Discovery of a Novel Mutation (X8Del) Resulting in an 8-bp Deletion in the Hepatitis B Virus X Gene Associated with Occult Infection in Korean Vaccinated Individuals

Universal infantile hepatitis B virus (HBV) vaccination may lead to an increase in vaccine escape variants, which may pose a threat to the long-term success of massive vaccination. To determine the prevalence of occult infections in Korean vaccinated individuals, 87 vaccinated subjects were screened for the presence of HBV DNA using both the nested PCR protocol and the VERSANT HBV DNA 3.0 assay. The mutation patterns of variants were analyzed in full-length HBV genome sequences. Their HBsAg secretion and replication capacities were investigated using both in vitro transient transfection and in vivo hydrodynamic injection. The presence of HBV DNA was confirmed in 6 subjects (6.9%). All six variants had a common mutation type (X8Del) composed of an 8-bp deletion in the C-terminal region of the HBV X gene (HBxAg). Our in vitro and in vivo analyses using the full-length HBV genome indicated that the X8Del HBxAg variant reduced the secretion of HBsAg and HBV virions compared to the wild type. In conclusion, our data suggest that a novel mutation (X8Del) may contribute to occult HBV infection in Korean vaccinated individuals via a reduced secretion of HBsAg and virions, possibly by compromising HBxAg's transacting capacity.

Effects of hepatitis B virus S protein on human sperm function

BACKGROUND

Hepatitis B virus (HBV) has been determined to exist in semen and male germ cells from patients with chronic HBV infection, but no data are yet available on the impact of HBV S protein (HBs), the main component of HBV envelop protein, on the human reproductive system. The purpose of this article was to investigate the effect of HBs on human sperm function.

METHODS

Sperm motility analyses, sperm penetration assays, mitochondrial membrane potential assays, immunolocalizations with confocal microscopy and flow cytometry analyses were performed.

RESULTS

HBs reduced sperm motility in a dose- and time-dependent manner and caused the loss of sperm mitochondrial membrane potential. HBs-HBs monoclonal antibody (MAb) complex apparently aggravated such impairments. After 4 h incubation with HBs at concentrations of 25, 50, 100 microg/ml, the percentages of sperm motility a+b significantly decreased compared with the control (P < 0.01). The fertilization rate and the fertilizing index in HBs-treated group were 40% and 0.57, respectively, which were significantly lower than 90% and 1.6, respectively, in the control (P < 0.01). The asialoglycoprotein receptor (ASGP-R) and HBs were found to localize mainly on the postacrosomal region. Both ASGP-R MAb and asialofoetuin, a high-affinity ligand of ASGP-R, inhibited the HBs-caused loss of sperm motility and mitochondrial membrane potential.

CONCLUSIONS

HBs had adverse effects on human sperm function, and ASGP-R may play a role in the uptake of HBs into sperm cells, as demonstrated by the competitive inhibition of ASGP-R MAb or asialofoetuin, resulting in diminished impairment caused by HBs.

Infectivity determinants of the hepatitis B virus pre-S domain are confined to the N-terminal 75 amino acid residues

The N-terminal pre-S domain of the large hepatitis B virus (HBV) envelope protein plays a pivotal role at the initial step of the viral entry pathway. In the present study, the entire pre-S domain was mapped for infectivity determinants, following a reverse-genetics approach and using in vitro infection assays with hepatitis delta virus (HDV) or HBV particles. The results demonstrate that lesions created within the N-terminal 75 amino acids of the pre-S region abrogate infectivity, whereas mutations between amino acids 76 and 113, overlapping the matrix domain, had no effect. In contrast to the results of a recent study (L. Stoeckl, A. Funk, A. Kopitzki, B. Brandenburg, S. Oess, H. Will, H. Sirma, and E. Hildt, Proc. Natl. Acad. Sci. 103:6730-6734, 2006), the deletion of a cell membrane translocation motif (TLM) located between amino acids 148 and 161 at the C terminus of pre-S2 did not interfere with the infectivity of the resulting HDV or HBV mutants. Furthermore, a series of large deletions overlapping the pre-S2 domain were compatible with infectivity, although the efficiency of infection was reduced when the deletions extended to the pre-S1 domain. Overall, the results demonstrate that the activity of the pre-S domain at viral entry solely depends on the integrity of its first 75 amino acids and thus excludes any function of the matrix domain or TLM.

