Effect of dibutyryl cyclic AMP on the induction of Epstein-Barr virus in hybrid cells.

Treatment of Epstein-Barr virus (EBV) negative somatic cell hybrids with 5'-iododeoxyuridine (IUdR) induced synthesis of EBV antigens and virus particles. When dibutyryl cAMP (Bt(2)-cAMP) was present in medium after exposure of cultures to IUdR, the incidence of cells synthesizing EBV early and virus capsid antigens was increased. The time necessary for appearance of EBV particles after induction by IUdR was significantly reduced in the presence of Bt(2)-cAMP.

Activation of a latent measles virus infection in hamster cells.

The characteristics of infectious measles virus released from latently infected hamster embryo fibroblast cells are described. Low levels of virus were released spontaneously when the cultures were incubated at 37 C; this phenomenon was observed 19 passages after the cells had been exposed to the virus and has continued through cell passage 45. The virus yield could be significantly increased by cocultivation of the hamster cells with BSC-1 cells or incubation of the latently infected cells at 33.

Cytomegalovirus: conversion of nonpermissive cells to a permissive state for virus replication.

Human embryonic kidney cells are epithelioid cells which are normally nonpermissive for in vitro replication of human cytomegalovirus. These cells were converted to a permissive state for the virus by prior treatment with 5-iodo-2'-deoxyuridine. When this method was used, a nonpermissive cell was made permissive to an infecting virus.

Oncogenic transformation of hamster embryo cells after exposure to inactivated herpes simplex virus type 1.

The in vitro transformation of hamster embryo fibroblasts by herpes simplex virus type 1 (HSV-1) after exposure of the virus to UV irradiation is described. Cell transformation was induced by 2 out of 12 strains of HSV-1 that were tested for transforming potential. Cells transformed by the KOS strain of HSV-1 were not oncogenic when injected into newborn Syrian hamsters.

Cytomegalovirus replication in cells pretreated with 5-iodo-2'-deoxyuridine.

The replication of human cytomegalovirus (CMV) in cells pretreated with 5-iodo-2'-deoxyuridine (IUdR) was studied. Pretreatment of cells with IUdR enhanced several parameters of virus replication. Virus grown in drug-treated cells exhibited a shorter eclipse period and the cells produced more infectious virus sooner than did untreated cells.

Immunologic manipulation of metastases due to herpesvirus transformed cells.

Herpes simplex virus type 1 (HSV-1), type 2 (HSV-2), and simian virus 40 (SV40) fail to induce immunity in weanling Syrian hamsters to transplant of hamster cells transformed by HSV-2. However, the development of metastatic tumors is markedly enhanced by prior immunization with HSV-1. Immunization with SV40, ultraviolet-irradiated tumor cells, or ultraviolet-irradiated normal hamster embryo cells inhibits the development of metastases.

Production of mucopolysaccharides by normal and transformed cells.

The rate of hyaluronic acid and sulfated mucopolysaccharide production was measured for hamster embryo fibroblasts and for general oncogenic lines derived by virus transformation. A striking increase in both the rate of hyaluronic acid synthesis and the amount of cell-associated polymer was observed after transformation by herpes simplex type-2 or SV40 virus. Although no corresponding change was observed for the sulfated polysaccharides, the proportion of heparan sulfate increased significantly after transformation.