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A comparison of measles and canine distemper virus polypeptides.

The polypeptides induced by canine distemper virus (CDV) strains have been characterized by polyacrylamide slab gel electrophoresis of infected cell lysates labelled with 35S-methionine, 14C-amino acids, 3H-glucosamine and 3H-mannose, or 32P-orthophosphate. Seven virus-induced polypeptides have been asigned the following nomenclature and mol. wt.: a large polypeptide L (180,000); a large glycoprotein G (77,000); a nucleocapsid-associated protein P (73,000); the nucleocapsid protein N (60,000); the smaller glycoprotein F0 (59,000); a membrane protein M (35,000) and a small polypeptide S (15,000). During pulse-chase experiments with 3H-glucosamine and 14C-amino acids the intensity of the F0 band decreases and that of the F1 and F2 bands increases; the H polypeptide band becomes more diffuse and the S-protein disappears. The N- and P- but not the M-proteins have been found to be phosphorylated. The polypeptide pattern of the Onderstepoort strain of CDV has been compared with that of two other CDV and with 17 measles and subactue sclerosing panencephalitis (SSPE) strains. Differences in the mobilities of various polypeptides have been observed between CDV and measles and SSPE strains; however, the only consistent difference is the mol. wt. of the M-protein of CDV strains which is smaller by 2000 than that of MV and this may be a biochemical marker to distinguish CDV from measles and SSPE virus strains.

Animals↗

Immunological relationships between homologous structural polypeptides of measles and canine distemper virus.

The major structural polypeptides of measles and canine distemper virus (CDV) were isolated by SDS-polyacrylamide slab gel electrophoresis. Rabbit hyperimmune sera directed against the isolated HA, P, NP, F and M polypeptides were prepared. In addition, rabbit hyperimmune sera directed against purified native internal components of measles virus and against purified virions of measles and CDV, untreated or treated with trypsin, were prepared. These sera were used to study the immunological relationships between measles and CDV in immune precipitation tests with 35S-methionine-labelled extracellular virions and intracellular virus polypeptides and by use of component fixation and mixed haemadsorption tests. An immunological relationship between the M polypeptides was demonstrated with sera against both native partially denatured antigens. A reciprocal immunological cross-reactivity between the NP polypeptides was demonstrated by the use of sera directed against native antigens. However, antisera directed against the NP polypeptides isolated from gels did not show any cross-reaction, indicating that they lacked antibodies against the shared antigenic determinants. The immunological cross-reactivity between envelope components of the two viruses was analysed. A close reciprocal immunological relationship between the F polypeptides was demonstrated by immune precipitation of labelled polypeptides. Immunological cross-reactivity between the HA polypeptides of the two viruses could not be demonstrated by use of the same technique neither with sera directed against denatured antigen nor with sera against native antigen when extracellular denatured 35S-methionine-labelled purified virions were used in immune precipitation. A slight cross-reactivity could, however, be demonstrated with sera against native antigens in immune precipitation tests with 35S-methionine-labelled intracellular antigens. It is concluded that all the major structural polypeptides of measles and CDV show varying degrees of reciprocal immunological cross-reactions. The M polypeptides of the two viruses appear most closely related, whereas the HA polypeptides show the most pronounced differences.

Cross Reactions↗

Molecular cloning of the nucleoprotein gene of canine distemper virus.

Messenger RNAs labelled in vivo in Vero cells infected with canine distemper virus were analysed by electrophoresis on 1.5% agarose gels containing 2 M-formaldehyde. Seven virus-specific RNA bands could be distinguished which were not sensitive to actinomycin D treatment and were confined to the polyadenylated RNA fraction. The most abundant virus-specific mRNA species had a molecular weight of 0.52 X 10(6) and its coding capacity was consistent with it being the mRNA for the most abundant virus-specific protein, the nucleoprotein. Polyadenylated RNA of this size class was purified by electrophoresis on a polyacrylamide gel and cloned into the PstI site of plasmid pBR322. A virus-specific clone obtained, clone 224, was then used to select messenger RNA from infected cells. The messenger RNA selected had a molecular weight of 0.52 X 10(6) and directed the synthesis of only the virus-specific nucleoprotein when used to stimulate a wheat germ cell-free system.

