1887

Abstract

is an obligately intracellular, tick-transmitted, bacterial pathogen of humans and other animals. In order to evade host immunity during the course of infection, utilizes gene conversion to shuffle approximately 100 functional pseudogenes into a single expression cassette of the gene, which encodes the major surface antigen, major surface protein 2 (Msp2). The role and extent of recombination in a reservoir host for have not been evaluated. In the current study, we explored patterns of recombination and expression site variability of the gene in three chronically infected woodrats, a reservoir for the disease in the Western USA. All three woodrats developed persistent infection of at least 6 months duration; two of them maintained active infection for at least 8 months. In total, we detected the emergence of 60 unique expression site variants with no common temporal patterns of expression site recombination among the three populations. Both the strength of infection (i.e. pathogen load) and the genetic diversity of pseudogenes detected at the expression site fluctuated periodically during the course of infection. An analysis of the genomic pseudogene exhaustion rate showed that the repertoire of pseudogenes available to the population could in theory become depleted within a year. However, the apparent emergence of variant pseudogenes suggests that the pathogen could potentially evade host immunity indefinitely. Our findings suggest a tightly co-evolved relationship between and woodrats in which the pathogen perpetually evades host immunity yet causes no detectable disease.

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2012-10-01
2024-03-28
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