Louassini M, Adroher F J, Foulquié M R, Benítez R
Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, Campus Universitario de Cartuja, Spain.
Acta Trop. 1998 Jul 30;70(3):355-68. doi: 10.1016/s0001-706x(98)00041-2.
The in vitro metacyclogenesis of a visceral (VL) and cutaneous (CL) human strain of Leishmania infantum was monitored in order to find out the kinetics of this process and the in vitro infective capacity for macrophages of the metacyclic promastigotes developed. To identify, enumerate, and separate the metacyclic population, the complement-dependent lysis by normal serum and the agglutination by peanut agglutinin (PNA) were used, as they were shown to be useful for the purpose of this study. Maximum percentage of metacyclics was detected by both techniques on the 4th day of growth for VL and the 6th day for CL, and was higher for the VL strain. The in vitro infectivity for macrophages of two strains was assayed, and the high parasitization data obtained were transformed in order to determine the increase of the parasite burden for macrophages throughout the incubation time of the experiments (2-72 h post-infection (p.i.)). This parameter is denominated the infectivity ratio (%I) and calculated as follows: (number of intracellular parasites per infected macrophage at 'x' time p.i./number of intracellular parasites per infected macrophage at 2 h p.i.) x 100. When %I was calculated for promastigotes unagglutinated by PNA (PNA-)--metacyclic or infective promastigotes--at any time of culture, the %I at 72 h p.i. was always much higher than for agglutinated promastigotes (2.1-12.5 times)--non-infective promastigotes--and unfractionated promastigotes from culture (1.7-9.5 times), especially with VL parasites. Likewise, the %I for VL PNA- promastigotes from the 4th day of culture was 1.9 times higher than for CL PNA- promastigotes from the 6th day of culture. The higher resistance to lysis by serum, percentage of metacyclics (PNA-), and infectivity ratio of VL than CL could be related to a higher spreading capability into the host body associated with higher pathogenic effects of the visceral strain than the cutaneous one.
为了了解婴儿利什曼原虫内脏型（VL）和皮肤型（CL）人源菌株的体外循环前鞭毛体发育过程的动力学以及所发育的循环前鞭毛体对巨噬细胞的体外感染能力，对其进行了监测。为了鉴定、计数和分离循环前鞭毛体群体，使用了正常血清的补体依赖性裂解和花生凝集素（PNA）的凝集，因为它们已被证明对本研究目的有用。两种技术在VL生长的第4天和CL生长的第6天检测到循环前鞭毛体的最大百分比，且VL菌株的该百分比更高。测定了两种菌株对巨噬细胞的体外感染性，并对获得的高寄生数据进行转换，以确定在整个实验孵育时间（感染后2 - 72小时）内巨噬细胞中寄生虫负荷的增加情况。该参数称为感染率（%I），计算如下：（感染后‘x’小时每个感染巨噬细胞内的寄生虫数量/感染后2小时每个感染巨噬细胞内的寄生虫数量）×100。当计算培养任何时间未被PNA凝集的前鞭毛体（PNA -）——循环前鞭毛体或感染性前鞭毛体——的%I时，感染后72小时的%I总是比凝集的前鞭毛体（2.1 - 12.5倍）——非感染性前鞭毛体——和培养物中的未分级前鞭毛体（1.7 - 9.5倍）高得多，尤其是对于VL寄生虫。同样，培养第4天的VL PNA - 前鞭毛体的%I比培养第6天的CL PNA - 前鞭毛体高1.9倍。VL比CL对血清裂解的抵抗力更高、循环前鞭毛体百分比（PNA -）更高以及感染率更高，这可能与内脏型菌株比皮肤型菌株具有更高的向宿主体内扩散的能力以及更高的致病作用有关。
