Inhibition of growth of Toxoplasma gondii in cultured fibroblasts by human recombinant gamma interferon

Publisher Website
Google Scholar
Abstract
The growth of T. 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. When the pretreatment was omitted and parasites and .gamma.-interferon were added at the same time, no inhibition of parasite growth could be detected 1 day later, although it was apparent after 2 days. Cultures from which the .gamma.-interferon had been removed by washing after a 1-day treatment showed inhibition of T. gondii growth. .gamma.-Interferon had no effect on the viability of extracellular parasites, but it did inhibit the synthesis of host cell RNA and protein by .apprx. 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 growth of T. gondii.