Screening and cloning for proteins transactivated by the PS1TP5 protein of hepatitis B virus: A suppression subtractive hybridization study

AIM: To clone and identify human genes transactivated by PS1TP5 by constructing a cDNA subtractive library with suppression subtractive hybridization (SSH) technique.

METHODS: SSH and bioinformatics techniques were used for screening and cloning of the target genes transactivated by PS1TP5 protein. The mRNA was isolated from HepG2 cells transfected with pcDNA3.1(-)-myc-his(A)-PS1TP5 and pcDNA3.1(-)-myc-his(A) empty vector, respectively, and SSH technique was employed to analyze the differentially expressed DNA sequence between the two groups. After digestion with restriction enzyme RsaI, small size cDNAs were obtained. Then tester cDNA was divided into two groups and ligated to the specific adaptor 1 and adaptor 2, respectively. The tester cDNA was hybridized with driver cDNA twice and subjected to nested PCR for two times, and then subcloned into T/A plasmid vectors to set up the subtractive library. Amplification of the library was carried out with E. coli strain DH5α. The cDNA was sequenced and analyzed in GenBank with Vector NTI 9.1 and NCBI BLAST software after PCR amplification.

RESULTS: The subtractive library of genes transactivated by PS1TP5 was constructed successfully. The amplified library contained 90 positive clones. Colony PCR showed that 70 clones contained 200-1000-bp inserts. Sequence analysis was performed in 30 clones randomly, and the full-length sequences were obtained by bioinformatics technique. Altogether 24 coding sequences were obtained, which consisted of 23 known and 1 unknown. One novel gene with unknown functions was found and named as PS1TP5TP1 after being electronically spliced, and deposited in GenBank (accession number: DQ487761).

CONCLUSION: PS1TP5 is closely correlated with immunoregulation, carbohydrate metabolism, signal transduction, formation mechanism of hepatic fibrosis, and occurrence and development of tumor. Understanding PS1TP5 transactive proteins may help to bring some new clues for further studying the biological functions of pre-S1 protein.

Hepatitis B virus-induced oncogenesis

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world with an annual incidence of more than 500 000 in the year 2000. Its incidence is rising in many countries. Recently, it has been estimated that about 53% of HCC cases in the world are related to hepatitis B virus (HBV). The epidemiological association of HBV with HCC is well established. In recent studies, it was revealed that HBsAg carriers have a 25-37 times increased risk of developing HCC as compared to non-infected people. At present, HBV-associated carcinogenesis can be seen as a multi-factorial process that includes both direct and indirect mechanisms that might act synergistically. The integration of HBV DNA into the host genome occurs at early steps of clonal tumor expansion. The integration has been shown in a number of cases to affect a variety of cancer-related genes and to exert insertional mutagenesis. The permanent liver inflammation, induced by the immune response, resulting in a degeneration and regeneration process confers to the accumulation of critical mutations in the host genome. In addition to this, the regulatory proteins HBx and the PreS2 activators that can be encoded by the integrate exert a tumor promoter-like function resulting in positive selection of cells producing a functional regulatory protein. Gene expression profiling and proteomic techniques may help to characterize the molecular mechanisms driving HBV-associated carcinogenesis, and thus potentially identify new strategies in diagnosis and therapy.

