- Volume 67, Issue 8, 1986

Monoclonal antibodies directed against four structural components of the ATCC strain C243 of parainfluenza virus type 3 were produced. The specific reaction of the antibodies with individual structural components was determined by radioimmune precipitation assay. In the collection of monoclonal antibodies, 21 reacted with the haemagglutinin-neuraminidase (HN) glycoprotein (mol. wt. 72000), eight with the fusion (F) glycoprotein (mol. wt. 64000), 27 with the nucleocapsid (NP) protein (mol. wt. 69000) and 24 with the matrix (M) protein (mol. wt. 40000). The F-specific monoclonal antibodies precipitated two proteins which were interpreted to represent intact F protein and the large cleavage product F1 (mol. wt. 52000). The numbers of epitopes were determined in a competition ELISA with the monoclonal antibodies. The epitopes found were six for the HN, two for the F, six for the NP and six for the M protein. The six groups of antibodies reacting with different epitopes on the HN molecule showed varying capacities to inhibit biological activities. Two exhibited high neutralization (NT), haemagglutination inhibition (HI) and haemolysis inhibition (HLI) activity. Three groups had somewhat lower NT, lower HI and no detectable HLI activity. One group showed no activity in these tests. Of the eight monoclonal antibodies directed to the F protein two had demonstrable HLI activity.

Intracellular virus-specific proteins induced by equine arteritis virus (EAV) have been compared with in vitro translation products of virion and intracellular EAV RNAs. In infected BHK-21 cells, the two major virion proteins (C and E1) and polypeptides with mol. wt. of 60000 (p60), 42000 (p42) and 30000 (p30) were found. There were no indications that the viral proteins were processed from a larger precursor as shown by pulse-chase, amino acid analogue and protease inhibitor experiments. The six polyadenylated RNAs that occur in EAV-infected cells were isolated and translated in an mRNA-dependent reticulocyte cell-free system. Translation of RNA6 resulted in the appearance of a product having the mol. wt. (14000) of the nucleocapsid protein (C). EAV genomic RNA was translated into proteins of mol. wt. 30000 and 200000, while RNA1, the intracellular homologue of genomic RNA only encoded p30. The absence of large precursor molecules in infected cells and the results from the in vitro translation experiments both suggest that at least some of the proteins are primary translation products.

Two reassortant viruses were selected from a mixed infection of MA104 cells with human rotavirus strains Wa (serotype 1-subgroup II) and HN126 (serotype 2-subgroup I). Antigenic characterization and genotype analysis by polyacrylamide gel electrophoresis revealed that they were reassortants with novel antigenic compositions, i.e. serotype 1-subgroup I (C116) and serotype 2-subgroup II (C15). Furthermore one of them, C15, was considered to have a mosaic antigenicity defined by two serotype-specific antigens, namely the serotype 1-specific VP3 antigen and the serotype 2-specific VP7 antigen. Although this reassortant was shown to be a serotype 2 virus on the basis of its preferential reactivity in neutralization reactions with serotype 2 antiserum, unexpectedly the antiserum prepared against C15 equally neutralized both serotype 1 and serotype 2 strains.

We have attempted to rescue presumptive human endogenous retrovirus(es) by using a competent animal oncovirus as a helper. Human melanoma cells (line HMB2) were fused, using polyethylene glycol, with mouse NIH-3T3 cells which had been infected and transformed by the Harvey murine leukaemia and sarcoma virus complex (MLV and MSV). The heteropolykaryons obtained were co-cultivated with fresh NIH-3T3 cells; filtered (Millipore 0.22 µm) medium from these was used to infect further NIH-3T3 cells. In these cells after several passages, vesicular stomatitis virus (VSV) pseudotypes could be produced. These were infectious not only for mouse cells (manifesting the helper MLV), but also for human cells (HeLa, HEC human embryo fibroblasts, HMB2); they were not infectious for CCL64 (mink) or for Vero (African green monkey) cells. The presence of such VSV pseudotypes infectious for human cells indicated that a human ecotropic virus [provisionally named rescued human virus (RHV)] had been rescued by the fusion of human melanoma cells with MLV-infected mouse cells. This was supported by the following evidence. (i) The human-specific pseudotype was neutralized by sheep antisera raised to antigens selected by VSV from human tumour cell lines HMB2, T47D and HeLa. (ii) These antisera also aggregated NIH cells infected with MLV and RHV. (iii) Mouse antisera raised to antigens present in NIH cells infected with MLV and RHV, in contrast to sera raised to NIH cells infected with MLV only, immunoprecipitated an 85000 mol. wt. protein band from human cells (HEC, HMB2 and HeLa) surface-labelled with 125I.

