Humoral immune response in dogs naturally infected with Borrelia burgdorferi sensu lato and in dogs after immunization with a Borrelia vaccine

Abstract

Lyme arthritis in dogs can be induced under experimental and natural conditions. However, the veterinary relevance of canine borreliosis is still under extensive investigation. The prevalence of symptoms is clearly low, although the risk of tick exposure is high. Current research focuses on case definitions, methods for diagnosing clinical disease in dogs, and discrimination between an immune response to a natural infection and an immune response to vaccination. In this experimental study, 23 dogs raised under tick-free conditions were allocated to two groups. The 11 dogs in the first group were vaccinated with a commercial borrelia vaccine and subsequently developed detectable antibody titers. The 12 dogs in the second group were walked on two consecutive days in an area where ticks were endemic. On day 5 after exposure, engorged ticks were removed from the 12 dogs and were analyzed for Borrelia DNA by a real-time PCR assay. Blood samples were taken before exposure/vaccination and at defined time points thereafter. Antibody responses were evaluated using an immunofluorescence antibody test (IFAT) and Western blotting. Seven dogs from which Borrelia-positive ticks were removed seroconverted and developed individual immune responses. Blood and urine samples taken from the tick-exposed group at weeks 1 and 3 for real-time PCR analysis and culture were always negative for bacterial DNA. In conclusion, despite serological evidence of infection/immunization, no clinical signs of disease were observed. The antibody patterns in a single Western blot did not permit differentiation between the different antigen sources (vaccine versus natural infection). However, repeated Western blot analyses may be useful for the confirmation of infection or vaccination status, since the time courses of the levels of specific antibodies seem to be different.

FIG. 1.

Schedules for the vaccination and infection studies of 23 dogs. i, infection study group; v, vaccination study group.

FIG. 2.

Frequencies of Borrelia bands in baseline Western blots (recomBlot and MegaBlot, IgG and IgM) for 23 dogs.

FIG. 3.

Frequencies of Borrelia Western blot bands (recomBlot and MegaBlot) for IgG (a) and IgM (b) in dogs after vaccination (early, 2 to 6 weeks after the 2nd or 3rd vaccination; late, 9 to 48 weeks after the 2nd vaccination) and after infection (early, 2 to 7 weeks after infection; late, 9 to 15 weeks after infection). p41int./g., p41int.garinii; p41int./a., p41int.afzelii.

FIG. 4.

Mean intensities (± standard deviations) of IgG Western blot bands for dogs after B. burgdorferi vaccination or natural infection (at week 0). Asterisks indicate significant differences (*, P < 0.05; **, P < 0.01).

FIG. 5.

Mean percentages of positive bands in IgG Western blots for dogs after B. burgdorferi vaccination or natural infection (at week 0). Asterisks indicate significant differences (**, P < 0.01).