Groups of 15 laboratory-bred beagles were vaccinated and boosted with either a placebo or adjuvanted bivalent bacterin comprised of a traditional Borrelia burgdorferi strain and a unique ospA- and ospB-negative B. burgdorferi strain that expressed high levels of OspC and then challenged with B. burgdorferi-infected Ixodes scapularis ticks. The vaccinated dogs produced high titers of anti-OspA and anti-OspC borreliacidal antibodies, including borreliacidal antibodies specific for an epitope within the last seven amino acids at the OspC carboxy terminus (termed OspC7) that was conserved among pathogenic Borrelia genospecies. In addition, spirochetes were eliminated from the infected ticks that fed on the bacterin recipients, B. burgdorferi was not isolated from the skin or joints, and antibody responses associated specifically with canine infection with B. burgdorferi were not produced. In contrast, B. burgdorferi was recovered from engorged ticks that fed on 13 (87%) placebo-vaccinated dogs (P<0.0001), skin biopsy specimens from 14 (93%) dogs (P<0.0001), and joint tissue specimens from 8 (53%) dogs (P=0.0022). In addition, 14 (93%) dogs developed specific antibody responses against B. burgdorferi proteins, including 11 (73%) with C6 peptide antibodies (P<0.0001). Moreover, 10 (67%) dogs developed Lyme disease-associated joint abnormalities (P<0.0001), including 4 (27%) dogs that developed joint stiffness or lameness and 6 (40%) that developed chronic joint inflammation (synovitis). The results therefore confirmed that the bacterin provided a high level of protection against Lyme disease shortly after immunization.

Laboratory-reared beagles were vaccinated with a placebo or a bacterin comprised of Borrelia burgdorferi S-1-10 and ospA-negative/ospB-negative B. burgdorferi 50772 and challenged after 1 year with B. burgdorferiinfected Ixodes scapularis ticks. For the placebo recipients, spirochetes were recovered from 9 (60%) skin biopsy specimens collected after 1 month, and the organisms persisted in the skin thereafter. Ten (67%) dogs also developed joint infection (3 dogs), lameness or synovitis (7 dogs), or B. burgdorferi-specific antibodies (8 dogs). For the vaccine recipients, spirochetes were recovered from 6 (40%) skin biopsy specimens collected after 1 month. However, subsequent biopsy specimens were negative, and the dogs failed to develop joint infection (P ‫؍‬ 0.224), lameness/synovitis (P ‫؍‬ 0.006), or Lyme disease-specific antibody responses (P ‫؍‬ 0.002). The bacterin provided a high level of protection for 1 year after immunization, and the addition of the OspCproducing B. burgdorferi 50772 provided enhanced protection.

We characterized the antibody response to decorin-binding protein A (DbpA) or DbpB from immune serum samples collected from 27 dogs infected with Borrelia burgdorferi by Ixodes scapularis ticks. Immunoglobulin M (IgM) antibodies to DbpA or DbpB were rarely detected, but high levels of IgG antibodies to DbpA were detected in 16 of 27 of the immune sera collected 1 mo after infection, 20 of 25 of the sera collected after 2 mo, and each of the 23, 17, or 11 serum samples evaluated after 3, 4, or 5 mo, respectively. In addition, IgG antibodies to DbpB were detected in 22 of 27 ( p = 0.005) tested dogs after 1 mo, and the frequency of detecting the antibodies thereafter closely mimicked the antibody responses to DbpA. Moreover, antibodies to DbpA or DbpB were not produced by dogs vaccinated with a whole-cell B. burgdorferi bacterin; removing the antibodies to DbpA by adsorption to recombinant DbpA (rDbpA) did not affect the reactivity detected by a rDbpB ELISA. Therefore, the findings from our preliminary study showed that antigenically distinct antibodies to DbpA or DbpB are produced reliably during canine infection with B. burgdorferi, and the response is not confounded by vaccination with a Lyme disease bacterin. Larger studies are warranted to more critically evaluate whether detecting the antibody responses can improve serodiagnostic confirmation of canine Lyme disease.

bBeagles received placebo or ospA-and ospB-negative Borrelia burgdorferi before a tick challenge. A total of 28 (41%) ticks and skin biopsy specimens from each control dog (n ‫؍‬ 10) contained B. burgdorferi. In contrast, 12 (19%) ticks recovered from the vaccine recipients (n ‫؍‬ 10) were infected (P ‫؍‬ 0.0077), and 5 dogs yielded spirochetes from the skin biopsy specimens (P ‫؍‬ 0.0325). In addition, 9 (90%) placebo recipients and 4 (40%) vaccine recipients developed joint abnormalities (P ‫؍‬ 0.0573). Therefore, vaccination with the ospA-and ospB-negative spirochete provided significant protection against Lyme disease. L yme disease, due primarily in the United States to the transmission of Borrelia burgdorferi from infected Ixodes ticks, causes significant morbidity in canines. However, infected dogs rarely develop acute illness (1); instead, the illness manifests as chronic subclinical polyarthritis and/or periarteritis (2, 3) that may progress to frank arthritis (4, 5). In addition, Labrador retrievers, golden retrievers, and Shetland sheepdogs appear more susceptible to kidney nephropathy (6).Canine vaccines that provide protection by inducing antiOspA borreliacidal antibodies to kill B. burgdorferi in the midgut as the infected tick ingests blood (7, 8) have been commercially available for several decades, and the approach has been partially effective (9, 10). However, vaccinated dogs may still become infected, because the expression of OspA is downregulated immediately after the infected tick begins taking a blood meal (11), and the ticks may also transmit ospA-negative Lyme spirochetes (12). In addition, borreliacidal antibodies specific for OspA are genospecies specific (13,14), which is less problematic in the United States, where B. burgdorferi predominates, but significantly impacts efficacy in Europe and Asia, where other genospecies, such as Borrelia garinii, may infect canines (15,16).Researchers therefore sought to overcome the shortcomings of the traditional vaccines by developing a bivalent bacterin comprising a traditional OspA-expressing B. burgdorferi strain and a unique ospA-and ospB-negative B. burgdorferi strain that expressed high levels of OspC. Subsequent studies (17, 18) confirmed that the approach provided a high level of protection against canine Lyme disease for at least 1 year. In addition, the investigators demonstrated that the bacterin induced significant amounts of anti-OspC borreliacidal antibodies (17) and postulated that the high level of protection was likely due at least in part to the inclusion of the OspC-producing spirochete. We therefore examined this possibility more critically by evaluating the protection afforded by vaccination with only the ospA-and ospB-negative B. burgdorferi strain.Vaccination and tick challenge. Two groups (n ϭ 10 in each group) of 8-week-old laboratory-reared beagle puppies were randomized without regard to sex, vaccinated by subcutaneous injection with a 1-ml dose of bacterin or placebo, and boostered after 21 days by subcutaneous injecti...