Biomedical subjects
Tetsuo Nakayama
Publications and source records attributed to Tetsuo Nakayama.
Detection of human respiratory syncytial virus sequences in peripheral blood mononuclear cells.
Peripheral blood mononuclear cells (PBMC) obtained from patients with lower respiratory infections were examined for the detection of human respiratory syncytial virus (RSV) sequences in the N region using the reverse transcription polymerase chain reaction (RT-PCR). RSV infection was confirmed by at least one method, i.e., virus isolation, enzyme immunoassay for viral antigen, and RT-PCR of nasopharyngeal secretions (NPS) samples. The detection rate for RSV RNA in PBMC obtained from RSV-infected patients was 40% (38/94), compared to 5% (1/20) in controls (P = 0.002). Between the groups positive (38) and negative (56) for RSV RNA in PBMC, there was no significant difference in clinical parameters. Seven patients had eight episodes of reinfection and RSV RNA was detected in 50% (4/8) during consecutive infections. Sequences of their PBMC samples were distinct from those of prototype strains of subgroup A and B. However, they were not always consistent with those of paired NPS samples. The findings suggested that RSV RNA could be detected in PBMC even during reinfection and as might have the possibility of quasispecies dynamics, reflecting the nature of RNA viruses.
H1 genotype of measles virus was detected in outbreaks in Japan after 2000.
We investigated the molecular epidemiology and biological characteristics of wild measles viruses isolated since 1984 in Japan. The circulating measles virus was of genotype C1 before 1985, D3 from 1987 to 1990, and D5 from 1990 to 1997. It was replaced by the same cluster of Chicago-type D3 strain from 1997 to 1999. In 2000, D5 recirculated with sporadic cases caused by genotype H1. The H1 genotype became dominant in 2001 with a minor distribution of D5. No significant difference was observed in neutralizing titers against C1, D3, D5, and H1 when we used sera having high neutralizing titers. However, some D3 and H1 strains were not completely neutralized with low levels of neutralizing antibody, and maintaining high levels of measles antibodies would be required for the control measles outbreaks.
False-positive magnetic resonance imaging skeletal survey in a patient with sporadic hypophosphatemic osteomalacia.
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Current status of measles in Japan.
Approximately 20,000 to 30,000 cases of measles are reported annually in Japan, although the actual number of measles infections is considered to be five to ten times higher than the number of reported cases. Despite the availability of effective and safe live attenuated vaccines, regional outbreaks in Okinawa, transmission in adults, and secondary vaccine failures continue. Recent advances in molecular technology have contributed to molecular epidemiological studies, new concepts of asymptomatic infection, and the identification of different characteristics among measles virus genotypes. Measles virus strains isolated in Japan since 1984 were classified into the genotypes C1 (-1985), D3 (1985-1990), D5 (1990-1997), and Chicago-type D3 (1997-1999) from the results of sequencing the hemagglutinin gene. After 2000, the D5 genotype emerged, and, recently, the H1 genotype, which is now dominant, was introduced from Korea. Some of the currently circulating wild-types have different characteristics (high growth rate at 39 degrees C-40 degrees C). The cumulative vaccine coverage has reached 81%, but most measles cases involved unvaccinated individuals. Measles is a preventable disease and can be eradicated by increasing the vaccine coverage, and promoting the motivation for vaccination, in accordance with the worldwide measles strategy.
Combination therapy with intraventricular interferon-alpha and ribavirin for subacute sclerosing panencephalitis and monitoring measles virus RNA by quantitative PCR assay.
Subacute sclerosing panencephalitis (SSPE) is a degenerative disease of the central nervous system that leads to death within a few years. Recently, it has been reported that combination therapy with intraparenchymal interferon-alpha (INF-alpha) and intraventricular ribavirin is effective. An 11-year-old SSPE patient whose clinical symptoms progressed rapidly, was treated first with intraventricular INF-alpha and then with combined intraventricular INF-alpha and ribavirin therapy. To monitor viral load over the course of the therapy, measles virus RNA was quantified using a real-time polymerase chain reaction assay. Measles virus RNA decreased rapidly after the INF-alpha therapy was started, paralleling the decrease in the measles antibody titer in the cerebrospinal fluid and the improvement in the neurological disability. After intraventricular ribavirin was combined with INF-alpha therapy, no further improvement was observed. The neurological disability gradually progressed, although the amount of virus RNA remained low.
Determination of enterovirus serotype inferred from sequence analysis of PCR products.
BACKGROUND: Enterovirus infections are common in neonates. Virus isolation is the only diagnostic method to confirm enterovirus serotype infections, however, is not always successful. OBJECTIVES: A new approach for the diagnosis of enterovirus infections was performed, using the reference strain inferred from sequence analysis of PCR products. STUDY DESIGN: Virus isolation, enterovirus RT-PCR and sequence analysis were performed from clinical samples or stored sera from two neonates with fever and rash. Neutralizing test (NT) antibodies against prototype reference virus were measured in paired sera. RESULTS: Virus isolation was negative in both patients but the enterovirus genome was amplified in the acute phase sera obtained from the two patients. From the results of sequence analysis of 109 nucleotides located in the 5'-noncoding of the conserved region of enteroviruses, a high homology to echovirus types 25 and 30 was found. More than a 4-fold increase in NT antibodies against reference viruses was demonstrated in the acute and convalescent phase sera. They were confirmed as echovirus type 25 and 30 infection, respectively. CONCLUSIONS: These virological examinations are practical and useful for clinical settings for a diagnosis of enterovirus infections because of an insufficient positive rate in virus isolation.