Animals↗

Requirement of methionine for the replication of canine distemper virus in Vero cells.

The replication of canine distemper virus (CDV) in Vero cells was found to require certain amino acids such as arginine, methionine and valine. The deprivation of methionine caused the most marked reduction in virus yield. In cells cultured in medium deprived of methionine, the early processes of viral replication such as adsorption, penetration and uncoating of virus occurred at normal rates, but the syntheses of viral RNA and protein were markedly reduced. The addition of S-adenosylmethionine to methionine-free medium resulted in the growth of CDV to the level obtained in cells with complete medium. Moreover, cycloleucine, which is known to reduce the methylation of mRNA by inhibiting the synthesis of S-adenosylmethionine, also inhibited the growth of CDV, and the addition of methionine or S-adenosylmethionine reversed the inhibitory effect of cycloleucine. The possibility of an inhibition of methylation of mRNA in methionine-deprived cells is discussed.

Animals↗

cDNA cloning of the messenger RNAs of five genes of canine distemper virus.

Messenger RNAs from Vero cells infected with the Onderstepoort strain of canine distemper virus (CDV) were cloned into the PstI site of plasmid pAT153. Total polyadenylated RNA was used and resulting clones were screened with 32P-labelled cDNA probes from infected and mock-infected cells. The virus specificity of the clones was proven by Northern blot hybridization and by ability to select radioactive virus mRNAs labelled in vivo in the presence of actinomycin D. Clones from the N, P and M genes of CDV were identified by hybrid select translation; clones which presumably represent the H and F genes were also obtained. The clones allowed a designation of the major viral mRNA bands. Bicistronic mRNAs were identified, and their selection by various clones suggests a gene order of 3'-N-P-M-70K-65K-L-5' for this virus.

Cloning, Molecular↗

Preparation and characterization of monoclonal antibodies directed against four structural components of canine distemper virus.

Mouse hybridomas producing antibodies against structural proteins of canine distemper virus (CDV) were produced by fusion of Sp2/0 myeloma cells with spleen cells from BALB/c mice immunized with purified preparations of Vero cell-grown CDV. Ascites fluids collected after intraperitoneal inoculation with 149 CDV antibody-producing hybridoma cell lines were characterized by different serological tests. By immune precipitation tests with [35S]methionine-labelled extracellular virions and intracellular virus polypeptides, 57 clones were found to produce antibodies against the nucleocapsid protein (NP), 22 against the polymerase (P) protein, 10 against the fusion (F) protein and nine against the large uncleaved glycoprotein (named H in analogy with measles virus). By competitive binding enzyme-linked immunosorbent assay (ELISA) tests with monoclonal antibodies against each structural component, a minimum of 18, six, three and seven separate antigenic determinants were identified on the NP, P, F and H proteins, respectively. The reactions of clones directed against F and H surface components of the virus were tested for their ability to inhibit the infectivity of both CDV and measles virus in the absence and presence of anti-gamma-globulin. In addition, the inhibitory activity of the clones on measles haemagglutinating (HA) and haemolysis (HL) activity were examined. Monoclonal antibodies against six of the seven antigenic determinants of the H protein could neutralize the infectivity of the virus. After addition of anti-gamma-globulin to the test, increases of titres varying from twofold to several hundredfold were observed with the different clones. None of all the clones against H could block measles virus infectivity, HA or HL activity. The 10 clones directed against the F protein could not neutralize the infectivity of CDV even in the presence of anti-gamma-globulin. Further, the antibodies could not inhibit measles HA and HL activity in the absence of anti-gamma-globulin. However, after the addition of anti-gamma-globulin, antibodies against two of the three sites were found to block measles virus HL activity. The reactions of all clones were tested in immune fluorescence, ELISA and immune precipitation tests with three strains of CDV. Each strain had a few unique antigenic sites. Variation was found in four, one and three different antigenic sites of the NP, P and H proteins, respectively.

