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Biomedical subjects

S Govindarajan

Publications and source records attributed to S Govindarajan.

At least 109 records · Page 6Linked to original sources
PubMed1990

Characterization of hepatitis delta antigen: specific binding to hepatitis delta virus RNA.

It has previously been shown that human hepatitis virus delta antigen has an RNA-binding activity (Chang et al., J. Virol. 62:2403-2410, 1988). In the present study, the specificity of such an RNA-protein interaction was demonstrated by expressing various domains of the delta antigen in Escherichia coli as TrpE fusion proteins and testing their RNA-binding activities in a Northwestern protein-RNA immunoblot assay and RNA gel mobility shift assay. Hepatitis delta virus (HDV) RNA bound specifically to the delta antigen in the presence of an excess amount of unrelated RNAs and a relatively high salt concentration. Both genome- and antigenome-sense HDV RNAs and at least two different regions of HDV genomic RNA bound to the delta antigen. Surprisingly, these two different regions of HDV genomic RNA could compete with each other for delta antigen binding, although they do not have common nucleotide sequences. In contrast, this binding could not be competed with by other viral or cellular RNA. Since both the genomic and antigenomic HDV RNAs had strong intramolecular complementary sequences, these results suggest that the binding of delta antigen is probably specific for a secondary structure unique to the HDV RNA. By expressing different subdomains of the delta antigen, we found that the middle one-third of delta antigen was responsible for binding HDV RNA. Neither the N-terminal nor the C-terminal domain bound HDV RNA. Binding between the delta antigen and HDV RNA was also demonstrated within the HDV particles isolated from the plasma of a human delta hepatitis patient. This in vivo binding resisted treatment with 0.1% sodium dodecyl sulfate and 0.5% Nonidet P-40. In addition, we showed that the antiserum from a human patient with delta hepatitis reacted with all three subdomains of the delta antigen, indicating that all of the domains are immunogenic in vivo. These studies demonstrated the specific interaction between delta antigen and HDV RNA.

Amino Acid Sequence↗
PubMed1990

Study of preneoplastic changes of liver cells by immunohistochemical and molecular hybridization techniques.

The status of hepatitis B virus DNA was investigated by in situ hybridization in multifocal areas of a noncancerous hepatitis B virus-associated cirrhosis. This liver exhibited a marked degree of dysplasia and adenomatous hyperplasia. The results of these studies were correlated with the histopathology and immunohistochemical stains for hepatitis B core and surface antigens. There was clear evidence of a marked reduction to absence of hepatitis B viral DNA by in situ hybridization and absence of HBc and HBsAg in the foci of liver cell dysplasia and adenomatous hyperplasia. These results support the hypothesis that liver cell dysplasia and adenomatous hyperplasia are preneoplastic in nature.

DNA, Viral↗
PubMed1989

Correlation of IgM anti-hepatitis D virus (HDV) to HDV RNA in sera of chronic HDV.

One hundred forty-four serum samples from 52 patients with chronic hepatitis D virus infection were analyzed for hepatitis D virus RNA by dot-blot hybridization using hepatitis D virus cDNA probe labeled with 32P. The results were correlated with the presence of serum IgM anti-hepatitis D virus and hepatitis D antigen in liver biopsy specimens when available. Although there was a trend of positive correlation between serum hepatitis D virus RNA and IgM anti-hepatitis D virus, no statistical significance could be found. In the serum samples with hepatitis D virus RNA, 32% were found to be negative for IgM anti-hepatitis D virus. Therefore, in chronic hepatitis D virus, absence of IgM anti-hepatitis D virus does not rule out active viral infection, as suggested by previous studies. There was a strong correlation between serum hepatitis D virus RNA and hepatic hepatitis D virus antigen. These data indicate that detection of hepatitis D virus RNA in serum samples is a reliable noninvasive marker of active viral infection.

Antibodies, Viral↗
PubMed1989

Blood group antigens in the intrahepatic biliary tree. II. Type 1 chain N-acetyllactosamine-related carbohydrate antigens in the proliferated bile ductules.

