F10 - Bovine Myeloid Antimicrobial Peptide-28 (BMAP-28) mRNA Expression by Bovine Cells and Effects on Mannheimia haemolytica

Abstract: Background – Mannheimia haemolytica (MH) is the principal bacterial pathogen associated with bovine respiratory disease (BRD) in cattle. Existing antimicrobials do not consistently prevent BRD due to this pathogen; bovine antimicrobial peptides (AMP) have immune-stimulating and antimicrobial effects that could improve BRD control. Messenger RNA (mRNA) treatment could be used to induce AMP expression in cattle, but efficacy must first be confirmed in vitro.

Hypothesis/Objectives – We hypothesized that bovine cells can express synthetic mRNA coding for the AMP BMAP-28 and that synthetic BMAP-28 can inhibit the growth of MH.

Methods – Madin-Darby bovine kidney cells were cultured and transfected with mRNA coding for BMAP-28 linked to the reporter nanoluciferase. After 4, 12, 24, and 72 hrs, relative light units (RLU) and protein concentration were measured. Results were expressed as RLU/µg of protein.

MH at 500 cfu/ml was incubated with synthetic BMAP-28 at 10 or 100 µg/ml for 0, 12, or 24 hrs and quantitative culture was performed.

Results – Bovine kidney cells expressed mRNA coding for BMAP-28 with peak expression occurring at 24hs in cell lysates and supernatants. Synthetic BMAP-28 at 10µg/ml inhibited MH growth at 12 and 24hs post-treatment.

Conclusions and clinical importance – Treatment of bovine cells with synthetic mRNA induces BMAP-28 expression in vitro. MH growth can be inhibited by BMAP-28. These results provide support for further research to test the mRNA-expressed product against BRD pathogens in vitro and in vivo. mRNA treatment to induce AMP expression could lead to new BRD control strategies.