Antibodies, Monoclonal↗

The antigenic relationship between measles, canine distemper and rinderpest viruses studied with monoclonal antibodies.

Monoclonal antibodies (MAbs) were used to delineate the antigenic relationship between the three morbillivirus types: measles virus (MV), canine distemper virus (CDV) and rinderpest virus (RPV). Panels of six to 31 MAbs against the haemagglutinin (H), fusion (F), nucleocapsid protein (NP), phosphoprotein (P) and matrix (M) proteins of MV and the H, F, NP and P proteins of CDV were employed. Nine strains of MV, three strains of CDV and four strains of RPV were examined by radioimmunoprecipitation assay and immune fluorescence for reactivity with the heterologous MAbs. Overall, the NP and in particular the F proteins of the morbilliviruses showed a high degree of epitopic homology; the P and M proteins showed a partial epitopic homology, with the greatest variation between the M proteins of CDV and MV; the H proteins showed a low degree of epitopic homology and then only between MV and RPV. These data indicate that the major cross-protecting antigen in heterotypic vaccination amongst morbilliviruses is the F antigen. The epitopic relationships found between morbilliviruses as identified by the MAbs were classified as follows. (i) Group-specific epitopes were present on all strains of the three morbillivirus types. (ii) Group-cross-reactive epitopes were present on only some of the strains from each morbillivirus type (these epitopes identified the presence of intratypic strain variation in all proteins of all three virus types). (iii) Type-specific epitopes, i.e. MV unique or CDV unique, were found only on the homologous morbillivirus type. (iv) CDV-RPV intertypic and MV-RPV intertypic epitopes were, respectively, epitopes shared by CDV and RPV but not with any MV strain, and epitopes shared by MV and RPV but not with any CDV strain. These cross-reactivities and type-specific reactions were obtained with the internal viral proteins (M, P and NP). The epitopes of the F proteins were mainly group-specific and no CDV-RPV or MV-RPV intertypic epitopes were found. The epitopes of the H protein were either type-specific or MV-RPV intertypic. These data support the proposed evolutionary relationship between the morbilliviruses.

Antibodies, Monoclonal↗

Examination of eight cases of multiple sclerosis and 56 neurological and non-neurological controls for genomic sequences of measles virus, canine distemper virus, simian virus 5 and rubella virus.

In situ hybridization studies have been carried out on brain samples from eight cases of multiple sclerosis (MS) and 56 non-neurological and neurological controls, using single-stranded 35S-labelled RNA probes prepared against genomic RNA sequences of measles virus, canine distemper virus, rubella virus and simian virus 5. Foci of hybridization were found using probes against the measles virus nucleocapsid protein (N), phosphoprotein and fusion protein gene sequences in two of the MS cases, and also in one control, a case of disseminated cytomegalovirus infection with spinal cord necrosis. This result was confirmed using biotinylated probes prepared against the measles virus N genomic sequence. No hybridization was found in any of the MS or control cases using any of the other viral genome-specific probes.

Astrocytoma↗

Isolation and characterization of canine distemper virus nucleocapsid variants.

