Isolation of paramyxovirus glycoproteins. Association of both hemagglutinating and neuraminidase activities with the larger SV5 glycoprotein

Separation of Sendai virus glycoproteins by using glutaraldehyde-treated erythrocytes and preparation of monospecific antisera against the glycoproteins

Sendai virus hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins, F and HN, were separated from Triton X-100- or Nonidet P-40-solubilized envelopes as unadsorbed and eluted fractions, respectively, by using glutaralde-hyde-treated chicken erythrocytes. These separated glycoproteins were biologically active. Monospecific antisera (in terms of monoreactivity to virus glycoproteins in gel diffusion precipitation patterns) were prepared by using these fractions as immunogens. Anti-HN rabbit serum inhibited all of the viral activities tested (infectivity, neuraminidase, hemagglutinating, and viral hemolysis), whereas anti-F serum definitely inhibited viral hemolysis only, although the two antisera enhanced neutralization in the presence of complement. The advantages and disadvantages of this separation method were discussed.

Synthesis, stability, and cleavage of Newcastle disease virus glycoproteins in the absence of glycosylation

Polypeptides synthesized in Newcastle disease virus (NDV)-infected CHO cells in the absence of glycosylation were characterized. Incorporation of either [3H]mannose of [3H]glucosamine into NDV polypeptides was inhibited to greater than 99% by the antibiotic tunicamycin. Under these conditions, infected cells synthesized proteins which comigrated on polyacrylamide gels with the viral L protein, nucleocapsid protein, membrane protein, and a polypeptide with a molecular weight of 55,000 (P55). These cells did not synthesize polypeptides with the size of the hemagglutinin-neuraminidase (HN) protein or the fusion (F0) protein. They did, however, synthesize new polypeptides with molecular weights of 75,000 (P75), 67,000 (P67), and 52,000 (P52). Peptide analysis revealed that P75 was a host cell protein whose synthesis is enhanced by tunicamycin. P67 corresponded to the unglycosylated forms of the glycoproteins were found to be relatively stable in infected cells. P55, previously thought to correspond to the cleaved form of F0, was found to be a unique viral protein which is associated with intracellular nucleocapsid structures.

Conformation of the helical nucleocapsids of paramyxoviruses and vesicular stomatitis virus: reversible coiling and uncoiling induced by changes in salt concentration

The conformations of the helical nucleocapsids of the paramyxoviruses Sendai virus and simian virus 5, and of a rhabdovirus, vesicular stomatitis virus, have been found to vary extensively with changes in salt concentration. In 10 mM sodium phosphate buffer at pH 7.2, the nucleocapsids are loosely coiled or almost completely extended; with increasing concentrations of NaCl they become more tightly coiled and less flexible. Under isotonic conditions (150 mM) the Sendai virus nucleocapsid is moderately tightly coiled but still curved and apparently flexible, whereas at 400 mM or higher it is very tightly coiled, with the appearance of a rigid rod. These salt-dependent changes in conformation were also found with nucleocapsids composed of proteolytically cleaved protein subunits. Because of the effect of salt concentration, and the fact that it may change during the preparation of negatively stained samples of electron microscopy, it was necessary to fix that nucleocapsids before negative staining to preserve their original conformation. The striking changes in nucleocapsid conformation in response to the ionic milieu indicate the plasticity of its helical structure and suggest that changes in the microenvironment of the nucleocapsid could influence its conformation during viral RNA transcription and replication or during virus assembly by budding, processes in which changes in the coiling of the nucleocapsid or its flexibility could be important.

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.

Selective inactivation of hemagglutinin and neuraminidase on mumps virus

The thermal stability and the effect of guanidine on the hemagglutinin and neuraminidase of three strains of mumps virus were compared. The heat inactivation of hemagglutinin resulted in the concomitant loss of neuraminidase. The effect of guanidine at various molarities showed that the neuraminidase was more sensitive than the hemagglutinin and a selective inactivation was obtained after exposure to 1.5 M guanidine. However differences in sensitivity of both activities (hemagglutinin and neuraminidase) to heat and guanidine inactivations were observed among strains and correlated with differential susceptibility to non-specific inhibitors of the strains.