The phosphoprotein (NS) gene from the Indiana serotype of vesicular stomatitis virus (VSV; Mudd-Summers strain) was cloned and sequenced. The NS gene encodes a protein of 265 amino acids which was expressed from a simian virus 40 vector in COS cells. The post-translational modification characteristic of viral NS, the extensive phosphorylation of a cluster of serine and threonine residues, was also evident in recombinant NS protein. The NS gene displays a property common to the phosphoprotein genes of negative-strand RNA viruses: the phosphoprotein mRNA has a second open reading frame (ORF) which could encode a small (7500 mol. wt.) protein. Both measles virus and Sendai virus employ the second ORF of their phosphoprotein gene, and the resultant proteins have an amino acid composition similar to that predicted for the VSV ORF. Comparison of phosphoproteins from different VSV strains revealed two conserved domains that we propose are critical for the function of NS in transcription and replication.

The putative E1 gene product of papillomaviruses is thought to be involved in the initiation of viral replication, as large-T antigen (T antigen) is in the case of polyomaviruses. Mouse cell lines cloned after transformation by a plasmid consisting of the simian virus 40 (SV40) early region and the complete genome of human papillomavirus type 16 (HPV16) maintained episomal plasmid DNA. In contrast, the DNAs of either SV40 or HPV16, when employed separately in transfection experiments, were consistently integrated into the host DNA. To test the hypothesis that SV40 T antigen might be involved in the replication of the hybrid plasmids, HPV16 DNA was used in a transient replication assay for transfection of either CV-1 or COS-7 cells. The HPV16 DNA replicated to a high copy number in the T antigen-producing COS-7 cells, but failed to replicate in the CV-1 cells. To define the HPV16 sequences that were essential for the plasmid maintenance in SV40 T antigen-producing cells, restriction fragments of HPV16 were analysed for their replication capacity in COS-7 cells. Here it is reported that the presence of the coding region of the putative E1 gene product of HPV16 together with the 5′ transcriptional control elements is essential and is sufficient to support plasmid replication mediated by SV40 T antigen in trans.

Using vaccinia virus as a selection and cloning vehicle, a thymidine kinase (TK) gene of fowlpox virus (FPV) has been identified. A plasmid, pF130, containing part of the HindIII-F region of vaccinia virus was used to shotgun clone EcoRI fragments of FPV DNA into TK− vaccinia virus and select for TK+ recombinants. The TK+ recombinant vaccinia virus contained a 5.5 kb EcoRI fragment of FPV. This FPV fragment was cloned into pUC9 and the presence of the TK gene in this fragment was confirmed by its ability to rescue TK+ vaccinia virus from TK− virus, when inserted into pF130. A recombinant vaccinia virus containing this FPV fragment induced TK enzyme activity in the cytoplasm of infected cells. The vaccinia virus RNA polymerase appeared able to recognize the FPV promoter sequences of the FPV TK gene since the fragment operated in the marker rescue, irrespective of its orientation to the vaccinia virus promoter in pF130. Using restriction enzyme analysis, insertion of subfragments of the 5.5 kb FPV fragment into pF130 and marker rescue, we were able to map the position of the TK gene in the 5.5 kb EcoRI fragment. This approach may facilitate identification and cloning of TK genes from other poxviruses.

The production of antibody to specific herpes simplex virus type 2 (HSV-2) polypeptides, the recurrence patterns and the susceptibility to re-infection were studied in the guinea-pig model of genital HSV-2 infection. Further, we defined the effects of acyclovir (ACV) therapy on these parameters of infection. Treatment with ACV reduced the clinical severity of the initial disease but did not affect vaginal viral shedding. Production of neutralizing antibody as well as antibody to the nucleocapsid protein, and glycoproteins B, D and G were all delayed in ACV recipients. ACV treatment of initial infection did not significantly alter the pattern of subsequent recurrence although by several criteria treated animals tended towards decreased recurrences. Re-inoculation with a second strain of HSV-2 resulted in a local cervicovaginal infection but, except for one ACV-treated animal, neural tissue was protected from re-infection.