Nucleocapsid (NC) variants expressed by the Onderstepoort strain of canine distemper virus (CDV) were ultrastructurally and biochemically characterized. Three isolated variants were defined which corresponded to the three variants observed within the cytoplasm of infected cells. Dense NC (D-NC), isolated on discontinuous caesium chloride (CsCl) isopycnic gradients, had an average density of 1.2971 +/- 0.0042 g/ml. Ultrastructurally, D-NC were 1620.0 +/- 112.1 nm in length with a 20.1 +/- 1.3 nm outer and a 5.8 +/- 0.7 nm inner core diameter. The D-NC protein composition was 89.7% of a 61K protein (N), 8.4% of a 75K protein (P) and 1.9% of a 160K to 200K protein (L). A single species of nucleic acid, 15 kb in length, was isolated from D-NC. Light NC (L-NC), similarly isolated, had an average density of 1.2894 +/- 0.0040 g/ml. L-NC differed ultrastructurally from D-NC in that poor resolution of NC subunits, a larger outer diameter (32.0 +/- 2.8 nm), and a greater inner core diameter (10.4 +/- 0.6 nm) were observed. The average L-NC strand length was 1574.4 +/- 115.8 nm. The protein composition was the same as D-NC with the exception of an additional 70K protein, representing 4.0 to 7.7% of the total L-NC protein mass. A 15 kb nucleic acid was also identified in L-NC, although heightened sensitivity of encapsidated L-NC nucleic acid to non-specific nuclease degradation was observed. The ratio of D-NC to L-NC isolated from individual virus preparations varied and was independent of viral infectivity. A third NC variant, defective-NC (Df-NC), was also identified. This had the lowest density on CsCl gradients (1.2460 +/- 0.0046 g/ml). The Df-NC structures were truncated to a uniform length of 87.0 +/- 5.8 nm. Diameter measurements were between those of D-NC and L-NC, being 24.4 +/- 1.4 nm (outer) and 6.9 +/- 0.4 nm (inner core). Like L-NC, the 70K protein was present but in greater amounts, representing as much as 43.7% of the total Df-NC protein mass. RNase A-sensitive nucleic acid was isolated from Df-NC which ranged in size from 1.16 to 0.67 kb with a majority of the material being 0.86 kb in length. For both L-NC and Df-NC, canine CDV convalescent serum reacted with viral N and P proteins in Western blot analyses but not with the 70K protein, suggesting a host cellular origin for the latter.

Animals↗

Interaction of canine distemper virus nucleocapsid variants with 70K heat-shock proteins.

Cytoplasmic nucleocapsid (NC) isolated from Vero (V) cells infected in the logarithmic phase of growth with Onderstepoort canine distemper virus consists of light-NC (L-NC) and dense-NC (D-NC), encapsidating full-length genomic RNA, and defective-NC (Df-NC), encapsidating variably truncated RNAs. The 70K host cell protein constituent of L-NC and Df-NC was shown to be a member of the 70K heat-shock protein (70K hsp) family. Specifically, 72K hsp is associated with L-NC, and 72K and 73K hsp are associated with Df-NC. Variable L-NC production by three different Vero cell sublines was compared to cellular 70K hsp levels. V141 supported the highest level of L-NC production and expressed high basal levels of 70K hsp in uninfected cells. These high basal levels correspond to a large distribution of log phase V141s in the S phase of the cell cycle. V138-L and V138-H cells produced lower amounts of L-NC and exhibited similar low basal levels of 70K hsp expression, corresponding to low percentages of log phase cells in the S phase cell cycle compartment. Heat shock was effective in inducing L-NC expression in V138-H, which otherwise produced D-NC. Similar cell subline differences in L-NC production were obtained for eight different virus pools derived from the same plaque-purified parental stock. Enhanced biological activity was associated with L-NC based on correlation between L-NC production, viral titre, and plaque areas measured over infected cells.

Animals↗

The nucleotide sequence of the gene encoding the attachment protein H of canine distemper virus.

The sequence of the H gene and flanking sequences in the F and L genes of canine distemper virus (CDV) have been determined. The H gene of CDV (1946 nucleotides) contains one large open reading frame starting at position 21 and terminating at position 1835, encoding a protein of 604 amino acid residues. This protein contains three potential glycosylation sites in the extracellular domain and, like all other paramyxoviruses, a N-terminal membrane-spanning hydrophobic anchor domain. The deduced H protein sequence shows an identity of 36% with rinderpest virus (RPV) and measles virus (MV). The identities at the nucleotide level are higher (RPV 52% and MV 53%). The amino acid sequence shows conservation of all the structural determinants with the H proteins of MV and RPV. The data also show that CDV is evolutionarily equidistant to RPV and MV with respect to the H gene.

Amino Acid Sequence↗

Measles virus antigens induce both type-specific and canine distemper virus cross-reactive cytotoxic T lymphocytes in mice: localization of a common Ld-restricted nucleoprotein epitope.

