Barr S C, Rose D, Jaynes J M
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
J Parasitol. 1995 Dec;81(6):974-8.
Three cecropin-like lytic peptides (DC-1, DC-2, and DC-2R) were synthesized with virtually no sequence homology with the natural compound (cecropin B) while retaining the charge distribution, amphipathic, and hydrophobic properties of the natural compound. A fourth analog (alpha-Pi) without these later properties, but a similar molecular weight, was also synthesized as a nonlytic peptide control. The 3 lytic peptides were examined for their ability to kill Trypanosoma cruzi trypomastigotes in vitro, intracellular amastigotes in vitro, and their toxicity to a mammalian cell line. DC-2 at 5 microM and DC-1 and DC-2R at 10 microM were 100% effective in killing T. cruzi trypomastigotes in vitro, suggesting at least a 10-fold increase in lytic activity over previous tested lytic peptide analogues, SB-37 and Shiva-1. When T. cruzi-infected Vero cells were treated with a single or double exposure of low concentrations (2.5 microM) of DC-1, DC-2, and DC-2R there was a significant (P < 0.05) reduction in amastigote numbers/cell when compared to untreated and alpha-Pi-treated T. cruzi-infected cells. Vero cells alone treated with the lytic peptides showed no reduction in number or toxicity. One of the peptides (DC-1) was tested for its toxicity in AJ mice and its ability to reduce parasitemias in T. cruzi-infected AJ mice. No untoward effects were seen in AJ mice injected intravenously with 50 micrograms/mouse daily for 10 days. There was a significant (P < 0.05) reduction in parasitemia and mortality by day 14 postinoculation (from 100% to 0%) in T. cruzi-infected AJ mice given 25 micrograms of DC-1/mouse on days 2, 4, 6, 8, and 10 postinoculation.
合成了三种类天蚕素溶菌肽（DC-1、DC-2和DC-2R），它们与天然化合物（天蚕素B）几乎没有序列同源性，但保留了天然化合物的电荷分布、两亲性和疏水性。还合成了第四种类似物（α-Pi），它没有这些特性，但分子量相似，作为非溶菌肽对照。检测了这3种溶菌肽在体外杀死克氏锥虫锥鞭毛体、体外细胞内无鞭毛体的能力以及它们对哺乳动物细胞系的毒性。5微摩尔的DC-2以及10微摩尔的DC-1和DC-2R在体外杀死克氏锥虫锥鞭毛体的效率为100%，这表明其溶菌活性比之前测试的溶菌肽类似物SB-37和Shiva-1至少提高了10倍。当用低浓度（2.5微摩尔）的DC-1、DC-2和DC-2R单次或两次处理感染克氏锥虫的Vero细胞时，与未处理和用α-Pi处理的感染克氏锥虫的细胞相比，无鞭毛体数量/细胞显著减少（P<0.05）。单独用溶菌肽处理的Vero细胞数量没有减少，也没有毒性。检测了其中一种肽（DC-1）对AJ小鼠的毒性及其降低感染克氏锥虫的AJ小鼠寄生虫血症的能力。对每天静脉注射50微克/只、持续10天的AJ小鼠未观察到不良影响。在接种后第2、4、6、8和10天给感染克氏锥虫的AJ小鼠注射25微克/只的DC-1，到接种后第14天，寄生虫血症和死亡率显著降低（P<0.05）（从100%降至0%）。
