Plaque assay and primary isolation of influenza A viruses in an established line of canine kidney cells (MDCK) in the presence of trypsin

A wide variety of influenza A viruses, comprising human, equine, porcine, and avian strains, grew productively in an established line of canine kidney cells (MDCK) under an overlay medium containing trypsin, and formed well-defined plaques regardless of their prior passage history. Plaquing efficiency was comparable to the efficiency of infection in fertile eggs via allantoic route. MDCK cells have also been successfully employed for the primary isolation of influenza A virus from throat washings of patients. Parallel titration of several clinical specimens showed that the inoculation into MDCK cells followed by incubation in the presence of trypsin was an isolation procedure as sensitive as the amniotic inoculation into fertile eggs.

Marmoset lymphoblastoid cells as a sensitive host for isolation of measles virus

B95-8, an Epstein-Barr virus-transformed marmoset B-lymphoblastoid cell line, and its derivative B95a, capable of attachment to a substrate surface, were 10,000-fold more sensitive to measles virus present in clinical specimens than were Vero cells. B95-8 and B95a cells were thus thought to be useful host cells for the isolation of measles virus. Quantitation of measles virus present in clinical specimens showed that a large quantity of virus, exceeding 10(6) 50% tissue culture infective doses per ml of a nasal-swab eluate, is shed into secretions by patients with acute measles, consistent with the contagiousness of the disease. Measles viruses isolated in B95a cells differed in some biological properties from those adapted to Vero cells. First, the viruses isolated in B95a cells did replicate in Vero cells, but release into the fluid phase was less efficient than that of Vero cell-adapted viruses. Second, minor antigenic differences were found between virus strains isolated in B95a cells and those isolated in Vero cells from the same clinical specimens. Third, the viruses isolated and propagated in B95a cells caused clinical signs in experimentally infected monkeys resembling those of human measles. It was suspected that measles virus is subject to host cell-mediated selection and that the viruses grown in B95a cells are more representative of measles virus circulating among humans than are the viruses selected in Vero cells.

Isolation and preliminary characterization of temperature-sensitive mutants of influenza virus

Isolation of temperature-sensitive (ts) mutants was attempted from the WSN strain of influenza A virus which was grown and assayed in MDBK cells. After growth of wild-type virus in the presence of 5-fluorouracil, 15 ts mutants were selected for which the ratio of plaquing efficiency at 39.5 C to that at 33 C was 10(-3) or less. In pairwise crosses of ts mutants, recombination and complementation were either very efficient or undetectable. It is suggested, therefore, that the viral genome consists of physically discrete units and recombination occurs as an exchange of these units. All 15 mutants have been assigned with certainty into five recombination groups. Three mutants are suspected to be double mutants. Any two complementing mutants always recombined with each other, and noncomplementing mutants did not recombine. In physiological tests, mutants showed diverse patterns of functional defects at the nonpermissive temperature. However, it was not always possible to correlate these physiological defects with the results of genetic characterization.

A new antibiotic CJ-17,665 from Aspergillus ochraceus

A new antibiotic, CJ-17,665 (I) was isolated from the fermentation broth of Aspergillus ochraceus, CL41582. It inhibits growth of multi-drug resistant Staphylococcus aureus, Streptococcus pyogenes, and Enterococcus faecalis, with MICs of 12.5, 12.5 and 25 microg/ml, respectively. The structure contains a diketopiperazine and an indole N-oxide moiety that is unusual in natural products.

Signal-sensing mechanisms of the putative osmosensor KdpD in Escherichia coli

The KdpD protein is a membrane-located sensory kinase (or signal transducer) critically involved in the regulation of the kdpABC operon that is responsible for a high-affinity transport system in Escherichia coli. In this study, a set of KdpD mutants, each resulting in a single amino acid substitution around the membrane-spanning regions of KdpD, was isolated. Amino acid substitutions in these KdpD mutants were located non-randomly, particularly within the C-terminal half of the membrane-spanning regions. This set of KdpD mutants exhibited altered transmembrane-signalling properties in response to external K+ and other stimuli. In particular, these mutants were found to be insensitive, if not completely, to the K+ signal. However, they were able to respond to other stimuli such as high-salt stress, as in the wild type. Therefore, in contrast to the wild type, the cells carrying these mutations exhibited high levels of the steady-state expression of kdp, regardless of external K+, provided that high concentrations of ionic solutes were supplemented to the cultures. More interestingly, the set of KdpD mutants could also respond to high concentrations of external non-ionic solutes such as sucrose and D-arabinose, thereby increasing substantially the steady-state expression of kdp in response to the medium osmolarity. Furthermore, it was found that certain chemicals, ethanol, chlorpromazine and procaine, could function as effectors for the KdpD mutants at relatively low concentrations in the media. Based on these findings, we have examined the primary signal(s) that regulates the function of KdpD. We propose here that KdpD can be considered to be an environmental sensor that exhibits sensing mechanisms in response to both the level of K+ and the physico-chemical state of the cytoplasmic membrane.

