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Biomedical subjects

S K Panda

Publications and source records attributed to S K Panda.

At least 55 records · Page 3Linked to original sources
PubMed1994

Etiological role of hepatitis E virus in sporadic fulminant hepatitis.

Non-A, non-B hepatitis viruses have been implicated as the etiological agent(s) in up to 60% of patients with fulminant hepatitis. These agents are reported to induce a higher mortality than other causes of fulminant hepatitis. Hepatitis E virus (HEV) and hepatitis C virus (HCV) at present constitute the major identifiable non-A, non-B hepatitis agents. Of these, HEV has been established as the sole cause of epidemic hepatitis in Afro-Asian countries, and fulminant hepatitis has been recorded during such epidemics. However, in sporadic cases, the etiological role of HEV in fulminant hepatitis has remained uncertain. The role of HCV in acute liver disease and fulminant hepatitis remains unclear. The present study was undertaken to investigate the association of HEV and HCV in patients with fulminant hepatitis by direct detection of the viral genome using reverse transcription-polymerase chain reaction (RT-PCR). Serum samples from 50 serologically identified non-A, non-B fulminant hepatitis cases negative for cryptic hepatitis B virus (HBV) infection examined via PCR were tested for HEV and HCV RNA using RT-PCR. For HEV primers from the nonstructural region (ORF-1) were used, and for HCV primers from the highly conserved 5' untranslated regions were used. The products were analysed using agarose gel electrophoresis and confirmed by hybridisation with radiolabelled internal oligonucleotide probes. HEV was detected in 31 (62%) of the 50 fulminant non-A, non-B hepatitis cases. In 18 (36%) cases, HCV RNA was detected. In 11 (22%) of the HCV cases, the HEV genome was also amplified. In 20 (40%) cases, HEV was detected alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Detection of the negative strand of hepatitis E virus RNA in the livers of experimentally infected rhesus monkeys: evidence for viral replication.

Hepatitis E virus (HEV), the causative agent of enteric non-A, non-B hepatitis, is a positive-stranded RNA virus. Because of the virus's inability to grow in culture, several nonhuman primates have been used for the propagation of HEV. Using strand-specific reverse transcription-polymerase chain reaction (RT-PCR), we demonstrate the presence of negative-stranded HEV RNA replicative intermediates in the livers of infected animals. This constitutes the first direct evidence of HEV replication in the liver of the infected animals and reinforces the validity of such a model to study HEV infection, disease pathogenesis, and immunity.

Animals↗
PubMed1994

Diagnosis of hepatitis C virus-associated chronic liver disease in India: comparison of HCV antibody assay with a polymerase chain reaction for the 5' noncoding region.

The relative value of an anti-hepatitis C virus (HCV) serological assay and reverse transcriptase-nested polymerase chain reaction assays (RT-PCR) were investigated for the constant 5' putative noncoding region of HCV for the diagnosis of HCV-associated chronic liver diseases in India. One hundred fifteen patients with biopsy proven chronic active hepatitis and 140 cases of cirrhosis of the liver were investigated for anti-HCV antibody using a second generation commercial enzyme-linked immunosorbent assay (ELISA). A proportion of these patients: 42 with chronic hepatitis and 27 with cirrhosis of the liver were analysed further for HCV RNA in the serum using RT-nested PCR assay. Thirty-three (12.9%) of the 255 patients were positive for anti-HCV antibody and 23 of 69 (33.3%) patients were positive for HCV RNA in serum. Fifteen of the 33 (45.5%) anti-HCV positive patients had HCV RNA in the serum. Eight of 36 (22.2%) HCV seronegative patients tested were found with HCV RNA. This indicates that the diagnosis of HCV infection is not possible if it is based solely on the available serodiagnostic tests. Inclusion of both assays improved the diagnostic efficiency, 18.8% (13/69) were negative for all virological markers associated with HBV and HCV infection. Since a majority of the chronic liver disease patients (143/255 [56%]) were seronegative for either HBV or HCV infection, it is significant that HCV RNA was detected in 38% (8/21) of a randomly selected group from these patients. The antibody assay and PCR were compared using interclass correlation (kappa statistics).(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1994

Mapping of the hepatitis B virus genome in hepatocellular carcinoma using PCR and demonstration of a potential trans-activator encoded by the frequently detected fragment.

