- Volume 64, Issue 3, 1983

A hybrid murine myeloma (2-13F5) secreting a monoclonal antibody that specifically bound and neutralized murine interferon β has been isolated. Affinity chromatography with immobilized 2-13F5 monoclonal antibody of murine IFN (containing both IFN-α and IFN-β) separated an IFN-β preparation that demonstrated one band with Coomassie Brilliant Blue staining of SDS–PAGE at a molecular weight of 35000 and a specific activity of 4.3 × 108 units/mg of protein. This monoclonal antibody neither bound nor neutralized murine IFN-α. In addition, it bound only 87% of the interferon demonstrating a molecular weight of 35K. Possible explanations of this partial binding are discussed.

Infection of CV-1 monkey cells with SV40-GBM, a papovavirus isolated from a human glioblastoma multiforme, resulted in the appearance of defective viral DNA molecules. In contrast to SV40 wild-type, two main types of variant DNA molecules could be found after three viral passages at multiplicities of infection of about 10. The molecules of one variant DNA (GBM3-L) were about 19% shorter than the GBM3-H DNA molecules and the DNA of the original GBM isolate, as demonstrated by electron microscopy. Restriction enzyme analysis revealed that GBM3-L DNA had lost both the EcoRI and the HpaII cleavage sites which are located in the late viral genome region. Furthermore, SV40 GBM3-L did not possess the two PvuII sites which are located in the late genome region, and a portion of the GBM3-H and GBM3-L DNA molecules had lost the unique KpnI site. Heteroduplex analysis verified that the rearrangements in the GBM3-L DNA are located only in the late region of this DNA. The possible differences between SV40 wild-type and SV40-GBM are discussed on the basis of these results.

Titrations of hyperimmune antisera by indirect immunofluorescence using each virus of the Hughes serogroup (Hughes, Zirqa, Punta Salinas, Soldado and Farallon) demonstrated their individual antigenic identities. Furthermore, an antigenically related virus, designated Puffin Island (PI) virus, was shown both by indirect immunofluorescence and by neutralization in XTC cells to be distinguishable from the other viruses. These viruses readily established persistent infections in Vero cells after producing only moderate cytopathic effects. Treatment of persistently infected cultures with either fluorodeoxyuridine or bromodeoxyuridine made no significant difference to the percentage of immunofluorescent cells. Attempts to demonstrate haemagglutination by Zirqa virus were unsuccessful.

The ability of the compound 2′,3′-dideoxycytidine 5′-triphosphate (ddCTP) to serve as an inhibitor of viral RNA synthesis was examined using an in vitro system that supports vesicular stomatitis virus (VSV) protein synthesis, transcription and replication. Viral RNA synthesis was inhibited by 87 and 98% of control, respectively, in reactions containing 1 mm- and 10 mm-ddCTP in place of CTP. VSV RNA replication and transcription were inhibited equally by ddCTP. At a concentration of 1 mm-ddCTP, there was no inhibitory effect on viral protein synthesis; at 10 mm-ddCTP, total protein synthesis was inhibited by 30% as compared to control reactions. The presence of ddCTP had no effect on the size or relative molar amounts of each protein synthesized as analysed by electrophoresis on polyacrylamide gels. This is the first report describing a compound that will inhibit VSV RNA synthesis in vitro without compromising the concurrent synthesis and modification of proteins.

A variant, derived from both measles and subacute sclerosing panencephalitis virus preparations, incapable of producing intercellular fusion or syncytia typical of measles virus infections is described. This non-syncytiogenic (N-S) virus was easily detected using immunofluorescence, was genetically stable and replicated autonomously. The variant was defective in the production of both infectious virus and haemagglutinin in Vero and Hep2 cells. Persistent infections in Hep2 cells were readily established without the cooperation of defective interfering particles or temperature-sensitive mutants, although interferon could be detected. It is possible that such N-S variants may be involved with the regulation of persistent infections by measles virus.

A rat tumour induced by cells transformed with the sheared DNA of herpes simplex virus (HSV) type 1 HFEM α (RE2A) was injected with the intertypic virus HSV-2 HG52 ts 1. Separate plaques, isolated from cocultivation of excised tumour tissue with susceptible cells, yielded virus the DNA of which had the restriction enzyme profile either of the injected HSV-2 virus or that of the HSV-1 virus, originally used to transform the cells. No evidence of in vivo recombination was detected. In Hooded Lister rats, HSV may have the ability to remain in a latent or non-replicating state in fibroblasts.

The nucleotide sequences of the genome RNA species (RNA-1 and RNA-2) of three strains of tobacco rattle virus OR, SYM and CAM, were compared by hybridization with complementary DNA copies. Strain OR was found to contain two RNA-2 species, which differ by about 5 × 104 in mol. wt. (150 nucleotides), but about 90% of whose nucleotide sequences are homologous. The larger of the two contained the genetic information for yellow symptoms in infected Nicotiana spp., whereas the smaller, which probably arose from it by mutation, did not. The RNA-2 species of strains OR, SYM and CAM had no detectable nucleotide sequences in common. RNA-1 of strain OR and of strain SYM were almost identical in sequence, but had no detectable sequence in common with RNA-1 of strain CAM. Only in strain CAM was any nucleotide sequence homology between RNA-1 and RNA-2 detected, amounting to about 450 residues.

Methods were developed for preparing an Indiana isolate of barley yellow dwarf virus in amounts (1 to 2 mg/kg) and purity comparable to those recently achieved with other luteoviruses. Choice of host, and environmental conditions, period of infection and tissue used were critical factors for virus production. Aphid transmission, serological tests, and other properties defined the isolate as ‘PAV-like’ sensu Rochow, but the purification procedure worked well with ‘MAV’ and ‘RPV’, two other distinctive vector-specific isolates. The Indiana isolate had a particle diameter of 26 nm, s 20,w of approximately 115S, densities of 1.40 g/ml in CsCl and 1.335 g/ml in Cs2SO4, a single coat protein of mol. wt. 24400 (± 200) and an absorbance spectrum with an average A 260/A 280 ratio of 1.76.

Defective isolates of tomato spotted wilt virus (TSWV) which produce amorphous masses characteristic of TSWV in infected cells but do not produce enveloped virus particles have been studied. Nucleocapsid protein but no membrane proteins was detected by ELISA in plants infected with defective isolates. The protein of an infectious fraction purified from such plants consisted mainly of nucleocapsid protein. Electron microscope examination of this purified fraction revealed structures resembling the amorphous masses observed in thin sections of leaves infected with the defective isolates. This fraction from the three defective isolates studied contained three RNA segments, the mol. wt. of RNA 1 and RNA 3 being the same as those of normal TSWV particles. The mol. wt. of RNA 2 of the defective isolates was always smaller than that of the RNA 2 of normal TSWV particles. However, their mol. wt. were different for each isolate. Thus, the amorphous masses are aggregates of nucleocapsids of defective TSWV which do not produce normal particles since they have lost the ability to make at least one membrane protein species. This is possibly due to the deletion in RNA 2.

Galinsoga mosaic virus (GMV) has isometric particles about 34 nm in diameter when examined in preparations negatively stained with uranyl acetate. They are similar to the particles of viruses belonging to the tombusvirus and dianthovirus groups but not to those of the sobemovirus group. GMV induced the development of large multivesicular bodies from the mitochondria in infected cells which only superficially resembled those observed in cells infected by tombusviruses. The possible taxonomic and functional significance of the multivesicular bodies is discussed and it is concluded that GMV does not readily fit into any of the established virus taxonomic groups.