We have identified and characterized an origin of DNA replication in the genome of the human herpesvirus, varicella-zoster virus (VZV). This origin of replication (VZV ORIS) is located within the major inverted repeats in a position equivalent to that occupied by one of the herpes simplex virus type 1 (HSV-1) replication origins. Products encoded by both VZV and HSV-1 activate cloned copies of VZV ORIS, generating high molecular weight molecules consisting of tandem duplications of the input plasmid. The VZV ORIS region contains a tract of alternating A and T residues located at the centre of symmetry of an almost perfect palindrome of 45 bp, and the use of plasmid deletion mutants has demonstrated that this tract is an important functional element of the origin. Two sequences common to the VZV ORIS region and the regions specifying the two HSV-1 origins (ORIS, located within the TRS/IRS regions, and ORI l , located with in the U l region) were identified and these may represent important recognition sites. One is an 11 bp sequence (CGTTCGCACTT), and the other is represented by the tract of alternating A and T residues. VZV does not appear to contain an origin of replication in a position equivalent to that of HSV-1 ORI l .

2-Acetylpyridine thiosemicarbazone, a potent antiviral drug, and 13 analogues were examined as inhibitors of partially purified herpes simplex virus type 1-specified ribonucleoside diphosphate reductase. N 4,N 4-Azacycloheptane derivatives were more active than their N 4-unsubstituted analogues. Selenosemicarbazones were similar in potency to their thiosemicarbazone congeners, whereas a related semicarbazone was much less active. Maximum inhibition was observed when an ethylidene side-chain was present in the compounds. No discernible trend in potency was observed when the pyridine moiety was replaced by quinoline or isoquinoline. Thiosemicarbazide derivatives were less potent than their unsaturated thiosemicarbazone analogues. Inhibitory potencies increased at longer incubation times consistent with the hypothesis that thiosemicarbazones inactivate the enzyme in a time-dependent manner.

Two human recombinant lymphoblastoid interferon-α subtypes, LyIFN-B (α8) and LyIFN-D (α1), and 10 hybrids generated therefrom were produced in Escherichia coli and purified. The antiviral and antiproliferative activities and the induction of (2′–5′)oligoadenylate synthetase were compared to their receptor binding affinities. The IFN subtypes and their hybrids had similar specific antiviral activities on bovine cells. On human cells both the specific antiviral and antiproliferative activities of LyIFN-B were about 30-fold higher than those of LyIFN-D. This difference in activity could be attributed partly to the N-terminal amino acids 1 to 60 and partly to amino acids 61 to 92. A third domain affecting the biological activities was found within the carboxy-proximal segment from amino acids 93 to 150. The differences in these activities were found to correlate with their ability to bind the receptor, suggesting that the differences in activity might be due to altered binding of the IFNs to the cellular receptors. In contrast, the induction of (2′–5′)oligoadenylate synthetase did not follow the same activity profile. On mouse cells, the efficiency of the hybrids was affected by at least four sites on the IFN protein. A hybrid with the N-terminal segment 1 to 60 from IFN-B and amino acids 61 to 166 from IFN-D had a specific antiviral activity on mouse cells as high as on human cells corresponding to a 500- and 5000-fold increase in specific activity compared to IFN-D and IFN-B, respectively. We suggest that on mouse cells the IFN activity may be more dependent on conformational differences than on human cells, which in turn might reflect a less precise fit to the mouse receptor than to the human receptor.

The stabilities of the antiviral states induced by different types of murine interferons (IFNs) were compared to gain insight into possible differences in the modes of regulation of their respective antiviral states. Both type I (MuIFN-α and MuIFN-β) and type II (MuIFN-γ) IFNs were employed to establish antiviral states against mengovirus in mouse L-929 cells. At various times after IFN treatment, the IFNs were removed and the stability of the antiviral states was determined by single cycle mengovirus yield reduction experiments. The antiviral states induced by the two type I IFNs decayed significantly by 12 h following IFN removal. The rate of this decay was an exponential function of the level of the antiviral state induced. A transcriptional block effectively delayed the decay of the antiviral state, suggesting the involvement of a positive feedback mechanism of regulation. In contrast, the profile of the antiviral state induced by type II IFN showed a significant enhancement upon MuIFN-γ removal. This enhancement was not dependent upon de novo transcriptional and translational activity of the cells. These data suggest that the modes of regulation of the antiviral states against mengovirus induced by type I and type II IFNs are distinctly different.

