Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To obtain good antigenicity and high purity of the hepatitis B virus core antigen (HBcAg) in large quantities without using the fused protein technique employed in recombinant DNA technology, a protein molecule with the same primary sequence as that of wild-type HBcAg (subtype adr) was directly expressed in Escherichia coli JM109 (DE3) using pGd1 expression vector. Purification of the expressed HBcAg yielded high-quality protein by means of simple purification steps, such as sonication, ammonium sulphate precipitation and heat treatment, before final purification by conventional ultra-centrifugation. The HBcAg preparation thus obtained contains small round particles similar in appearance to the HBcAg particles from the HBV-infected human liver tissue.
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PMID:Simple method for efficient production of hepatitis B virus core antigen in Escherichia coli. 927 81

DNA immunization offers a novel means to induce humoral and cellular immunity in inbred or in outbred animals. Here we have tested the efficiency of genetic immunization with hepatitis B virus (HBV) envelope-based vectors. In naive primates, injection of a plasmid DNA encoding HBV envelope proteins induced an HBV-specific cytotoxic response and appearance of potentially protective anti-HBs antibodies. Moreover, intramuscular and intradermal injections of a DNA expression vector encoding an epitope of the human immunodeficiency virus envelope fused to the surface protein of the hepatitis B virus (HBsAg) induced strong humoral and cytotoxic responses to antigenic determinants of both viruses in mice and nonhuman primates alike. In addition, in protein-primed Rhesus monkeys B-cell memory was successfully boosted by DNA injection of hybrid vectors and animals subsequently developed a multispecific cellular response. This suggests that DNA-based immunization could be used to boost efficiently and broaden the immune response in individuals immunized with conventional vaccines, regardless of their genetic variability. These results also indicate that it might be possible to rationally design HBsAg-based expression vectors to induce multispecific immune responses for vaccination against hepatitis B and other pathogens.
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PMID:In vivo induction of specific cytotoxic T lymphocytes in mice and rhesus macaques immunized with DNA vector encoding an HIV epitope fused with hepatitis B surface antigen. 945 4

Balb/c mice were immunized with aluminium hydroxide [alum, Al (OH)3]-adjuvanted hepatitis B (HB) vaccines of subtypes adr, ayw or adw. Spleen cells from the immune animals were fused with SP2/O cells. Eight hybridoma clones producing antibodies specific for HB surface antigen (HBsAg) were selected. Monoclonal antibodies (mAbs) of four clones were specific for group-specific antigen/a, and the other of four clones were specific for subtype antigen/d, y, r, or w. The anti-HBs/a mAbs were classified into three non-competitive groups. Quantitation of group-specific determinant a of HBsAg (HBsAg/a) was performed by sandwich enzyme-linked immunosorbent assay (ELISA), in which a solid phase of anti-HBs guinea-pig polyclonal antibodies (pAb), the HBsAg for testing, anti-HBs/a mouse mAb and horseradish peroxidase (HRP)-conjugated anti-mouse IgG were used. The unadsorbed HBsAg was used to establish the standard curve of HBsAg/a. The lower detection limits were 0.5 to 1 ng/ml of HBsAg. Methods of solubilization of alum were investigated to quantify HBsAg/a in adsorbed HB vaccines. The recovery rate was more than 60% if vaccines were prediluted. The recovery of HBsAg/a in HB vaccines produced by the same manufacturer showed the similar recovery rate, and the contents of HBsAg/a in adsorbed HB vaccines could be estimated by the recovery rate determined for adsorbed HB vaccines.
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PMID:Quantitation of group-specific a antigen in hepatitis B vaccines by anti-HBs/a monoclonal antibody. 946 33

