A persistent infection of Vero cells by egg-adapted mumps virus

Chronic mumps virus encephalitis

A previously well 4-year-old girl developed frequent seizures and mental deterioration after mumps parotitis. Direct IgG antibody capture enzyme-linked immunosorbent assay revealed a high titer of anti-mumps viral antibodies in the cerebrospinal fluid. Chronic mumps encephalitis was diagnosed. Her mental state and seizures improved markedly with inosine pranobex therapy.

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.

Studies on the adaptation of mumps virus to chick embryo

About 15 serial passages of wild type mumps virus (Sasazaki strain) in the amnion sac of chick embryo (CE) yielded a CE-adapted strain which was poorly replicative and did not form plaques in Vero cells where the wild strain grew well. In the course of this limited replication of the CE-adapted strain in Vero cells, we have analysed the viral protein and RNA synthesis. It was found that protein synthesis took place very efficiently at least early in infection by 12 h. The subsequent rate of synthesis remained, however, at a low level without showing the progressively increasing synthesis observed with the wild strain. Furthermore, 50S genomic RNA was synthesized early in the limited infection, but the subsequent synthesis was markedly suppressed. In addition, the other virus-specific RNA species could not be detected throughout. Thus the amplified RNA synthesis observed in the permissive CE cells and in the wild strain-infection of Vero cells seemed not to occur in the limited replication. Neither interferon nor DI (defective interfering) RNA was involved in the limited virus growth. When Vero cells were infected with the wild strain 6 to 8 h before inoculation of CE-adapted strain, growth restriction was overcome and the yield of the latter virus was greatly enhanced by a factor more than 10(3). These results suggest that through adaptation to CE, mumps virus may be altered in such a way that there is a restriction, probably at a step (s) involved in amplification of the viral RNA synthesis in Vero cells and that the restriction may be overcome by the simultaneous genome expression of the prototype wild strain.

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.

Accumulation of altered viral nucleocapsids in mumps virus--persistently infected cell cultures

Two long-term human cell cultures persistently infected with mumps virus accumulated increased amounts of morphologically altered viral nucleocapsids. Alterations involved size, heterogeneity, fine structure and shape. RNA present in intracellular nucleocapsids was predominantly of subgenomic size.

Chronic encephalomyelitis with specific increase in intrathecal mumps antibodies

Symptoms of severe encephalomyelitis developed in a 31-year-old man in 1967. He had a high serum antibody titre to mumps virus associated with a polymorphic cell reaction and an increased protein concentration in cerebrospinal fluid (CSF). He recovered considerably within a year and was able to resume work. In 1975 his condition deteriorated again; it improved during the following few years, but a further deterioration then occurred. In March, 1981, the complement-fixing antibody titre to mumps virus was 1/32 in the serum and 1/4 in the CSF. In November, 1981, the CSF IgG index was increased and the altered serum/CSF antibody ratio persisted. The specificity of the altered antibody ratio was confirmed by the single radial haemolysis test and an immunoassay specific for mumps virus. Antibodies against the mumps virus envelope glycoprotein, M-protein, and nucleoprotein could be demonstrated by immunoprecipitation and the antibody patterns in serum and CSF were similar. Antibodies against other microorganisms were not detected in the patient's CSF, and mumps antibodies were not found in the CSF specimens of 57 control patients. This case may be an example of a new disease-chronic mumps virus infection in the central nervous system.