The association of hepatitis B virus (HBV) infection with hepatocellular carcinoma (HCC) is well established. Insertional mutagenesis, trans-activation by truncated X or preS2/S regions and activation of growth regulatory genes or oncogenes have all been suggested as possible mechanisms for this carcinogenesis. However, no consensus regarding the mechanism or region of the HBV genome involved has been established. Of the 36 HCC tissues analysed for the presence and extent of the HBV genome, using multiple overlapping PCR, 22 (61%) were found to be positive. Twenty of these showed the presence of a fragment (nucleotides 636 to 746) that covered part of the surface antigen gene. The recognized trans-activators, X and preS2/S, were present in only seven (31.8%) and 12 (54.5%) cases, respectively. In two cases the entire viral genome was detected. The trans-activation potential of the cloned S fragment (nucleotides 426 to 851) covering the frequently detected fragment (nucleotides 636 to 746) was investigated in cotransfection experiments. This fragment was able to trans-activate the HBV enhancer-X promoter target. To define the specificity of the trans-activation and the sequences involved, frameshift and deletion mutants of this fragment were constructed and analysed. The trans-activation activity was lost in the frameshift mutants. The deletion mutants that retained nucleotide sequences 436 to 679 showed trans-activation activity whereas the other ones (nucleotide sequences 436 to 611) did not show any activity. It is suggested that the frequently detected HBV genome fragment belonging to the S gene frame has a trans-activation potential. This may explain the mechanism for pathogenicity of HBV-associated HCC.

Base Sequence↗
PubMed1994

Development & use of antichlamydial monoclonal antibodies for rapid diagnosis of follicular conjunctivitis.

We developed four independent murine hybrid clones producing IgG class and genus specific monoclonal antibodies against the major outer membrane protein (MOMP) of Chlamydia trachomatis, L2 serovar. All antibodies reacted with a single epitope of MOMP. In indirect immunofluorescence assay using one of the antibodies chlamydiae could be detected in 12 of 23 conjunctival scrapings from patients of follicular conjunctivitis. Giemsa staining could detect classical inclusion bodies in only 5 of these 23 smears. Antigen detection using these monoclonal antibodies may be used as a rapid diagnostic test in clinical and epidemiological screening for chlamydial infection.

Animals↗
PubMed1993

Evaluation of Phyllanthus amarus and Phyllanthus maderaspatensis as agents for postexposure prophylaxis in neonatal duck hepatitis B virus infection.

The therapeutic potential of plant extracts of Phyllanthus amarus and Phyllanthus maderas patensis for postexposure prophylaxis against infection by Hepadnaviruses was studied in ducklings infected by the duck hepatitis B virus (DHBV). Forty-four Pekin ducklings were inoculated intraperitoneally with DHBV at 24 hr post-hatch. They were treated by intraperitoneal injection of Phyllanthus amarus (aqueous extract) (100 mg/kg body weight) or Phyllanthus mad eraspatensis (alcoholic extract) (100 mg/kg body weight) for a period of 4 weeks. Infected ducklings treated with saline served as controls. Weekly serum samples obtained before, during, and after treatment were analysed for the presence of DHBV DNA in serum by dot blot hybridisation using alpha 32P-labelled probes. Liver tissue was collected after killing the ducks at various time intervals and was studied for replicative status of the viral DNA and liver histopathology; 17 of 21 ducks were viraemic on completion of treatment with Phyllanthus amarus. At 16 week posttreatment follow-up four of seven animals remained viraemic. Similar results were obtained with Phyllanthus maderaspatensis. There was no alteration in DHBV replication in the liver. No toxicity was observed with this treatment. These observations suggest that Phyllanthus amarus and Phyllanthus maderaspatensis are not useful as therapeutic agents for postexposure prophylaxis against DHBV infection.

