Comparative Efficacy in Challenge Dose Models of a Toxin Expressing Whole-Cell Vaccine against Eight Serovars of Actinobacillus pleuropneumoniae in Pigs

SIMPLE SUMMARY: Vaccine use is considered an integral control method to prevent respiratory disease in pigs caused by the economically significant Actinobacillus pleuropneumoniae. As 19 different distinct subtypes (serovars) of this bacterium exists, and several of these can be present at the same time in the same farm, effective serovar-independent protection is desirable. Vaccines based on the killed bacterial contents of a few of the serovars, including three virulent toxins normally produced during the natural infection of pigs, may potentially provide cross-serovar protection. However, little data is available on multi-serovar vaccine protection. Such a commercially available vaccine, the C-vaccine (Coglapix(®), Ceva, France) was tested in a total of 13 similar infection studies mimicking on-farm situations with the most common serovars (1, 2, 4, 5, 6, 7, 9/11, and 13) in trials with identical design of detailed lung lesion investigations. Reliability of trial design was tested by high reproducibility in different studies on same serovar. The C-vaccine was producing highly significant protection against lung lesions following all serovar-infections. The trial design was determined highly reliable. We conclude that the C-vaccine gives high serovar-independent protection against disease and is suitable for this use in the field. ABSTRACT: Actinobacillus pleuropneumoniae is a major economically significant bacterial respiratory pig pathogen, and whole cell vaccines are used to prevent disease. However, there is little data available on multi-serovar whole cell vaccine protection. Therefore, we determined the protective efficacies of a whole-cell A. pleuropneumoniae serovar 1 and 2 vaccine comprising ApxI-III toxins (C-vaccine, Coglapix(®), Ceva, France) against serovars 1, 2, 4, 5, 6, 7, 9/11, and 13. The infection doses used induced disease representative of endemic field conditions, and standard protocols were used for all studies. Protection against homologous serovars 1 and 2 significantly reduced lung lesion scores (LLS) compared to positive controls: p = 0.00007 and p = 0.00124, respectively. The protection against heterologous serovars 4, 5, 6, 7, 9/11, and 13 also significantly reduced LLS: range p = 2.9 × 10(−10) to p = 0.00953. As adjudged by the estimated random effect, reproducibility between studies was high. A highly significant serovar-independent reduction of pathological lung lesions by the C-vaccine was found for all the serovars tested (1, 2, 4, 5, 6, 7, 9/11, and 13). We conclude that the C-vaccine gives high serovar-independent protection against disease and is suitable for this use in the field.