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Biomedical subjects

K Shimotohno

Publications and source records attributed to K Shimotohno.

At least 145 records · Page 8Linked to original sources
PubMed1993

Absence of HTLV-I infection among seronegative subjects in an endemic area of Japan.

To examine the prevalence of infection by human T-cell leukemia virus type I (HTLV-I) among seronegative subjects, healthy subjects on Tsushima Island, Japan, where the infection is endemic, were evaluated. A total of 209 healthy adults were examined for HTLV-I provirus in peripheral blood mononuclear cells by the polymerase chain reaction (PCR), as well as for anti-HTLV-I antibodies by the particle agglutination (PA) method, the enzyme-linked immunosorbent assay (ELISA) and by immunofluorescence analysis (IF). A total of 76 subjects were positive and 133 were negative for the provirus, showing a close correlation with the results of 3 assays for anti-HTLV-I serum antibodies. None of the seronegative subjects reacted positively on PCR analysis. These observations indicate that seronegative HTLV-I carriers are rare in an area of Japan in which this viral infection is endemic.

Adult↗
PubMed1993

GD2 ganglioside on human T-lymphotropic virus type I-infected T cells: possible activation of beta-1,4-N-acetylgalactosaminyltransferase gene by p40tax.

Ganglioside expression on adult T-cell leukemia (ATL) and human T-cell lymphotropic virus type I (HTLV-I)-infected cells was determined by using a panel of monoclonal antibodies. ATL lines and HTLV-I-infected cells specifically expressed GD2. Leukemia cells from ATL patients generally expressed low levels of GD2 but the percentage of GD2+ cells increased up to 40-70% after in vitro culture in the presence of interleukin 2 for about a week. No other type of leukemia cells and normal peripheral T cells expressed GD2 during in vitro culture under the same conditions. The appearance of GD2 in the cultured ATL cells corresponded with the expression of p40tax, a product of the HTLV-I gene. Peripheral lymphocytes infected with a p40tax-expressing retroviral vector expressed high levels of GD2 in comparison with control lymphocytes containing the neomycin-resistance gene alone. The apparently increased levels of beta-1,4-N-acetylgalactosaminyltransferase (GM2/GD2 synthase) mRNA in these cells were demonstrated by reverse transcription-polymerase chain reaction analysis. Concordance between mRNA expression for the HTLV-I tax1/rex1 genes and the beta-1,4-N-acetylgalactosaminyltransferase gene was also observed in uncultured ATL cells. These results suggest that high GD2 expression was due to neosynthesis from precursor GD3 by increased expression of this enzyme induced by p40tax in vitro and in vivo.

Base Sequence↗
PubMed1993

Base transitions and base transversions seen in mutations among various types of the hepatitis C viral genome.

We counted base transitions (Ts) and transversions (Tv) in mutations among various types of hepatitis C virus (HCV) sequences. The Ts/Tv ratio was useful for distinguishing the (geno)type of the compared HCV sequences, since the ratio was 4.0 or more among sequences of the same type, while it was less than 2.0 among sequences of different types. This observation reflects the evolutionary pathway of HCV in which Tv accumulate among distant genomes by mechanisms including multiple base substitutions.

DNA, Viral↗
PubMed1993

Two proteinase activities in HCV polypeptide expressed in insect cells using baculovirus vector.

Processing of HCV viral precursor protein requires at least two viral proteinases, Cpro-1 and Cpro-2, in addition to cellular proteinases. The HCV polypeptide that covers the region for the two viral proteinase domains was expressed in insect cells using a baculovirus expression system. The two proteinase activities were demonstrated in the infected cells. The Cpro-1-dependent cleavage site was estimated from the amino acid sequence of the N-terminus of the processed product. Analyses of the susceptibilities of various mutants altered at position P1 and P1' of the putative cleavage site suggested that amino acid residues at these positions is not essential for recognition and cleavage by Cpro-1-dependent activity.

Amino Acid Sequence↗
PubMed1993

Isolation of a cDNA clone encoding DNA-binding protein (TAXREB107) that binds specifically to domain C of the tax-responsive enhancer element in the long terminal repeat of human T-cell leukemia virus type I.

Five cDNA clones for TAXREB proteins that bind to the tax-responsive enhancer element of human T-cell leukemia virus type I (HTLV-I) were isolated from a Jurkat cell cDNA library. The beta-galactosidase fusion proteins of three of these clones specifically recognized the domain C within the enhancer. One of the three cDNAs, encoding TAXREB107, contained an open reading frame with 288 amino acid residues. RNA blot analysis showed that the level of mRNA for TAXREB107 increased transiently in Jurkat cells on treatment with TPA. Immunoblot analysis showed that polyclonal antibody against TAXREB107 specifically recognized a 34-kD protein in Jurkat cells. TAXREB107 may participate in tax-mediated trans-activation of transcription.

