Measles virus polypeptides synthesis in infected cells

Five measles virus antigens demonstrated by use of mouse hybridoma antibodies in productively infected tissue culture cells

Mouse hybridoma antibodies against 5 different structural components of measles virus were used in immune fluorescence tests to characterize the appearance of viral antigens in productively infected cell cultures. The antibodies employed in the tests reacted specifically with the hemagglutinin (H, 79K), polymerase (P, 72K), nucleocapsid (NP, 60K) hemolysin-fusion factor (F, 41+20K) and matrix (M, 36K) proteins. Syncytia formed in lytically infected cultures and single isolated cells in persistenly infected cell cultures were both examined. Antibodies against NP and P proteins stained cytoplasmic inclusions varying in size from small dots to more confluent masses, frequently in a perinuclear position. Nuclei of infected cells contained exclusively NP antigen. Antibodies to envelope components--H, F and M--stained cytoplasmic membrane structures and also gave a granular cytoplasmic staining, especially in syncytia. Although all persistently infected cells produced NP antigen and the associated P component, they had a restricted capacity to produce demonstrable amount of envelope antigens. The occurrence of cells containing envelope antigens varied between about 50 and 5 per cent with H and F antigens giving the highest and lowest frequence values, respectively. It is proposed that a restricted capacity of cells to produce biologically active fusion protein is a prerequisite for maintaining a persistent infection in actively dividing cells in vitro.

Analysis of structural proteins of measles, canine distemper, and rinderpest viruses

Serological relationships among measles virus (MV), canine distemper virus (CDV), and rinderpest virus (RV), which constitute morbillivirus subgroup of paramyxoviridae, were investigated by immunoprecipitation and SDS-polyacrylamide gel electrophoresis for their major structural proteins, i.e., hemagglutinin (H), nucleocapsid (NC), fusion (F), and matrix (M) proteins. The molecular weights of the four structural proteins of MV and CDV were confirmed to correspond to those previously reported by several investigators. Structural proteins of RV were analyzed for the first time in the present study and found to have molecular weights of 74,000, 62,000, 44,000, and 40,000 for H, HC, F, and M proteins, respectively. By labeling with glucosamine, the presence of carbohydrate moiety was found in H protein for all the three viruses and in F protein of CDV. The serums from the convalescent animals infected with respective virus disclosed one-way cross pattern depending on the combinations of virus and antiserums, but failed to show the reciprocal cross reactivity. On the other hand, hyperimmune serums to respective virus showed the reciprocal cross-reactivity with the four structural proteins indicating that each of the major structural proteins possesses the antigen common to all three morbilliviruses.

The measles virus-specific protein synthesis of persistently and lytically infected cells studied in vivo and in vitro

The virus-specific protein synthesis of the hamster brain cells persistently infected with a wild-type measles virus (M-MB/MVB) was investigated in vivo and in vitro and compared to the protein synthesis of the Vero-cells lytically infected with the wild-type measles virus and the SSPE-measles virus strain LEC. The virus-specific protein synthesis in the M-HB/MVB-cells in vivo was weak. Only two virus-specific polypeptides, corresponding to polypeptide G and nucleocapsid polypeptide NP, were detected. On the other hand, the in vitro translation products, coded by the RNA extracted from the actinomycin D-treated M-HB/MVB-cells, were similar compared to those products coded by the RNAs from the lytically infected Vero-cells. The polypeptides with MWs of 75 000, 61 000, 40 000, 37 000 and 18 000 were coded with all three RNA-extracts. So the similar mRNAs were induced in the actinomycin D-treated M-HB/MVB-cells, but their translation in vivo was limited. In addition to those polypeptides mentioned above the polypeptide with a MW of 42 000 was detected among the in vitro translation products of the M-HB/MVB-cells.

SSPE, measles virus, and the matrix protein: report of a case with unusual immunochemical findings

We report a case of atypical subacute sclerosing panencephalitis (SSPE) in which the diagnosis was confirmed by a new radioimmunoprecipitation method. Antimeasles antibody was absent in the cerebrospinal fluid (CSF) when measured by conventional immunoassay techniques, there was no clinical response to isoprinosine, and the patient showed a selective absence of CSF antibody response to the matrix protein and only a partial serum antibody response to this measles polypeptide. The value of this sensitive immunoprecipitation method in profiling the selective antibody responses to the several measles polypeptides and the advisability of using isoprinosine, an immunopotentiating agent, to treat SSPE are discussed.

