Actinobacillus pleuropneumoniae apxIIIB and apxIIID double mutant vaccine obsolete Actinobacillus pleuropneumoniae apxIIIB and apxIIID double mutant vaccine true Rebecca Racz Oliver He An apxIIID mutant, in combination with an apxIIIB mutation, is highly attenuated in pigs and induces significant protection from challenge with wild type A. pleuropneumoniae. The mutant also was slightly attenuated in mice and induced protection in mice against challenge from the parent strain terms merged