Castañeda-Ortiz Elizabeth J, Ueti Massaro W, Camacho-Nuez Minerva, Mosqueda Juan J, Mousel Michelle R, Johnson Wendell C, Palmer Guy H
Posgrado en Ciencias Genomicas, Universidad Autónoma de la Ciudad de México, México D.F., México.
Animal Disease Research Unit, USDA-ARS, Pullman, Washington, United States of America; Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, United States of America.
PLoS One. 2015 Mar 20;10(3):e0120748. doi: 10.1371/journal.pone.0120748. eCollection 2015.
Strain superinfection occurs when a second strain infects a host already infected with and having mounted an immune response to a primary strain. The incidence of superinfection with Anaplasma marginale, a tick-borne rickettsial pathogen of domestic and wild ruminants, has been shown to be higher in tropical versus temperate regions. This has been attributed to the higher prevalence of infection, with consequent immunity against primary strains and thus greater selective pressure for superinfection with antigenically distinct strains. However an alternative explanation would be the differences in the transmitting vector, Dermacentor andersoni in the studied temperate regions and Rhipicephalus microplus in the studied tropical regions. To address this question, we examined two tropical populations sharing the same vector, R. microplus, but with significantly different infection prevalence. Using two separate markers, msp1α (one allele per genome) and msp2 (multiple alleles per genome), there were higher levels of multiple strain infections in the high infection prevalence as compared to the low prevalence population. The association of higher strain diversity with infection prevalence supports the hypothesis that high levels of infection prevalence and consequent population immunity is the predominant driver of strain superinfection.
当第二种菌株感染已经感染了第一种菌株并对其产生免疫反应的宿主时，就会发生菌株重叠感染。边缘无形体是一种蜱传播的家畜和野生反刍动物立克次氏体病原体，在热带地区与温带地区相比，其重叠感染的发生率更高。这归因于感染的较高流行率，随之产生针对原发性菌株的免疫力，从而对抗原性不同的菌株进行重叠感染产生更大的选择压力。然而，另一种解释可能是所研究的温带地区的传播媒介安德逊革蜱与热带地区的微小扇头蜱之间的差异。为了解决这个问题，我们研究了两个共享相同媒介微小扇头蜱但感染流行率显著不同的热带种群。使用两个独立的标记，即msp1α（每个基因组一个等位基因）和msp2（每个基因组多个等位基因），与低流行率种群相比，高感染流行率种群中的多菌株感染水平更高。较高的菌株多样性与感染流行率之间的关联支持了这样一种假设，即高感染流行率和随之而来的群体免疫是菌株重叠感染的主要驱动因素。
