Villalta F, Kierszenbaum F
Am J Trop Med Hyg. 1987 May;36(3):529-32. doi: 10.4269/ajtmh.1987.36.529.
We report in this paper significant differences in the virulence of insect-derived and cultured metacyclic forms of Trypanosoma cruzi which are morphologically indistinguishable. Mice infected intraperitoneally with 10(3) metacyclic T. cruzi isolated from Rhodnius prolixus showed average parasitemia levels greater than 2 X 10(5) organisms/ml around day 10 post-infection (when first measured) and peak levels recorded on day 16 post-infection exceeded 4 X 10(7) organisms/ml. None of these animals survived after 30 days post-infection. In contrast, in mice infected with 10(3) or 10(4) metacyclic forms from axenic cultures the highest average parasitemia was approximately 10(4) organisms/ml and occurred around day 19 post-infection. In these animals, parasitemias declined with time to become undetectable and no mortality was recorded over the 100-day observation period. There was also a marked difference in the 50% lethal dose of insect- and culture-derived metacyclics. The value for the former was 670 parasites whereas none of the mice infected intraperitoneally with up to 10(6) cultured metacyclics died. These results point to a marked difference in the biological properties of insect-borne and cultured T. cruzi metacyclics under our experimental conditions and caution against extending results obtained with the latter to vector-transmissible metacyclics, at least in infectivity and virulence studies.
我们在本文中报告了克氏锥虫昆虫来源的和培养的形态上无法区分的循环后期形态在毒力上的显著差异。腹腔注射从长红猎蝽分离得到的10³个克氏锥虫循环后期形态的小鼠，在感染后第10天左右（首次测量时）显示平均寄生虫血症水平大于2×10⁵个生物体/毫升，感染后第16天记录的峰值水平超过4×10⁷个生物体/毫升。这些动物在感染后30天内均未存活。相比之下，在感染来自无菌培养物的10³或10⁴个循环后期形态的小鼠中，最高平均寄生虫血症约为10⁴个生物体/毫升，发生在感染后第19天左右。在这些动物中，寄生虫血症随时间下降至无法检测到，并且在100天的观察期内未记录到死亡情况。昆虫来源的和培养来源的循环后期形态的50%致死剂量也存在显著差异。前者的值为670个寄生虫，而腹腔注射多达10⁶个培养的循环后期形态的小鼠均未死亡。这些结果表明，在我们的实验条件下，昆虫传播的和培养的克氏锥虫循环后期形态在生物学特性上存在显著差异，并提醒至少在感染性和毒力研究中，不要将后者获得的结果推广到媒介传播的循环后期形态。
