Tascón Ri

Cross-reactivity between Actinobacillus pleuropneumoniae serotypes comparing different antigens and serological tests

Several antigens were prepared from suspensions of reference strains of the 12 serotypes of Actinobacillus pleuropneumoniae (saline extract [SE], capsular extract [CE], whole cell suspension [WCS], boiled extract [BE], and autoclaved cell antigen [ACA]). The cross reactions between each antigen and the antisera against reference strains of the other 11 serotypes were compared by using the complement fixation test, ELISA and the indirect haemagglutination test. ACA produced the most cross reactions, which, in some serotypes, took place in all the antisera tested. BE produced fewer cross reactions, but these were more abundant than those obtained with SE, CE or WCS. The least cross reactivity occurred with SE in the indirect haemagglutination test. This test is, therefore, the most reliable method for serotyping field strains of A pleuropneumoniae.

Quantifying by monoclonal antibodies of specific IgG, IgM and IgA in the serum of minipigs experimentally infected with Actinobacillus pleuropneumoniae

Fifteen minipigs were infected intratracheally with three different doses (10(8), 10(5) or 5 x 10(3) colony forming units) of the reference strains of serotypes 2 or 4 of Actinobacillus pleuropneumoniae, and three remained as controls. The titre of specific IgG, IgM and IgA in the serum was measured weekly for 15 weeks with an indirect ELISA using monoclonal antibodies specific for each isotype. IgG attained the highest titres, IgM lower and IgA the lowest, being only detected in four animals. Serotype 4 evoked significantly higher titres than serotype 2 (P < or = 0.01). In general the highest IgG titres were attained at four to six weeks after infection. Some of the minipigs were reinfected after seven weeks but this evoked an increased titre in only two instances.