Viral and cellular determinants involved in hepadnaviral entry

Hepadnaviridae is a family of hepatotropic DNA viruses that is divided into the genera orthohepadnavirus of mammals and avihepadnavirus of birds. All members of this family can cause acute and chronic hepatic infection, which in the case of human hepatitis B virus (HBV) constitutes a major global health problem. Although our knowledge about the molecular biology of these highly liver-specific viruses has profoundly increased in the last two decades, the mechanisms of attachment and productive entrance into the differentiated host hepatocytes are still enigmatic. The difficulties in studying hepadnaviral entry were primarily caused by the lack of easily accessible in vitro infection systems. Thus, for more than twenty years, differentiated primary hepatocytes from the respective species were the only in vitro models for both orthohepadnaviruses (e.g. HBV) and avihepadnaviruses (e.g. duck hepatitis B virus [DHBV]). Two important discoveries have been made recently regarding HBV: (1) primary hepatocytes from tree-shrews; i.e., Tupaia belangeri, can be substituted for primary human hepatocytes, and (2) a human hepatoma cell line (HepaRG) was established that gains susceptibility for HBV infection upon induction of differentiation in vitro. A number of potential HBV receptor candidates have been described in the past, but none of them have been confirmed to function as a receptor. For DHBV and probably all other avian hepadnaviruses, carboxypeptidase D (CPD) has been shown to be indispensable for infection, although the exact role of this molecule is still under debate. While still restricted to the use of primary duck hepatocytes (PDH), investigations performed with DHBV provided important general concepts on the first steps of hepadnaviral infection. However, with emerging data obtained from the new HBV infection systems, the hope that DHBV utilizes the same mechanism as HBV only partially held true. Nevertheless, both HBV and DHBV in vitro infection systems will help to: (1) functionally dissect the hepadnaviral entry pathways, (2) perform reverse genetics (e.g. test the fitness of escape mutants), (3) titrate and map neutralizing antibodies, (4) improve current vaccines to combat acute and chronic infections of hepatitis B, and (5) develop entry inhibitors for future clinical applications.

Screening of genes for proteins interacting with the PS1TP5 protein of hepatitis B virus: probing a human leukocyte cDNA library using the yeast two-hybrid system

BACKGROUND

The hepatitis B virus (HBV) genome includes S, C, P and X regions. The S region is divided into four subregions of pre-pre-S, pre-S1, pre-S2 and S. PS1TP5 (human gene 5 transactivated by pre-S1 protein of HBV) is a novel target gene transactivated by the pre-S1 protein that has been screened with a suppression subtractive hybridization technique in our laboratory (GenBank accession: AY427953). In order to investigate the biological function of the PS1TP5 protein, we performed a yeast two-hybrid system 3 to screen proteins from a human leukocyte cDNA library interacting with the PS1TP5 protein.

METHODS

The reverse transcription polymerase chain reaction (RT-PCR) was performed to amplify the gene of PS1TP5 from the mRNA of HepG2 cells and the gene was then cloned into the pGEM-T vector. After being sequenced and analyzed with Vector NTI 9.1 and NCBI BLAST software, the target gene of PS1TP5 was cut from the pGEM-T vector and cloned into a yeast expression plasmid pGBKT7, then "bait" plasmid pGBKT7-PS1TP5 was transformed into the yeast strain AH109. The yeast protein was isolated and analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting hybridization. After expression of the pGBKT7-PS1TP5 fusion protein in the AH109 yeast strain was accomplished, a yeast two-hybrid screening was performed by mating AH109 with Y187 containing a leukocyte cDNA library plasmid. The mated yeast was plated on quadruple dropout medium and assayed for alpha-gal activity. The interaction between the PS1TP5 protein and the proteins obtained from positive colonies was further confirmed by repeating the yeast two-hybrid screen. After extracting and sequencing of plasmids from blue colonies we carried out a bioinformatic analysis.

RESULTS

Forty true positive colonies were selected and sequenced, full length sequences were obtained and we searched for homologous DNA sequences from GenBank. Among the 40 positive colonies, 23 coding genes with known functions were obtained, including Homo sapien leukocyte adhesion protein p150, 95, interleukin 2 receptor gamma chain, PALM2-AKAP2 protein (PALM2-AKAP2), eukaryotic translation initiation factor 4A, beta-2-microglobin, solute carrier family 9 (sodium/hydrogen exchanger), calreticulin, asialoglycoprotein receptor 1 (ASGR1), MHC class II lymphocyte antigen, cytochrome c oxidase subunit 1, lymphocyte antigen 86 (LY86) and lymphocyte cytosolic protein 1. One novel gene with unknown function was found and named as PS1TP5BP1. After being electronically spliced, it was deposited in GenBank (accession number: DQ471327).

