Vaughan J A, Noden B H, Beier J C
Department of Immunology and Infectious Diseases, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland.
Am J Trop Med Hyg. 1994 Aug;51(2):233-43. doi: 10.4269/ajtmh.1994.51.233.
Sporogonic development of cultured Plasmodium falciparum was compared in six species of Anopheles mosquitoes. A reference species, A. gambiae, was selected as the standard for comparison. Estimates of absolute densities were determined for each lifestage. From these data, four aspects of parasite population dynamics were analyzed quantitatively: 1) successive losses in abundance as parasites developed from gametocyte to ookinete to oocyst stages, 2) oocyst production of sporozoites, 3) correlation between various lifestage parameters, and 4) parasite distribution. Parasite populations in A. gambiae incurred a 316-fold loss in abundance during the transition from macrogametocyte to ookinete stage, a 100-fold loss from ookinete to oocyst stage, yielding a total loss of approximately 31,600-fold (i.e., losses are multiplicative). Comparative susceptibilities in order were A. freeborni >> A. gambiae, A. arabiensis, A. dirus > A. stephensi, A. albimanus. The key transition(s) determining overall susceptibility differed among species. Despite species differences in oocyst densities and infection rates, salivary gland sporozoite production per oocyst (approximately 640) was the same among species. The most consistent association among lifestage parameters was a positive correlation between densities and infection rates of homologous lifestages. A curvilinear relationship between ookinete and oocyst densities in A. gambiae indicated a threshold density was required for ookinete conversion to oocysts (approximately 30 ookinetes per mosquito). The same relationship in A. freeborni was linear, with no distinct threshold. Ookinete and oocyst populations were negative binomially distributed in all species. Indices of heterogeneity in mosquito susceptibility to infection indicated that gene frequencies determining susceptibility fluctuated with time in all species, except A. freeborni where susceptibility remained homogenous throughout the study. This approach provides a framework for identifying mechanisms of susceptibility and evaluating Plasmodium sporogonic development in naturally occurring vector species in nature.
在六种按蚊中比较了培养的恶性疟原虫的孢子增殖发育情况。选择冈比亚按蚊作为参考物种作为比较标准。确定了每个生活阶段的绝对密度估计值。根据这些数据，对寄生虫种群动态的四个方面进行了定量分析：1）随着寄生虫从配子体发育到动合子再到卵囊阶段，丰度的连续损失；2）卵囊产生子孢子的情况；3）不同生活阶段参数之间的相关性；4）寄生虫分布。在冈比亚按蚊中，寄生虫种群在从大配子体到动合子阶段的转变过程中丰度损失了316倍，从动合子到卵囊阶段损失了100倍，总共损失约31600倍（即损失是成倍的）。按敏感性顺序排列为：弗里伯恩按蚊>>冈比亚按蚊、阿拉伯按蚊、大劣按蚊>斯氏按蚊、白跗按蚊。决定总体易感性的关键转变在不同物种之间有所不同。尽管不同物种在卵囊密度和感染率上存在差异，但每个卵囊的唾液腺子孢子产量（约640个）在各物种之间是相同的。生活阶段参数之间最一致的关联是同源生活阶段的密度与感染率之间呈正相关。冈比亚按蚊中动合子和卵囊密度之间的曲线关系表明，动合子转化为卵囊需要一个阈值密度（每只蚊子约30个动合子）。弗里伯恩按蚊中的相同关系是线性的，没有明显的阈值。动合子和卵囊种群在所有物种中均呈负二项分布。蚊子对感染易感性的异质性指数表明，决定易感性的基因频率在所有物种中随时间波动，除了弗里伯恩按蚊，在整个研究过程中其易感性保持一致。这种方法为确定易感性机制和评估自然界中自然存在的媒介物种中的疟原虫孢子增殖发育提供了一个框架。
