Characterization of temperature-sensitive strains of Neospora caninum in mice.
Temperature-sensitive (ts) strains of the Neospora caninum tachyzoites were selected by chemical mutagenesis and selection for growth at 32 C. Three ts strains and the parental, N. caninum wild-type strain, NC-1, were examined in the present study for their ability to cause disease in inbred BALB/c mice, outbred ICR mice, and chemically immunosuppressed ICR mice. In BALB/c mice, all 3 strains failed to induce clinical disease, whereas infection with the NC-1 strain caused central nervous system disease and death in some mice. No disease was observed in ICR mice inoculated with the 3 ts strains or the NC-1 strain. All immunosuppressed ICR mice inoculated with the NC-1 strain died, whereas no immunosuppressed mice inoculated with the NCts-4 strain and only 1 of 5 mice inoculated with the NCts-8 and NCts-12 strains died. The NCts-4 and NCts-12 strains reverted to a wild-type phenotype when grown at 37 C. Vaccination of BALB/c mice with live, but not frozen NCts-8 strain tachyzoites induced significant (P < 0.05) protection following NC-1 strain challenge.
Lindsay
D S
DS
Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg 24061-0442, USA.
Lenz
S D
SD
Blagburn
B L
BL
Brake
D A
DA
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D003048:Coccidiosis / Q000276:immunology / Q000469:parasitology* / Q000517:prevention & control; D004195:Disease Models, Animal; D004660:Encephalitis / Q000276:immunology / Q000469:parasitology* / Q000517:prevention & control; D005260:Female; D007165:Immunosuppression Therapy; D051379:Mice; D008807:Mice, Inbred BALB C; D018688:Neospora / Q000276:immunology / Q000472:pathogenicity*; D016052:Protozoan Vaccines / Q000592:standards*; D013696:Temperature; D014611:Vaccination
D000913:Antibodies, Protozoan; D016052:Protozoan Vaccines