Sami A. Mayyasi

Feasibility studies of oncornavirus production in microcarrier cultures

SummaryStudies conducted with virus-infected monolayer cell cultures have demonstrated the feasibility of producing several tumor-associated viruses in microcarrier (mc) cultures (Sephadex G50 beads treated with DEAE-chloride). The efficiency of cell adherence to mc varied with the cell type, the pH of the growth medium, and the stirring force applied to keep the mc in suspension. Most cells attached firmly to the mc and could not be removed easily with routine trypsinization procedures. Techniques using Enzar-T and Pronase were effective in detaching cells from mc in 10 to 15 min while retaining 95% cell viability. After detachment, Ficoll gradients were used for rapid and complete separation of viable cell suspensions from the mc. Retrovirus production in large volumes of mc cultures was investigated with periodic harvesting of growth fluids. Physical, biochemical, and biological properties of the Mason-Pfizer monkey virus and the RD114 virus recovered from the mc cultures were identical to those produced in conventional cultures. The utilization of mc has several applications in research and short-term cultures, but the as-yet-unsolved technical problems met were found to be serious limitations when attempting mass cell culturing on a long-term basis.

Characterization of Mason-Pfizer virus induced cell transformationin vitro

SummarySeveral types of cell strains and established cell lines of simian and human origin failed to demonstrate foci of altered cells following infection with the Mason-Pfizer monkey virus (M-PMV). However, most diploid cultures, after infection, lived longer and displayed the ability to grow in soft agar medium. The number of cell colonies developing in the soft agar was directly proportional to the amount of virus added to the culture. Two types of cell colonies were isolated from soft agar after infection of monkey foreskin cells with M-PMV. One had characteristic fibroblastic morphology, and the other showed an epithelioid cell phenotype. The ratio of fibroblastic colonies to epithelioid colonies was in excess of 20:1. The epithelioid cultures displayed a complete lack of topoinhibition, formed three dimensional cellular dome structures, and demonstrated significant karyotypic alterations. Fibroblastic sublines, on the other hand, did not show formation of domes but presented some lack of topoinhibition. The majority of cells in fibroblastic sublines also continued to show a normal rhesus chromosome complement. Although both epithelioid and fibroblastic transformed cell types produced intracellular M-PMV antigen and virus particles, the infectious virus titers were significantly different. The noninfectious virus preparations recovered from some of the fibroblastic sublines contained a high percentage of aberrant forms of M-PMV.

Antigenic Comparison of Rauscher Murine Leukemia Virus Cultivated in Human Embryo and Mouse Cells

Summary We have compared antigens of Rauscher leukemia virus (RV) derived from a human cell line with antigens of RV grown in mouse cells. Group specific rat antisera (GSS) to murine leukemia viruses show no reactivity with the outer membranous coat of either type of virus. The GSS demonstrates that the core of the disrupted HRV retained the murine leukemia group specific antigens. Rabbit antisera, prepared against each virus, showed specificity for the homologous virus reflecting antigenic differences in the outer membranous coats.

Biochemical and morphological studies of Simian sarcoma virus, type 1

Abstract A productive infection has been established in a primary human-embryo fibroblastic cell line (HE) by Simian Sarcoma Virus, Type 1 (SSV-1). The C-type virus particles observed in the HE and marmoset lung cells are similar in morphology. Rate zonal centrifugation and acrylamide-agarose gel electrophoretic analysis of radioactively labeled SSV-1 ribonucleic acid reveal a 60–70-S component which is heat sensitive, as well as 28-S, 18-S, and 4–10-S components, all of which are hydrolyzed by alkali. Studies employing the simultaneous detection assay for viral enzyme and 60–70-S RNA show that the virus has biochemical properties similar to other oncorna viruses.