Inhibition of host cellular ribonucleic acid synthesis by glycoprotein of mumps virus

Induction of interferon by virus glycoprotein(s) in lymphoid cells through interaction with the cellular receptors via lectin-like action: an alternative interferon induction mechanism

When animals and cells are infected with a virus, interferon is produced. Viral-nucleic acid is considered to be one of actual components for interferon induction. In addition, viral glycoproteins trigger interferon induction in lymphoid cells by membrane-membrane interaction via a lectin-like activity. A biological significance of lectin-like activity of viral glycoproteins is discussed.

Detection and characterization of mumps virus V protein

By cDNA cloning, DNA sequencing, and RNAse mapping analyses two distinct mRNA species were shown to be transcribed from the mumps virus P gene; one faithful and the other edited copies. The former was found to direct the synthesis of the V protein (25K), while the latter, after the addition of two nontemplated G residues, was found to direct the synthesis of the P protein (40K-42K). The carboxy terminal of the V protein contained a cysteine-rich region which was similar but not identical to the metal binding domain motif found in several nucleic acid binding proteins. The V protein was detected not only in mumps virus-infected cells but also in the virions by antiserum raised against a synthetic peptide.

Extensive antigenic diversity among human parainfluenza type 2 virus isolates and immunological relationships among paramyxoviruses revealed by monoclonal antibodies

A panel of 128 monoclonal antibodies (MAbs) directed against hemagglutinin-neuraminidase (HN), fusion (F), matrix (M), and polymerase (P) proteins, and nucleoprotein (NP) of the Toshiba strain of human parainfluenza type 2 virus (PIV2) was prepared to examine the antigenic relationships among clinical isolates of PIV2 and among paramyxoviruses by indirect enzyme-linked immunosorbent assays. The HN proteins of 18 clinical isolates of PIV2 showed extensive antigenic diversity: 23 of 33 anti-HN MAbs showed no or limited reactivity to many isolates, while other structural proteins were antigenically well conserved. Some anti-HN MAbs recognizing conserved epitopes of the isolates exhibited two types of neutralizing activity, that is, these antibodies inhibited viral infectivity through attachment inhibition or fusion inhibition. This result also showed the presence of a potential third function of the HN protein which might affect the fusing activity of the F protein besides the hemagglutinating and neuraminidase activities. Many of the anti-NP and anti-P MAbs reacted with simian virus 41 (SV41) and simian virus 5 (SV5), whereas a few reacted with mumps virus or PIV4. Two of 6 anti-F MAbs reacted with SV41. None of the 128 MAbs showed reactivity with PIV1, PIV3, Newcastle disease virus (NDV), and measles virus. This result confirmed antigenic proximity of SV5 and SV41 to PIV2 and revealed comparatively restricted immunological relatedness among PIV2, PIV4, and mumps virus.

Virus-specific polypeptides of human parainfluenza virus type 4 and their synthesis in infected cells

We have studied the structural components of human parainfluenza virus type 4A (PIV-4A) and identified some virus-specific polypeptides by immunoprecipitation with polyclonal and monoclonal antibodies followed by one- or two-dimensional SDS-PAGE. HN polypeptides existed as monomer, disulfide-linked dimer, and disulfide-linked larger oligomer in cells infected with PIV-4A. Interestingly, the nonreduced NP, the nonreduced fusion, and the reduced F1 proteins migrated as doublets. Two F1 polypeptides were derived from different F1 + 2 proteins which migrated separately under nonreducing condition. In Vero cells infected with two strains of PIV-4A, two lower-molecular-weight proteins related to NP were detected. Oligopeptide patterns of the lower-molecular-weight protein were similar to those of NP protein synthesized in primary monkey kidney cells. The NP-related low-molecular-weight protein(s) was immunoprecipitated by 1 of 11 monoclonal antibodies against mumps virus NP protein. The MAb also reacted with NP proteins of PIV-2 and SV5. Thus, the epitope recognized by the MAb was common among PIV-2, PIV-4, mumps virus, and SV5, suggesting that the epitope might have an important biological function. However, the MAb did not react with the intact NP protein from cells infected with PIV-4, indicating that the epitope of PIV-4A was presented only when NP was cleaved. Phosphorylation was demonstrated for NP and P proteins.

Modification of membrane permeability by animal viruses

Animal viruses modify membrane permeability during lytic infection. There is a co-entry of macromolecules and virion particules during virus penetration and a drastic change in transport and membrane permeability at the late stages of the lytic cycle. Both events are of importance to understand different molecular aspects of viral infection, as virus entry into the cell and the interference of virus infection with cellular metabolism. Other methods of cell permeabilization of potential relevance to understand the mechanism of viral damage of the membrane are also discussed.