CONCLUSIONS

Genes of proteins interacting with PS1TP5 were successfully screened from leukocyte cDNA library. These results suggested that PS1TP5 was closely correlated with immunoregulation, carbohydrate metabolism, signal transduction, the formation of hepatic fibrosis and initiation and development of tumors and also brought some new clues for further studying the biological functions of the pre-S1 protein.

The role of the HBV envelope proteins in the HDV replication cycle

The hepatitis delta virus (HDV) is a subviral agent that utilizes the envelope proteins of the hepatitis B virus (HBV) for propagation. When introduced into permissive cells, the HDV RNA genome replicates and associates with multiple copies of the HDV-encoded proteins to assemble a ribonucleoprotein (RNP) complex. The mechanism necessary to export the RNP from the cell is provided by the HBV envelope proteins, which have the capacity to assemble lipoprotein vesicles that bud into the lumen of a pre-Golgi compartment before being secreted. In addition to allowing the release of the HDV RNP, the HBV envelope proteins also provide a means for its targeting to an uninfected cell, thereby ensuring the spread of HDV. This chapter covers the molecular aspects of the HBV envelope protein functions in the HDV replication cycle, in particular the activity of the small envelope protein in RNP export and the function of the large envelope protein at viral entry.

A tryptophan-rich motif in the carboxyl terminus of the small envelope protein of hepatitis B virus is central to the assembly of hepatitis delta virus particles

The small hepatitis B virus surface antigen (S-HBsAg) is capable of driving the assembly and secretion of hepatitis delta virus (HDV) particles by interacting with the HDV ribonucleoprotein (RNP). Previously, a specific domain of the S-HBsAg protein carboxyl terminus, including a tryptophan residue at position 196 (W196), was proven essential for HDV maturation (S. Jenna and C. Sureau, J. Virol. 73: 3351-3358, 1999). Mutation of W196 to phenylalanine (W196F) was permissive for HBV subviral particle (SVP) secretion but deleterious to HDV virion assembly. Here, the W196F S-HBsAg deficiency was assigned to a loss of its ability for interaction with the large HDV antigen (L-HDAg), a major component of the RNP. Because the overall S-HBsAg carboxyl terminus is particularly rich in tryptophan, an amino acid frequently involved in protein-protein interactions, site-directed mutagenesis was conducted to investigate the function of the S-HBsAg Trp-rich domain in HDV assembly. Single substitutions of tryptophan between positions 163 and 201 with alanine or phenylalanine were tolerated for SVP secretion, but those affecting W196, W199, and W201 were detrimental for HDV assembly. This was proven to result from a reduced capacity of the mutants for interaction with L-HDAg. In addition, a W196S S-HBsAg mutant, which has been described in HBV strains that arose in a few cases of lamivudine-treated HBV-infected patients, was deficient for HDV assembly as a consequence of its impaired capacity for interacting with L-HDAg. Interestingly, the fact that even the most conservative substitution of phenylalanine for tryptophan at positions 196, 199, or 201 was sufficient to ablate interaction of S-HBsAg with L-HDAg suggests that W196, W199, and W201 are located at a binding interface that is central to HDV maturation.

Prevalence of occult HBV infection in haemodialysis patients with chronic HCV

AIM: To study the prevalence and clinical effects of occult HBV infection in haemodialysis patients with chronic HCV.

METHODS: Fifty chronic hemodialysis patients with negative HbsAg, and positive anti-HCV were included in the study. These patients were divided into two groups: HCV-RNA positive and HCV-RNA negative, based on the results of HCV-RNA PCR. HBV-DNA was studied using the PCR method in both groups.

RESULTS: None of the 22 HCV-RNA positive patients and 28 HCV-RNA negative patients revealed HBV-DNA in serum by PCR method. The average age was 47.2 ± 17.0 in the HCV-RNA positive group and 39.6 ± 15.6 in the HCV-RNA negative group.

CONCLUSION: The prevalence of occult HBV infection is not high in haemodialysis patients with chronic HCV in our region. This result of our study has to be evaluated in consideration of the interaction between HBsAg positivity (8%-10%) and frequency of HBV mutants in our region.

[Effect of HBsAg pulsed dendritic cells on the functions of cytokine-induced killer cells]

AIM

To explore the effects of HBsAg-pulsed dendritic cells (DCs) on the proliferation and killing functions of cytokine-induced killer (CIK) cells.

