title: Evolution of antigenic diversity in the tick-transmitted bacterium Borrelia afzelii: a role for host specialization?
abstract: 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 whether 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 < 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.
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: L
authors.identifier: 0000-0001-5219-7448
authors.initials: L
authors.lastname: Råberg
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: Å
authors.initials: Å
authors.lastname: Hagström
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Andersson
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Bartkova
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Scherman
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Strandh
authors.affiliation: Department of Biology, Lund University, Lund, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Tschirren
mesh_terms: D000818:Animals; D000940:Antigenic Variation; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D015748:Borrelia burgdorferi Group / Q000235:genetics* / Q000472:pathogenicity; D018884:Ixodes / Q000469:parasitology; D008193:Lyme Disease; D016133:Polymerase Chain Reaction
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins
keywords: Lyme borreliosis; antigenic diversity; ecological specialization