Purification of measles virus H polypeptide and of F polypeptide

Measles virus was disrupted by Tween 80 and ether and subjected to isoelectric focusing in granular gel. The two surface envelope polypeptides, the one showing haemagglutinating activity (H) and the one making up the structural basis of the haemolytic and fusion activity (F) banded together at pH 5.2. The two envelope polypeptides were also isolated together after adsorption to a Lentil-lectin column. Separation of the two polypeptides was performed by gel filtration on Sephadex G-150 in the presence of 8 M urea. After separation both the H and F polypeptides fixed to the lectin column. It was demonstrated that the column, after having fixed the two polypeptides, absorbed anti-H and anti-F antibodies from a rabbit anti-measles virus immune serum. Thus the antigenic reactivity of the isolated surface polypeptides remained intact.

Noncytopathic mutants of Newcastle disease virus are defective in virus-specific RNA synthesis

We have studied virus-specific RNA synthesis in cells infected by six noncytopathic (nc) mutants of the Australia-Victoria wild-type strain (AV-WT) of Newcastle disease virus (NDV) (19). The rates of NDV-specific RNA synthesis in mutant infection were three to sevenfold lower than those observed in wild-type infection. Velocity sedimentation of this NDV-specific RNA revealed that the lower rates of synthesis in mutant infection correlated with reduced accumulation of 18S and 35S mRNA. Electrophoresis in polyacrylamide-urea gels showed that accumulation of all of the 18S mRNA species was reduced and no new species could be detected. Primary transcription appeared unaltered in mutant infection. Cells infected with two naturally occurring avirulent strains of NDV also showed less accumulation of 18S mRNA. Electrophoresis of this RNA resulted in patterns which differed from those obtained with RNA from either AV-WT or nc mutant infection. Complementation for RNA accumulation between the nc mutants and RNA- temperature-sensitive mutants of AV-WT (32) suggested a common defect in the nc mutants. Analysis of plaque-forming revertants of five of the nc mutants revealed that viral RNA synthetic capacity, cell killing, and plaque-forming ability correlated absolutely. These results suggest that viral RNA synthesis and cytopathogenicity may be causally related. In addition, several of the plaque-forming (and cell-killing) revertants were found to be unable to induce fusion from within in infected cell cultures. This result, coupled with the finding that several of the nc mutants are capable of wild-type levels of fusion from within, suggests that the ability to cause such fusion does not correlate with the ability to kill cells.

Structural polypeptides of canine distemper virus

The structural polypeptides of two strains of canine distemper virus and the Lec strain of measles virus were analysed by SDS-polyacrylamide-slab-gel electrophoresis. One strain of canine distemper virus derived from a live vaccine (Convac, Dumex), contained six major structural polypeptides with mol.wt. of 85, 78, 59, 43, 41 and 34 x 10(3). The 85K polypeptide was glycosylated. It was interpreted to be equivalent ot the 79K glycoprotein of the measles hemagglutinin. The second strain, a rapidly growing variant of the Onderstepoort strain of canine distemper virus characterized by extensive syncytium forming cytopathic effects in tissue culture, contained the 5, 43, 41 and 34K polypeptides, but the 85 and 78K polypeptides were not present in detectable amounts. The 43K polypeptide was identified as cellular actin by limited proteolysis. By use of monospecific rabbit hyperimmune sera against each of the major structural polypeptides of measles virus, the 59, 41 and 34K structural polypeptides could be identified as nucleocapsid protein (NP), fusion (F) polypeptide, and the membrane (M) polypeptide, respectively. In neutralization tests with rabbit hyperimmune sera against each of the two strains, this Onderstepoort strain, which contained reduced amounts of the hemagglutinin glycoprotein, gave higher neutralization titers than the vaccine strain.

Absence of M protein in a cell-associated subacute sclerosing panencephalitis virus

Measles virus has been suggested to cause subacute sclerosing panencephalitis (SSPE), a slow central nervous system disease of children. However, several questions remain about the pathogenesis of SSPE. For example, it is not known whether alteration of the measles virus genome has a role in the initiation and persistence of the disease. Several studies have compared the RNA and protein composition of wild-type (wt) and SSPE strains of measles virus in a search for markers characteristic of the latter. All the studies used SSPE strains that had reverted to the budding, virion-producing form, similar to wt. We have shown, however, that only cell-associated non-budding strains of SSPE virus cause an SSPE-like persistent infection in young ferrets. Strong cell association and cell-fusing activity were essential for the virulence of measles virus in the brains of experimental animals and possibly humans. We have, therefore, compared the protein composition of virulent SSPE strains to that of the budding, non-virulent SSPE and wt strains. We report here that the M protein was not detectable in non-budding SSPE strains D.R., Biken and IP-3, and strain D.R. contained very little H protein.

