A cutaneous gene therapy approach to treat infection through keratinocyte-targeted overexpression of antimicrobial peptides.

Infection represents a major associated problem in severely burned patients, as it causes skin graft failure and increases the risk of mortality. Topical and systemic antibiotic treatment is limited by the appearance of resistant bacterial strains. Antimicrobial peptides (AMPs) are gene-encoded "natural antibiotics" that form part of the innate mechanism of defense and may be active against such antibiotic-resistant microorganisms. Several microbicidal peptides are expressed in human skin under inflammatory conditions, and their function is not only limited to microbial killing but also influences tissue repair and adaptive immunity. Protein delivery through cutaneous gene therapy is a promising therapeutic tool for both skin and nonskin diseases. Here we present a gene transfer approach aimed at delivering antimicrobial peptides from keratinocytes. Adenoviral vectors encoding antimicrobial peptide genes were used to infect human keratinocytes growing either on plastic or as part of cultured skin equivalents. Inhibition of bacterial growth occurred both in conditioned media and in direct contact with AMPs gene-transduced keratinocytes. In addition, we showed cooperative effects after transfer of combinations of genes encoding for AMPs with structural differences. Combined cutaneous tissue engineering in conjunction with (microbicidal) gene therapy emerges as a tailored therapeutic approach that is useful for wound coverage and, in this case, concomitantly combating infection.