Intracellular localization of viral RNA in Eimeria necatrix of the domestic fowl

Abstract

The intracellular localization of viral RNA in three different stages of Eimeria necatrix, namely, the first- and second-generation meronts and the macrogamonts, were examined at the light microscopy level by in situ hybridization. Digoxigenin-labeled riboprobes generated from partial cDNA clones from 5.6-kb and 4.5-kb dsRNA (pzenv1 and pzenv2) were used in this study. Viral RNA was found to be confined to the cytoplasm of the eimerian host; no viral RNA was detected in chicken tissue. The intense hybridization signal observed in the cytoplasm of the immature meronts with the SP6 riboprobe of pzenv1 or the T7 riboprobe of pzenv2 was probably due to their hybridization to positive strands that had been extruded from the virus during transcription. In mature meronts the intensity of the signal is lower, signifying a decrease in transcription activity. Viral replicase activity may thus be synchronized with the growth phase of the eimerian host.