The expression of the carbohydrate antigens related to type 1 chain N-acetyllactosamine (1NAcLc) in the proliferated bile ductules was immunohistochemically examined in liver tissues of 10 cases of chronic hepatitis (CH), 9 of liver cirrhosis (LC) and 8 of alcoholic hepatitis. The ductular expression of the examined blood group antigens was essentially the same among these pathological conditions. The backbone structure, i.e., 1NAcLc (Gal beta 1----3GlcNAc beta 1----3Gal beta 1----3R), was not detected in the proliferated ductules as in the normal bile ductules. Its fucosylated structures (Le(a), Le(b) and type 1 chain H) were more strongly expressed in the proliferated ductules than in the normal ductules. Sialyl-Le(a) which was not found in the normal ductules was detected weakly but definitely in the proliferated ductules. Besides proliferated ductules, single or small numbers of epithelial cells expressing the 1NAcLc-related antigens were found intralobularly. This suggests possible migration of biliary epithelial cells into the hepatic lobules. In conclusion, within the proliferated bile ductules (a) synthesis of the 1NAcLc-related antigens is increased compared to the normal ductules, (b) the backbone structure is completely sialylated or fucosylated as in the normal ductules and (c) alpha 1----4fucosylation of sialyl-1NAcLc, i.e., sialyl-Lea, formation occurs despite its absence in the normal ductules.

Adolescent↗
PubMed1989

Study of reactivation of chronic hepatitis delta infection.

Five patients with chronic hepatitis delta virus (HDV) infection suffered spontaneous episodes of liver enzyme elevation on a background of otherwise biochemically stable liver disease. In all five patients these episodes were accompanied by a rise in serum levels of anti-HDV IgM, HDV antigen and HDV RNA. These episodes of increased HDV replication accompanied by biochemical evidence of liver injury are reminiscent of reactivation in chronic hepatitis B. Surges of increased HDV replication may be important in the progression of liver disease in chronic HDV infection.

Adult↗
PubMed1989

Detection of hepatitis delta virus in serum and liver tissue by molecular hybridization. Validation of a rapid spot-hybridization technique.

Serologic tests for detection of delta hepatitis virus (HDV) antigen and antibody have recently been supplemented with a Northern blot hybridization assay for HDV RNA. However, this technique is cumbersome for analysis of multiple samples. In order to simplify detection of HDV RNA, the authors have tested a spot-hybridization method with a new HDV cDNA probe. Their method has proved to be rapid, sensitive, and specific for HDV RNA even when less ultracentrifugation was used for recovering serum RNA. Results for HDV RNA were concordant by both spot and Northern blot hybridization in 12 serum samples from patients with known delta hepatitis, whereas in seven cases spot-hybridization was superior in detecting liver HDV RNA. The concordance between HDV RNA by spot hybridization and delta antigen was complete, whereas that between delta IgM (44% overall) or IgG (67% overall) was less strong. The authors' observations indicate that this new technology permits detection of HDV RNA with relative ease and could be applicable to the evaluation of large numbers of cases with delta hepatitis.

Animals↗
PubMed1989

Alpha-fetoprotein and its concanavalin A affinity in acute exacerbation of chronic hepatitis B.

Serum samples from 20 patients with acute exacerbation of chronic hepatitis due to hepatitis B virus and 20 patients with hepatocellular carcinoma arising from B viral cirrhosis with elevated levels of alpha-fetoprotein (AFP) were analyzed by affinity column chromatography for concanavalin A binding. Serum AFP was tested at regular intervals in all of these patients. Acute exacerbation was defined as elevation of serum transaminase greater than 300 IU/L in patients with chronic hepatitis B. In hepatocellular carcinoma, serum AFP levels fluctuated but remained higher than 92 ng/ml, whereas, in acute exacerbation of chronic hepatitis B, serum AFP levels returned to normal within 3-12 months of follow-up. The results of concanavalin A-binding assay revealed that AFP from both these groups had a high affinity for concanavalin A, and this assay could not be used to discriminate between the two conditions.

Adult↗
PubMed1988

Permanent HBsAg clearance in chronic hepatitis B viral infection following acute delta superinfection.

