Laboratorio de Ecofisiología, Departamento de Biología, Universidad Nacional de Mar del Plata, CONICET, CC 1245, Mar del Plata, Argentina.
Infect Genet Evol. 2011 Jul;11(5):1023-36. doi: 10.1016/j.meegid.2011.03.016. Epub 2011 Apr 8.
Parasites and pathogens can play a significant role in shaping the genetic diversity of host populations, particularly at genes associated with host immune response. To explore this relationship in a natural population of vertebrates, we characterized Major Histocompatibility Complex (MHC) variation in the subterranean rodent Ctenomys talarum (the talas tuco-tuco) as a function of parasite load and ability to mount an adaptive immune response against a novel antigen. Specifically, we quantified genotypic diversity at the MHC class II DRB locus in relation to (1) natural variation in infection by multiple genera of parasites (potential agents of selection on MHC genes) and (2) antibody production in response to injection with sheep red blood cells (a measure of immunocompetence). Data were analyzed using co-inertia multivariate statistics, with epidemiological proxies for individual condition (hematocrit, leukocyte profile, body weight) and risk of parasite exposure (season of capture, sex). A significant excess of DRB heterozygotes was evident in the study population. Co-inertia analyses revealed significant associations between specific DRB alleles and both parasite load and intensity of humoral immune response against sheep red blood cells. The presence of specific DRB aminoacid sequences appeared to be more strongly associated with parasite load and response to a novel antigen than was heterozygosity at the DRB locus. These data suggest a role for parasite-driven balancing selection in maintaining MHC variation in natural populations of C. talarum. At the same time, these findings underscore the importance of using diverse parameters to study interactions among physiological conditions, immunocompetence, and MHC diversity in free-living animals that are confronted with multiple simultaneous immune challenges.
寄生虫和病原体在塑造宿主种群的遗传多样性方面可以发挥重要作用，尤其是在与宿主免疫反应相关的基因上。为了在脊椎动物的自然种群中探索这种关系，我们研究了地下啮齿动物 Ctenomys talarum（塔拉斯 tuco-tuco）的主要组织相容性复合体 (MHC) 变异，作为寄生虫负荷和对新抗原产生适应性免疫反应能力的函数。具体来说，我们量化了 MHC 类 II DRB 基因座的基因型多样性，与（1）多种寄生虫属的自然变异（对 MHC 基因选择的潜在因素）以及（2）对绵羊红细胞注射的抗体产生有关（免疫能力的衡量标准）。使用共惯性多变量统计分析数据，使用个体状况（红细胞压积、白细胞谱、体重）和寄生虫暴露风险（捕获季节、性别）的流行病学指标。在研究人群中明显存在 MHC 杂合子过多的情况。共惯性分析显示，特定的 DRB 等位基因与寄生虫负荷和针对绵羊红细胞的体液免疫反应强度之间存在显著关联。特定的 DRB 氨基酸序列的存在似乎与寄生虫负荷和对新抗原的反应比 DRB 基因座的杂合性更强相关。这些数据表明，寄生虫驱动的平衡选择在维持 C. talarum 自然种群的 MHC 变异方面发挥了作用。与此同时，这些发现强调了使用多种参数来研究生理状况、免疫能力和 MHC 多样性之间相互作用的重要性，这些参数适用于面临多种同时免疫挑战的自由生活动物。
