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.