Three patients are described with chronic hepatitis B virus infection for three to six years before hepatitis delta virus superinfection occurred. Liver biopsy performed in two patients prior to their delta illness revealed chronic persistent hepatitis and chronic active hepatitis, respectively. Within one to seven months of the acute delta event, all three patients lost their circulating hepatitis B surface antigen. Subsequently, delta antibody also cleared. Clinical well-being and normal transaminases were documented over 10-44 months of follow-up. Although most cases of delta infection in chronic hepatitis B result in severe or progressive disease, a small number of patients may develop clearance of the HBsAg with clearance of both B and delta infections.

Adult↗
PubMed1988

Clonal origin of hepatitis B virus-associated hepatocellular carcinoma.

The clonal origin of tumors was studied in two multifocal hepatocellular carcinomas arising from hepatitis B viral cirrhosis. DNA extracted from several tumor nodules was analyzed for the presence of hepatitis B virus genome by the Southern blot technique. Unique clonal integration of the viral DNA sequences occurred in both cases. In each case, identical integration bands occurred among multiple nodules of liver tumor. These results are strong evidence of a unicentric origin of these tumors, although the tumors' gross appearance is suggestive of multifocal origin.

Carcinoma, Hepatocellular↗
PubMed1988

Markers of viral replication in patients with chronic hepatitis B virus infection.

Serum samples from 56 patients with biopsy-proven chronic B viral hepatitis without superimposed delta hepatitis were analyzed for the various markers of viral replication, including serum hepatitis B e Ag (HBeAg), hepatitis B virus deoxyribonucleic acid (HBV-DNA), and hepatitis B core antigen (HBcAg) in the liver tissues. Twenty-seven patients had persistent viral hepatitis (PH) and 29 patients had chronic active hepatitis (CAH) with or without cirrhosis. HBV-DNA was identified in the sera of 81% of patients with PH and 60% of patients with CAH. Significantly higher levels of HBV-DNA were found in patients with PH than in those with CAH. Both HBeAg in serum and HBcAg in liver correlated positively with serum HBV-DNA. Nine patients had serum HBV-DNA in the absence of HBeAg (four had anti-HBe), and seven of these nine patients had stainable HBcAg in the liver (two did not have staining). None of these patients had hepatic HBcAg in the absence of serum HBV-DNA. When these patients were stratified according to their epidemiologic background, serum HBV-DNA was present in a significantly higher number of male homosexuals than in any other groups. This was unrelated to their status of human immunodeficiency viral serology.

Chronic Disease↗
PubMed1988

Experience with human immunodeficiency virus infection in patients with hepatitis B virus and hepatitis delta virus infections in Los Angeles, 1977-1985.

Stored serum specimens from 723 patients with acute hepatitis B and 228 patients with chronic hepatitis B seen between 1977 and 1985 in the Hepatitis Clinic of the Los Angeles County-University of Southern California Medical Center, Los Angeles, CA, were tested for antibody to human immunodeficiency virus (anti-HIV). Risk factors were ordered hierarchically; cases with multiple risk factors were tabulated only in the risk group listed first on the clinic records. Anti-HIV was first detected in 1979, and by 1983 was found in about half of all homosexual men with chronic hepatitis B. The prevalence was significantly lower in patients with acute hepatitis B than in patients with chronic hepatitis B, and in nonhomosexual subjects compared with homosexual subjects. By 1985, 30 per cent of intravenous drug users with chronic hepatitis B were anti-HIV-positive. The highest annual seroconversion rate for anti-HIV, 21 per cent, was found in homosexual men in 1983. A significant association existed between anti-HIV positivity and hepatitis delta virus infection in homosexual men but not in drug abusers. This study provides data on the natural history of the human immunodeficiency virus epidemic in Los Angeles. Further study on the interaction of these different viruses is warranted.

Acute Disease↗
PubMed1988

Intrahepatic periductal glands in graft-versus-host disease.

Degenerative epithelial changes with cytoplasmic eosinophilia and nuclear pleomorphism were found in the intrahepatic periductal glands in two patients who died following allogeneic bone marrow transplantation. These changes, which have not been described in the literature to our knowledge, were closely associated with clinicopathologic signs of graft-versus-host disease (GVHD), and histologically they resembled small bile ductal lesions, a characteristic finding of hepatic GVHD. In addition, periductal glandular and small bile ductal lesions frequently coexisted. Neither livers from patients given autologous marrow transplantation nor other control livers including those from patients given abdominal irradiation revealed such glandular lesions. These results suggest that the observed changes in the intrahepatic periductal glands were a manifestation of GVHD.