Amino Acid Sequence↗
PubMed1993

Proliferative response of Tax1-transduced primary human T cells to anti-CD3 antibody stimulation by an interleukin-2-independent pathway.

The growth properties of human T-cell leukemia virus Tax1-transduced primary human T cells derived from peripheral blood lymphocytes were compared with those of the same subset of T cells transduced with a control vector. Tax1-transduced T cells exhibited slightly elevated responsiveness to externally added interleukin-2 (IL-2) and a markedly higher proliferative response to stimulation with anti-CD3 antibody. The proliferation after anti-CD3 antibody stimulation was mainly via an IL-2-independent pathway. Therefore, some other mechanism than the previously proposed IL-2 autocrine model seems to be involved in the process of deregulation of T-cell proliferation by Tax1. Moreover, Tax1-transduced T cells have continued to proliferate in medium containing IL-2 long after control T cells ceased to grow, and so they are considered to be immortalized.

CD3 Complex↗
PubMed1993

Humoral immune response to hypervariable region 1 of the putative envelope glycoprotein (gp70) of hepatitis C virus.

We recently found that alterations of amino acids in hypervariable region 1 (HVR1) of the putative envelope glycoprotein (gp70) of hepatitis C virus (HCV) occurred sequentially in the chronic phase of hepatitis at intervals of several months. This finding suggests that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection involving escape from the immunosurveillance system. To explore this possibility, we examined the humoral immune response to HVR1 with our assay system, in which immunoprecipitation was carried out with sera from patients by using an HVR1 (27-amino-acid) dihydrofolate reductase fusion protein synthesized by in vitro transcription and translation. Results showed that HVR1 contains a sequence-specific immunological epitope that induces the production of antibodies restricted to the specific viral isolate. Furthermore, analysis of the kinetics of the appearance of antibodies in two patients with chronic hepatitis, with whom successive alterations of amino acids of HVR1 have been observed, showed that the titers of anti-HVR1 antibodies usually reached maximal levels several months after the isolation of HCV having the specific sequence of HVR1. This observation suggests that anti-HVR1 antibodies are involved in the genetic drift of HVR1 (minor antigenic variation) by immunoselection. However, the coexistence of HVR1 as an antigen and its specific antibody was sometimes observed. The possibility that HVR1 acts as a neutralizing epitope is discussed.

Adult↗
PubMed1993

Two distinct proteinase activities required for the processing of a putative nonstructural precursor protein of hepatitis C virus.

Gene products of hepatitis C virus (HCV), a possible major causative agent of posttransfusion non-A, non-B hepatitis, are considered to be produced from a precursor polyprotein via proteolytic processing mediated by either host cell or viral proteinases. The presence of HCV serine proteinase has been proposed from analyses of amino acid sequence homology. To examine the processing mechanism of the HCV precursor polyprotein, the amino-terminal region of the putative nonstructural protein region of the HCV genome, containing the serine proteinase motif, was expressed and analyzed by using an in vitro transcription/translation system and a transient expression system in cultured cells. Two distinct proteinase activities which function in the production of a 70-kDa protein (p70) from the precursor polyprotein were detected. One of these proteinase activities, which cleaved the carboxyl (C)-terminal side of p70, required the presence of the serine proteinase motif, which is located in the amino (N)-terminal region of p70. That suggested that the predicted HCV serine proteinase was functional. The other activity, which was responsible for the cleavage of the N-terminal side of p70, required the expression of the region upstream and downstream of that cleavage site, including the p70 serine proteinase domain. From the results of pulse-chase analysis, using proteinase inhibitors coupled with a point mutation analysis, the latter activity was proposed to be a novel zinc-dependent metalloproteinase.

Amino Acid Sequence↗
PubMed1993

[Sequence diversity and variability in the putative envelope proteins including hypervariable regions of hepatitis C virus].

Hepatitis C virus (HCV) genomes show sequence diversities among virus isolates. In particular, the putative envelope region encoding gp35 and gp70 shows on extensive sequence diversity in the whole viral genome. We identified two hypervariable regions [HVR1 (27 amino acids) and HVR2 (7 amino acids)] in the N-terminal region of gp70 of the HCV-II genotype. In the HCV-I genotype, extensive diversity of amino acid sequence in HVR1 is also observed in the same region (21 amino acids), but such diversity in HVR2 is not clearly observed like HCV-II genotype. In addition, the alteration of amino acids in HVR1 was also observed in patients with chronic hepatitis. It is suggested mutation in HVR1 is involved in the mechanism of persistent HCV infection.

Amino Acid Sequence↗
PubMed1992

Characterization of hypervariable regions in the putative envelope protein of hepatitis C virus.