Novel tubular and crystalline structures in purified preparations of Newcastle disease virus. Brief report

Hitherto undescribed tubular and crystalline structures were detected by negative contrast electron microscopy in purified preparations of Newcastle disease virus. It is suggested that these are viral in origin and are composed of aggregates of viral glycoprotein.

Characterization of bovine parainfluenza virus type 3

Bovine parainfluenza virus type 3 (PIV-3) has a buoyant density of 1.197. The RNA of PIV-3, like that of Sendai virus, is a single continuous chain which lacks polyadenylic acid sequences and tends to self-anneal to a marked extent. It has a sedimentation coefficient of 42S and a molecular weight of 4.5 X 10(6), being slightly smaller than Sendai virus RNA (47S, 5.3 X 10(6)). PIV-3 has 5 main structural proteins, of which 2 are glycoproteins. The molecular weights of protein 1, protein 2, protein 3, glycoprotein 1, and glycoprotein 2 were estimated to be 79,000, 68,000, 35,000, 69,000, and 55,000, respectively. Protein 2 was suggested to be nucleocapsid protein.

Analysis of immunoprecipitated surface glycoproteins in measles virions and in membranes of infected cells

Measles viral envelope proteins were immune precipitated from membranes of infected cells and from purified virus and analyzed by polyacrylamide gel electrophoresis. Under reducing conditions, specific precipitates contained two major polypeptide bands, designated virus glycopeptides 1 and 2 (VGP-1 and VGP-2). Both polypeptides appeared to be glycosylated, as indicated by their incorporation of [(14)C]glucosamine in infected cells. VGP-2 appeared as a single band in specific precipitates of infected cells and as a double band in precipitates of purified virus. Trypsin treatment of infected cells showed that reduced VGP-2 may be composed of two unrelated polypeptides. One may be F(1), which is unglycosylated, and the other may correspond to the proteolytic cleavage product of VGP-1, which is glycosylated. The relation of VGP-1 and VGP-2 to smaller surface antigens (X and Y) obtained by tryptic treatment of infected cells remains to be elucidated. In cells taken at various times postinfection and analyzed for viral membrane proteins, VGP-1 was detected at all times, indicating that the input virus VGP-1 was inserted into the cell and could not be differentiated from newly synthesized VGP-1. VGP-2 was not detectable before 24 h postinfection. In precipitates of cells 4 h postinfection and of infected cells incubated at pH 5.8, an additional polypeptide band migrated immediately ahead of VGP-1. We conclude that VGP-2 (molecular weight, 42,000) possibly consists of two components, one of which is the tryptic cleavage product of VGP-1 and the other of which is the unglycosylated polypeptide, F(1).

Glycoproteins of measles virus under reducing and nonreducing conditions

Measles virus has two glycoproteins. The larger glycoprotein (HA) is composed of 76,000-dalton subunits that are bound by disulfide bonds. The smaller glycoprotein (F) appears to contain a glucosamine-rich portion that is linked to an unglycosylated protein by disulfide bonds.

Components of parainfluenza-3 virus, SLP-strain, reacting in assays of cell-mediated immunity in cattle

Parainfluenza-3 virus was isolated by affinity chromatography, including a purification step with immobilized lectin Vicia erwilia. The peplomers of disintegrated virus were similarily isolated using another carbohydrate-specific lectin Vicia crotalaria. The whole virion and the peplomers were both active as antigens in the leucocyte migration inhibition, lymphocyte stimulation and skin hypersensitivity tests. The remaining virus material, freed of detergents used for virus disintegration and containing nucleocapsids, did not act as antigen in these tests of cell-mediated immunity.

