Antimicrobial peptides (AMPs) are short strings of amino acids, about 12-50 residues long, that show potent antibacterial, antiviral, and antifungal activity. They are found throughout the tree of life as part of the innate immune system. Many AMPs are in clinical use, such as vancomycin.
A class of AMPs called the cecropins were first isolated from the moth Hyalophora cecropia. Magainins were first isolated from the frog Xenopus laevis. An analog of magainin went through clinical trials as a treatment for infected diabetic foot ulcers, but failed.
Researchers from the Jilin Agricultural University in China are interested in developing AMPs for livestock feed as an alternative to antibiotics. Previous research suggested that the fusion of peptides from two AMPs may enhance their antibacterial activity. Zhang et al. decided to test the properties of a magainin II – cecropin B fusion.
The group was also interested in testing whether the fungus Cordyceps militaris would make a suitable expression vehicle for fusion proteins. They constructed a plasmid that coded for the magainin II – cecropin B fusion and transformed cordyceps to express it. Then they extracted protein from the transformed fungus.
They tested the extract using ELISA, PAGE, and Western blotting and found that the cordyceps did express the fusion protein. Then, they swabbed the protein onto plates containing various species of bacteria to test whether it inhibited bacterial growth. Magainin II – cecropin B inhibited bacterial growth better than cecropin B alone.
The researchers also administered magainin II – cecropin B to mice infected with E. coli. The fusion inhibited E. coli growth in the mouse gut, and the mice suffered less intestinal damage. The same effect was observed when they fed the transformed cordyceps straight to the mice.
Zhang et al. conclude that magainin II – cecropin B is an effective antimicrobial. Cordyceps militaris that expresses magainin II – cecropin B could potentially be added to livestock feed.
Zhang M, Shan Y, Gau H, Wang B, Liu X, Dong Y, Liu X, Yao N, Zhou Y, Li X, Li H. Expression of a recombinant hybrid antimicrobial peptide magainin II-cecropin B in the mycelium of the medicinal fungus Cordyceps militaris and its validation in mice. 2018. Microb Cell Fact. 17:18. PMID: 29402269.