CategorySwine Health - General Disease
Date Full Report Received04/29/2005
Date Abstract Report Received07/26/2006
InvestigationInstitution: National Animal Disease Center, USDA-ARS
Primary Investigator: Karen B. Register
Funded ByIowa Pork Producers Association
The bacteria P. multocida and B. bronchiseptica are widespread and costly swine pathogens. They have multiple roles in respiratory disease and both contribute to complicated respiratory infections that also involve other bacteria and viruses. A toxic protein produced by P. multocida (PMT) is primarily responsible for the disease this agent causes. It is well-known that antibodies to PMT are very effective at preventing disease development. Although the situation is not as clear-cut for B. bronchiseptica, the protein pertactin is clearly of major importance in protecting against disease. Currently available vaccines induce only weak responses against these proteins. Large-scale purification of PMT and pertactin, which would permit their use as stand-alone vaccines or as additives to traditional ones, is not feasible due to technical difficulties and expense. PMT used as a vaccine must also be inactivated in some way, to eliminate the toxic effects that it has under natural conditions. DNA vaccine technology may overcome these limitations and provide a practical solution for improving vaccine efficacy.
We have constructed several potential DNA vaccines designed to induce immune responses against PMT and pertactin. The PMT vaccines have been manipulated such that the usual toxicity of the protein should be eliminated. Several slightly different versions were tested for their ability to induce immune responses in mice and one vaccine in particular has been found superior. This vaccine was tested in pigs and shown to be immunogenic and completely nontoxic. Seventy-five percent of pigs injected with the DNA vaccine produced PMT-specific antibodies after 2 sets of injections. These responses are expected to be protective based on past research. Future studies will specifically address protection against bacterial challenge. A pertactin vaccine with characteristics of the successful PMT vaccine has also been constructed and will also be tested in piglets in the near future.