Susceptibility to chronic infection with Toxoplasma gondii does not correlate with susceptibility to acute infection in mice.
Resistance against acute and chronic infection with Taxoplasma gondii in BALB/c and CBA/Ca mice was compared. Intraperitoneal inoculation of either 20, 40, or 80 cysts of the ME49 strain resulted in mortality rates in BALB/c mice of 12% (2 of 17), 50% (6 of 12), and 75% (9 of 12), respectively, within 3 weeks after infection (acute stage). There was no mortality in the CBA/Ca mice for any of the doses. In marked contrast, CBA/Ca mice were highly sensitive to chronic infection with developing toxoplasmic encephalitis; they began dying 2 months after infection with 10 cysts of the ME49 strain, and mortality reached 53% (16 of 30) by the sixth month postinfection. No mortality (0 of 20) was observed in the chronically infected BALB/c mice. CBA/Ca mice had markedly more cysts in their brains than BALB/c mice in the chronic stage. Severe inflammatory changes were observed only in the brains of CBA/Ca mice. Interestingly, in the acute stage (the first 3 weeks), numbers of cysts in the brains were significantly greater in CBA/Ca than BALB/c mice, whereas only BALB/c mice showed mortality in that time period. No inflammatory changes were observed in brains of BALB/c mice during the acute stage of the infection. Thus, resistance against chronic infection appears to be regulated by a mechanism(s) that is different from those conferring resistance against acute infection. There was no difference in gamma interferon levels in sera between CBA/Ca and BALB/c mice during the acute stage. However, during the chronic stage, only BALB/c mice had detectable levels of gamma interferon in their sera.
Department of Parasitology, Jikei University School of Medicine, Tokyo, Japan.
Y
Y
Suzuki
M A
MA
Orellana
S Y
SY
Wong
F K
FK
Conley
J S
JS
Remington
D000208:Acute Disease; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D001921:Brain / Q000473:pathology; D002908:Chronic Disease; D004198:Disease Susceptibility; D005260:Female; D007371:Interferon-gamma / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D014122:Toxoplasma; D014124:Toxoplasmosis, Animal / Q000097:blood / Q000276:immunology* / Q000473:pathology; D016781:Toxoplasmosis, Cerebral / Q000097:blood / Q000276:immunology* / Q000473:pathology
D000913:Antibodies, Protozoan; D007371:Interferon-gamma