title: Cross-reactive acquired immunity influences transmission success of the Lyme disease pathogen, Borrelia afzelii.
abstract: Cross-reactive acquired immunity in the vertebrate host induces indirect competition between strains of a given pathogen species and is critical for understanding the ecology of mixed infections. In vector-borne diseases, cross-reactive antibodies can reduce pathogen transmission at the vector-to-host and the host-to-vector lifecycle transition. The highly polymorphic, immunodominant, outer surface protein C (OspC) of the tick-borne spirochete bacterium Borrelia afzelii induces a strong antibody response in the vertebrate host. To test how cross-immunity in the vertebrate host influences tick-to-host and host-to-tick transmission, mice were immunized with one of two strain-specific recombinant OspC proteins (A3, A10), challenged via tick bite with one of the two B. afzelii ospC strains (A3, A10), and infested with xenodiagnostic ticks. Immunization with a given rOspC antigen protected mice against homologous strains carrying the same major ospC group allele but provided little or no cross-protection against heterologous strains carrying a different major ospC group allele. There were cross-immunity effects on the tick spirochete load but not on the probability of host-to-tick transmission. The spirochete load in ticks that had fed on mice with cross-immune experience was reduced by a factor of two compared to ticks that had fed on naive control mice. In addition, strain-specific differences in mouse spirochete load, host-to-tick transmission, tick spirochete load, and the OspC-specific IgG response revealed the mechanisms that determine variation in transmission success between strains of B. afzelii. This study shows that cross-immunity in infected vertebrate hosts can reduce pathogen load in the arthropod vector with potential consequences for vector-to-host pathogen transmission.
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland. Electronic address: maxime.jacquet@unine.ch.
authors.forename: Maxime
authors.initials: M
authors.lastname: Jacquet
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Durand
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Rais
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Voordouw
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000276:immunology; D025065:Borrelia burgdorferi / Q000235:genetics / Q000276:immunology; D015748:Borrelia burgdorferi Group / Q000235:genetics / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology*; D004195:Disease Models, Animal; D005260:Female; D054884:Host-Pathogen Interactions; D006801:Humans; D007114:Immunization; D018884:Ixodes / Q000382:microbiology; D008193:Lyme Disease / Q000276:immunology* / Q000382:microbiology / Q000473:pathology / Q000635:transmission*; D051379:Mice; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; C079616:OspC protein; D011994:Recombinant Proteins
keywords: Acquired immunity; Borrelia afzelii; Cross-immunity; Lyme borreliosis; Outer surface protein C; Pathogen transmission