Asymmetry of the lipid-bilayer of Sindbis virus

The organization of the lipid bilayer of the enveloped Sindbis virus has been studied. In the model membrane which consists only of two virus specific glycoproteins and host derived lipids the latter were radioactively labelled with 14C-palmitic acid by prelabelling their BHK 21 host cell lipids. The purified virus particles were submitted to neuramidase, bromelain and combromelain-neuraminidase treatment. It could be demonstrated that N-acetyl neuraminic acid residue of the total hematoside present in the virion is hydrolyzed by neuraminidase leaving the particles fully intact. Proteolysis of the spikes leads to particle aggregation yet an unchanged hematoside content. This was fully transformed into ceramidelactoside by subsequent neuraminidase treatment. The analyses of the ceramide species present in hematoside of the control particles and ceramidelactoside derived thereof by neuraminidase hydrolysis are in very close agreement. From these experiments it is concluded that all hematoside molecules are organized in the outer half of the bilayer of the envelope.

Semlike Forest virus membrane proteins. Preparation and characterization of spike complexes soluble in detergent-free medium

After Triton X-100 delipidation and subsequent Triton X-100 removal in a sucrose gradient the membrane protein spikes of Semliki Forest virus remained soluble in aqueous buffers. It was shown they were present as octameric complexes with a molecular weight of 95-10(4) and that they contain less than 4% lipid and detergent by weight. In electron microscopy after negative staining they appeared as "rosette"-shaped particles. Part of the protein could also be found associated in ordered paracrystalline arrays.

Immunity after infections with Myxoviruses

Influenza, parainfluenza and respiratory syncytial viruses cause respiratory infections in man with consequent transient and sometimes imperfect against reinfection. Humoral immunity and probably cell-mediated immunity contribute to resistance. Whereas circulating antibodies are more important for influenza viruses, secretory antibody are relatively speaking more important for parainfluenza and respiratory syncytial virsues. Measles and mumps induced longlasting immunity which can be correlated with circulating neutralizing antibodies. Certain immune responses against measles and respiratory syncytial virus cause pathological reactions after infection with the same virus.

Relationship between hemagglutinin and sialidase from Clostridium perfringens CN3870: chromatographic characterization of the biologically active proteins

Biochemical characterization of hemagglutinin and sialidase activities from Clostridium perfringens strain CN3870 revealed that this strain produced three sialidase enzymes that were separable to gel filtration, ion exchange chromatography, and polyacrylamide gel electrophoresis. The molecular weights of sialidase I, II, and III activities were 310,000 +/- 10,000, 105,000 +/- 4,000 and 64,000 +/- 2,000, respectively, the first figure being an approximate value only.

Polypeptides of mumps virus

Mumps virus was propagated in the extra-embryonic fluids of embryonated chicken eggs and was labeled by cionjection of radioactively labeled amino acids. The virus was purified by density gradient centrifugation, and its polypeptides were analyzed by polyarylamide gel electrophoresis. The virus was found to be composed of six polypeptides, ranging in size from 40,000 to 64,000 daltons. Viral proteins 1 and 3 were the glycoproteins of the virons. When the virus particle was treated with noniontic detergents, a small fraction of these glycoproteins could be released into the supernatant. After treatment with nonionic detergents in high salt and alkaline conditions, more of the surface glycoproteins were removed. This treatment also released the smallest viral polypeptide from the virion. The glycoproteins were separated using an affinity chromatographic column of agarose-fetuin. The heavier glycoprotein, viral protein 1, was found to contain both the neuraminidase and hemagglutinating activity. The two glycoproteins were tested for their ability to react in complement-fixing tests with mumps antisera. Only the heavier glycoprotein reacted with antisera possessing both anti-S and anti-V activity. Neither glycoprotein reacted with antisera specific for the S antigen. Thus, it was concluded that this glycoprotein corresponds to the classical V antigen of mumps virus.