Importance of antibodies to the fusion glycoprotein of paramyxoviruses in the prevention of spread of infection

The effects of monospecific antibodies to the viral glycoprotein with hemagglutinating and neuraminidase activity (HN) and the viral glycoprotein with membrane-fusing activity (F) of the paramyxovirus simian virus 5 (SV5) on the spread of infection in two cell types have been investigated. In CV-1 cells, infection can spread by either released progeny virus adsorbing to and infecting other cells, or by fusion of an infected cell with an adjacent cell as a result of the cell-fusing activity of the F glycoprotein. In these cells, antibodies specific for the HN glycoprotein prevented the dissemination of infection by released infectious virus, but spread by cell fusion was not inhibited. Antibodies to the F glycoprotein completely prevented the spread of infection in these cells. In Madin-Darby bovine kidney cells, which are relatively resistant to SV5-induced fusion, antibodies to either the HN or F glycoproteins were capable of preventing the dissemination of infection. These results indicate that effective immunological prevention of the spread of paramyxovirus infection requires the presence of antibodies that inactivate the F glycoprotein. This requirement for anti-F antibodies has obvious implications for the design of effective paramyxovirus vaccines and provides an explanation for previous failures of formalin-inactivated paramyxovirus vaccines as well as additional insight into the possible immunopathological mechanisms involved in the atypical and severe infections that have occurred in individuals who received inactivated paramyxovirus vaccines and were subsequently infected by the virus.

Immunolabeling of SSPE and wild-type measles viruses in ferret brain cell culture

Immunocytochemical studies using horseradish peroxidase labeled antibody were undertaken in an attempt to determine whether there are detectable antigenic differences which correlate with the biological properties of differences which correlate with the biological properties of different strains of SSPE and wild-type measles virus grown in ferret bran cell cultures. The rabbit anti-measles hyperimmune serum used in this experiment contained antibodies to all the measles virus proteins when tested by immunoprecipitation. When cells infected with the wild-type measles or productive SSPE virus strains were treated with this serum, heavy deposits of reaction product were seen on the cell membrane and virion envelope. When SSPE serum which contained relativly little antibody to the M protein was applied, a clear unlabeled area was evident just beneath the surface label. Cells infected with the non-productive SSPE strains were labeled by both sera in a spotty or discontinuous pattern on the outer surface of the cell membrane. The differences in membrane labeling seem to reflect differences in the expression of viral membrane proteins by the various SSPE and measles virus strains.

Measles virus-specified polypeptides in infected cells

The synthesis of wild-type measles virus-specified polypeptides in Vero cells in pulse-chase experiments, in cells with synchronized protein synthesis by high salt concentration, and in the presence of proteolytic enzyme inhibitors was analyzed by polyacrylamide slab-gel electrophoresis. Six major (L, G, 2, NP, 5 and M) structural polypeptides were identified in infected cells. The results of pulse-chase experiments suggested that most of the structural polypeptides were synthesized at their final length. Polypeptide M was found to be sensitive to trypsin. In TLCK-treated cells its molecular weight was about 1000--2000 daltons higher than in untreated cells. A minor virus-specific polypeptide with a molecular weight of about 23,000 was found as a very faint and diffuse band. In addition, three nonstructural polypeptides with molecular weights of 65,000, 38,000 and 18,000 were also detected. The experiments with proteolytic enzyme inhibitors and with synchronized protein synthesis suggested that the polypeptide with a molecular weight of 65,000 might be a precursor of the structural polypeptide 5.

Isolation and characterisation of a defective measles virus from a subacute sclerosing panencephalitis patient

A cytopathic measles virus was isolated from a brain biopsy of a subacute sclerosing panencephalitis (SSPE) patient. The agent could be transferred to Vero cells by cocultivation, but the infectivity always remained cell-associated -ie, a defective virus infection. The cell-associated nature of the virus was retained through 25 passages in Vero cells. Intracerebral inoculation of hamsters (2-6 days old) with the cocultured Vero cells gave rise to 100% mortality in 5-7 days. The virus retained its cell-associated nature after passage in hamsters. Electron microscopy of the brain and Vero cocultures showed the presence of virus-like ribonucleoparticles mainly in the nucleus. The presence of viral antigens in the nucleus, cytoplasm, and on the plasma membranes was confirmed by immunofluorescence. Using a combination of immunological and biochemical techniques, it was shown that all the viral proteins were synthesized with the exception of the haemagglutinin. Inclusion of the fusion inhibitor SV4814 (CBZ-D phenylalanine-L-phenylalanine-L-arginine-NO2) in the culture medium led to the elimination of the SSPE infection.