Viral matrix inclusion bodies in myocardium of lymphoid leukosis virus-infected chickens.

Chicken embryos and healthy adult chickens naturally infected with lymphoid leukosis virus were used to investigate viral inclusion bodies in myocardial cells by light and electron microscopies and by immunocytochemical technique. Intracytoplasmic viral matrix inclusion bodies frequently appeared in the myocardium of adult chickens, but not in that of embryos. In light microscopic preparations, inclusions were irregularly distributed, were basophilic, and contained ribonucleic acid. Ultrastructurally, inclusions in myocardial cells were in areas containing numerous interstitial C-type particles. Early inclusions were composed of clusters of ribosomes associated with sarcoplasmic tubules; spherical bodies developed among these ribosomes. Mature inclusions were composed of numerous spherical bodies (50 to 75 nm) with interspersed ribosomes and of ribosomes clustered at the periphery. Inclusions were not membrane-enclosed. Occasionally, spherical bodies were in paracrystalline arrays. Multiple budding occurred on cell membranes adjacent to matrix inclusions. The viral group-specific protein, p27, was demonstrated by the peroxidase-antiperoxidase method and by the protein A-gold method in the spherical bodies, in nucleoids of mature virus particles, and among ribosomes of inclusions. The results indicate that the matrix inclusions were the result of lymphoid leukosis virus infection and were the product of viral protein synthesis on ribosomes.