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Immunity and intracellular infection: resistance to bacteria in mice infected with a protozoan
Abstract:
Mice infected with the intracellular parasite Toxoplasma gondii for periods of as long as 7 months were resistant to challenge with numbers of Listeria monocytogenes and Salmonella typhimurium that were uniformly lethal to normal mice. This resistance did not appear to depend on the strain of toxoplasma employed or the route of inoculation of either toxoplasma or bacteria. Onset of immunity to listeria was demonstrable as early as 1 to 2 days after infection with toxoplasma. Resistance to toxoplasma was not demonstrable in mice immune to listeria. Interferon did not appear to be a mediator of the immunity observed in toxoplasma-infected mice.
Insights
Mice infected with Toxoplasma gondii showed resistance to lethal Listeria monocytogenes and Salmonella typhimurium infections. This cross-resistance developed rapidly and was not mediated by interferon.
Area of Science:
- Immunology
- Infectious Diseases
- Parasitology
Background:
- Toxoplasma gondii is an intracellular parasite.
- Listeria monocytogenes and Salmonella typhimurium are bacterial pathogens.
- Understanding cross-species immunity is crucial for developing novel therapeutic strategies.
Purpose of the Study:
- To investigate the potential for Toxoplasma gondii infection to induce resistance against unrelated bacterial pathogens.
- To determine the onset and characteristics of this induced immunity.
Main Methods:
- Mice were infected with Toxoplasma gondii for up to 7 months.
- Infected and control mice were subsequently challenged with lethal doses of Listeria monocytogenes and Salmonella typhimurium.
- Immunity to Listeria was assessed in mice previously immunized against Listeria.
Main Results:
- Toxoplasma gondii-infected mice exhibited significant resistance to challenge with lethal doses of Listeria monocytogenes and Salmonella typhimurium.
- This resistance was observed regardless of Toxoplasma strain or inoculation route.
- Immunity to Listeria was detectable within 1-2 days post-Toxoplasma infection, but resistance to Toxoplasma was not observed in Listeria-immune mice.
Conclusions:
- Toxoplasma gondii infection confers a robust, non-specific resistance to subsequent bacterial infections.
- The observed cross-resistance is rapid in onset and does not appear to be interferon-dependent.
- This study highlights a novel host-parasite interaction with potential implications for immunotherapy.