Characterization of Canine Humoral Immune Responses to Outer Surface Protein Subunit Vaccines and to Natural Infection by Lyme Disease Spirochetes

: Canine antibody responses to Lyme disease subunit vaccines and to natural borrelial infection were investigated. Vaccines were formulated with QS21 and outer surface proteins A (OspA) and B (OspB) derived from Borrelia burgdorferi B31. Vaccines containing QS21 and the lipoproteins gave 4-fold higher IgG1 and 8-fold higher IgG2 antibody responses than without QS21. Antisera to lipidated OspA or OspB vaccines containing QS21 had high antiborrelial activity against isolates B31 and CA-2-87, similar to those with a vaccine containing both OspA and OspB. Only the combination vaccine induced antiborrelial activity against heterologous isolates 24008 Fr and Borrelia garinii G25. Nonlipidated OspA- and OspB-based vaccines with QS21 elicited lower antibody and antiborrelial activity than did lipidated OspA and OspB vaccines; 49% of naturally exposed dogs had low titers to OspA or OspB. Thus, vaccines using lipidated OspA, OspB, and QS21 could induce higher antiborrelial activity than did natural exposure.