Carryn Stéphane, Schaefer Deborah A, Imboden Michael, Homan E Jane, Bremel Robert D, Riggs Michael W
Department of Veterinary Science and Microbiology, University of Arizona, Tucson, Arizona 85721, USA.
J Parasitol. 2012 Feb;98(1):199-204. doi: 10.1645/GE-2822.1. Epub 2011 Jul 25.
The apicomplexan parasite Cryptosporidium parvum is an important cause of diarrhea in humans and cattle, and it can persistently infect immunocompromised hosts. No consistently effective parasite-specific pharmaceuticals or immunotherapies for control of cryptosporidiosis are presently available. The innate immune system represents the first line of host defense against a range of infectious agents, including parasitic protozoa. Several types of antimicrobial peptides and proteins, collectively referred to herein as biocides, constitute a major effector component of this system. In the present study, we evaluated lactoferrin, lactoferrin hydrolysate, 5 cationic peptides (lactoferricin B, cathelicidin LL37, indolicidin, β-defensin 1, β-defensin 2), lysozyme, and 2 phospholipases (phospholipase A2, and phosphatidylinositol-specific phospholipase C) for anti-cryptosporidial activity. The biocides were evaluated either alone or in combination with 3E2, a monoclonal antibody (MAb) against C. parvum that inhibits sporozoite attachment and invasion. Sporozoite viability and infectivity were used as indices of anti-cryptosporidial activity in vitro. All biocides except lactoferrin had a significant effect on sporozoite viability and infectivity. Lactoferrin hydrolysate and each of the 5 cationic peptides were highly parasiticidal and strongly reduced sporozoite infectivity. While each phospholipase also had parasiticidal activity, it was significantly less than that of lactoferrin hydrolysate and each of the cationic peptides. However, each phospholipase reduced sporozoite infectivity comparably to that observed with lactoferrin hydrolysate and the cationic peptides. Moreover, when 3 of the cationic peptides (cathelicidin LL37, β-defensin 1, and β-defensin 2) were individually combined with MAb 3E2, a significantly greater reduction of sporozoite infectivity was observed over that by 3E2 alone. In contrast, reduction of sporozoite infectivity by a combination of either phospholipase with MAb 3E2 was no greater than that by 3E2 alone. These collective observations suggest that cationic peptides and phospholipases neutralize C. parvum by mechanisms that are predominantly either parasiticidal or non-parasiticidal, respectively.
顶复门寄生虫微小隐孢子虫是人类和牛腹泻的重要病因，它能持续感染免疫功能低下的宿主。目前尚无持续有效的针对该寄生虫的药物或免疫疗法来控制隐孢子虫病。固有免疫系统是宿主抵御包括寄生原生动物在内的一系列感染因子的第一道防线。几种抗菌肽和蛋白质，在此统称为杀生物剂，构成了该系统的主要效应成分。在本研究中，我们评估了乳铁蛋白、乳铁蛋白水解产物、5种阳离子肽（乳铁蛋白B、抗菌肽LL37、吲哚杀菌素、β-防御素1、β-防御素2）、溶菌酶以及2种磷脂酶（磷脂酶A2和磷脂酰肌醇特异性磷脂酶C）的抗隐孢子虫活性。这些杀生物剂单独或与3E2（一种抗微小隐孢子虫的单克隆抗体，可抑制子孢子的附着和侵入）联合进行评估。子孢子活力和感染力用作体外抗隐孢子虫活性的指标。除乳铁蛋白外，所有杀生物剂对子孢子活力和感染力均有显著影响。乳铁蛋白水解产物和5种阳离子肽中的每一种都具有高度杀寄生虫作用，并能显著降低子孢子感染力。虽然每种磷脂酶也具有杀寄生虫活性，但其活性明显低于乳铁蛋白水解产物和阳离子肽中的任何一种。然而，每种磷脂酶降低子孢子感染力的程度与乳铁蛋白水解产物和阳离子肽相当。此外，当3种阳离子肽（抗菌肽LL37、β-防御素1和β-防御素2）分别与单克隆抗体3E2联合使用时，观察到子孢子感染力的降低程度明显大于单独使用3E2时。相反，任何一种磷脂酶与单克隆抗体3E2联合使用时对子孢子感染力的降低程度均不大于单独使用3E2时。这些总体观察结果表明，阳离子肽和磷脂酶分别通过主要为杀寄生虫或非杀寄生虫的机制中和微小隐孢子虫。