We have studied the induction of the cytotoxic T lymphocyte (CTL) response to measles virus (MV) antigens expressed as vaccinia virus (VV) recombinants in a murine model. In C3H mice (H-2k) only the nucleoprotein (NP) induced a CTL response and this was shown to be cross-reactive with the closely related canine distemper virus (CDV). The presentation of this antigen was shown to be Kk-restricted. In BALB/c mice (H-2d), both the haemagglutinin (HA) and the NP induced a strong CTL response, the former being serotype-specific, whereas the latter cross-reacted with CDV. Both responses were found to be Ld-restricted. Based on the prediction for Ld T cell motifs, we tested a number of MV NP-derived nonapeptides for their capacity to sensitize P815 cells (H-2d) for lysis by spleen cells from VV-NP-immunized mice. One of these peptides, comprising amino acids 281 to 289 (Tyr-Pro-Ala-Leu-Gly-Leu-His-Glu-Phe) was as effective as cells expressing the complete NP protein. This motif is conserved in the CDV NP.

Amino Acid Sequence↗

The highly inducible member of the 70 kDa family of heat shock proteins increases canine distemper virus polymerase activity.

The cellular stress response is characterized by the production of heat shock proteins (HSP) which serve important cytoprotective functions. Paradoxically, in vitro induction of the stress response promotes cytopathic effect mediated by infection with canine distemper virus (CDV). The stress-mediated increase in cytopathic effect is correlated to the formation of complexes between the viral nucleocapsid (NC) and the major inducible member of the approximately 70 kDa family of HSP (hsp72). The objective of the present study was to document the functional significance of CDV NC-HSP interaction. Cytoplasmic NC was purified from Vero cells lytically infected with the Onderstepoort strain of CDV. Both ultrastructural variants of CDV NC interacted with both hsp72 and the constitutively expressed member of the approximately 70 kDa family of HSP (hsp73) in a reversible and ATP-dependent manner. An effect of hsp72/73 on NC polymerase activity was demonstrated using cell-free assays derived from either Vero or HeLa cell lines. Antibody specific to hsp72 suppressed both basal and stress-enhanced polymerase activity whereas hsp73-specific antibody had no affect. Supplementation of purified hsp72/73, but not hsp73 alone, enhanced basal polymerase activity in a dosage-dependent manner. Using purified NC variants, polymerase activity was demonstrated in pre-formed hsp72/73-NC complexes but not in NC devoid of HSP. These results suggest that the stimulatory effect of the stress response upon CDV gene expression may, in part, be mediated by a reversible and direct interaction between hsp72 and the viral core particle.

Adenosine Triphosphate↗

Genetic diversity of the attachment (H) protein gene of current field isolates of canine distemper virus.

To characterize the variability of recent field isolates of canine distemper virus (CDV) from different hosts and geographical areas, we conducted nucleotide sequence analysis of the gene encoding the haemagglutinin (H), the attachment protein of this virus. Pronounced differences between field isolates were revealed in comparison to the Convac and Onderstepoort vaccine strains. The diversity of CDV appeared to exceed that determined for measles virus. Phylogenetic analysis also separated the field isolates of CDV from the vaccine strains and provided evidence for the existence of different contemporary genotypes of CDV. Isolates from a Greenlandic sledge dog and a Siberian seal formed a distinct lineage. The remaining isolates formed a group. This group contained two European isolates from mink and ferret, a single lineage comprising three European dog isolates, and another separate lineage of North American isolates from dog, javelina, raccoon and captive leopards.

Amino Acid Sequence↗

Measles virus and canine distemper virus target proteins into a TAP-independent MHC class I-restricted antigen-processing pathway.

After infection of CEM174.T2 cells [deficient for the transporter of antigen presentation (TAP)] with measles virus (MV) the nucleocapsid protein is recognized by L(d)-restricted cytotoxic T cells in a TAP-independent, chloroquine-sensitive fashion. Presentation via the TAP-independent pathway requires virus replication. During MV infection of the cell the nucleocapsid as well as the matrix protein enter the endolysosomal compartment as indicated by colocalization with the lysosomal-associated membrane protein 1 (LAMP-1). Similarly, the nucleocapsid protein of canine distemper virus (CDV) is recognized in a TAP-independent fashion. In addition, a recombinant MV expressing bacterial beta-galactosidase protein is able to introduce the recombinant antigen into the TAP-independent pathway whereas a vaccinia virus expressing beta-galactosidase is not. These data and a report about TAP-independent recognition of parainfluenza virus type 1 suggest that members of the Paramyxoviridae family regularly introduce viral proteins into the TAP-independent antigen-processing pathway.

