Immunization of mice with plasmid DNA coding for NcGRA7 or NcsHSP33 confers partial protection against vertical transmission of Neospora caninum.

The purpose of the present study was to use direct plasmid deoxyribonucleic acid (DNA) injection to identify specific antigens that confer protection against congenital transfer of Neospora caninum. Inbred BALB/c mice were vaccinated before pregnancy with a recombinant plasmid containing sequences encoding N. caninum antigen NcGRA7 or NcsHSP33. The mice were challenged with N. caninum tachyzoites at 10-12 days of gestation. Whereas 100% of pups born from dams immunized with control plasmid contained detectable levels of N. caninum DNA in a Neospora-specific polymerase chain reaction assay, only 46% of pups from pCMVi-NcGRA7-immunized mice and 53% of pCMVi-NcsHSP33-immunized mice were N. caninum positive, and none of the mice immunized with tachyzoite extract contained N. caninum DNA. Thus, immunization of mice with plasmid DNA expressing N. caninum antigens conferred partial protection against congenital neosporosis.