Michael E, Bundy D A
Department of Biology, Imperial College, University of London.
Parasitology. 1992 Aug;105 ( Pt 1):139-50. doi: 10.1017/s0031182000073790.
The influence of host dietary protein on acquired immunity and intestinal helminth population dynamics during repeated infection was studied using the mouse-Trichuris muris experimental model. CBA/Ca mice fed a 2% (by mass) protein diet ad libitum maintained body weight during the experiment, but when fed diets containing either 4% or 16% (by mass) protein gained weight steadily. Infection with T. muris did not affect the growth of the latter mice but significantly reduced the growth of animals fed on the 2% protein diet. When repeatedly infected with either 5 or 50 eggs every 10 days, the mice fed the 2% or 4% protein diet accumulated adults in proportion to infection dose. The results show that this is due to both the establishment of larvae at each repeated infection and the survival of established adults. In contrast, very few worms were recovered from animals fed the 16% protein diet, principally as a result of the development of strong acquired immunity to reinfection. T. muris egg output/mouse increased with infection dose in animals fed the low protein diets, but no parasite eggs were detected in the faeces of hosts fed the 16% protein diet. Mouse antibody responses to adult worm excretory/secretory antigen were time- and infection dose-dependent in all 3 dietary groups. The major finding was that the specific antibody response was more intense, both quantitatively (serum OD levels) and qualitatively (antigen recognition by IgG1), in mice fed the low protein diets, even though they remained susceptible to infection. This study shows that host dietary protein deficiency, even at levels irrelevant to normal growth, can markedly potentiate the transmission of T. muris via alterations in host resistance. The high levels of antibody in susceptible animals suggest that this defect in resistance is unlikely to be due to nutrient deficiency-associated defects in humoral immunity.
利用小鼠-鼠鞭虫实验模型，研究了宿主饮食蛋白质在重复感染期间对获得性免疫和肠道蠕虫种群动态的影响。随意喂食2%（质量分数）蛋白质饮食的CBA/Ca小鼠在实验期间体重保持稳定，但喂食含4%或16%（质量分数）蛋白质饮食的小鼠体重稳步增加。感染鼠鞭虫对后一组小鼠的生长没有影响，但显著降低了喂食2%蛋白质饮食小鼠的生长。当每10天重复感染5或50个虫卵时，喂食2%或4%蛋白质饮食的小鼠体内成虫数量与感染剂量成正比积累。结果表明，这是由于每次重复感染时幼虫的定植以及已定植成虫的存活。相比之下，喂食16%蛋白质饮食的动物体内回收的蠕虫很少，主要是由于对再感染产生了强大的获得性免疫。在喂食低蛋白饮食的动物中，鼠鞭虫的产卵量/小鼠随感染剂量增加，但在喂食16%蛋白质饮食的宿主粪便中未检测到寄生虫卵。在所有3个饮食组中，小鼠对成虫排泄/分泌抗原的抗体反应具有时间和感染剂量依赖性。主要发现是，即使喂食低蛋白饮食的小鼠仍易受感染，但它们的特异性抗体反应在数量上（血清OD水平）和质量上（IgG1对抗原的识别）都更强烈。这项研究表明，宿主饮食蛋白质缺乏，即使在与正常生长无关的水平，也可通过改变宿主抵抗力显著增强鼠鞭虫的传播。易感动物体内的高抗体水平表明，这种抵抗力缺陷不太可能是由于营养缺乏相关的体液免疫缺陷所致。
