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The HEp-2 cell mitochondria were found to harbor electronoptically dense subvirus particles with a byouant density of 1.27-1.28 g/cm3 which formed in the mitochondria de novo (experiments on incubation of isolated mitochondria with 32P). The intramitochondrial localization of proteins of oncornavirus type D was proven by different methods of the antigenic analysis (CFT, immune precipitation, autoradiography). The additional evidence of the participation of mitochondria in biosynthesis of this virus was obtained by the use of inhibitory tests (a different effect of chloramphenicol and cycloheximide). The possible role of mitochondria in biosynthesis of oncornaviruses is discussed.

The characteristics of human embryo lung culture spontaneously contaminated with mouse cells (HELCCM) are presented. Changes in the cytological and karyological characteristics of the cells were observed as compared with those of the initial human embryo lung (HEL) cell strain. The culture acquired the resistance to adenovirus type 7; at the same time RNA metabolism in HELCCM culture culture chronically infected with adenovirus practically did not differ from that of the control. Electron microscopic examination of the culture revealed virions of oncornavirus types A and C as well as minimal forms of oncornaviruses which morphologically were close to murine oncornaviruses. The results indicate that in the process of passages the initial diploid cells of HEL were eliminated by mouse cells. Therefore at present, the HELCCM cell line is considered to be a mouse line.

The method of differential centrifugation was used for concentration and purification of the minimal form of oncornaviruses type A and C. The structures showed heterogeneous distribution in sucrose density gradient and formed a peak in the zone of 1.135 g/ml. Electron microscope examinations of negatively stained preparations showed that the size of the minimal forms of oncornaviruses type A and C was 25-60 nm, the diameter of nucleoids 10-30 nm.

The results of the study of host antigens in Venezuelan equine encephalomyelitis virus by means of neutralization test in tissue culture using sera containing antibody for the species-specific antigens, Forssman antigen and group A and B antigens are presented. They show the inhibiting effect of the sera to be not uniform. The greatest neutralizing effect on the virus was exerted by immune sera to chick embryo fibroblasts and their fractions (by 0.5-3.9 lg PFU/ML). The lack of the virus neutralizing effect in sera for the Forssman antigen and for group A antigen appears to depend upon their deeper localization in the structure of virion.

A comparative study of the reproduction of an alphavirus. Venezuelan equine encephalomyelitis virus (VEE), in chick embryo fibroblasts (CEF) and oncornavirus type D (OV-D) produced spontaneously by human continuous cells (HEp-2) was carried out. The differential index of reproduction of both viruses was the yield of RNA-containing virus structures released from the cells. For VEE this index increased in the course of infection 100-150-fold. For OV-D the index changed little during long-term cultivation of the cells and was only 0.2%--1%. The effect of inhibitors, ethidium bromide and cycloheximide, on the RNA synthesis and production of virus structures was studied. Ethidium bromide was shown to inhibit reproduction of both the viruses considerably, whereas the effect of cyclohemimide on them was dissimilar: its effect on VEE virus depended on the time of its addition, while OV-D virus production did not depend on the time of its addition and was even stimulated in the presence of cycloheximide.

A method is described which permits simultaneous comparative study of cell metabolism and extracellular virus structures in minimal volumes. The method is based on the growing of cells in vials for scintillation count and it has been tested on a HEp-2 cell culture chronically producing oncornavirus type D. A comparative analysis of acid-insoluble radioactivity in heterogenous systems has been shown to be justified. For demonstration of the fields of possible utilization of the method, data are presented from the studies of the effect of various inhibitors (ethidium bromide, chloramphenicol, cycloheximide and anti-PPLO agent) on 3H-uridine incorporation into cells and extracellular virus structures.