Absence of leukosis virus markers in hamster cells transformed by herpes simplex virus type 2

Electron microscopic studies of tumor viruses. II. Entry and uncoating of Epstein-Barr virus

Entry of Epstein-Barr virus into human lymphoblastoid cells (Daudi cells) was studied by electron microscopy. At the site of viral attachment, two distinct interactions conducive to penetration of the virus occurred between the viral envelope and cell membrane, namely, (i) simultaneous dissolution of both the envelope and cell membrane, presumably resulting in passage of viral capsids into the cytoplasm and (ii) dissolution confined to the cell membrane with resulting penetration of enveloped virus. In the latter case envelope dissolution appears to occur subsequently in the cytoplasm with release of capsids. Fusion of the viral envelope with the cell membrane was not observed. The capsids exhibited two distinct structural forms--one dense, the other translucent or light in appearance. The former disrupted near the cell membrane with release of viral cores into the cytoplasm whereas the light capsids containing dense cores migrated toward the nucleus and accumulated in the perinuclear region. Apparently the process of releasing deoxyribonucleic acid (DNA) from the light capsid is slowed down or prevented in Daudi cells. A hypothesis is presented concerning the manner in which these two types of capsids initiate infection.

A Murine Oncornavirus Marker in Adenovirus 7-Transformed Mouse Cells

The presence of oncornavirus particles in BALB/c mouse cells transformed by adenovirus 7 was investigated. The particles detected had a buoyant density of 1.16 g/cm3; both p30 and adenovirus T-specific immunofluorescence was demonstrated in the cell cytoplasm. No C-particles were shown by the electron microscope.

Oncogenic transformation of primary hamster cells by herpes simplex virus type 2 (hsv-2) and an hsv-2 temperature-sensitive mutant

Six oncogenically transformed cell lines were obtained following infection of hamster embryo fibroblasts with UV-irradiated herpes simplex virus type 2 (HSV-2) or with an HSV-2 temperature-sensitive mutant. All lines produced undifferentiated fibrosarcomas in newborn hamsters, four of the six lines produced metastatic tumors in the lung, and sera from tumor-bearing hamsters contained neutralizing antibody to HSV-2. HSV-specific cell-surface antigen (s) was detected by immunogluorescence tests in all six of the lines established from primary tumors. Antibody to an early, HSV-specific, non-structural polypeptide (VP134) reacted by immunofluorescence with antigen(s) in fixed preparation of three of the six tumor-cell lines.

Quantitative assay for transformation of 3T3 cells by herpes simplex virus type 2

The interaction of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) with Swiss/3T3 cells was investigated. Virus-induced cytopathic effects developed in the absence of production of infectious virus. HSV-2 inactivated with UV light (2, 4, 6, and 8 min) also induced cell death in the absence of virus replication. Cell death was not detectable after infection by HSV-2 that had been inactivated by UV irradiation for 10, 12, and 14 min. 3T3 cells infected with UV-inactivated virus (10 and 12 min) continued to replicate past the contact-inhibited monolayer normally associated with these cells. Infection of 3T3 cells with UV-irradiated USV-2 also induced the development of transformed foci. Transformed cells with an epithelioid of fibroblastoid morphology were identified and isolated. All HSV-2-transformed cell lines contained HSV-2-specific antigens detectable by immunofluorescence techniques. The maximum frequency of HSV-2-induced transformation was 3 times 105 PFU per transformed focus, and the observed transformation could be inhibited by pretreatment of the virus with specific antiserum. No type C particles were detected within five cell culture passages after transformation by HSV-2. Type C virus particles were detected after 10 cell culture passages of the HSV-2-transformed cell lines.

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. However, cells transformed by HSV-1 strain 14-012 induced tumors in 47% of the newborn hamsters injected. HSV-specific antigens were found in the cytoplasm of cells transformed by both virus strains. Sera from tumor-bearing hamsters contained HSV-1- and HSV-2-neutralizing antibodies as well as antibodies which reacted specifically with HSV antigens by the indirect immunofluorescence technique. Hamster oncornavirus antigens were not detected by immunofluorescence methods. These observations represent the first evidence of the oncogenic potential of HSV-1.