The ratio of Th1-type antibodies is increased in the serum of aPV/BcfA-immunized mice. Serum collected on day 7 postinoculation was tested by multiplex Luminex assay for the presence of FHA-, PRN-, and PT-specific antibodies. The total IgG levels and isotypes were determined, and the ratio of IgG2b/c to IgG1 was calculated. **, P < 0.05; ***, P < 0.005.