Animals↗

CD9-dependent regulation of Canine distemper virus-induced cell-cell fusion segregates with the extracellular domain of the haemagglutinin.

Antibodies to CD9, a member of the tetraspan transmembrane-protein family, selectively inhibit Canine distemper virus (CDV)-induced cell-cell fusion. Neither CDV-induced virus-cell fusion nor cell-cell fusion induced by the closely related morbillivirus Measles virus (MV) is affected by anti-CD9 antibodies. As CDV does not bind CD9, an unknown, indirect mechanism is responsible for the observed inhibition of cell-cell fusion. It was investigated whether this effect was restricted to only one viral glycoprotein, either the haemagglutinin (H) or the fusion (F) protein, which form a fusion complex on the surface of virions and infected cells, or whether it is dependent on both in transient co-transfection assays. The susceptibility to CD9 antibodies segregates with the H protein of CDV. By exchanging portions of the H proteins of CDV and MV, it was determined that the complete extracellular domain, including the predicted stem structure (stem 1, barrel strand 1 and stem 2) and globular head domain, of the CDV-H protein mediates the effect. This suggests that interaction of the CDV-H protein with an unknown cellular receptor(s) is regulated by CD9, rather than F protein-mediated membrane fusion.

Amino Acid Sequence↗

Characterization of canine distemper viruses adapted to neural cells and their neurovirulence in mice.

Interaction of the Onderstepoort strain of canine distemper virus (CDV) with three established human neural cells, i.e. IMR-32 neuroblastoma, 118-MGC glioma and KG-1 oligodendroglioma, was examined, and adaptation of CDV to these cells was also attempted. The unadapted virus was found to grow at relatively low titers in the three neural cells inducing moderate to minimal cytopathic effects (CPE). The virus was successfully grown at high titers in these cells after 8 to 10 passages. Biological characteristics such as growth rate, morphology of CPE and plaque size changed after adaptation. Analysis by SDS-polyacrylamide gel electrophoresis, however, failed to show any difference in the molecular weight of component proteins among the unadapted and three adapted viruses. Inbred DDD strain of mice developed clinical signs after intracerebral inoculation with the unadapted virus but most of them survived with histological lesions of encephalitis. Neuroblastoma-adapted virus induced only transient clinical signs in some animals with mild encephalitic lesions in the gray matter. Increases in neurovirulence were found for viruses adapted to glioma and oligodendroglioma cells. Almost all mice inoculated with these two viruses at 3 weeks of age died within 8 days with histological lesions consisting of hyperemia, edema, severe degeneration of nerve cells and a few giant cells. Demyelinating lesions in the absence of inflammatory changes were observed in the cerebellum, pons and medulla oblongata of animals inoculated with oligodendroglioma-adapted virus.

Animals↗

Isolation and characterization of canine distemper virus-specific RNA.

Ten species of virus-specific RNA were detected in Vero cells infected with the FXNO strain of canine distemper virus (CDV). The largest RNA was the genome-sized RNA and the nine smaller species were polyadenylated RNAs. Similar results were obtained for nine other strains of CDV. The molecular weights of these ten RNAs were determined to be 4.61 X 10(6), 2.46 X 10(6), 1.52 X 10(6), 1.32 X 10(6), 1.19 X 10(6), 1.07 X 10(6), 0.77 X 10(6), 0.65 X 10(6), 0.58 X 10(6), and 0.48 X 10(6). By in vitro translation of the polyadenylated RNAs in a rabbit reticulocyte lysate system, three different proteins which probably correspond to H, NP, and M were synthesized from the fraction containing RNAs 7, 8, 9, and 10.

Animals↗