PMAP-37: A versatile cathelicidin for neutralizing bacteria and viruses

Antimicrobial peptides (AMPs), such as cathelicidins, show dual functionality by directly combating pathogens and indirectly eliminating them through stimulation of the immune system, generating interest in their therapeutic potential. Pigs have a large set of 11 cathelicidins, of which PMAP-37 is relatively understudied compared to some of the better-known cathelicidins. This study describes the effectiveness of PMAP-37 against both bacteria and viruses. PMAP-37 exhibited potent in vitro antimicrobial activity against both Gram-positive (Bacillus globigii) and Gram-negative bacteria (Escherichia coli) with minimum bactericidal concentrations (MBCs) of 2.5 and 5 μM, respectively. PMAP-37 caused a rapid permeabilization of E. coli's outer and inner membranes within 5 min, indicating its efficacy in disrupting bacterial cell membranes. Furthermore, PMAP-37 neutralized nitric oxide production in a macrophage cell line stimulated with various forms of LPS, Lipid A, or LTA in a dose-dependent manner. Flow cytometric analysis confirmed PMAP-37's capacity to inhibit LPS binding to macrophages, while zeta potential analysis showed the peptide's capacity to neutralize the negative charge of both the E. coli membrane and LPS micellular surfaces. Interestingly, PMAP-37 also exhibited antiviral activity against an important porcine pathogen, the porcine epidemic diarrhea virus (PEDV). These findings underscore the multifunctional properties of PMAP-37, and provide potential leads for future therapeutic use within the pig industry.