Aseptic meningitis as a complication of mumps vaccination

In 1989 a nationwide surveillance of neurologic complications after the administration of mumps vaccine was conducted in Japan, based on the notification of cases and the testing of mumps viruses isolated from cerebrospinal fluid for their relatedness to the vaccine by nucleotide sequence analysis. Among 630,157 recipients of measles-mumps-rubella trivalent (MMR) vaccine containing the Urabe Am9 mumps vaccine, there were at least 311 meningitis cases suspected to be vaccine-related. In 96 of these 311 cases, mumps virus related to the vaccine was isolated from cerebrospinal fluid. The unusually high incidence may have been partly a result of the adverse media publicity of the problem at the time of surveillance. We analyzed clinical features of 165 and 27 laboratory-confirmed mumps vaccine-related meningitis cases that occurred among the recipients of MMR and monovalent mumps vaccines, respectively, during a 1-year period after the introduction of MMR vaccine. The incidence of vaccine-related meningitis was similar among the recipients of MMR and monovalent Urabe Am9 mumps vaccines. Meningitis was generally mild and there were no sequelae from the illness. The complication was more frequent among male than among female children.

Transient ventricular wall thickening in acute myocarditis: a serial echocardiographic and histopathologic study

The present study was designed to determine whether the wall thickening seen in acute myocarditis is caused by interstitial edema. The study group comprised 25 patients (idiopathic myocarditis, 17; eosinophilic myocarditis, 8) in whom acute myocarditis was diagnosed histologically and who underwent echocardiography and endomyocardial biopsy during both the acute and convalescent phases. The following echocardiographic parameters were measured: interventricular septum and left ventricular posterior wall thickness, left ventricular end-diastolic dimension, and left ventricular ejection fraction. Based on the myocardial biopsy specimens, the degree of interstitial edema was classified into 3 grades [(-), 1(+), 2(+)] and the transverse diameter of cardiac myocytes was measured using light microscopy. The thickness of both the interventricular septum and left ventricular wall decreased from 14.3+/-3.7 mm and 13.3+/-2.4 mm in the acute phase to 9.7+/-1.7 mm (p<0.001) and 10.2+/-1.7 mm (p<0.0001), respectively, in the convalescent phase. Edema was present in 22 patients (88.0%) in the acute phase, but in the convalescent phase, edema was present in only 7 patients (28.0%), indicating a significant reduction in the degree of edema (p<0.0001). Cardiac myocyte diameter did not differ significantly between the acute (13.6+/-1.1 microm) and convalescent (13.8+/-1.8 microm) phases.

Clarification of the structural and functional features of the osmoregulated kdp operon of Escherichia coli

Expression of the Escherichia coli kdpABC operon, which is responsible for a high-affinity potassium-uptake system, is regulated in response to a change in the medium osmolarity. In this study, we clarified the structure and function of the kdpABC promoter including its regulatory sequence at the molecular level. The canonical -35 and -10 regions determined for the promoter were not fully functional, i.e. in addition to them, a cis-acting sequence located upstream of the -35 region was essential for full activation of the promoter. This upstream sequence was demonstrated to be the target site for the trans-acting activator, KdpE.

Signal transduction between the two regulatory components involved in the regulation of the kdpABC operon in Escherichia coli: phosphorylation-dependent functioning of the positive regulator, KdpE

The proteins KdpD and KdpE are crucial to the osmotic regulation of the kdpABC operon that is responsible for the high-affinity K+ ion transport system in Escherichia coli. We demonstrated previously that the response regulator, KdpE, is capable of undergoing phosphorylation mediated by the sensory protein kinase, KdpD. In this study, we obtained biochemical evidence supporting the view that when KdpE is phosphorylated, it takes on an active form that exhibits relatively high affinity for the kdpABC promoter, which in turn results in activation of the kdpABC operon. It was also suggested that the central hydrophobic domain of KdpD, which is conceivably responsible for membrane anchoring of this protein, plays a role in the signalling mechanism underlying KdpE phosphorylation in response to hyperosmotic stress.

Origin of small RNA in von Magnus particles of influenza virus

A clone of recombinant virus obtained from the cross between WSN and Hong Kong strains of influenza virus gave rise to progeny containing predominantly von Magnus particles. In the electropherogram of virus RNA, the P3 gene was markedly diminished, and a new species of RNA (extra RNA) was present in addition to eight gene segments. The origin of the extra RNA was studied by two-dimensional gel electrophoresis of T1 RNase-generated oligonucleotides. Four out of five large oligonucleotide spots present in the extra RNA matched to those contained by the P3 gene. It was concluded that the extra RNA was derived from the P3 gene probably by deletion. The possible origin of the spot which was present in the extra RNA but not in eight gene segments including P3 was discussed.

