Human Chemokines as Antimicrobial Peptides with Direct Parasiticidal Effect on Leishmania mexicana In Vitro

Abstract

Chemokines and chemokine receptor-mediated effects are important mediators of the immunological response and cure in human leishmaniasis. However, in addition to their signalling properties for leukocytes, many chemokines have also been shown to act directly as antimicrobial peptides on bacteria and fungi. We screened ten human chemokines (CXCL2, CXCL6, CXCL8, CXCL9, CXCL10, CCL2, CCL3, CCL20, CCL27, CCL28) for antimicrobial effects on the promastigote form of the protozoan parasite Leishmania mexicana, and observed direct parasiticidal effects of several, CCL28 being the most potent. Damage to the plasma membrane integrity could be visualised by entrance of propidium iodide, as measured with flow cytometry, and by scanning electron microscopy, which showed morphological changes and aggregation of cells. The findings were in concordance with parasiticidal activity, measured by decreased mitochondrial activity in an MTT-assay. This is the first report of direct antimicrobial activity by chemokines on parasites. This component of immunity against Leishmania parasites identified here warrants further investigation that might lead to new insight in the mechanisms of human infection and/or new therapeutic approaches.

Serum Cytokines as Biomarkers of Early Trypanosoma cruzi infection by Congenital Exposure

“…In this study, MIG, a potent chemoattractant for Th1 cells (20) secreted by activated monocytes and macrophages, was increased in congenitally infected infants and positively associated with the risk for vertical transmission. Previous studies have shown that MIG has a parasiticidal effect on Leishmania mexicana promastigotes in vitro and that it induces small lesions in the plasma membrane of the parasite that can eventually lead it to death, but also that it is unable to generate immediate lysis (21). Previous studies have also shown increased MIG levels in the circulation of infants infected with malaria (22,23) and visceral leishmaniasis (24), supporting an important role for this chemokine in vivo.…”

CK11, a Teleost Chemokine with a Potent Antimicrobial Activity

“…These results have been confirmed by scanning electron microscopy and TEM in which a complete disorganization of the cellular content, loss of cilia, and membrane disruption in response to CK11 have been confirmed. Interestingly, a previous study showed direct parasiticidal effects of several human chemokines on the promastigote form of Leishmania mexicana, CCL28 being the most potent chemokine against this protozoan (35). Furthermore, we demonstrated that through the course of an experimental infection with I. multifiliis, the transcription of CK11 was significantly upregulated in the skin at day 1 postinfection and afterward suppressed at day 8 postinfection.…”

“…1A), which contribute to this cationic character (isoelectric point [pI] of 10.62). Taking into account that the cationic properties of antimicrobial peptides and chemokines are considered responsible for their antimicrobial properties (35), the similar cationic nature of CK11 and mammalian CCL28 seems to anticipate similar antimicrobial capacities for these chemokines. Interestingly, despite the similar secondary structure of mammalian CCL27 proteins, their lower pI values have been proposed to account for their lack of antimicrobial activity (35).…”

“…In all these cases, similar morphological changes were observed in the cell membrane of the bacteria, which lead to the leakage of bacterial contents as a result of membrane disruption. Thus, rainbow trout CK11, although phylogenetically related to both CCL27 and CCL28, shares a higher amino acid identity with CCL27 but has maintained the antimicrobial properties of CCL28 that CCL27 does not show, most probably as a consequence of its lower pI value (9.11 in the case of human CCL27) (35). In contrast, CK11 is strongly expressed in homeostasis in the skin, similarly to CCL27 (47), whereas CCL28 is not expressed on the skin but is expressed in other mucosal surfaces, such as intestines, reproductive tracts, lungs, stomach, lactating mammary glands, and salivary glands (14,48,49).…”

“…Finally, as some human chemokines have shown antiparasitic activity against protozoa (35,61), we investigated whether CK11 was capable of affecting the viability of I. multifiliis, an external protozoan parasite of rainbow trout. Our experiments confirmed that CK11 exerts a direct effect on the cellular membrane of I. multifiliis theronts and, consequently, on their viability.…”