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.