dsRNA associated with virus-like particles in Eimeria spp. of the domestic fowl

Abstract

 RNA segments, identified as double-stranded, were found in sporozoites of the Guelph strains of Eimeria acervulina, E. brunetti, E. maxima and E. necatrix and in 8 of 11 strains of E. acervulina obtained from poultry houses across the United States. These RNAs were resistant to RNase A digestion in the presence of high salt concentrations (0.3 M NaCl). On agarose-gel electrophoresis, E. acervulina had one obvious band at 1.7 kb and a faint band at 3.5 kb; E. brunetti had two bands at 2.1 and 3.3 kb, respectively; E. maxima had one band at 4.5 kb; and E. necatrix had two major bands at 4.5 and 5.6 kb, respectively. No dsRNA band was seen in the three strains of E. tenella examined. Virus-like particles were purified by cesium chloride density centrifugation of homogenates of E. necatrix sporulated oocysts. The fraction at peak virus concentration had a buoyant density of 1.39 g ml^–1. These virus-like particles were icosahedral, had no envelope and measured 42–44 nm in diameter. Only one RNA band at 5.6 kb was observed when nucleic acids from gradient fractions containing virus were subjected to electrophoresis. The 4.5-kb dsRNA segment of E. necatrix was not associated with a virus-like particle.