We previously identified two hypervariable regions [HVR1 (27 amino acids) and HVR2 (7 amino acids)] in the putative envelope glycoprotein (gp70) by comparison of the amino acid sequences of many isolates of the HCV-II genotype. To understand the functional features of these HVRs, using the polymerase chain reaction we analyzed the rate of actual sequence variability in the region including HVR1 and HVR2 of HCV isolated successively at intervals of several months from two patients with chronic C-type hepatitis. In both patients, the amino acid sequence of HVR1, but not HVR2, was found to change dramatically during the observation period (about one amino acid per month). However, no alteration of the amino acid sequence of HVR1 of HCV was observed in a patient in the acute phase of chronic hepatitis. Restriction digestion analysis of sequence diversity showed that a HCV genome with a newly introduced mutation in HVR1 often became the predominant population at the next time of examination. Alterations of amino acids in HVR1 occurred sequentially in the two patients in the chronic phase. These findings suggest that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection.

Alanine Transaminase↗
PubMed1992

Correlation between the serum level of hepatitis C virus RNA and disease activities in acute and chronic hepatitis C.

The influence of viremia on hepatic injury in patients infected with hepatitis C virus was examined by analysis of the relationship between alanine aminotransferase activity and the amount of hepatitis C virus RNA in sequential serum samples from I untreated patient with acute hepatitis C and 3 untreated patients with chronic hepatitis C. Semiquantitative analysis by the competitive-reverse-transcription/polymerase-chain-reaction method indicated that the quantity of hepatitis C virus RNA in the serum affected the disease activities of acute and chronic hepatitis C through their natural clinical courses in all these patients. The nucleotide sequence encoding the putative envelope region of the viral genome in the patient with acute hepatitis C was examined. Blood samples taken serially at 2 times of exacerbation of the hepatitis revealed 2 nucleotide mutations, resulting in changes of predicted amino acid residues. This finding suggests that nucleotide mutations in the envelope region of the viral genome may be responsible for the recurrent hepatic injury attributed to recurrence of viremia in patients with hepatitis C. From these aspects, the serial divergence of the virus genome in infected individuals, especially in the region encoding the viral envelope protein, may possibly play an important role in developing chronic infection of hepatitis C virus.

Amino Acid Sequence↗
PubMed1992

Quantification of gene expression over a wide range by the polymerase chain reaction.

We investigated the usefulness of the polymerase chain reaction (PCR) method for the relative quantification of gene expression using a simultaneously amplified sequence of beta-actin mRNA as an internal control for the target sequence of tax/rex mRNA of human T-cell leukemia virus type I. The PCR product of the internal control was reduced by delaying the addition of the primers for its sequence. The photostimulated luminescence of the bands was measured with a laser image analyzer, and the values were plotted against the cycle number. The cycle differences between the logarithmic phase of the curves for the target sequence and for beta-actin (delta cycle) showed a linear correlation with the initial concentration of the sample. This method is highly sensitive for evaluating gene expression over a wide range.

Actins↗
PubMed1992

K-sam-related gene, N-sam, encodes fibroblast growth factor receptor and is expressed in T-lymphocytic tumors.

We recently reported the isolation of the K-sam complementary DNA (cDNA), which was amplified preferentially in poorly differentiated types of stomach cancer and codes for one of the heparin-binding growth factor or fibroblast growth factor (FGF) receptor families. The K-sam-related gene, N-sam (NCC-IT-cell-derived sam), was isolated by screening of the cDNA libraries of human immature teratoma cells, NCC-IT. Sequence analysis of the N-sam cDNAs showed that N-sam encodes a human FGF receptor, the FLG protein. N-sam was expressed in lymphocytic leukemia/lymphoma cells, predominantly in the thymic T-cell phenotype. In a T-cell leukemia line, MOLT3, N-sam mRNA expression was markedly enhanced by 12-O-tetradecanoylphorbol-13-acetate treatment and was also up-regulated by basic FGF exposure. These results indicate that N-sam expression is regulated during T-cell ontogeny and modulated by its putative ligand exposure. The results also suggested that interaction between immature T-cell and marrow or thymic interstitial cells might be mediated by N-sam and basic FGF stored in the extracellular matrix of stromal cells.

Base Sequence↗
PubMed1992

A new type of hepatitis C virus in patients in Thailand.

Partial nucleotide sequences in the tentative NS5 region of the hepatitis C viral genome obtained from patients with chronic hepatitis in Thailand were analyzed by reverse transcription followed by the polymerase chain reaction. Of ten samples studied, four showed low homologies to any known type of HCV: the homologies of the nucleotide sequences of these clones with HCV-J, -US, -K2a and -K2b were 66.5-69.1%, 66.5-68.2%, 61.2-64.1% and 64.4-66.2%, respectively, and the homologies of their deduced amino acids sequences were 71.7-75.2%, 71.7-75.2%, 69.0-72.6% and 69.9-73.5%, respectively. These four clones were classified a new distinct type of HCV, named HCV-T. Moreover, the nucleotide and amino acid sequence homologies of the four HCV-T clones showed that the HCV-T type could be classified into two genotypes, HCV-Ta and HCV-Tb.

