Targeting expression of antimicrobial peptide CAMA-Syn by adenovirus vector in macrophages inhibits the growth of intracellular bacteria

Although purified and synthesized Cecropin A-magainin 2 (CAMA-syn) shows potent antibacterial activity in vitro, its ability to inhibit bacteria within mammal cells mediated by virus vector has not yet been investigated. To enhance its antimicrobial potential and reduce systemic side effects, it would be desirable to deliver CAMA-syn in macrophages by adenovirus vector. In this study,recombinant adenovirus Ad-MSP-CAMA/GFP were used to infect macrophages RAW264.7 cells in vitro and macrophages cells of lungs in vivo and the expression of CAMA-syn was detected by RT-PCR and observation of co-expression of GFP. Antimicrobial activity in cells was evaluated by colony enumeration. The results showed that expression of CAMA-syn in macrophages conferred antimicrobial activity against a series of bacteria, including E. coli and BCG(Bacillus Calmette-Guérin). To establish BCG infection animal model, 40 Kunming mice were randomly divided into the following four groups: adenoviral delivery of Ad-MSP-CAMA/GFP, Ad-CMV-CAMA/GFP, empty-virus Ad-GFP, and control PBS, respectively. The expression of CAMA-syn in mouse was confirmed by real-time PCR and GFP co-expression. In brief, 3 days after injection of adenoviral vector, mice were scarified, different tissues were sectioned and homogenized and colony-forming efficiency by these treated tissues was determined. The colony-forming efficiency of Ad-MSP-CAMA/GFP (78.31%) and Ad-CMV-CAMA/GFP (61.68%) showed significant reduction compared to control groups. No inhibition of bacterial colony was observed from tissues treated by the PBS or empty-virus control. In conclusion, our results demonstrated that macrophages-specific expression of antimicrobial peptide CAMA-syn in macrophages inhibited the growth of intracellular bacteria, providing a promise approach for the control of refractory intracellular infection.