Expression and Functional Characterization of a Novel Antimicrobial Peptide: Human Beta-Defensin 118.

Purpose: -Defensin 118 (DEFB118) is a novel host defense peptide (HDP) identified in humans. To evaluate its potentials for future utilization, the DEFB118 gene was expressed in () and the recombinant protein was fully characterized.

Methods: The DEFB118 protein was obtained by heterologous expression using Rosetta (DE3). Antibacterial activity of DEFB118 was determined by using various bacterial strains. IPEC-J cells challenged by K88 were used to determine its influences on inflammatory responses.

Results: The transformants yielded more than 250 g/mL DEFB118 protein after 4 h induction by 1.0 mM IPTG. The DEFB118 was estimated by SDS-PAGE to be 30 kDa, and MALDI-TOF analysis verified that it is a human -defensin 118. Importantly, the DEFB118 showed antimicrobial activities against both Gram-negative bacteria ( and ) and Gram-positive bacteria ( and ), with a minimum inhibitory concentration (MIC) of 4 g/mL. Hemolytic assays showed that DEFB118 had no detrimental impact on cell viability. Additionally, DEFB118 was found to elevate the viability of IPEC-J2 cells upon K88 challenge. Moreover, DEFB118 significantly decreased cell apoptosis in the late apoptosis phase and downregulated the expression of inflammatory cytokines such as IL-1 and TNF- in IPEC-J2 cell exposure to K88.

Conclusions: These results suggested a novel function of the mammalian defensins, and the antibacterial and anti-inflammatory properties of DEFB118 may allow it as a potential substitute for conventionally used antibiotics or drugs.