Data from: Evolution of antigenic diversity in the tick-transmitted bacterium Borrelia afzelii: a role for host specialization?

Antigenic diversity in pathogenic microbes can be a result of at least three different processes: diversifying selection by acquired immunity, host-pathogen coevolution, and/or host specialization. Here, we investigate if host specialization drives diversity at ospC (which encodes an immunodominant surface protein) in the tick-transmitted bacterium Borrelia afzelii. We determined prevalence and infection intensity of ospC strains in naturally infected wild mammals (rodents and shrews) by 454 amplicon sequencing in combination with qPCR. Neither prevalence nor infection intensity of specific ospC strains varied in a species-specific manner (i.e. there were no significant ospC × host species interactions). Rankings of ospC prevalences were strongly positively correlated across host species. Rankings of ospC infection intensities were correlated more weakly, but only in one case significantly less than 1. ospC prevalences in the studied mammals were similar to those in ticks sampled at the study site, indicating that we did not miss any mammal species that are important hosts for specific ospC strains. Based on this we conclude that there is at best limited host specialization in B. afzelii, and that other processes are likely the main drivers of ospC diversity.

致病微生物的抗原多样性至少可由三种不同过程产生：获得性免疫介导的歧化选择、宿主-病原体协同进化，以及（或）宿主特化。本研究针对蜱传病原菌阿氏疏螺旋体（Borrelia afzelii）中ospC（编码免疫显性表面蛋白的基因）的多样性，探究宿主特化是否为其驱动因素。我们通过454扩增子测序结合定量聚合酶链反应（qPCR），测定了自然感染的野生哺乳动物（啮齿类与鼩鼱类）体内ospC菌株的流行率与感染载量。研究发现，特定ospC菌株的流行率与感染载量均未呈现宿主物种特异性差异（即未检测到显著的ospC×宿主物种交互作用）。不同宿主物种间的ospC流行率排名呈现极强的正相关；而ospC感染载量的排名相关性则较弱，但仅在一例中显著小于1。本研究涉及的哺乳动物体内的ospC流行率，与研究地点采集的蜱样本中的流行率相近，表明我们未遗漏对特定ospC菌株而言至关重要的宿主哺乳动物物种。基于上述结果，我们得出结论：阿氏疏螺旋体的宿主特化程度至多十分有限，而其他过程或为ospC基因多样性的主要驱动因素。