Human peripheral blood lymphocytes (PBL) of non-immune donors produced interferon (IFN) when cultured with dengue virus-infected cells. IFN was detected as early as 2 h after exposure of PBL to dengue virus-infected cells, and the titres reached a maximum by 16 h of incubation. Dengue virus-infected cells treated with glutaraldehyde, which produced no infectious dengue virus, also induced IFN. These results indicate that PBL produce IFN in response to dengue virus-infected cells and that the production of IFN by PBL is due to stimulation of PBL by dengue virus-infected cells. Characterization of IFN-producing PBL with monoclonal antibodies demonstrated that the predominant producing cells were contained in M1+ and T3− subsets, and that the Leu11+ subset contains some IFN-producing cells. The IFNs that were produced by the PBL exposed to dengue virus-infected cells were analysed by radioimmunoassay employing monoclonal antibodies specifically to detect IFN-α or IFN-γ. IFN-γ as well as IFN-α was produced by PBL exposed to dengue virus-infected cells. Both IFN-α and IFN-γ were predominantly produced by PBL contained in M1+ and T3− subsets. The observation that PBL of non-immune donors produced IFN-γ as well as IFN-α in response to dengue virus-infected cells is of interest in view of the immunoregulatory roles of IFNs and the hypothesis that the complications of dengue virus infection (haemorrhagic fever and shock) may be due to immunopathology.

The inner capsid structure of the OSU strain of porcine rotavirus was studied by electron microscopy of freeze-dried preparations and of negatively stained chemically disrupted virus particles. The analysis of the particles by the freeze-drying technique revealed a T:13 l (laevo) symmetry for the organization of the inner capsid. Treatment of single-capsid rotavirus particles with 30% formamide or 5 m-urea resulted in their degradation, giving rise to very similar products, corresponding to isolated vertices, edges and faces of the virus icosahedron. An analysis of such structures confirmed the triangulation number and handedness of the rotavirus inner capsid, and provided evidence for the open-mesh model, in which the five- and six-coordinated axes are represented by ‘holes’ formed by smaller trimeric morphological subunits.

The lethal encephalitis caused in mice by Semliki Forest virus (SFV) is modulated to a subclinical infection by administration of defective interfering SFV, although virus still multiplies both in the central nervous system (CNS) and systemically. Here we report that such infections result in unique and selective changes in the normal levels of CNS neurotransmitters some of which persist after infectious virus can no longer be detected. This represents a previously undocumented category of infection which may have a bearing on the aetiology of those human neurological and neuropsychiatric diseases to which viruses are believed to contribute.

One unique feature of the prototype JC virus (JCV) (Mad 1) genome is the occurrence of a second TATA sequence within the early promoter region. A naturally occurring oncogenic variant of JCV (Mad 4) lacks this second TATA box. Several cell lines transformed by Mad 1, Mad 4 and simian virus 40 were characterized, in part to investigate whether the second TATA sequence is functional. S1 nuclease mapping of early JCV gene transcription products revealed a major set of start sites common to both Mad 1 and Mad 4 mRNAs. In addition, a second set of early transcripts was found exclusively in Mad 1 transformants, presumably positioned by the second TATA box. The presence of these unique mRNAs in the Mad 1-transformed cells did not appear to have any bearing on the other parameters investigated, including size and quantity of early viral proteins, integration patterns of viral DNA and growth properties of the cells.

Hepatitis A virus (HAV) strain HM-175 was passaged six times in marmosets, 59 times in cell culture and purified from infected cell culture supernatant fluid. The viral RNA was extracted, copied into cDNA and the cDNA:RNA hybrids were cloned into the PstI site of plasmid pBR322. The cDNA clones were authenticated by hybridization to RNA extracted from HAV-infected cells and clones representing the 3′ end of the genome were identified using a previously authenticated cDNA clone. The clones represented all but 29 bases of the HAV genome. They were compared to HAV strain HM-175 cDNA cloned from viral RNA after three passages in marmosets on the basis of restriction endonuclease mapping and DNA sequencing. No differences were found in either the presence or absence of restriction endonuclease sites using 33 different restriction enzymes. Sequencing of cDNA representing bases 29 to 1002 of the HAV genome revealed eight base changes all of which were within the 5′ non-coding region.