Immunization of NMRI mice against virulent Toxoplasma gondii. Differing efficacy of eleven cyst-forming Toxoplasma strains.
Mice were infected with eleven cyst-forming Toxoplasma strains of varying virulence and challenged 1 month later with highly virulent BK strain parasites. The early cellular reaction in vivo was estimated by collecting the peritoneal exudates 24 h after challenge. This consisted of 54.34--77.61% lymphocytes and 0-8.88% infected macrophages in the eleven immunized groups in contrast to 27.17% lymphocytes and 18.64% infected macrophages in the control group. The peritoneal exudate 72 h after challenge comprised of 55.88-73.86% lymphocytes and 0-6.97% infected macrophages compared to 25.88% lymphocytes and 92% infected macrophages in the control group. Following the virulent challenge, deaths occurred in seven of the eleven groups immunized with live strains and ranged 5-42% at the end of a 6-week observation period. The most virulent of the Toxoplasma strains used - Alt and Gail - gave higher mortality while the least virulent ones - 558, 1070, K8 and KSU - were solidly resistant. The significantly different mortality obtained with strains Alt, Gail and Witting in a similar experiment performed at an interval of 7 months is discussed.
D000818:Animals; D000917:Antibody Formation; D001202:Ascitic Fluid / Q000166:cytology; D007114:Immunization; D008214:Lymphocytes / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains; D013045:Species Specificity; D014122:Toxoplasma / Q000276:immunology* / Q000472:pathogenicity; D014123:Toxoplasmosis / Q000517:prevention & control*; D014612:Vaccines; D014774:Virulence
D014612:Vaccines