Toxoplasma gondii is an obligate intracellular parasite that can cause severe congenital birth defects and fatal encephalitis in immunocompromised hosts. In February 21 Nature, Barbara Fox and David Bzik from Dartmouth Medical School, New Hampshire, USA, show that de novo pyrimidine biosynthesis is required for virulence of T. gondii.

Fox & Bzik examined the virulence of T. gondii mutant uracil auxotrophs that lacked carbamoyl phosphate synthetase II, a key enzyme involved in de novo pyrimidine biosynthesis. They found that these mutant T. gondii are completely avirulent not only in immune competent mice, but also in mice that lack interferon-γ. In addition, they showed that a single injection of the mutant T. gondii strain could induce long-term protective immunity to toxoplasmosis in mice (Nature 2002, 415:926-929).

"The findings have implications for designing drugs to combat parasitic infections, and may offer a new vaccination approach," said David...

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