LAUSR

Host defense peptides (HDPs) are evolutionarily conserved molecules that protect the host against microbial infections and inflammation. Rabbit sacculus rotundus antimicrobial histone (RSRAH), which was identified as a novel antimicrobial HDP, has been shown to function as an antimicrobial agent capable of killing microbes in vitro and could promote cellular immune function in immunosuppressed mice (Chen in Int J Pept Res Ther 21:443–450, 2015). However, its anti-infection activity in vivo remains to be elucidated. In the present study, we demonstrate that RSRAH protected mice against pathogenic Escherichia coli challenge, and was capable of significantly enhancing the survival rate of mice after challenge. RSRAH significantly decreased the number of E. coli in the blood and spleen, suggesting that RSRAH was able to block the multiplication/dissemination of E. coli in mice. Additionally, the anti-inflammatory cytokine IL-10, leukocyte and granulocytes in E. coli-infected mice was significantly increased by RSRAH treatment. Collectively, these results indicate that RSRAH can protect mice from E. coli challenge by its antimicrobial properties as well as protecting mice from excessive inflammatory response by modulating the immune system.