- Volume 26, Issue 2, 1975

Only doses of complexed polyriboinosinic: polyribocytidylic acids sufficient to induce interferon, stimulated hyporesponsiveness to re-induction in rabbit kidney cells. Results of experiments designed to delineate the earliest time of appearance of hyporesponsiveness suggested the time of onset was less than 1 h after the end of a 1 h exposure to the inducer. The duration of hyporesponsiveness was about 24 h. Interferon itself did not produce hyporesponsiveness. Hence hyporesponsiveness must be related to an event or a substance synthesized before interferon production. The best candidate is a control protein inhibiting interferon production which is rapidly synthesized following exposure to an inducer.

The kinetics of formation, the stability at 40 °C and the serological properties of thymidine kinase and deoxycytidine kinase activities induced by herpes simplex virus have been examined. The results are consistent with the hypothesis that both activities are carried on the same molecule − a deoxypyrimidine kinase.

Mutants deficient in deoxypyrimidine kinase have been used to produce, by absorption of general antisera, deoxypyrimidine kinase-specific antisera. Using immunoprecipitation and SDS-polyacrylamide gel electrophoresis, only one size of polypeptide (mol. wt. 42400 ± 200) has been found, constituting the type 2 enzyme.

This is close to published values for the type 1 enzyme but co-electrophoresis demonstrated that the polypeptide of the type 1 enzyme was slightly bigger.

The release of hydroxyurea-treated, herpes simplex virus-infected cells from the drug-induced block resulted in the prompt assembly of infectious virus. Electron microscope observations at sequential intervals following removal of the drug revealed considerable synchrony of replication. This synchrony permitted stages in the complex process of core assembly to be examined in detail. The data suggest that after partial or complete assembly the nucleoprotein enters the differentiated capsid to become enfolded.

A group of RNA viruses, echovirus, poliovirus, reovirus, respiratory syncytial virus and Semliki Forest virus have been examined for ability to grow in enucleate African green monkey kidney (BSC1) cells. Semliki Forest virus produced an almost normal yield of virus but poliovirus, echovirus, reovirus and respiratory syncytial virus, although showing clear evidence of virus replication when compared with a nuclear DNA virus (pseudorabies virus) gave much lower yields than those from nucleate cells. Analysis of enucleate cells infected with echovirus and reovirus showed no evidence of a specific block in the synthesis of any virus-specified polypeptide. Infection with vesicular stomatitis virus at intervals after enucleation demonstrated a diminishing ability to support virus growth with increasing time. It is suggested that the yield of virus obtained from an enucleate cell is related to the length of the growth cycle of the virus, the reduced yield obtained with some viruses reflecting the declining ability of the enucleate cell to support virus growth.

The effect of emetine on the in vivo production of interferon by Swiss mice stimulated with poly-I:poly-C, was studied. 100 μg of emetine per mouse yielded a 16-fold increase in interferon production. Maximal production of interferon was achieved 2 h after the simultaneous injection of emetine and poly-I:poly-C.

A new surface antigen (S antigen) can be detected by immunofluorescence during the abortive transformation of hamster cells by polyoma virus. It was found that addition of interferon greatly reduces the percentage of cells positive for S antigen.

A quantal microassay for the titration of LCM virus strains is described. It is based on the detection of virus-specific complement-fixing antigen in the medium of infected L cell microcultures.

RNA was extracted from primary chicken embryo kidney (CEK) cells infected with chicken embryo lethal orphan (CELO) virus and exposed to a pulse of [5-3H]-uridine late in infection. When this RNA was self-annealed, 4.5% became resistant to pancreatic ribonuclease digestion. The ribonuclease-resistant RNA was isolated by chromatography on Sephadex G-100, and the RNA was found to have the characteristics of a double-stranded molecule of sedimentation coefficient 8 S. Half of the column-isolated RNA hybridized to CELO DNA with equal amounts of virus RNA binding to the heavy or light stands of the CELO DNA, indicating the presence of complementary RNA species late in the infectious cycle of CELO.

The International Committee on Taxonomy of Viruses (formerly International Committee on Nomenclature of Viruses) has made decisions about family and generic names for viruses belonging to three families. Definitions and distinguishing features of these families and genera, as approved by International Committee on Taxonomy of Viruses, have been published in ‘Intervirology’ (Fenner et al. 1974). In order to disseminate this information widely and rapidly, a brief summary of the decisions follows.

Family Togaviridae. A family that includes all the viruses that were previously classified as Alphavirus and Arbovirus Group B (Wildy, 1971).

Genera Alphavirus = Alphavirus (Wildy, 1971).

Flavivirus (note spelling) = Arbovirus group B (Wildy, 1971).

Family Reoviridae. Non-enveloped spherical viruses with genomes consisting of several pieces of double-stranded RNA encapsidated within a single virus particle.

Genera Reovirus (Wildy, 1971).

Orbivirus (suggested by Borden et al. 1971; for description of genus, see Fenner et al. 1974).