After the first in vitro cultivation of Plasmodium falciparum 21 years ago, the prospect of anti-malarial vaccination arose many hopes, but, in the end, it so far has mainly given rise to doubts and disappointments. Technically, the problem is particularly difficult. Plasmodium falciparum has a very complex antigenic structure with several hundreds, if not several thousands, of different epitopes for each of the four main evolutive stages of the parasite (sporozoites, merozoites, gametocytes, ookinetes) which correspond to different phase of the infection and could be a target for vaccination. Many of these epitopes are stage-specific and some of them vary from one strain to another. Adjuvants also play a major role and can qualitatively modify the type of immune response. The immune mechanisms also differ according to the final goal: anti-Plasmodium infection or anti-disease vaccine. Over the last few years, the first clinical assays have been carried out with the Spf66 vaccine, a synthetic complex protein directed against sporozoites and merozoites. In adults and children, the first results in South America and in East Africa were modest but encouraging. Unfortunately they were not confirmed by further studies in West Africa and South-East Asia. Two new types of vaccines are under preliminary clinical evaluation. One is directed against ookinetes of Plasmodium falciparum (Pfs25 and Pfs28) and can stop the transmission from the mosquito. The other is an anti-sporozoite vaccine with a new immunogen (RTS,S) in which the circumsporozoite protein is fused to the hepatitis B surface antigen and can protect against infestation. New prospects and improvements are offered by the technique of DNA vaccines and will probably also result from better knowledge of cellular and molecular biology of the parasite which is being extensively studied (genomic structure). If new promising perspectives exist, it is particularly important to be careful to avoid such disappointments as those caused, in the past, by a too-optimistic and over-publicized presentation of some preliminary results. It is now certain that one or several malaria-vaccines will be available, but no one can seriously say when, for whom and how. In any case, it is unrealistic to hope that vaccine(s) alone will be able to eradicate such an epidemiologically complex disease as malaria. It is probable that only the coordinated use of all the techniques available (anti-vectorial protection and fight, chemoprophylaxis and chemotherapy, vaccination) will lead to success.
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PMID:[Vaccination against malaria. Disappointments and hopes]. 955 23

We have used direct DNA inoculation to study the in vivo induction of both humoral and cellular immune responses to hepatitis C virus (HCV) encoded structural antigens. Following immunisation of mice, immune responses were compared using plasmids encoding full-length or partial HCV gene sequences for the nucleocapsid and envelope E2 proteins. Plasmids encoding secreted or non-secreted forms of the immunogens, including constructs expressing HCV sequences fused with the hepatitis B virus surface antigen (HCV-HBV chimeras), were evaluated. Results indicate that: (i) all constructs induced specific anti-HCV antibodies; (ii) antibody titres ranged from 1:100 to > 1:100,000; (iii) all HCV DNA immunogens induced a predominant Th1 response with the induction of IgG2a antibodies; (iv) the secretion level of the antigens and immune responses was not always correlated and (v) CTL could be detected against both HCV and HBV determinants.
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PMID:Immune responses against hepatitis C virus structural proteins following genetic immunisation. 955 71

Genes encoding the small (S) surface antigen (HBsAg) or the core (C) antigen (HBcAg) of hepatitis B virus (HBV) were cloned into the monocistronic expression vectors pCMV-1 or pCMV-2 under HCMV-IE promoter control. Coding fragments of these vectors were fused to generate a dicistronic expression construct pCMV/C-S in which the antigens HBcAg and HBsAg are coexpressed. Transient in vitro transfection studies demonstrated that HBcAg and HBsAg are coexpressed from this construct. Vaccination of mice of different H-2 haplotypes with mono- or dicistronic expression plasmids induced humoral and cellular immune responses to HBsAg and the HBcAg. In particular, intramuscular injection of 'naked' dicistronic plasmid DNA into mice elicited polyvalent humoral and cytotoxic T lymphocyte responses to HBsAg and HBcAg. The studies demonstrate that dicistronic expression plasmids are a novel way to construct a polyvalent vaccine against HBV that comprises HBsAg and HBcAg as immunogens.
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PMID:Polyvalent vaccination against hepatitis B surface and core antigen using a dicistronic expression plasmid. 960 55

An approach to develop fully human monoclonal antibodies in a human/mouse radiation chimera, the Trimera system, is described. In this system, functional human lymphocytes are engrafted in normal strains of mice which are rendered immuno-incompetent by lethal total body irradiation followed by radioprotection with severe combined immunodeficient (SCID) mouse bone marrow. Following transplantation, human lymphocytes colonize murine lymphatic organs and secrete human immunoglobulins. We have established this system as a tool to develop fully human monoclonal antibodies, and applied it for the generation of monoclonal antibodies specific for hepatitis B virus surface antigen. A strong memory response to hepatitis B surface antigen was elicited in Trimera engrafted with lymphocytes from human donors positive for antibodies to hepatitis B surface antigen. The human specific antibody fraction in the Trimera was 10(2)-10(3)-fold higher as compared with that found in the donors. Spleens were harvested from Trimera mice showing high specific-antibody titres and cells were fused to a human-mouse heteromyeloma fusion partner. Several stable hybridoma clones were isolated and characterized. These hybridomas produce high-affinity, IgG, anti-hepatitis B surface antigen antibodies demonstrating the potential of the Trimera system for generating fully human monoclonal antibodies. The biological function and the neutralizing activity of these antibodies are currently being tested.
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PMID:Human monoclonal antibodies specific to hepatitis B virus generated in a human/mouse radiation chimera: the Trimera system. 961 63

