INTERFERON-GAMMA INHIBITS THE INTRACELLULAR MULTIPLICATION OF NEOSPORA-CANINUM, AS SHOWN BY INCORPORATION OF H-3 URACIL

An assay was developed to quantify the growth of two different isolate s of the protozoon Neospora caninum within ovine fibroblast cells in v itro by differential uptake of H-3 uracil. The NC-1 isolate of N. cani num multiplied more quickly in culture than the NC Liverpool isolate, as reflected by increased incorporation of isotope by the former over a shorter period of time. After the parasites had left the ruptured ho st cells, there was very little incorporation of isotope. This suggest ed that multiplication occurred within and not outside the cells. Trea tment of the cells with ovine recombinant interferon gamma for 24 h be fore infection significantly inhibited intracellular multiplication of the parasite. (C) 1995 Academic Press Limited