The Study on the Virulence of Trypanosoma cruzi

虽然克氏锥虫锥马鞭毛体转化为无尾鞭毛体的过程似乎是自发发生的，但研究表明，将锥马鞭毛体保持在低pH下，用10 mM柠檬酸-磷酸盐缓冲液调节，可以加速这一过程。这个过程需要一定的营养物质，并涉及化学物质的分离，这些化学物质甚至可以裂解寄生虫。在添加1%牛白蛋白的低pH（4.5-6.0）组织培养基中，快速完成转化。用10 mM醋酸缓冲液调节低pH值，对寄生虫剧毒。有趣的是，高毒力克隆或菌株的裂解作用比低毒力克隆或菌株强得多。溶酶的表征表明它可能是脂质。在pH值为7.4的培养基中，血清的存在抑制了这种转化，导致长时间维持锥马鞭毛虫阶段。牛白蛋白云可替代全血清，但维持乳糜虫的能力较差。对各种限制性酶切后的着丝体DNA进行比较发现，高毒力克隆或菌株中EcoRl酶切的DNA片段模式与低毒力克隆或菌株中EcoRl酶切的DNA片段模式截然不同，两者具有相同的模式。利用从不同片段中获得的探针进行杂交试验，证明存在高毒力克隆的特定序列。

Although the process of transformation of Trypanosoma cruzi trypomastigote to amastigote seemed to take place spontaneously, it was demonstrated that the process was accelerated by keeping trypomastigotes at low pH that was adjusted by 10 mM citrate-phosphate buffer. The process required certain nutrients and involved the separation of chemical substances which lysed even parasites. The lytic effect was neutralized by bovine albumin, accordingly the transformation was rapidly completed in tissue culture medium at low pH, 4.5-6.0, supplemented with 1% bovine albumin. Low pH adjusted by 10 mM acetate buffer was highly toxic to parasites. The interesting point is that the lytic effect was much stronger in high-virulent clone or strains than in low virulenct. Characterization of the lysin suggested that it might be lipid.The presence of serum in media at pH 7.4 suppressed the transformation, resulting in the long maintenance of the trypomastigote stage. Bovine albumin cloud replace whole serum but the ability to maintain the trypomastigote was less. Comparison of minicircle DNA of the kinetoplast after digestion by various restricted enzymes revealed that the pattern of DNA fragments digested by EcoRl in the high-virulent clone or strains was very distinct from the low-virulent clone or strains, which shared the same pattern. Hybridization test using the probe obtained from the distinct fragment demonstrated presence of the specific sequence to the high-vireulent clone.