The major surface‐metalloprotease of the parasitic protozoan, Leishmania, protects against antimicrobial peptide‐induced apoptotic killing

Abstract

SummaryHuman infection by the vector-borne protozoan Leishmania is responsible for substantial worldwide morbidity and mortality. The surface-metalloprotease (leishmanolysin) of Leishmania is a virulence factor which contributes to a variety of functions including evasion of complement-mediated parasite-killing and host intramacrophage survival. We tested the hypothesis that leishmanolysin serves to protect parasites from the cytolytic effects of various antimicrobial peptides (AMPs) which are important components of the innate immune system. We found that members of the a-and q-defensins, magainins and cathelicidins had substantially higher leishmanicidal activity against leishmanolysin-knock out mutants of L. major. Using the magainin analogue, pexiganan, as a model peptide we show that AMP evasion is due to rapid and extensive peptide degradation by wild-type parasites. Pexiganan-treatment of knock out mutants induced disruption of surface-membrane permeability and expression of features of apoptosis including smaller cell size, loss of mitochondrial membrane potential, exposure of surface phosphatidyl serine as well as induction of caspase 3/7 activity. These results demonstrate leishmanolysin as a virulence factor preventing AMP-mediated apoptotic killing. This study serves as a platform for the dissection of the AMP-mediated death pathways of Leishmania and demonstrates the potential that AMP evasion plays during host infection by this parasite.

Therapeutic Efficacy of Stable Analogues of Vasoactive Intestinal Peptide against Pathogens

“…1). Moreover, the VIP derivatives showed lower EC 50 values than VIP for all of the bacteria strains assayed (Table 2). Interestingly, the VIP derivatives, but not VIP, were able to efficiently kill Gram-positive bacteria (Fig.…”

“…We calculated EC 50 , which represents the concentration of the peptide that reduces to 50% the viability of each bacteria and parasite strain, by using four-parameter logistic curve-fitting software (SigmaPlot).…”

Fibronectin Binding and Proteolytic Degradation byLeishmaniaand Effects on Macrophage Activation

“…Leishmanolysin-deficient para- sites have been shown to have diminished virulence in mice, which has been attributed to their enhanced susceptibility to complement-mediated lysis (13,25). We hypothesize that multiple additional leishmanolysin-dependent events may account for these results, including the inability of these parasites to degrade FN and generate FNd for M deactivation and the ability of these parasites to degrade and inactivate host antimicrobial peptides (15). CPs may also contribute to these processes.…”

“…We tested both L. amazonensis promastigotes and amastigotes for this analysis and found that preincubation with antileishmanolysin antibody did not diminish the association of FN-FITC with either parasite form. Second, we compared both the wild type and the gp63 KO mutant of L. major lines (13,15) for their degree of FN-FITC binding (Fig. 2C).…”

Synthesis of Bioinorganic Antimicrobial Peptide Nanoparticles with Potential Therapeutic Properties

“…3,4,18 In addition, inhibitory enzymes present in bodily fluids and expressed extracellularly from pathogenic microorganisms will also decrease effective concentration levels of AMPs. [19][20][21][22] One challenge, therefore, is to develop methods that will increase the stability of cationic AMPs and protect them from inactivation without repressing their antimicrobial effect. In many applications in biochemical and biomedical engineering, protein stability and protection is maintained through the use of mineralization or polymerization reagents to encapsulate and retain protein activity (e.g., sol gels, epoxy resins, synthetic phospholipid vesicles, and polymer sponges).…”