Animals↗
PubMed1993

Evaluation of anti-hepadnavirus activity of Phyllanthus amarus and Phyllanthus maderaspatensis in duck hepatitis B virus carrier Pekin ducks.

Extracts of the two traditional Indian herbs, Phyllanthus amarus (P. amarus) and Phyllanthus maderaspatensis (P. maderaspatensis), described by others as useful in the treatment of chronic hepatitis B virus infection were studied for antiviral properties on duck hepatitis B virus infection. One hundred and fourteen ducks infected posthatch with the duck hepatitis B virus (DHBV) were divided into groups at three months of age and treated intraperitoneally with the aqueous, butanol, and alcoholic extracts of these two plants at doses of 25, 50, or 200 mg/kg body weight. Saline-treated animals served as controls. In the ducks negative for DHBV in serum after treatment, we observed replicative intermediates in the liver. There was no definite antiviral property observed in the treated ducks.

Animals↗
PubMed1993

A self-associating hepatitis B surface antigen-derived peptide that is immunogenic in alum.

We previously described an oligomeric synthetic peptide derived from the hepatitis B surface antigen that displayed a limited tendency to form self-associating macromolecular structures in solution. Here it is demonstrated that amino-terminal myristylation of this peptide results in near quantitative aggregation of the oligomeric peptide. The myristylated peptide is highly immunogenic when used in conjunction with alum as adjuvant in both the rabbit and rhesus monkey models. The antibody response generated by peptide also cross-reacted with native antigen and was long-lasting. Collectively the results described in this and previous reports offer an attractive new approach for generating immunogenic peptide mimetics of conformational epitopes that may find application as vaccines.

Alum Compounds↗
PubMed1993

Human T-helper cell responses to a synthetic peptide derived from the hepatitis B surface antigen.

Hepatitis B virus surface antigen peptide OS (aa124-147) self oligomerizes to form conformational B-cell immunogen with several properties of a candidate peptide vaccine. It gives a T-cell blastogenic response in vaccinated as well as naturally infected individuals. To study the nature and localization of the T-helper cell epitopes, the T-lymphocyte proliferative responses in humans exposed to hepatitis B surface antigen (HBsAg) were examined with a synthetic peptide representing residues 124-147 of this antigen [peptide OS (aa24-147)]. Positive responses were obtained in most cases regardless of whether HBsAg exposure was due to vaccination or a hepatitis B viral infection. Epitope localization studies with truncated peptides indicated the presence of more than two HBsAg-relevant T-helper cell epitopes. This was also corroborated by our fine mapping studies which revealed that the amino acid residues crucial for eventual T-helper cell activation were diverse amongst the various individuals. Together these studies suggest that immunization with peptide OS (aa124-147) may result in an HBsAg cross-reactive T-helper cell response in a broad spectrum of the human population.

Amino Acid Sequence↗
PubMed1993

Gingival fibromatosis: study of three generations with consanguinity.

Familial gingival fibromatosis affecting six members among three generations of an Islamic family is reported. Clinical findings are reported and the inheritance pattern is discussed. Histopathologic examination of the excised tissue revealed mainly fibroblasts with prominent, rough-surfaced endoplasmic reticulum. Cells with vesicular nuclei, resembling mast cells, were also observed.

Adolescent↗
PubMed1992

Identification of a new group-specific determinant on hepatitis B surface antigen with a synthetic peptide.

In a recent study we demonstrated that a synthetic peptide representing residues 124-147 of the major protein of hepatitis B surface Ag (HBsAg) undergoes spontaneous oligomerization to reconstruct one or more conformational group-specific determinants on HBsAg. The present study was undertaken to identify and characterize the HBsAg-related antigenic determinants on this oligomeric peptide (peptide OS[124-147]). A panel of nine analogs of this peptide was generated by either deleting, substituting, or chemical side chain modification of specific amino acid residues. With HBsAg subtype-specific antisera a single "a" epitope was identified as one that includes Met133 and Lys141. In addition a "d" epitope toward the amino-terminal end of the sequence was also observed. Perturbation of certain amino acid residues was found to enhance a antigenicity and subsequent experiments indicated that maximal expression of this a antigenicity is dependent in part on accessibility of the Lys141 side chain and in part on the primary sequence. With a total of 50 human anti-HBsAg serum samples obtained from individuals vaccinated against hepatitis B, it was demonstrated that these sera recognize the Met133-Lys141-dependent a epitope as the dominant, and in many cases the only, determinant on peptide OS[124-147]. Finally, on immunization, peptide OS[124-147] elicits an anti-HBsAg response that is predominantly anti-a though a lesser contribution from an anti-d response was also obtained.