Amino Acid Sequence↗
PubMed1992

Marked sequence diversity in the putative envelope proteins of hepatitis C viruses.

The nucleotide sequences of cDNAs (414 base pairs) encoding parts of putative envelope proteins (gp35 and gp70) of 40 isolates of hepatitis C virus (HCV-J) derived from 30 independent plasma or liver specimens from Japanese patients (13 with chronic hepatitis, 14 with hepatocellular carcinoma and 3 hemophiliacs who had received imported clotting factors), were analyzed using the polymerase chain reaction. Approximately 29-38% of the nucleotide sequences of the HCV-J isolates examined differed from those of isolates from the United States (HCV-US). Furthermore, 12-24% and 8-17% sequence diversities were found within the isolates of HCV-J and HCV-US, respectively. The diversities of the amino acid sequences were the same or greater than those of the nucleotide sequences. We confirmed that two hypervariable regions (HVR1 and HVR2) were present in this amplified region, as described in our previous report (Hijikata et al., 1991a) and we found that the HVR1 regions of HCV-J and HCV-US were 27 and 21 amino acids in length, respectively, and began from the N-terminal amino acid of gp70. HVR2 was found in HCV-J, but not in HCV-US isolates, in which the corresponding region of the genome was conserved. During the analysis, plural HCV genomes were found in 6 of 30 specimens. These plural HCV genomes in a single specimen were concluded to be derived from the same HCV ancestor, because of their relative low sequence diversities (about 10% in their nucleotide sequences).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Molecular cloning of hepatitis C virus genome from a single Japanese carrier: sequence variation within the same individual and among infected individuals.

A hepatitis C virus (HCV) genome was isolated and sequenced from a single Japanese patient with chronic non-A, non-B hepatitis. The genome (HCV-JT), which was constructed with 23 cDNA clones, consisted of 9436 nucleotides with a long open reading frame which could encode a sequence of 3010 amino acid residues. To study the sequence variation of the HCV genome in an individual, we analyzed another sequence of the HCV genome (HCV-JT') constructed with different cDNA clones derived from the same patient. The nucleotide variation between HCV-JT and -JT' was less than 1%, and was distributed throughout the genome except in the 5' non-coding region, where no variation was observed. The diversity was higher (1.6%) in the putative envelope protein region than in other regions. The nucleotide and deduced amino acid sequences of HCV-JT showed homologies of about 91 and 95%, respectively, with those of other Japanese HCV isolates. The nucleotide diversity was high in the gp 70 region (corresponding to the NS 1 region of flaviviruses) and low in the 5' non-coding and p22 (putative core protein) regions. A similar pattern of distribution of nucleotide changes was observed on comparison of HCV-JT with an American isolate HCV-US, where the homologies in nucleotide and amino acid sequences were about 79 and 85%, respectively. Base transversions contributed about 50% of the total base exchanges between the Japanese and American HCV sequences, but only 20% or less of those among Japanese HCV or among American HCV sequences. Thus, the Japanese and American HCVs are genetically distinguishable, supporting our earlier prediction that these two HCVs could be classified as different subtypes.

Amino Acid Sequence↗
PubMed1992

Evaluation of enzyme immunoassay using a recombinant envelope protein expressed in insect cells for serological confirmation of HTLV-I infection.

A recombinant human T-lymphotropic virus type I (HTLV-I) envelope protein expressed in insect cells using a recombinant baculovirus was employed as the antigen in an enzyme immunoassay (renvEIA). Peripheral blood samples were obtained from asymptomatic carriers or healthy individuals. Plasma was tested for HTLV-I antibody by renvEIA, particle agglutination, and Western immunoblot (WB), and lymphocyte DNA was tested for HTLV-I proviral DNA amplification by polymerase chain reaction (PCR). Of 61 people aged 9 months or older, 23 were positive (gag+, env+) and 19 others were in the "indeterminate" category (gag+, env-) when their WB results were interpreted according to the WHO-proposed criteria. Thirty-seven cases, including all of the WB+ cases and 14 of 19 WB indeterminate cases, were positive by renvEIA. In 34 of 37 renvEIA-positive cases, the presence of long terminal repeat (LTR) and tax/rex region of HTLV-I proviral DNA was detected by polymerase chain reaction (PCR) and following Southern blot hybridization. Thus, renvEIA would be a useful supplemental assay to confirm the presence of HTLV-I antibody in HTLV-I asymptomatic carriers.

Adolescent↗