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Biomedical subjects

Y Akahane

Publications and source records attributed to Y Akahane.

At least 73 records · Page 4Linked to original sources
PubMed1990

Defects in the precore region of the HBV genome in patients with chronic hepatitis B after sustained seroconversion from HBeAg to anti-HBe induced spontaneously or with interferon therapy.

Hepatitis B virus DNA clones were propagated from sera of six patients with chronic hepatitis B who seroconverted from HBeAg to antibody to HBeAg either spontaneously or after administration of alpha-interferon. Defects in the precore region blocking synthesis and secretion of HBeAg were detected in all 46 hepatitis B virus DNA clones from three patients who remained positive for antibody to HBeAg and in whom hepatitis resolved. Defective clones had point mutations from guanine to adenine at nucleotide 83 in the precore region, converting codon 28 from tryptophan (TGG) to a stop codon (TAG). In contrast, this defect was not found in any of 39 hepatitis B virus DNA clones from three patients who seroconverted to antibody to HBeAg but then redeveloped HBeAg with reactivation of hepatitis. Using these results, the G-to-A point mutation at nucleotide 83 in the precore region would predict sustained positivity for antibody to HBeAg and remission of hepatitis in patients who have seroconverted either spontaneously or with interferon therapy.

Adult↗
PubMed1990

Chronic active hepatitis with hepatitis B virus DNA and antibody against e antigen in the serum. Disturbed synthesis and secretion of e antigen from hepatocytes due to a point mutation in the precore region.

Some patients with type B chronic active hepatitis have a high titer of hepatitis B virus DNA despite antibody against e antigen in the serum. Clones of hepatitis B virus were propagated from the sera of seven patients with this disease, and the precore region was sequenced. Essentially all clones (128/131 or 98%) showed a point mutation from guanine to adenine at nucleotide 83, converting codon 28 for tryptophan (TGG) to a stop codon (TAG); the second guanine-to-adenine point mutation at nucleotide 86 was identified in only 29 clones from two patients. In patients followed up since they had hepatitis B e antigen, a shift from guanine to adenine was observed at nucleotide 83 along with the seroconversion to the antibody to e antigen. The precore-region product is required for the synthesis and secretion of e antigen from hepatocytes. A point mutation from guanine to adenine at nucleotide 83 observed in the seven patients, therefore, would be responsible for disturbed secretion of e antigen.

Aged↗
PubMed1990

Hepatitis B surface antigen particles with all four subtypic determinants: point mutations of hepatitis B virus DNA inducing phenotypic changes or double infection with viruses of different subtypes.

Hepatitis B surface antigen (HBsAg) particles carry the common determinant, a, as well as d or y and w or r subtype determinants, and are classified into the four major subtypes, i.e., adw, adr, ayw and ayr. Rare sera contain HBsAg particles with all four subtype determinants (adywr). Target sequences (nucleotides 38-550) in the S gene of hepatitis B virus (HBV) DNA in two such sera were amplified by the polymerase chain reaction. Individual amplification products were cloned in an M13 phage vector. The HBV DNA clones obtained were subtyped by determining the second letters of codon 122 and 160 for lysine (AAA/AAG) or arginine (AGA/AGG), which specify the d or y and w or r determinants, respectively. From one serum (S-63), two adw, 10 adr and 58 ayr clones were obtained. When the two adw clones and two representatives each of the adr and ayr clones were compared against each other, for the sequence of 235 base pairs representing nucleotides 295-529 in the S gene, they differed only by 0.4-2.1% (average 1.2%). These results indicated multiple point mutations of a single HBV strain of subtype ayr and co-infection of hepatocytes with the original HBV strain and its mutant of subtype adw as the mechanism for the production of HBsAg/adywr particles. From the other serum (K-45), 1 adw, 73 adr and 4 ayw clones were obtained. The adw clone and two representative adr clones differed only by 0-1.7% in the S gene sequences, but they differed by 8.5% or greater from two representative ayw clones. HBsAg/adywr particles in this serum, therefore, could be explained by double infection of hepatocytes with two HBV strains of different subtypes (adr and ayw).

Arginine↗
PubMed1990

Hepatitis B viruses with precore region defects prevail in persistently infected hosts along with seroconversion to the antibody against e antigen.

