# Identification and characterisation of LEAP2 from Chinese spiny frogs (Quasipaa spinosa) with antimicrobial and macrophage activation properties

## TL;DR

This study identifies and characterizes LEAP2 in Chinese spiny frogs, showing it has antimicrobial properties and activates macrophages.

## Contribution

The study is the first to characterize LEAP2 in Chinese spiny frogs and demonstrate its immune-related functions.

## Key findings

- QsLEAP2 is expressed in multiple tissues, with the highest levels in the liver.
- QsLEAP2 shows antimicrobial activity by disrupting bacterial membranes and DNA.
- QsLEAP2 activates macrophages, enhancing their phagocytic and respiratory burst activities.

## Abstract

The liver-expressed antimicrobial peptide 2 (LEAP2) family is an important group of antimicrobial peptides (AMPs) involved in vertebrate defence against bacterial infections. However, research on LEAP2 in amphibians is still in its infancy.

This study aimed to explore the role of LEAP2 in the Chinese spiny frog (Quasipaa spinosa). The cDNA of the LEAP2 gene (QsLEAP2) was cloned from a Chinese spiny frog. The QsLEAP2 protein comprises a signal peptide, a prodomain, and a mature peptide. Sequence analysis indicated that QsLEAP2 is a member of the amphibian LEAP2 cluster and closely related to the LEAP2 of the African clawed frog (Xenopus laevis). Expression of QsLEAP2 was detected in various tissues, with the liver exhibiting the highest expression. Following infection with Aeromonas hydrophila, QsLEAP2 expression was significantly upregulated in the spleen, lungs, kidneys, liver, and gut. The synthetic mature peptide QsLEAP2 exhibited selective antimicrobial activity against several bacterial strains in vitro. It disrupted bacterial membrane integrity and hydrolysed bacterial genomic DNA, exhibiting bactericidal effects on specific bacterial species. Furthermore, QsLEAP2 induced chemotaxis in RAW264.7 murine leukemic monocytes/macrophages, enhancing their phagocytic activity and respiratory bursts. Docking simulations revealed an interaction between QsLEAP2 and QsMOSPD2.

These findings provide new insights into the role of LEAP2 in the amphibian immune system.

The online version contains supplementary material available at 10.1186/s12917-025-04617-y.