Adult↗
PubMed1988

A single antigenomic open reading frame of the hepatitis delta virus encodes the epitope(s) of both hepatitis delta antigen polypeptides p24 delta and p27 delta.

On the basis of the complete nucleotide sequence of the single-stranded, covalently closed circular hepatitis delta virus RNA genome (K.-S. Wang, Q.-L. Choo, A. J. Weiner, J.-H. Ou, R. C. Najarian, R. M. Thayer, G. T. Mullenbach, K. J. Denniston, J. L. Gerin, and M. Houghton, Nature [London] 323:508-514, 1986 [Author's correction, 328:456, 1987]), five long open reading frames (ORFs) encoding polypeptides containing a methionine proximal to the amino terminus were expressed in bacteria. Only polypeptides encoded by the antigenomic ORF5 cross-reacted with antisera obtained from patients with hepatitis delta virus infections. Immunological analysis of viral extracts and the recombinant ORF5 polypeptides synthesized in bacteria and yeast cells revealed that ORF5 encodes the immunogenic epitope(s) shared by both hepatitis delta viral polypeptides p27 delta and p24 delta and probably represents the complete structural gene for p27 delta and p24 delta. We also present evidence that ORF5 encodes the hepatitis delta antigen, an antigen originally found in the nuclei of hepatocytes of infected individuals (M. Rizzetto, M. G. Canese, S. Arico, O. Crivelli, F. Bonino, C. G. Trepo, and G. Verme, Gut 18:997-1003, 1977). A comparison of the primary structure of the predicted hepatitis delta antigen polypeptides with that of the core antigen of the hepatitis B virus shows that these polypeptides are very dissimilar.

Amino Acid Sequence↗
PubMed1988

Human hepatitis delta antigen is a nuclear phosphoprotein with RNA-binding activity.

The genetic origin, structure, and biochemical properties of the delta antigen (HDAg) of a human hepatitis delta virus (HDV) were investigated. A cDNA fragment containing the open reading frame encoding the HDAg was transcribed into RNA and used for in vitro translation in rabbit reticulocyte lysates. The HDAg open reading frame was also inserted into an expression vector containing a simian virus 40 T-antigen promoter and expressed into COS 7 cells. In both systems, a protein species of 26 kilodaltons was synthesized from this open reading frame and could be specifically immunoprecipitated with antisera obtained from patients with delta hepatitis. A similar protein was also synthesized from antigenomic-sense monomeric HDV RNA in both systems, although the efficiency of translation was lower than that of the isolated open reading frame. This protein was found to be phosphorylated at the serine residues. Immunoperoxidase studies with anti-HDV sera demonstrated that the HDAg was expressed mainly in the nuclei of the transfected COS 7 cells. Moreover, the HDAg was shown to bind the genomic RNA of HDV. These studies indicate that HDAg is encoded by the antigenomic-sense RNA of HDV and is a nuclear phosphoprotein associated with an RNA-binding activity.

Animals↗
PubMed1988

Hepatic inflammation, hepatitis B replication, and cellular immune function in homosexual males with chronic hepatitis B and antibody to human immunodeficiency virus.

We measured serum aspartate transaminase (AST) concentration and serum hepatitis B virus (HBV) DNA concentration in homosexual men with chronic HBV infection and a spectrum of immune deficiency as a result of exposure to human immunodeficiency virus (HIV). Serum AST and HBV DNA concentrations were similar in patients with varying immune function as indicated by in vivo criteria (diagnosis and skin tests reactivity) and in vitro criteria (lymphocyte transformation responses to mitogens and Candida and tetanus antigens) and were unrelated to the number of circulating T cells, suppressor/cytotoxic cells, helper cells, natural killer cells, and the helper:suppressor ratio. Serum AST concentration and indices of cellular immune function were similar in patients with varying HBV replicative activity (high and low HBV DNA concentrations). The observed lack of relationship between serum AST concentration and indices of cellular immune function and HBV replication suggests either that other factors determine the severity of hepatic inflammation in chronic HBV infection, or that currently available tests of cellular immune function and HBV replicative activity do not accurately reflect processes in the liver.

Adult↗