The C gene of hepatitis B virus (HBV) codes for a nucleocapsid protein made of 183 amino acid residues and is preceded in phase by the precore (pre-C) region, encoding 29 residues. The pre-C-region product is required for the synthesis and secretion of hepatitis B e antigen (HBeAg), which is made of the C-terminal 10 amino acid residues of the pre-C-region product and the N-terminal 149 residues of the C-gene product. HBV mutants with pre-C-region defects prevailed in the circulation of three asymptomatic carriers as they seroconverted from HBeAg to the corresponding antibody (anti-HBe), and these mutants finally replaced nondefective HBV. HBV DNA clones were propagated from sera of an additional 15 carriers with anti-HBe and sequenced for the pre-C region. Essentially all HBV DNA clones (56 of 57 [98%]) revealed mutations that prohibited the translation of a functional pre-C-region product. A point mutation from G to A at nucleotide 83, converting Trp-28 (TGG) to a stop codon (TAG), was by far the commonest and was observed in HBV DNA clones from 16 (89%) of 18 carriers seropositive for anti-HBe. In addition, there were point mutations involving ATG codon to abort the translation initiation of the pre-C region, as well as deletion and insertion to induce frameshifts. Such mutations leading to pre-C-region defects were rarely observed in persistently infected individuals positive for HBeAg or in patients with type B acute hepatitis after they had seroconverted to anti-HBe. These results would indicate a selection of pre-C-defective mutants in persistently infected hosts, along with seroconversion to anti-HBe, by immune elimination of hepatocytes harboring nondefective HBV with the expression of HBeAg.

Amino Acid Sequence↗
PubMed1990

Detection of hepatitis C virus RNA by a two-stage polymerase chain reaction with two pairs of primers deduced from the 5'-noncoding region.

The 5'-noncoding region of hepatitis C virus (HCV) genomes is highly conserved. A two-stage polymerase chain reaction (PCR), involving two pairs of primers deduced from the 5'-noncoding region of the HCV genome, was developed for a sensitive and specific detection of HCV RNA. The first stage of PCR was performed for 35 cycles with primers capable of multiplying fragments of 221 base pairs. PCR products in samples negative for HCV RNA were subjected to the second stage of PCR for 30 cycles with primers located internal to those employed in the first stage of PCR. The two-stage PCR detected up to 10 chimpanzee infectious doses/ml of HCV, and HCV RNA in 11 (92%) of 12 sera from patients with chronic non-A, non-B hepatitis without detectable antibodies to HCV by a commercial assay kit. Primers from the 5'-noncoding region of the HCV genome would be suitable for detecting HCV RNA by PCR, since the other regions of the HCV genome diverge extensively in sequence because of its nature as an RNA virus.

Animals↗
PubMed1990

Enzyme-linked immunosorbent assay for antibodies against the capsid protein of hepatitis C virus with a synthetic oligopeptide.

An enzyme-linked immunosorbent assay was developed for the determination of antibodies against the putative capsid protein of hepatitis C virus (HCV). A 36-mer oligopeptide with a sequence of RRGPRLGVRATRKTSERSQPRGRRQPIPKVRRPEGR (CP9) was synthesized; it was selected on the translation product of the presumptive HCV core gene, because of a high local hydrophilicity and excellent conservation by different HCV strains. The synthetic peptide was immobilized on a solid-support to capture antibodies directed to CP9 (anti-CP9) in test sera, which were detected by Fab' fragments of monoclonal anti-human IgG/gamma labeled with horseradish peroxidase. The specificity of anti-CP9 was confirmed by absorption tests. Anti-CP9 was detected in 13 (68%) of 19 patients with sporadic acute non-A, non-B (NANB) hepatitis and in 15 (83%) of 18 patients with post-transfusion acute NANB hepatitis. In 7 cases of acute NANB hepatitis who were followed, anti-CP9 developed earlier than antibodies against HCV (anti-HCV) detectable by a commercial assay kit. Among patients with chronic NANB liver diseases, anti-CP9 was detected in 103 (77%) of 133 with chronic hepatitis, 70 (62%) of 113 with liver cirrhosis and 31 (76%) of 41 with hepatocellular carcinoma. Anti-CP9 and anti-HCV overlapped in 175 (54%) among 324 cases of acute or chronic NANB liver diseases; 58 (18%) were positive only for anti-CP9 while 49 (15%) were positive only for anti-HCV. HCV RNA was detected, by amplifying HCV cDNA with polymerase chain reaction, in 10 of 11 sera positive only for anti-CP9. Among sera from 606 blood donors, 21 were positive only for anti-CP9. HCV RNA was detected in 5 (24%) of them, all of which had A492 values greater than 0.600 in ELISA for anti-CP9. Based on these results, anti-CP9 would complement anti-HCV for the diagnosis of HCV infection and contribute toward further decreasing posttransfusion NANB hepatitis.

