Department of Medicine, Division of Infectious Diseases and Immunology
Bacterial Infections and Mycoses | Immunopathology
Pathogens possess the ability to adapt and survive in some host species but not in others-an ecological trait known as host tropism. Transmitted through ticks and carried mainly by mammals and birds, the Lyme disease (LD) bacterium is a well-suited model to study such tropism. Three main causative agents of LD, Borrelia burgdorferi, B. afzelii, and B. garinii, vary in host ranges through mechanisms eluding characterization. By feeding ticks infected with different Borrelia species, utilizing feeding chambers and live mice and quail, we found species-level differences in bacterial transmission. These differences localize on the tick blood meal, and specifically complement, a defense in vertebrate blood, and a polymorphic bacterial protein, CspA, which inactivates complement by binding to a host complement inhibitor, Factor H (FH). CspA selectively confers bacterial transmission to vertebrates that produce FH capable of allele-specific recognition. CspA is the only member of the Pfam54 gene family to exhibit host-specific FH-binding. Phylogenetic analyses revealed convergent evolution as the driver of such uniqueness, and that FH-binding likely emerged during the last glacial maximum. Our results identify a determinant of host tropism in Lyme disease infection, thus defining an evolutionary mechanism that shapes host-pathogen associations.
Nymphs, Blood, Quails, Spirochetes, Lyme disease, Borrelia infection, Borrelia burgdorferi, Tropism
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Copyright © 2021 Hart et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI of Published Version
Hart TM, Dupuis AP 2nd, Tufts DM, Blom AM, Starkey SR, Rego ROM, Ram S, Kraiczy P, Kramer LD, Diuk-Wasser MA, Kolokotronis SO, Lin YP. Host tropism determination by convergent evolution of immunological evasion in the Lyme disease system. PLoS Pathog. 2021 Jul 29;17(7):e1009801. doi: 10.1371/journal.ppat.1009801. PMID: 34324600; PMCID: PMC8354441. Link to article on publisher's site
Hart TM, Dupuis AP, Tufts DM, Blom AM, Starkey SR, Rego RO, Ram S, Kraiczy P, Kramer LD, Diuk-Wasser MA, Kolokotronis S, Lin Y. (2021). Host tropism determination by convergent evolution of immunological evasion in the Lyme disease system. Open Access Publications by UMass Chan Authors. https://doi.org/10.1371/journal.ppat.1009801. Retrieved from https://escholarship.umassmed.edu/oapubs/4860
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