- Volume 43, Issue 3, 1979

In vitro interactions between murine cytomegalovirus (MCMV) and murine leukaemia viruses (MuLV), two groups of enveloped viruses capable of causing persistent or latent infections in vivo, were examined for evidence of phenotypic mixing. The growth of MCMV in murine cells productively infected with ecotropic MuLV was shown to result regularly in the production of phenotypically mixed particles having the envelope antigens of MuLV and the genome of MCMV [MCMV(MuLV) pseudotypes]. The identity of such pseudotype particles was confirmed by the use of specific anti-MuLV serum and by the demonstration of restriction due to viral interference of penetration of these particles on MuLV-infected murine cells. This restriction was independent of N- or B-tropism. The production of reverse pseudotypes could not be examined because of the lytic effects of MCMV on the requisite assay cells.

Six of 16 meningiomas tested in early subcultures by indirect immunofluorescence showed SV40 T-antigen. Two different antisera specific for T-antigen were used. One serum gave a positive reaction with six tumours and the other with only two. In one T-antigen positive meningioma, the typical nuclear fluorescence changed, beginning with the second subculture, into an unusual brilliant granular pattern irregularly distributed over the nuclei. In six meningiomas, a specific chromosome aberration (monosomy G 22) was established. However, up to now, no clear correlation between karyotype and T-antigen expression could be found: cells from three meningiomas with positive reactions had normal karyotypes, whereas those from three tumours with typical chromosome loss showed no T-antigen.

Human fibroblast and human leucocyte interferons display a strong affinity for the copper chelate of bis-carboxymethyl amino agarose, binding tenaciously over a wide pH range (7.4 to 4.0). Their binding is apparently irreversible on a sorbent saturated with copper (24.8 µmol of Cu2+/ml of column bed). However, both interferons can be partially recovered from sorbents of lower copper content, prepared by leaching the columns with sodium citrate at pH 9.0. The recovery of fibroblast interferon from a leached sorbent (5.8 µmol of Cu2+/ml of column bed) is about 30% and that of leucocyte interferon about 60%. Moreover, the strength of binding of leucocyte interferon can be modulated by leaching copper chelate-agarose with citrate of varying concentration.

The antigens of strain AD169 of human cytomegalovirus (CMV) were extracted by various methods and at different times following the appearance of cytopathic effects (c.p.e.) in infected fibroblasts. Assay with a pooled human serum in electro-immunodiffusion (EID) revealed that the most reactive preparations were obtained by shell-freeze (SF) extraction on the fourth day after 4 + c.p.e. As many as 20 antigens could be detected in the original gels, most of which were stable upon storage at 4 °C for up to 4 weeks; of these, about 14 can be reproducibly seen on photographs. EID runs on day 4 SF preparations from high-passage CMV strains C87 and Davis and low passage recent isolates VD14, 1694 and 1723 resolved, respectively, 15, 15, 13, 11 and 11 antigens in the original gels (11, 9, 11, 8 and 9 are visible in photographs). Strains 1694 and 1723 shared fewer antigens with one another and with high passage strains than were shared among the latter, whereas VD14 had relatively large numbers of antigens common to both low and high passage strains. At least six antigens were common to all strains.

Guinea pigs immunized with polypeptides derived from plantar and hand wart viruses developed both humoral and cell mediated immunity. The specificity of the antiserum was determined by indirect immunofluorescence (IF) tests and cellular immunity by intradermal tests. While whole plantar and hand wart virus particles (PV and HV) appeared to be immunologically analogous, they had different polypeptide patterns as shown by analysis on acrylamide slab gels. In particular, the P2 polypeptide (major virus protein) with different mol. wt. for PV (56750) and HV (54500) induced the production of high antibody titres in the animals and the immune sera specifically labelled wart substrates as shown in the IF test, demonstrating that no cross humoral reaction occurs between these two polypeptides. Furthermore, a delayed hypersensitivity reaction was observed in P2 polypeptide-inoculated guinea pigs when whole particles were introduced in skin tests, but a total cross reactivity between PV and HV was noticed at the cellular level. However, the study of the virus isolated from the lesions of a patient (Ri) bearing extensive common hand warts has shown that the virus particles possessed all the biochemical and immunological characteristics of PV, in particular with regard to the P2 polypeptide. Such a case may represent plantar-like warts located on the hands.

Recombination of phage T4 can be stimulated more than sixfold above the spontaneous level by treatment with nitrous acid, indicating that the lesions induced by this agent are strongly recombinogenic. Two temperature sensitive mutants defective in exonuclease functions showed less than the wild-type spontaneous level of recombination even after nitrous acid treatment and a ligase mutant showed a highly elevated frequency of recombination after treatment. Since these same mutants have analogous effects on spontaneous recombination, the results imply that nitrous acid-induced lesions in DNA stimulate a recombinational repair process similar in some of its enzymic steps to spontaneous recombination.

Total RNAs from four BALB/c mouse tissues, containing mostly non-dividing cells (liver and kidney) or variable proportions of dividing cells (uterus and embryo) were analysed for sequences complementary to 3H-DNA transcripts synthesized from BALB/c endogenous, N- and X-tropic retroviruses. Extensive transcription of virogene information was detected in the tissues examined, but such transcription was found to be mostly limited to the homologous regions of the two virus genomes. No additivity of hybridization values could be detected when RNAs from two different tissues were mixed, which suggests that BALB/c mouse liver, kidney, uterus and embryo transcribe a common set of nucleic acid sequences of the homologous regions of the N- and X-tropic viral genomes, in addition to other sequences of the same region that are specific for individual tissues.

We have proved by acrylamide gel electrophoresis that DNA-free ghosts of bacteriophage λ obtained by osmotic shock (S-ghosts), or by incubation in 5 m-L-Cl (L-ghosts) do not possess the proteins specified by the genes J and H. Electron microscopy of L-ghosts showed that they are devoid of the whole tail tip, composed of the basal part and the tail fibre. The lack of the J-gene product, which is believed to be the tail fibre, explains why S- and L-ghosts do not adsorb to susceptible bacteria. Our results suggest that the H-gene product, which is modified after translation, is situated in the basal part of the tail.

The two RNA species of tobacco ringspot virus (TRSV) had about the same radioactivity per molecule when iodinated by treatment with Na125I and chloramine T. The radioactivity was not separated from the RNA by heating for 1 min at 70 °C in 100% formamide followed by rate zonal sedimentation in sucrose density gradients containing SDS, or by equilibrium centrifugation in caesium trichloroacetate, indicating that the labelled material is covalently linked to the RNA; these treatments had little effect on infectivity. Incubation with Pronase or proteinase K made 90 to 97% of the radioactivity soluble in 70% ethanol, but did not noticeably alter the size of the RNA molecules. Polyacrylamide gel electrophoresis of acetone-precipitable material, liberated from the RNA by ribonuclease treatment, revealed a radioactive component with the mobility of a polypeptide of mol. wt. about 4000. The protease-sensitive structure previously shown to be needed for infectivity of TRSV-RNA probably is the covalently linked polypeptide now detected.