Intracellular processing of mumps virus glycoproteins

Using newly isolated monoclonal antibodies (MoAb) directed to the hemagglutinin-neuraminidase (HN) and the fusion (F) glycoproteins of mumps virus, we have analyzed post-translational modification of both glycoproteins. The HN glycoprotein synthesized as a monomer slowly acquires immunoreactivity with a monoclonal antibody (MoAb) to the HN in conjunction with the formation of oligomers. The oligomerization of the HN protein appeared to take place during transport of the protein through the Golgi apparatus. The immunoreactivity of the F protein evolved quickly in the rough endoplasmic reticulum, and the precursor of the F protein appeared to be proteolytically cleaved into F1 and F2 at the trans Golgi cisternae.

Cloning and sequencing of the mumps virus fusion protein gene

The fusion protein (F) gene of mumps virus was cloned from a cDNA library constructed from infected cell mRNA. The F-specific plasmids were identified by hybridization to a degenerate oligonucleotide probe whose sequence was deduced from the N-terminal amino acid sequence of the F2 protein. The complete nucleotide sequence of the F gene was determined. The gene is 1786 nucleotides long and encodes one long open reading frame of 538 amino acids. The F protein has a 19-amino acid signal peptide cleaved between Cys and Val residues. The cleavage site for activation of the F0 protein into the mature F1,2 is Arg-Arg-His-Lys-Arg. A stretch of 30 hydrophobic amino acids near the C-terminus of the protein is followed by several charged amino acids and appears to serve as the anchoring domain for the protein in the lipid bilayer. The F gene of mumps virus is highly related to the F gene of the paramyxovirus SV-5.

Effects of antibodies and interferon on mumps virus persistently infected L929 cells. Generation of variant viruses in the cells during incubation with monoclonal antibodies and interferon

We studied the effect of antibodies and interferon (IFN) on L929 cells persistently infected with mumps virus (MuV). The persistent infection was maintained by horizontal transmission of the virus within the culture but was regulated by endogenously produced IFN (8). The maintenance of the persistently infected cells in the continuous presence of anti-MuV serum suppressed the production of infectious virus. No virus antigen-positive cells were detected beyond 14 passages. Once antiserum was removed from the seemingly "cured cultures", however, a small number of antigen-positive cells appeared and the release of infectious virus into the culture fluid resumed. Even after 67 passages (200 days) of culture in the presence of anti-serum, the virus reappeared in the culture. At least 0.01 per cent of L929 cells in cultures maintained under antiserum harbored the virus without expression of virus antigen. The virus recovered from such cells was temperature sensitive. The infection of fresh L929 cells with the variant led to noncytocidal persistent infection which was maintained by propagation of virus-infected cells. MuV carrier cultures could be cured by serial cultivation in medium containing the mixture of antiserum and IFN. When L-MuV cells were subcultured with medium containing neutralizing monoclonal antibodies (MoAbs), antibody-resistant variant viruses were rapidly generated and selected. In the presence of IFN variant viruses resistant to IFN were generated. In view of the small amount of virus produced from persistently infected cells, variant viruses appeared to be generated in an unusually high frequency in carrier cultures. Thus, this experimental system may offer a useful in vitro model for studying antigenic variation and generation of various variant viruses.

Persistence of mumps virus in mouse L929 cells

The characteristics of a persistent infection of L929 cells with mumps virus (MuV) is presented. The persistent infection (L-MuV cells) was regulated by interferon (IFN) produced endogenously and almost all the properties showed that the carrier culture was maintained by horizontal transmission of the virus. Small-plaque mutants, but not temperature-sensitive variants, were selected during the persistent infection. MuV released from L-MuV cells (MuV-pi) replicated efficiently in L929 cells, while infection of L929 cells with the original MuV-o resulted in an abortive infection. The efficient replication of MuV-pi in L929 cells can be explained by the findings that MuV-pi induced IFN more slowly and had lower susceptibility to IFN in L929 cells than MuV-o did. M protein was synthesized to a considerable degree in MuV-pi-infected cells, while it could not be detected in MuV-o-infected cells. By contrast, MuV-pi formed small plaques in Vero cell monolayers and the yield of MuV-pi in Vero cells was lower than that of MuV-o. M protein induced by MuV-pi decayed easily in Vero cells. M protein was considered to be a limiting factor for MuV replication in both cell lines.