Evaluation of multicomponent recombinant vaccines against Actinobacillus pleuropneumoniae in mice.
BACKGROUND
Porcine contagious pleuropneumonia (PCP) is a highly contagious disease that is caused by Actinobacillus pleuropneumoniae (APP) and characterized by severe fibrinous necrotizing hemorrhagic pleuropneumonia, which is a severe threat to the swine industry. In addition to APP RTX-toxins I (ApxI), APP RTX-toxin II (ApxII), APP RTX-toxin III (ApxIII) and Outer membrane protein (OMP), there may be other useful antigens that can contribute to protection. In the development of an efficacious vaccine against APP, the immunogenicities of multicomponent recombinant subunit vaccines were evaluated.


METHODS
Six major virulent factor genes of APP, i.e., apxI, apxII, apxIII, APP RTX-toxins IV (apxIV), omp and type 4 fimbrial structural (apfa) were expressed. BALB/c mice were immunized with recombinant ApxI ( rApxI), recombinant ApxII (rApxII), recombinant ApxIII (rApxIII) and recombinant OMP (rOMP) (Group I); rApxI, rApxII, rApxIII, recombinant ApxIV (rApxIV), recombinant Apfa (rApfa) and rOMP (Group II); APP serotype 1 (APP1) inactivated vaccine (Group III); or phosphate-buffered saline (PBS) (Control group), respectively. After the first immunization, mice were subjected to two booster immunizations at 2-week intervals, followed by challenge with APP1 Shope 4074 and APP2 S1536.


RESULTS
The efficacy of the multicomponent recombinant subunit vaccines was evaluated on the basis of antibody titers, survival rates, lung lesions and indirect immunofluorescence (IIF) detection of APP. The antibody level of Group I was significantly higher than those of the other three groups (P < 0.05). The survival rate of Group I was higher than that of Groups II and III (P < 0.05) and the control (P < 0.01). Compared with the other three groups, the lungs of Group I did not exhibit obvious hemorrhage or necrosis, and only showed weak and scattered fluorescent dots by IIF detection.


CONCLUSIONS
The result indicates that the multicomponent recombinant subunit vaccine composed of rApxI, rApxII, rApxIII and rOMP can provide effective cross-protection against homologous and heterologous APP challenge.
Shao
Meili
M
Division of Bacterial Diseases, National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
Wang
Yong
Y
Wang
Chunlai
C
Guo
Yang
Y
Peng
Yonggang
Y
Liu
Jiandong
J
Li
Guangxing
G
Liu
Huifang
H
Liu
Siguo
S
D000189:Actinobacillus Infections / Q000382:microbiology / Q000401:mortality / Q000517:prevention & control / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000276:immunology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology*; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology*; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007114:Immunization / Q000379:methods / Q000592:standards / Q000662:veterinary*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011897:Random Allocation; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control; D022223:Vaccines, Subunit / Q000235:genetics / Q000276:immunology
D000907:Antibodies, Bacterial; D001427:Bacterial Toxins; D001428:Bacterial Vaccines; D011994:Recombinant Proteins; D022223:Vaccines, Subunit