- Volume 54, Issue 2, 1981

The distribution of guanine-cytosine (GC) pairs in the DNA of the highly oncogenic simian adenovirus type 7 (SA7) and the non-oncogenic human adenovirus type 6 (Ad6) has been studied by thermal denaturation and CsCl density-gradient centrifugation. The differential of the DNA thermal denaturation curves shows the presence of pronounced peaks which indicates uneven distribution of GC pairs along the DNA chains and the presence of regions with GC content from 30 to 74% in SA7 DNA and from 40 to 68% in Ad6 DNA. The DNA restriction fragments obtained by treatment with EcoRI, BamHI, SalI, BglII and HindIII were subjected to CsCl density-gradient centrifugation. GC content of the fragments ranged from 45 to 70% for SA7 DNA and from 43 to 61% for Ad6 DNA. The GC content of the extreme left-hand fragments, where the transforming gene(s) is located, was higher than the average for SA7 DNA and lower than the average for Ad6 DNA. The most GC-rich regions were localized in the centre of the genome. The GC content of the right-hand part of both viral genomes was lower than the average.

Human papovavirus BK DNA resistant to digestion with EcoRI endonuclease had the capacity to direct synthesis of T antigen in human embryonic kidney cells. The study demonstrated the natural occurrence of defective deletion mutants with intact early functions of the viral genome.

A mouse hybridoma cell line (Mo56) secreting IgG antibody to poliovirus type 3 D-antigen was obtained by fusion of a mouse myeloma cell line with spleen cells from mice immunized with Saukett virus. The monoclonal antibody was specific for Saukett virus strains in virus-neutralization and single-radial-diffusion tests. In immunoprecipitation tests the monoclonal antibody reacted with intact infectious virus particles (155S) and with a previously undescribed 70S poliovirus particle with D-antigenic reactivity.

Cell cultures of the alfalfa looper, Trichoplusia ni (Tn-368), codling moth, Laspeyresia pomonella (Cp-169) and viper spleen cells (viper-VSW) were inoculated with Autographa californica non-occluded nuclear polyhedrosis virus (AcMNPV-NOV). In both Tn-368 and Cp-169 cells an increase in the concentration of virus protein was detected by ELISA from 9 to 20 h after virus inoculation. An average of 2 ng AcMNPV protein was detected in homogenates of T. ni larvae from 12 to 14 h post-infection (p.i.). HzSNPV proteins were first detected in Heliothis zea larvae 16 h p.i. At this time approx. 60 ng HzSNPV protein was detected in homogenates of the virus-infected larvae. Virus protein was not detected in viper spleen cells, and Lymantria dispar larvae inoculated with AcMNPV, or in Estigmene acrea larvae inoculated with HzSNPV.

Carrier cultures of L cells infected with wild-type vesicular stomatitis virus (VSVo) were initiated without the use of defective-interfering particles or homologous interferon. The cloned viruses recovered from such carrier cultures after passage 21 were characterized as temperature-sensitive. Furthermore, these clones of the mutant showed restricted replication at permissive temperature in HEp-2 cell cultures as compared to the wild-type VSVo. This restrictive replication of the mutant in HEp-2 cells was not due to a defect in the expression of virion-associated primary transcriptase activity in vivo, but due to the marked reduction in virus-specific amplified RNA synthesis. These results suggest that a host function(s) yet to be characterized may govern the synthesis of mutant virus-specific amplified RNA in HEp-2 cells.

The protein subunits of the XN strain of potato virus X (PVX) were cross-linked by di-imidates to produce a series of polymers in the proportion expected from the random cross-linking of subunits in an extensive heterologous array. Polymerization of the subunits of chemically modified forms of the virus, as well as of other strains, suggests that the cross-links are heterogeneous, and may, but need not, involve the two amino groups that have been previously characterized as either reacting with chlorogenoquinone or being sensitive to trypsin.