Amino Acid Sequence↗
PubMed1989

Combined hepatitis B immune globulin and vaccine for postexposure prophylaxis of accidental hepatitis B virus infection in hemodialysis staff members: comparison with immune globulin without vaccine in historical controls.

Twenty-three staff members serving in a hemodialysis unit were exposed accidentally to needlestick contaminated with blood containing hepatitis B surface antigen and hepatitis B e antigen, as well as high levels of DNA polymerase activity (greater than 100 cpm). They received hepatitis B vaccine (20 micrograms) simultaneously with hepatitis B immune globulin (5 ml, 200 IU per ml) within 48 hr after the exposure, and the vaccination was repeated at 1 and 3 months. The protective efficacy was compared with that in a past study in the same unit in which 33 members were given hepatitis B immune globulin alone within 48 hr after the exposure to blood with similarly high levels of DNA polymerase activity. No differences were noted in age or sex between the staff members who were vaccinated and those who were not, nor were there any differences between their inocula in the titers of hepatitis B virus markers. During 12 months after the accident, only one (4%) of the 23 vaccinated members contracted hepatitis B virus infection, at a frequency significantly lower than 11 (33%) of the 33 members who did not receive vaccine (p less than 0.02). These results indicate that hepatitis B vaccine, when given in combination with hepatitis B immune globulin, is efficacious for postexposure immunoprophylaxis of accidental infection.

Adult↗
PubMed1989

The loss of subtypic determinants in alleles, d/y or w/r, on hepatitis B surface antigen.

Hepatitis B surface antigen possesses the group-specific determinant called a and one or another member from each of two pairs of allelic determinants, d and y as well as w and r, thereby creating the four major subtypes, adw, adr, ayw and ayr. In the sequence of major surface antigen polypeptides made of 226 amino acid residues, lysine or arginine at amino acid position 122 specifies d or y determinant, and lysine or arginine at position 160 specifies w or r determinant, respectively. By means of site-directed mutagenesis and expression of mutant genes in cultured cells, the mechanism for the loss of subtypic determinants on surface antigens was investigated at the molecular level. A rare sample of surface antigen of subtype ad, devoid of w or r determinant, had asparagine at position 160. When it was converted to lysine, the surface antigen of subtype adw was obtained. Two samples of surface antigen were subtyped as ar. They lacked d determinant, despite having lysine at position 122 which usually specified it. They differed from all reported sequences of surface antigen in amino acid 144 or 145. They displayed d determinant when amino acid 144 was converted from glutamic acid to aspartic acid, or when amino acid 145 was changed from alanine to glycine. These results indicate that the key amino acid residue at position 122 or 160 is indispensable for the expression of subtypic determinants and that some distant residues are also crucially involved in conforming them.

Alleles↗
PubMed1989

Hepatitis B surface antigen with an excess or deficiency in subtypic determinants in sera from asymptomatic carriers in Japan.

Using the solid-phase enzyme immunoassay with monoclonal antibodies, hepatitis B surface antigen (HBsAg) was subtyped in sera from 5082 asymptomatic carriers who donated blood units at regional blood centers in Japan. Among them, 5004 sera contained HBsAg of a regular subtype, i.e., adw, adr, ayw or ayr, while 74 contained HBsAg with excessive subtypic determinants, such as adyw, adyr, adwr, aywr, or adywr. The presence of subtypic determinants on the selfsame particle was ascertained by sandwiching HBsAg between two monoclonal antibodies of distinct subtypic specificities. The remaining 4 sera contained HBsAg that possessed only one subtypic determinant, such as ad, ar or aw. HBsAg particles of atypical subtypes would have been given rise to by a point mutation in the S gene involving the codons regulating subtypic specificities.

Antibodies, Monoclonal↗
PubMed1989

[Infection by non-A, non-B acute viral hepatitis in hospital employees].

