Concomitant infection by Toxoplasma gondii and Trypanosoma cruzi

Studies were performed in an attempt to define underlying mechanisms of resistance in mice infected with strains of bacteria or protozoa which confer on the animals resistance against phylogenetically unrelated organisms. The rates of clearance of an intravenously inoculated suspension of carbon particles in resistant and control animals were the same, suggesting that enhanced reticuloendothelial clearance was not involved. Attempts to transfer resistance by injection of “hyper-immune” serum were unsuccessful. In vitro monolayer cultures of peritoneal macrophages from resistant mice were protected against necrotization by bacterial and protozoal challenge when compared with monolayers from normal mice, and there appeared to be a more rapid killing of the intracellular organisms by macrophages from the resistant mice. These findings suggest that the macrophage plays a major role in the heterologous cross-resistance observed in these animals. Continued macrophage “activation” in Toxoplasma and Besnoitia-infected mice is probably due to the continued activity of these parasites during the entire life span of the host.

Studies on the Mechanisms of Resistance to Phylogenetically Diverse Intracellular Organisms

Immunodepression in mice infected with Toxoplasma gondii.

In a series of experiments varying in the order of, and in the intervals between infections, albino mice were concomitantly exposed to S. mansoni and T. cruzi . A most striking finding was the pronounced enhancement of parasitaemia due to T. cruzi in mixed infections, present in all the series, whose interval between exposures ranged from 4 to 66 days. In some groups of animals the peripheral blood remained positive for T. cruzi long after controls had been found to be negative. When Chagas's infection preceded exposure to cercariae worm recovery was also affected. Worm recovery was always significantly lower in mixed infections, in series where the interval between exposures ranged from 5 to 16 days. At longer intervals (63 days) the number of flukes recovered at autopsy was significantly higher than in the control mice.

Concomitant infection by Toxoplasma gondii and Trypanosoma cruzi

References

Studies on the Mechanisms of Resistance to Phylogenetically Diverse Intracellular Organisms

Immunodepression in mice infected with Toxoplasma gondii.

Concomitant infection of albino mice by Trypanosoma cruzi and Schistosoma mansoni. Parasitological parameters.

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