Expression of an additional cathelicidin antimicrobial peptide protects against bacterial skin infection

Abstract

Cathelicidin antimicrobial peptides are effectors of innate immune defense in mammals. Humans and mice have only one cathelicidin gene, whereas domesticated mammals such as the pig, cow, and horse have multiple cathelicidin genes. We hypothesized that the evolution of multiple cathelicidin genes provides these animals with enhanced resistance to infection. To test this, we investigated the effects of the addition of cathelicidins by combining synthetic cathelicidin peptides in vitro, by producing human keratinocytes that overexpress cathelicidins in culture, or by producing transgenic mice that constitutively overexpress cathelicidins in vivo. The porcine cathelicidin peptide PR-39 acted additively with human cathelicidin LL-37 to kill group A Streptococcus (GAS). Lentiviral delivery of PR-39 enhanced killing of GAS by human keratinocytes. Finally, transgenic mice expressing PR-39 under the influence of a K14 promoter showed increased resistance to GAS skin infection (50% smaller necrotic ulcers and 60% fewer surviving bacteria). Similarly constructed transgenic mice designed to overexpress their native cathelicidin did not show increased resistance. These findings demonstrate that targeted gene transfer of a xenobiotic cathelicidin confers resistance against infection and suggests the benefit of duplication and divergence in the evolution of antimicrobial peptides.innate immunity ͉ keratinocyte

Cathelicidin Antimicrobial Peptides Block Dendritic Cell TLR4 Activation and Allergic Contact Sensitization

“…Their presence in cells and tissues inhibits microbial growth and provides protection against invasive infections in animal models (1)(2)(3). In addition, some of these peptides, such as cathelicidins and ␤-defensins, stimulate chemokine and cytokine secretion from a variety of cell types and can act through receptor-dependent mechanisms (4 -6).…”

“…The overexpression of cathelicidin or ␣-defensins in transgenic models has failed to demonstrate an increase in acute local inflammation that might be predicted by work in cultured cells (2,3), although experiments specifically directed to detect this effect have not been reported. Therefore, to better understand the role of cathelicidins on inflammation, we analyzed the effect in mice of cathelicidin by investigating contact hypersensitivity to epicutaneously applied hapten, a model representing allergic contact dermatitis.…”

Innate barriers against skin infection and associated disorders

“…Elimination of the gene Cnlp encoding the sole murine cathelicidin mCRAMP rendered the knockout mice mice highly susceptible to necrotizing skin infection produced by GAS [19]; conversely, a GAS mutant in transcriptional regulator crgR increased cathelicidin resistance and virulence of GAS in normal mice [40]. Consistent with a front line role of AMPs in GAS defense, keratinocyte-specific expression of porcine cathelicidin in transgenic mice restricted GAS disease progression in the skin infection model [24].…”

“…For example, the knockout mouse lacking cathelicidin is more susceptible to bacterial infection of the skin [19], conjuctivae [20], gastrointestinal tract [21], urinary tract [22], and bloodstream [23]. Conversely, enhanced resistance to bacterial infection is provided by augmenting cathelicidin levels by transgenics [24], viral gene therapy [25], or pharmacologic administration [26]. Consequently, loss of virulence in mouse infection models has allowed corroboration of candidate bacterial AMP resistance factors identified by altered susceptibility during in vitro testing.…”

Porcine Cathelicidins Efficiently Complex and Deliver Nucleic Acids to Plasmacytoid Dendritic Cells and Can Thereby Mediate Bacteria-Induced IFN-α Responses

“…The porcine cathelicidin family includes the prophenin-1 and -2, proline-arginine-rich 39-aa peptide (PR-39), disulfide-bridged cysteine-rich protegrins (PG-1 to PG-5), and a-helical porcine myeloid antimicrobial peptides (PMAP-23, PMAP-36, and PMAP-37) (3). Antimicrobial activity has been well characterized for PR-39 (4,5), PMAP-23 (6, 7), PMAP-36 (8), and PG-1 (9,10). It was also shown that PR-39 displays chemotactic activity in neutrophils (11).…”