The aim of this study is to evaluate the risk of infection of non-A, non-B acute hepatitis (NANB-AH) in hospital employees. Among 593 patients with acute viral hepatitis (AVH), hospital employees were 3/147 (2%) in type A, 19/174 (11%) in type B and 21/272 (8%) in non-A, non-B (NANB). All 43 patients were medical staffs such as doctors, nurses and laboratory technicians. Out of 21 patients with NANB hepatitis of hospital employees, 7 were doctors, 14 nurses and 6 laboratory technicians. Eight of them had preceding accidental needlestick exposures. Out of 17,290 employees of our hospital during 18 years, 27 medical persons developed AVH. They were 2 hepatitis A, 10 hepatitis B and 15 hepatitis NANB. No non-medical staff developed AVH. Out of 15 NANB hepatitis patients, 7 had needlestick accidents 4 to 6 weeks before development of the illness, and all donor patients showed liver diseases. During 3 years (1985 to 1987), there were 116 needlestick accidents in our hospital which happened in medical staffs alone, and 50 of them were NANB hepatitis-related accidents. Three ml of human immune serum globulin (ISG) was administered intramuscurally just after accidents to 23 persons but not to 27 persons. NANB hepatitis were developed in 2 doctors who were not treated with ISG. In conclusion, NANB hepatitis occurred in hospital employees especially in medical staffs.

Accidents, Occupational↗
PubMed1987

A synthetic peptide coded for by the pre-S2 region of hepatitis B virus for adding immunogenicity to small spherical particles made of the product of the S gene.

Small spherical particles produced in the non-permissive phase of hepatitis B virus infection, when the viral genome is integrated into the chromosome of hosts, are rich in the product of the S gene, but poor in the product of the pre-S2 region. For the purpose of adding immunogenicity to spherical particles deficient in the pre-S2 region product, they were conjugated with a synthetic peptide of 19 amino acid residues. The peptide reproduced a hydrophilic area of the pre-S2 region product encoded by viral genomes of subtypes adr, ayw and ayr. The spherical particles supplemented with the pre-S2 peptide raised antibody to the pre-S2 region product in mice, in addition to antibody to the product of the S gene. Antibody to pre-S2 region product, prepared from sera of immunized mice by absorption with the S gene product, bound to spherical particles bearing pre-S2 region product, irrespective of adr, adw, ayw or ayr subtype, and agglutinated hepatitis B virions in immune electron microscopy. Based on the results obtained, the synthetic peptide may prove useful in adding protective efficacy to small spherical particles poor in pre-S2 region product.

Absorption↗
PubMed1987

Interaction between human albumin polymers and the envelope polypeptide of hepatitis B virus (P31) containing the translation product of the pre-S2 region.

Two preparations of human serum albumin (Cohn fraction V), when subjected to high-performance liquid chromatography, were found to contain albumin polymers with molecular sizes of 35 X 10(4) daltons or greater (breakthrough fraction), as well as tetramers, trimers and dimers. They bound to the envelope polypeptide of hepatitis B virus composed of translation products of the pre-S2 region and the S gene (P31), carrying the receptor for polymerized human serum albumin, with an activity increasing in parallel with the degree polymerization.

Genes↗
PubMed1986

Evolution of HBeAg/anti-HBe status and its relationship to clinical and histological outcome in chronic HBV carriers in childhood.

Fifty-five Japanese HBV carriers under 15 yr of age were followed for 12 months or longer, during which time we investigated the evolution of HBeAg/anti-HBe status and clinical and histological aspects of the liver disease. Of 45 cases positive for HBeAg at the initial examination, 34 remained positive for HBeAg during the follow-up periods, while the remaining 11 lost HBeAg and eight of these seroconverted to anti-HBe. At the final observation, HBeAg positivity in serum was found in as many as approximately 90% of the HBV carriers under 6 yr, but had fallen to 48% in carriers between 12 and 15 yr. The serum transaminase values in 11 cases who lost HBeAg were abnormally elevated for variable periods, but eventually returned to normal. In six of these 11 who had liver dysfunctions, liver biopsy was performed during the HBeAg positive phase or shortly after the disappearance of HBeAg. The histologies of liver were chronic persistent hepatitis in two cases and chronic active hepatitis in four. Repeat liver biopsies of two cases with chronic active hepatitis at the first examination showed nonspecific reactive hepatitis 2 and 4 yr after seroconversion or disappearance of HBeAg. These results indicate that HBeAg-positive HBV carriers with overt liver dysfunctions in childhood are prone to lose HBeAg or to seroconvert to anti-HBe, followed by a marked histological regression, and therefore that special antiviral therapy is probably unnecessary.

Adolescent↗