Unique differences in infectivity and seroreactivity of Toxoplasma harvested from mice infected for different lengths of time.
For use in experiments, Toxoplasma of the RH strain are usually harvested from mouse peritoneal cavities 48 hr (2-day Toxoplasma) or more after intraperitoneal inoculation. In this report we show that Toxoplasma harvested at 24 hr (1-day Toxoplasma) after inoculation are much more infective for and replicate to a greater degree within mouse resident peritoneal macrophages in vitro and are much more resistant to the cidal activity of activated mouse peritoneal macrophages and resident rat peritoneal macrophages than are 2-day Toxoplasma. Ingestion of 1-day Toxoplasma by macrophages did not trigger the respiratory burst as measured by reduction of nitroblue tetrazolium (NBT), but coating 1-day Toxoplasma with specific antibody did result in reduced NBT. However, coating 1-day Toxoplasma with specific antibody did not markedly decrease infectivity for macrophages in vitro, unlike decreased infectivity observed when 2-day Toxoplasma are coated with specific antibody. Use of 1-day Toxoplasma in the dye test resulted in a 5-fold decrease in titer of specific antibody in human sera. Use of Toxoplasma harvested 24 hr after infection may serve as a new tool to probe virulence factors of Toxoplasma and of host cells' antimicrobial mechanisms.
Department of Immunology and Infectious Diseases, Palo Alto Medical Foundation, California 94301.
R E
RE
McCabe
J R
JR
Catterall
J S
JS
Remington
D000818:Animals; D000913:Antibodies, Protozoan / Q000032:analysis / Q000276:immunology; D002478:Cells, Cultured; D005347:Fibroblasts; D006801:Humans; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000469:parasitology*; D051379:Mice; D010587:Phagocytosis; D051381:Rats; D013997:Time Factors; D014122:Toxoplasma / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D014774:Virulence
D000913:Antibodies, Protozoan