On Feb. 8, 1984, Elmer R. Pfefferkorn published his discovery that treatment of human fibroblasts with human recombinant interferon gamma blocks the growth of T. gondii.

The growth of Toxoplasma gondii in cultured human fibroblasts was inhibited by recombinant human gamma interferon at concentrations of 8 to 16 U/ml. The interferon was titrated by observing a total inhibition of parasite plaque formation 7 days after infection. Inhibition of the growth of T. gondii in the early days after infection was measured by marked reductions in the incorporation of radioactive uracil, a precursor that can only be used by the parasites.

This assay showed that when cells were pretreated with gamma interferon for 1 day and then infected, inhibition of T. gondii growth could be readily detected 1 or 2 days after infection. Gamma interferon had no effect on the viability of extracellular parasites, but it did inhibit the synthesis of host cell RNA and protein by ca. 50% 3 days after treatment. This degree of inhibition is unlikely, of itself, to compromise the growth of T. gondii. Recombinant alpha and beta interferons had no effect on the growth of T. gondii.