A lipid-conjugated immunostimulating complex subunit vaccine against Salmonella infection in turkeys.

Immunostaining complexes (ISCOMs) are multimeric particles and have been used successfully for presentation of membrane proteins. In this study, outer-membrane proteins (OMPs) from Salmonella heidelberg were incorporated into lipid-conjugated ISCOM particles and evaluated for their use in a vaccine for turkeys against homologous and heterologous Salmonella challenge. Two types of lipid-conjugated ISCOMs were examined: ISCOM-phospholipid and ISCOM-sphingolipid preparations. The turkeys were challenged with one of the three Salmonella serotypes: S. heidelberg, S. reading, or S. enteritidis. The turkeys were monitored for clinical signs, shedding pattern post-challenge, and clearance of the challenge Salmonella from selected internal organs. Vaccines containing OMP with either lipid-conjugated ISCOM preparation produced significantly greater (P < 0.01) immune response than OMP alone. Cloacal swabs from turkeys given OMP along with ISCOM-phospholipid and challenged with a homologous serotype were completely negative for Salmonella. A certain degree of cross-protection against heterologous Salmonella was afforded by both OMP-ISCOM vaccines. The isolation rate of Salmonella from internal organs was significantly lower (P < 0.0001) in vaccinated turkeys than in unvaccinated controls.