Characterization of major structural proteins of measles virus with monoclonal antibodies

We have prepared and characterized monoclonal antibodies against five major structural proteins, i.e. the HA, P, NP, F and M proteins, of measles virus. At least three non-overlapping antigenic sites were delineated on the HA protein, three on the P, four on the NP, four on the F and five on the M proteins by competitive binding assays. Antigenic sites on the HA and F proteins roughly represented functional domains defined by serological tests. The reactivity of monoclonal antibodies with various measles virus strains including those from subacute sclerosing panencephalitis (SSPE) and other members of the morbillivirus family was studied by immunofluorescence. A monoclonal antibody or set of monoclonal antibodies to each of the antigenic sites showed a characteristic pattern of cross-reactivity with heterologous strains. The HA and NP proteins were antigenically the most variable, followed by the F and M proteins, while the P protein was relatively stable. None of the 14 anti-M monoclonal antibodies reacted with non-virus-producing SSPE cells, strongly suggesting the absence of M protein in these cells.

Molecular epidemiology and clinical spectrum of hereditary spastic paraplegia in the Japanese population based on comprehensive mutational analyses

Hereditary spastic paraplegia (HSP) is one of the most genetically heterogeneous neurodegenerative disorders characterized by progressive spasticity and pyramidal weakness of lower limbs. Because >30 causative genes have been identified, screening of multiple genes is required for establishing molecular diagnosis of individual patients with HSP. To elucidate molecular epidemiology of HSP in the Japanese population, we have conducted mutational analyses of 16 causative genes of HSP (L1CAM, PLP1, ATL1, SPAST, CYP7B1, NIPA1, SPG7, KIAA0196, KIF5A, HSPD1, BSCL2, SPG11, SPG20, SPG21, REEP1 and ZFYVE27) using resequencing microarrays, array-based comparative genomic hybridization and Sanger sequencing. The mutational analysis of 129 Japanese patients revealed 49 mutations in 46 patients, 32 of which were novel. Molecular diagnosis was accomplished for 67.3% (33/49) of autosomal dominant HSP patients. Even among sporadic HSP patients, mutations were identified in 11.1% (7/63) of them. The present study elucidated the molecular epidemiology of HSP in the Japanese population and further broadened the mutational and clinical spectra of HSP.

Phosphotransfer signal transduction between two regulatory factors involved in the osmoregulated kdp operon in Escherichia coli

The proteins KdpD and KdpE are regulatory factors critically involved in the osmotic regulation of the kdpABC operon that is responsible for a high-affinity transport system in Escherichia coli. In this study, we obtained biochemical evidence supporting the view that the KdpD protein is a sensory protein kinase that exhibits autophosphorylation and KdpE-phosphotransfer characteristics. During the course of such studies we established a procedure for purifying the KdpE protein in large quantities. We also developed a procedure for preparing cytoplasmic membrane enriched with the KdpD protein that exhibits in vitro ability with regard to phosphorylation of KdpE protein.

Variations of nucleotide sequences and transcription of the SH gene among mumps virus strains

We have compared nucleotide sequences of the SH genes as well as their flanking regions of six mumps virus strains and found a high amino acid diversity (up to 23%) of the putative SH proteins among these strains. It was found, in addition, that one of these strains (Enders strain) contained a point mutation in putative polyadenylation signal for the F gene mRNA (TTTAGAAAAAAA to TTTAGAAGAAAA). Northern blot analysis showed that the Enders strain was also unique in that neither monocistronic SH nor bicistronic SH-HN mRNA could be detected in the cells infected with this particular strain.

Enzyme-linked immunosorbent assay compared with neutralization tests for evaluation of live mumps vaccines

Mumps-specific antibody levels before and after vaccination with live mumps vaccines were determined by enzyme-linked immunosorbent assay (ELISA) and neutralization tests. A correlation was found between neutralization titers and optical density in ELISA. However, postvaccination sera from some vaccinees who failed to seroconvert by neutralization contained significant levels of mumps-specific antibody detectable by ELISA. In some of these serum specimens, the antibody directed to the F polypeptide of mumps virus was predominant. Most sera positive in ELISA neutralized mumps virus upon the addition of fresh guinea pig serum to the virus-serum mixture.

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.

Antibody response to individual rubella virus proteins in congenital and other rubella virus infections

Serum samples from patients with various forms of rubella virus infection were tested for antibodies to each of three viral structural proteins by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In most sera antibody to E1 protein was the predominant species. Sera from patients with congenital rubella syndrome, however, contained significantly more E2 antibody relative to E1 antibody than did sera from other rubella patients.