiota changed some immune cells’ composition in the spleen and mesenteric lymph nodes of mice and also conferred a faster and higher proportion of natural killer cell activation. Conclusion: This result provides new evidence for the regulatory immune function of bat gut microbiota and contributes to a deeper insight into the unique immune system of bats.