Antigenic and genetic heterogeneity of Borrelia burgdorferi populations transmitted by ticks.
The genome of Borrelia burgdorferi encodes a large number of lipoproteins, many of which are expressed only at certain stages of the spirochete's life cycle. In the current study we describe the B. burgdorferi population structure with respect to the production of two lipoproteins [outer surface protein A (OspA) and outer surface protein C (OspC)] during transmission from the tick vector to the mammalian host. Before the blood meal, the bacteria in the tick were a homogeneous population that mainly produced OspA only. During the blood meal, the population became more heterogeneous; many bacteria produced both OspA and OspC, whereas others produced only a single Osp and a few produced neither Osp. From the heterogeneous spirochetal population in the gut, a subset depleted of OspA entered the salivary glands and stably infected the host at time points >53 hr into the blood meal. We also examined genetic heterogeneity at the B. burgdorferi vlsE locus before and during the blood meal. In unfed ticks, the vlsE locus was stable and one predominant and two minor alleles were detected. During the blood meal, multiple vlsE alleles were observed in the tick. Tick feeding may increase recombination at the vlsE locus or selectively amplify rare vlsE alleles present in unfed ticks. On the basis of our data we propose a model, which is different from the established model for B. burgdorferi transmission. Implicit in our model is the concept that tick transmission converts a homogeneous spirochete population into a heterogeneous population that is poised to infect the mammalian host.
Ohnishi
J
J
Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599, USA.
Piesman
J
J
de Silva
A M
AM
D000483:Alleles; D000818:Animals; D000940:Antigenic Variation / Q000235:genetics; D000942:Antigens, Bacterial / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics* / Q000502:physiology; D001179:Arthropod Vectors / Q000382:microbiology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D001733:Bites and Stings / Q000382:microbiology; D015748:Borrelia burgdorferi Group / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification / Q000472:pathogenicity; D005247:Feeding Behavior; D005798:Genes, Bacterial; D014644:Genetic Variation; D007422:Intestines / Q000382:microbiology; D008074:Lipoproteins / Q000235:genetics*; D008193:Lyme Disease / Q000382:microbiology* / Q000635:transmission; D022123:Lyme Disease Vaccines / Q000235:genetics*; D051379:Mice; D008809:Mice, Inbred C3H; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012469:Salivary Glands / Q000382:microbiology; D012867:Skin / Q000382:microbiology; D013987:Ticks / Q000382:microbiology*; D013997:Time Factors
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D008074:Lipoproteins; D022123:Lyme Disease Vaccines; C072045:OspA protein; C079616:OspC protein; C105546:VlsE protein, Borrelia burgdorferi