Malignant transformation of hamster cells following infection with bovine herpesvirus (infectious bovine rhinotracheitis virus

Propagation of infectious bovine rhinotracheitis (bovine herpes-1) virus in murine primary cell cultures

Virus synthesis in BALB/C mouse lung and kidney primary cultures infected with infectious bovine rhinotracheitis (IBR) virus started between 6 and 8 hours after virus inoculation and reached a maximum titer of 5.5 log10 plaque forming units (PFU) at 48 hours postinfection (PI). Cytopathic effect (CPE) in cell cultures occurred at 8-10 hours and over 90% of the cells had CPE by 48 to 72 hours PI. The bulk of the newly replicated virus (60-80%) was cell-associated as determined by plaque assay of extracellular and intracellular virus. Pulse-chase experiments demonstrated incorporation of radioactive precursors into viral DNA and protein macromolecules. Viral DNA synthesis was initiated between 2 and 4 hours PI and was maximum at 4 to 6 hours. Viral proteins were detected at 4 hours and peaked between 6 and 8 hours PI. Enzyme-linked immunosorbant assay (ELISA) confirmed synthesis of specific viral proteins, which gradually increased during the virus growth cycle. Abstract in French is given at the end of the article.

Destruction of bacterial viruses in serum by heat and radiation under conditions that sustain the ability of serum to support growth of cells in suspended culture

Methods for inactivating bacterial viruses in serum were developed through the use of heat and ionizing radiation, and the effects of these treatments on the growth rates of cultured cells were tested. Viruses chosen for this study were the radiation-resistant bacteriphage f2 and heat-resistant phage T4. The viabilities of these phages were reduced more than 2 and 4 orders of magnitude, respectively, by a treatment at 60 degrees C for 30 min followed by 420 krads of ionizing radiation. Simultaneous application of heat and radiation caused a considerably greater reduction in viability of both phages in serum, but also caused a significant decrease in the growth rates of L cells in medium supplemented with serum treated in this manner. Treatment of serum with these same doses but given in the sequential fashion of heat followed by radiation caused little or no change in the growth rates of L cells. Finally, it was found that simultaneous treatment of serum with these doses of heat and radiation had little effect on the growth rates of either HeLa or Chinese hamster cells.

Persistent infection with bovine herpesvirus-1 (infectious bovine rhinotracheitis virus) in cultured hamster cells

Bovine herpesvirus-1 infection in hamster embryo cells was found to be dependent upon input multiplicity; productive infection was achieved at input multiplicities greater than one, while persistent infection was established when input multiplicities were about 0.5. This persistence was characterized by a noncyclic, minimal degree of cytopathic effect with a low level of released virus. Maintenance of the persistently infected cultures did not require external supportive measures. Subcultivation of the persistently infected cultures led to virus replication followed by CPE and then cell regrowth. With 3 to 4 weeks after subcultivation a persistent infection was re-established. The possible mechanism for the bovine herpesvirus persistence in hamster cells is discussed.