Measles outbreak in a suburb of Tokyo, Japan, in 1998-1999.
A 1998-1999 outbreak of measles in Kawasaki City was studied to provide an up-to-date epidemiological understanding of the disease in Japan. 21 of the 69 total patients (30.4%) seen at the hospital were under 1 y of age. None of the 69 patients had received measles vaccine. 43 out of 50 nasopharyngeal swabs subjected to polymerase chain reaction assay (86%) were positive for the hemagglutinin (H) gene. The measles strain isolated from patients was classified as a D3 genotype. Such outbreaks are important epidemiologically, and these findings shed light on vaccination and immunity patterns in this urban population.
[Prevention of infectious diseases and vaccine benefit].
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Supratentorial convexity leptomeningeal schwannoma: case report.
OBJECTIVE AND IMPORTANCE: Leptomeningeal schwannomas are very rare; to our knowledge, only one case has been previously reported. The possible histogenesis and differential diagnosis of intracranial schwannomas not related to cranial nerves are discussed. CLINICAL PRESENTATION: A 53-year-old man presented with a sudden onset of seizures. Computed tomographic scans revealed a small hypodense mass in the peripheral aspect of the left frontal lobe. The mass was hypointense on T1-weighted and hyperintense on T2-weighted magnetic resonance imaging scans, with ring enhancement after contrast medium administration. INTERVENTION: A craniotomy was performed for total removal of the tumor, revealing a well-demarcated, firm, spherical tumor beneath the dura. The tumor was easily separated from the brain. Histologically, the tumor was observed to be within the subarachnoid space, intimately attached to the pia mater. The adjacent brain tissue and dura mater were free of tumor cells. The histological diagnosis was schwannoma. CONCLUSION: Computed tomographic and magnetic resonance imaging findings in our case were consistent with those for a schwannoma, although the subarachnoid space is an extremely rare location for schwannomas. We emphasize that schwannomas may arise in the subarachnoid space.
Detection of measles virus genome in bone-marrow aspirates from adults.
We investigated the presence of the measles virus genome in order to identify asymptomatic infections in the adult population. Bone-marrow aspirates were obtained from 179 patients, 20-96 years of age, for the diagnosis of malignant diseases (29 with malignant lymphoma, 28 with acute leukaemia, 21 with myelodysplastic syndrome, five with multiple myeloma and 96 with other diseases). The measles virus genome was detected in 17 (9.5%) of 179 individuals by RT-PCR and 28 (15.6%) through hybridization. The genomes detected in bone marrow were all in the same cluster, D5, the strain circulating during the study period, and no evidence of persistent infection was obtained. We conclude that asymptomatic infections of measles virus are common in adults and the presence of the measles virus genome would not be related to the pathogenesis of illness.
[Field trial of combined measles and rubella live attenuated vaccine].
We investigated the antibody responses and clinical adverse reactions after immunization with live combined measles and rubella vaccine (HF vaccine) in 442 healthy children, aged 12-90 months of age. We obtained 368 paired sera. Among them, 363 were initially sero-negative against measles virus and 343 (94.5%) became sero-positive after immunization. Sero-conversion against rubella virus was demonstrated in 349 (96.7%) of 361 initially sero-negatives against rubella virus. We investigated the clinical adverse reactions in 406 recipients. In 102 (25.1%) recipients, febrile reaction (> 37.5 C) developed on the day 6.7 of vaccination on average, with a mean duration of 2.2 days. Only two (0.5%) developed high body temperature over 39.5 C. Skin rash was noted in 87 (21.4%) on day 7.1 of vaccination on average, with a mean duration of 4.8 days. Lymphoadenopathy was demonstrated in 12 (3.0%). Thus, measles and rubella combined vaccine was safe and sufficiently immunogenic as well as each monovalent one, having clinical advantage in immunization practice.
Leucine at position 278 of the AIK-C measles virus vaccine strain fusion protein is responsible for reduced syncytium formation.
The live measles virus (MV) vaccine strain AIK-C was attenuated from the wild-type strain Edmonston by plaque purification at 33 degrees C. Strain AIK-C grew well at 33 degrees C with a mixture of small-and medium-sized plaques in Vero cells, but did not grow well at 40 degrees C. To investigate fusion inducibility, expression plasmids for the fusion (F) and haemagglutinin (H) protein regions of MV strains AIK-C (pAIK-F01 and pAIK-H) and Edmonston (pEdm-F and pEdm-H) were constructed. pEdm-F induced extensive cell fusion in B95a and Vero cells under the control of T7 RNA polymerase, whereas a sharp reduction in syncytium formation was observed when pAIK-F01 was used. Six amino acid differences were determined between pAIK-F01 and pEdm-F. Direct sequencing showed that the seed strain AIK-C contained either Leu or Phe at position 278 of the F protein. Experiments using recombinant F protein plasmids demonstrated that those with Leu at position 278 induced poor syncytium formation, while those with Phe at position 278 (Edmonston type) induced extensive cell fusion. Replacement of Phe with Leu at position 278 of pEdm-F reduced fusion-inducing capability. A full-length infectious clone of AIK-C with Leu at position 278 of the F protein was constructed. The rescued virus produced small plaques in Vero cells. However, the same rescued virus with Phe at position 278 produced large plaques. It was concluded that Leu at position 278 of the F protein of the MV vaccine strain AIK-C is responsible for the formation of small plaques.