Non-lytic antibodies in H-2-controlled resistance to acute infection with Trypanosoma cruzi
Juri, M.A.; Ferreira, A.; Ramos, A.; Hoecker, G.
Brazilian Journal of Medical and Biological Research 23(8): 685-695
1990
ISSN/ISBN: 0100-879X PMID: 2129269 Document Number: 352330
Resistance to acute T. cruzi infection in mice is a polygenic character linked to the murine major histocompatibility system (H-2). It was found that F1 hybrids A.CA(H-2f)/B10.Br(H-2k) between 2 susceptible strains are strongly resistant. Resistant B10(H-2b) and A.SW(H-2s) female mice (12-14 weeks old) survived 60 or more days after an intraperitoneal injection of 104 T. cruzi Tulahuen strain blood trypomastigotes. The specific antibody response of these individuals increased continuously up to 100 days or more. Parasitaemia reached a peak at day 8 in all strains. Thereafter, the number of blood parasites in resistant animals showed an irregular but persistent decrease. Susceptible congenic B10.Br and A.CA animals showed lower levels of specific anti-T. cruzi antibodies and an increase in parasitaemia until death. B10.Br mice died 14 to 20 days pi. A.CA animals were extremely susceptible, showing a sharp and sustained increase in parasitaemia starting on day 12, followed by death no later than day 15 pi. A significant correlation was found between IgG levels present in serum of resistant mice from 20 days on and protection against acute death. Whole immune anti-T. cruzi serum or its purified IgG class fraction neutralized T. cruzi inocula in vitro, as shown by a significantly increased survival of recipient susceptible A.CA mice. This IgG protective effect is independent of the protective effect mediated by the terminal activation of the complement cascade, since the parasites were inoculated with heat-inactivated immune sera and both recipient (A.CA) and donor (A.SW) strains lack C5.