The Hepatitis B virus encodes the secreted e antigen (HBe) whose function in the viral life cycle is unknown. HBe derives from a 25-kDa precursor that is directed to the secretory pathway. After cleavage of the signal sequence, the resulting 22-kDa protein (P22) is processed in a post-endoplasmic reticulum compartment to mature HBe by removal of the 34-amino acid C-terminal domain. The efficiency of HBe secretion is specifically decreased in cells grown in the presence of tunicamycin, an inhibitor of N-glycosylation. Inasmuch as HBe precursor is not N-glycosylated, our data suggest that a cellular tunicamycin-sensitive protein increases the intracellular transport through the HBe secretory pathway. The study of the secretion of HBe derived from C-terminal-truncated precursors demonstrates that the tunicamycin-sensitive secretion absolutely requires a part of the C-terminal region that is removed to form mature HBe, indicating that the cellular tunicamycin-sensitive protein increases the efficiency of the intracellular transport of P22. We have also shown that the Escherichia coli beta-galactosidase can be secreted when fused to the HBe precursor signal sequence and that the P22 C-terminal domain renders the secretion of this reporter protein also tunicamycin-sensitive.
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PMID:The C terminus of the hepatitis B virus e antigen precursor is required for a tunicamycin-sensitive step that promotes efficient secretion of the antigen. 966 Aug 31

Hepatitis B virus (HBV) polymerase (P) gene is translated from the bicistronic pregenomic RNA with the core (C) gene in the first cistron. The P ORF is preceded by the C AUG and three AUG codons within the C region, where a minicistron of 7 amino acids can potentially be translated. Our results indicate that the efficiency of the P gene translation initiation was about 10% of that of the C gene when both genes were fused in-frame to a lacZ reporter in an mRNA similar in structure to the pregenomic RNA. By mutational analysis, about 74% of the translation initiation of HBV P gene was shown to be by ribosomes that reinitiated after terminating translation of this minicistron, while the rest was by two mechanisms: one by ribosomes leaky scanning through every upstream AUG and the other by ribosomal backwards scanning to the P AUG after finishing the translation of the C gene. The efficiency of termination-reinitiation depended on the size of the minicistron, i.e. the reinitiation efficiency decreased about 50% when the size increased from 24 nt to 57 nt. When a 44 nt HBV sequence comprising the minicistron was inserted at the 5' untranslated region of the cat gene, CAT expression was regulated in a similar way to that of the HBV P gene. Moreover, when transfection occurred with an HBV expression plasmid containing an inactivated minicistron, production of virus-like particles dropped to about one-third of the wild-type level, suggesting that the termination-reinitiation mechanism is indeed important for HBV P gene expression.
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PMID:Translational regulation of hepatitis B virus polymerase gene by termination-reinitiation of an upstream minicistron in a length-dependent manner. 974 27

Hepatitis B virus X protein (HBx) transactivates viral and cellular genes through a wide variety of cis-elements, but the mechanism has not been well elucidated. Evidence for nuclear events in HBx transactivation has been reported. Here we examine the role of HBx in modulation of transcription with a transient transfection system and an in vitro transcription assay. Reporters bearing Gal4-binding sites were applied to avoid the effects of endogenous transcription factors with or without signaling processes. The Gal4-DNA binding domain fused form of HBx exhibited no effect on Gal4-responsive reporters. However, HBx augmented activated transcription by transcriptional activators, suggesting HBx retains a co-activator but not a transcriptional activator function. The functional domain for co-activation was the same as that for HBx transactivation, and the transcription factor IIB- and RNA polymerase II subunit 5-interacting sites of HBx, which were critical for HBx transactivation, were shown to be crucial for the co-activation function. Importantly, HBx stimulated transcription on templates bearing the X responsive elements in vitro with endogenous activators. These results imply that HBx acts as a co-activator that modulates transcriptional machinery and distal-binding activators, which may explain one of the mechanisms of transactivation by HBx when localized in nuclei.
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PMID:The hepatitis B virus X protein is a co-activator of activated transcription that modulates the transcription machinery and distal binding activators. 976 26


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