Berger B J, Carter N S, Fairlamb A H
Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, UK.
Mol Biochem Parasitol. 1995 Feb;69(2):289-98. doi: 10.1016/0166-6851(94)00215-9.
Following selection in vitro by exposure to increasing concentrations of the aromatic diamidine pentamidine, a Trypanosoma brucei brucei clone has been characterised in vivo and in vitro. The resistant clone, designated T.b. brucei S427/118/PR32.6, was found to be less virulent than the parental clone T.b. bruci S427/118, with an intraperitoneal injection of 2.5 x 10(6) resistant organisms required to produce a course of disease equivalent to 1 x 10(4) sensitive trypanosomes. This lowered virulence is not associated with an increased susceptibility to the host's immune system, and is not due to the in vitro culturing process. The pentamidine-resistant clone was found to be 26- and 4.5-fold resistant to pentamidine in vitro and in vivo, respectively. Although not cross-resistant in vivo to any other aromatic diamidines (stilbamidine, berenil and propamidine), a 2.4-fold increase in resistance to the melaminophenylarsine melarsoprol was observed. While pentamidine completely inhibited uptake of 1 microM [3H]adenosine in the presence of 1 mM inosine, suggesting that pentamidine is transported by the inosine-insensitive P2 transporter, the pentamidine-resistant clone appeared to have a fully functional P2-adenosine transport system. Both resistant and parental cloned lines accumulated approx. 6 nmol pentamidine (10(8) cells)-1 over the course of 3 h, representing an internal concentration of 0.7-1.0 mM. Thus, unlike previously characterised drug-resistant trypanosomes, T.b. brucei PR32.6 is not deficient in drug accumulation, suggesting that other resistance mechanisms are likely to be involved.
通过暴露于浓度不断增加的芳香二脒喷他脒进行体外筛选后，对布氏布氏锥虫克隆株进行了体内和体外特性研究。该抗性克隆株命名为布氏布氏锥虫S427/118/PR32.6，发现其毒力低于亲本克隆株布氏布氏锥虫S427/118，腹腔注射2.5×10⁶个抗性虫体才能产生与1×10⁴个敏感锥虫相当的病程。这种降低的毒力与对宿主免疫系统易感性增加无关，也不是由于体外培养过程导致的。发现喷他脒抗性克隆株在体外和体内对喷他脒的抗性分别为26倍和4.5倍。虽然在体内对任何其他芳香二脒（司替巴脒、贝尼尔和丙脒）无交叉抗性，但观察到对美拉胂醇的抗性增加了2.4倍。在存在1 mM肌苷的情况下，喷他脒完全抑制了1 μM [³H]腺苷的摄取，这表明喷他脒是由肌苷不敏感的P2转运体转运的，而喷他脒抗性克隆株似乎具有功能完全正常的P2 - 腺苷转运系统。抗性克隆株和亲本克隆株在3小时内均积累了约6 nmol喷他脒（10⁸个细胞）⁻¹，代表内部浓度为0.7 - 1.0 mM。因此，与先前表征的耐药锥虫不同，布氏布氏锥虫PR32.6在药物积累方面并不缺乏，这表明可能涉及其他抗性机制。
