- Volume 67, Issue 12, 1986

The long terminal repeat (LTR) of Rauscher murine leukaemia virus (MuLV) has been sequenced. It differs in only three positions from the LTR of Rauscher spleen focus-forming virus (SFFV), and in four positions from the LTR of Rauscher mink cell focus-inducing virus (MCFV). It is unlikely that these differences account for differences in leukaemogenicity or tissue tropism of Rauscher MuLV, SFFV and MCFV. In contrast to the LTR of Friend MuLV, the Rauscher MuLV LTR contains only one copy of a tandem direct repeat. This repeat includes an enhancer core sequence.

The RNA-dependent DNA polymerase (RDDP) of human immunodeficiency virus (HIV) was purified from sucrose density gradient-banded virus by four successive procedures: anion exchange chromatography, cation exchange chromatography, affinity chromatography on oligo(dT)-cellulose and adsorption chromatography on hydroxyapatite. The enzyme preparation was free of cellular DNA-dependent DNA polymerase activity. The properties of HIV RDDP were determined with a variety of template-primers. Generally, the enzyme used Mg2+ for optimal activity except with (Cm)n.(dG)12–18 as template-primer. Kinetic data (Michaelis constant, Hill coefficient) were calculated for several substrates.

The antiviral properties of a herpex simplex virus type 1-specific ‘helper’ T cell clone were investigated. The clone was found to be deficient in interleukin 2 production, although it produced interleukin 3 and interferon-γ upon stimulation with the virus in vitro. Supernatants containing these lymphokines were observed to increase the virocidal activity of macrophages in vitro and furthermore induced these cells to mediate cytotoxic activity against virus-infected target cells. Macrophage activation was linked to the presence of interferon-γ in the clone supernatant. The implications of these results for protection against this virus in vivo are discussed.

Bunyamwera virus and snowshoe hare virus (family Bunyaviridae) were passaged up to six times through mosquito cells in culture and the resultant viruses were compared to the input, mammalian cell-passed virus using monoclonal antibodies raised against the input virus. The mosquito cell-adapted virus population consisted of mutants which were better adapted to replication in the new host than was the input mammalian cell-passed virus and were differentially susceptible to neutralization by antibody.

Ten different RNA species associated with measles virus were detected in virus-infected cells. The largest RNA (no. 1) was considered to be genomic RNA and the other nine RNAs were found to have a methylated cap as well as a poly(A) tail. Northern blot hybridization indicated that RNAs no. 2 and 7 to 10 correspond to mRNAs encoding structural proteins, and that RNAs no. 3 to 6 are intermediate-sized (IS) RNAs. The possibility that the ISRNAs represent defective interfering RNA or a precursor form of the mRNA seems to be unlikely since the amounts of IS RNAs did not increase after undiluted passages or decrease in a pulse-chase experiment. These results indicate that IS RNAs are readthrough transcripts of neighbouring cistrons.

The time course and temperature requirements for fusion of influenza virus membranes with liposomes at pH 7.5 were found to be consistent with the requirements for cell entry. At 37 °C, fusion was most rapid during the first 5 min and then continued more slowly up to at least 1 h. The amount of fusion increased semilogarithmically with increasing temperature up to 50 °C.

Newborn (within 24 h after birth), 1-week-old and 6-week-old (adult) rats were inoculated with a Hantaan-related virus (B-1) and attempts were made to isolate the virus from various organs. Virus-specific antigens were detected in various organs of newborn rats. Moreover virus could be isolated from almost all their organs even 25 weeks after infection. In contrast, in rats infected at 6 weeks of age the virus could be isolated from various organs but its concentration decreased progressively with time. The levels of haemagglutination-inhibiting (HI) and neutralizing antibodies to B-1 virus in the sera were measured. In adult rats, HI antibodies were first detected 2 weeks after infection and their titre rose to a maximum after 5 weeks. On the other hand, in newborn rats the levels of antibodies remained low until 5 or 6 weeks after infection and started to increase to a high level more than 9 weeks after infection. Furthermore, in rats infected soon after birth IgM antibodies predominated for a long time and these antibodies also neutralized infectivity at a high level. These data suggest that the induction of a high titre of neutralizing antibodies mainly of the IgM type does not result in virus clearance in new born rats and that cellular immunity may be important for virus clearance in vivo.

The nucleotide sequences of the spike precursor genes of infectious bronchitis virus strains M41 and 6/82 have been determined and compared with that of the Beaudette strain which we have previously sequenced. The two Massachusetts strains, M41 and Beaudette, were found to be remarkably similar, having only 3.7% of the amino acids different. The situation with 6/82, one of the new field isolates, is quite different and this strain had 13.8% of its amino acids different from Beaudette. The differences identified are discussed in terms of the structural features of the spike protein.

The complete sequence of the double-stranded RNA segment that codes for a non-structural protein (P8) of bluetongue virus serotype 10 has been determined from a cDNA clone inserted into the plasmid pBR322. The segment 10 RNA of the virus (S10 RNA) is deduced to be 822 base pairs long (0.5 × 106 daltons) and has an open reading frame in one strand capable of coding for a protein with a calculated size of 25572 daltons (229 amino acids) and a net charge of +5.5 at neutral pH.

The antigenic relatedness of minute virus of mice (MVM), Kilham rat virus (KR), H-1 virus (H-1), haemorrhagic encephalopathy of rats virus (HER), porcine parvovirus (PPV), canine parvovirus (CPV), feline panleukopenia virus (FPV), goose parvovirus (GPV) and bovine parvovirus (BPV) was studied by immunofluorescence microscopy (FA) and by serum neutralization (SN). An antigenically related group comprising MVM, KR, HER, PPV, CPV and FPV was recognized by FA and most reactions within the group were reciprocal. Antigenic relatedness was less evident when the same viruses and antisera were tested by SN. Only CPV and FPV were closely and reciprocally related. Other cross-reactions by SN were quantitatively minor and included neutralization of CPV and FPV by pig anti-PPV serum and neutralization of H-1 and HER by rat anti-KR serum. Neither FA nor SN revealed any antigenic relationship of BPV and GPV either with each other or with any of the other viruses tested.