Gómez L E, Nasser J R, Basombrío M A
Facultad de Ciencias de la Salud, Universidad Nacional de Salta, Argentina.
Mem Inst Oswaldo Cruz. 1996 Jan-Feb;91(1):55-61. doi: 10.1590/s0074-02761996000100009.
Experimental systems to assay immunity against Trypanosoma cruzi usually demonstrate partial resistance without excluding the establishment of sub-patent infections in protected animals. To test whether Swiss mice immunized with attenuated parasites might develop complete resistance against virulent T. cruzi, experiments were performed involving challenge with low numbers of parasites, enhancement of local inflammation and the combination of natural and acquired resistance. Absence of infection was established after repeated negative parasitological tests (including xenodiagnosis and hemoculture), and lack of lytic antibody was tested by complement mediated lysis. Immunization with 10(7) attenuated epimastigotes conferred protection against the development of high levels of parasitemia after challenge with Tulahuen strain, but was unable to reduce the number of infected animals. However, when a strong, delayed-type hypersensitivity reaction was triggered at the site of infection by injecting a mixture of virulent and attenuated T. cruzi, a significant proportion of immunized animals remained totally free of virulent infection. The same result was obtained when the immunization experiment was performed in four month old Swiss mice, displaying a relatively high natural resistance and challenged with wild, vector-borne parasites. These experiments demonstrate that complete resistance against T. cruzi can be obtained in a significant proportion of animals, under conditions which replicate natural, vector delivered infection by the parasite.
用于检测针对克氏锥虫免疫力的实验系统通常显示出部分抗性，且无法排除受保护动物体内亚临床感染的发生。为了测试用减毒寄生虫免疫的瑞士小鼠是否可能对强毒克氏锥虫产生完全抗性，进行了一系列实验，包括用少量寄生虫进行攻击、增强局部炎症以及天然抗性与获得性抗性的联合应用。在反复进行阴性寄生虫学检测（包括异体接种诊断和血液培养）后确定无感染，并通过补体介导的溶解作用检测溶细胞抗体的缺乏情况。用10(7)个减毒的前鞭毛体免疫可使小鼠在受到图拉洪株攻击后免受高水平寄生虫血症的影响，但无法减少受感染动物的数量。然而，当通过注射强毒和减毒克氏锥虫的混合物在感染部位引发强烈的迟发型超敏反应时，相当比例的免疫动物完全没有受到强毒感染。在四个月大的瑞士小鼠中进行免疫实验时也得到了相同的结果，这些小鼠显示出相对较高的天然抗性，并受到野生的、由媒介传播的寄生虫的攻击。这些实验表明，在模拟寄生虫通过媒介进行自然传播感染的条件下，相当比例的动物可以获得对克氏锥虫的完全抗性。