Amino Acid Sequence↗
PubMed1992

A synthetic peptide spontaneously self-assembles to reconstruct a group-specific, conformational determinant of hepatitis B surface antigen.

A cysteine-rich peptide of sequence 124 to 147 of the major protein of hepatitis B surface Ag (HBsAg) was synthesized. On cleavage and subsequent work-up it was found that all of the cysteine sulfhydryl groups had spontaneously formed disulfide bonds to yield a heterogenous mixture of multiple forms with molecular masses ranging from 8 to 35 kDa (peptide OS[124-147]). In a direct ELISA peptide OS[124-147] showed a high degree of cross-reactivity with polyclonal anti-HBsAg antiserum whereas the HBsAg-related antigenicity of its disulfide-reduced analogs was insignificant. Peptide OS[124-147] was also recognized by all 15 of the anti-HBsAg-positive human sera tested. Further studies revealed that peptide OS[124-147] represents the conformational, disulfide-dependent "a" determinant of HBsAg and elicits antibodies that cross-react with a variety of HBsAg subtypes. Anti-peptide antibodies bound to the corresponding native epitope with an apparent affinity higher than that of homologous antisera. Finally, polyclonal anti-OS[124-147] antibodies could also immunoprecipitate purified Dane particles in solution. Together these studies indicate that peptide OS[124-147] represents an excellent candidate component of a peptide-based vaccine for hepatitis B.

Amino Acid Sequence↗
PubMed1992

Design and synthesis of a self-assembling peptide derived from the envelope proteins of HIV type 1. An approach to heterovalent immunogens.

A chimeric peptide that included sequences from gp120 and gp41 of HIV type 1 was synthesized. Cleavage from solid support yielded a composite of self-oligomerized products with molecular masses ranging from 5 to about 9 kDa. The oligomer but not its reduced, monomeric form was recognized by human anti-HIV sera and at least one of the two lysines in the sequence was involved in antibody binding. The oligomeric peptide was immunogenic, yielding a conformation-specific antibody response. Co-oligomerization of a hepatitis B surface Ag-derived peptide and the HIV type 1-derived peptide yielded a bivalent product in which conformational integrity of the individual components was maintained. Immunization with this hybrid peptide resulted in conformation-specific antibodies to both epitopes in all four murine strains tested. Lymphocyte proliferation assays revealed that the T epitopes resident in both peptide sequences remained active in the hybrid peptide. These results demonstrate the potential of this approach in generating multi- and heterovalent immunogens which may eventually find application as vaccines.

Amino Acid Sequence↗
PubMed1992

Receptor for pre-S1(21-47) component of hepatitis B virus on the liver cell: role in virus cell interaction.

Attachment of hepatitis B virus to a hepatoblastoma cell line (HepG2) was examined using a synthetic peptide corresponding to the pre-S1 (21-47) region of the envelope protein. Scatchard analysis revealed a single class binding site of Kd 104 +/- 27 nM/l and 5.4 +/- 1.2 x 10(5) sites per cell. Competition of HBV with pre-S1 peptides was dose dependent, and demonstrated it as the dominant binding site. In view of the suggested sequence homology between the peptide and IgA, cross-competition studies were carried out. The results indicate no direct role of IgA receptor in HBV binding. The receptor for the pre-S1 peptide was identified as a single major peptide of molecular weight 31 kD using in-situ ligand receptor crosslinking.

Amino Acid Sequence↗