Abstract: The study was focused on the comparison of protective efficacy between inactive vaccine (trial group I)and two recombinant subunit vaccines against serotype 1and serotype 2 of Actinobacillus pleuropneumoniae in mice, with one containing recombinant ApxI, ApxII, ApxIII and OMP(trial group II) and the other containing recombinant ApxI, ApxII, ApxIII, ApxIV, OMP and Apfa(trial group III). Then immunologic mechanism was determined preliminarily in mice on basis of humoral immunity and cell immunity. The BALB/c mouse were vaccinated at days 0 and 14 and 28, and then challenged with serotype 1（5×109cfu） and serotype 2 （5×1010cfu）intranasally at day 35. The results suggested that trial group II had a higher antibody level to four antigens and IL-2 production than others (P<0.05) .It had a slightly higher lymphocytes proliferation than others (P>0.05). The protective efficacy against serotype 1of trial group II （9/10） was obviously better than trial group I（6/10）, trial group III(5/10)and control group（0/10）, and the protective efficacy against serotype 2 of that (no lung lesion) was obviously better than others( typical lung lesion)., which demonstrated that antibody level had a positive correlation to protective efficacy. The study revealed that the recombinant subunit vaccine containing ApxI, ApxII, ApxIII and OMP provided significantly crossing protection by stimulating humoral immunity and cell immunity simutaneously.

Key words: porcine contagious pleuropneumonia, recombinant subunit vaccine, protective efficacy, antibody, lymphocytes proliferation, IL-2