METHODS

The peripheral blood mononuclear cells (PBMCs) were isolated from the patients with chronic hepatitis B by the routine method, and induced into specific DCs with HBsAg pulsed. The (3)H-TdR incorporation method was used to determine the stimulation effect of HBsAg-pulsed DCs on the proliferation of CIK cells. LDH release assay was used to measure the specific killing activity of CIK cells on HepG2215 cells.

RESULTS

The HBsAg-pulsed DCs could induce the memory proliferation of CIK cells and strengthen the killing activity of CIK cells (P<0.05).

CONCLUSION

HBsAg-pulsed DCs can enhance the proliferation and killing functions of CIK cells.

Screening for PreS specific binding ligands with a phage displayed peptides library

AIM: To construct a random peptide phage display library and search for peptides that specifically bind to the PreS region of hepatitis B virus (HBV).

METHODS: A phage display vector, pFuse8, based on the gene 8 product (pVIII) of M13 phage was made and used to construct a random peptide library. E.coli derived thioredoxin-PreS was purified with Thio-bond beads, and exploited as the bait protein for library screening. Five rounds of bio-panning were performed. The PreS-binding specificities of enriched phages were characterized with phage ELISA assay.

RESULTS: A phage display vector was successfully constructed as demonstrated to present a pVIII fused HBV PreS1 epitope on the phage surface with a high efficiency. A cysteine confined random peptide library was constructed containing independent clones exceeding 5±10⁸ clone forming unit (CFU). A pool of phages showing a PreS-binding specificity was obtained after the screening against thio-PreS with an enrichment of approximately 400 times. Five phages with high PreS-binding specificities were selected and characterized. Sequences of the peptides displayed on these phages were determined.

CONCLUSION: A phage library has been constructed, with random peptides displaying as pVIII-fusion proteins. Specific PreS-binding peptides have been obtained, which may be useful for developing antivirals against HBV infection.

Novel Autoregulatory Function of Hepatitis B Virus M Protein on Surface Gene Expression

The hepatitis B virus surface gene consists of a single open reading frame divided into three coding regions: pre-S1, pre-S2, and S. By alternate translation at each of the three initiation codons, L, M, and S proteins can be synthesized. Studies have shown that M protein is not essential for viral replication, virion morphogenesis, or in vitro infectivity. In this study, we show that native M protein can regulate surface gene expression at the transcriptional level. The regulatory effect of M protein is mediated through the CCAAT box within the S promoter. Deletion mapping analysis indicated that the transactivating effect of M protein is mediated through amino acids 1-57 of M protein (the MHBs(au) domain), although its maximal transactivation activity coincides with that of the pre-S2 domain. This conclusion is supported by the fact that disruption of the putative V8 protease site at the pre-S2/S domain junction not only rendered M protein incapable of transactivating the S promoter but also inactivated its nuclear translocation potential. Immunoprecipitation and immunoblot experiments demonstrated that pre-S2 interacts with the three subunits of the CCAAT box-binding factor/nuclear factor Y, the cognate binding protein of the CCAAT box. These results demonstrate and define a novel regulatory role of M protein, which, under natural conditions, may undergo a proteolytic process to generate an MHBs(au) species that will be translocated inside the nucleus, where it will interact with the CCAAT box-binding factor to regulate surface gene expression. Because the CCAAT box is located at a fixed position within numerous promoters, these observations might provide a plausible explanation for hepatitis B virus-associated hepatocarcinogenesis.

NACA as a potential cellular target of hepatitis B virus preS1 protein

The mechanisms of the attachment and penetration of hepatitis B virus remain obscure. It has been demonstrated that the preS1 region is essential for viral assembly and infectivity, however, as its cellular receptor has still not been identified unequivocally, we used a yeast two-hybrid system to screen the cellular proteins that can interact with preS1 protein. The protein recovered from a human liver cDNA library was nascent polypeptide-associated complex alpha polypeptide. The interaction between preS1 and nascent polypeptide-associated complex alpha polypeptide was verified by mating experiment and coimmunoprecipitation of COS7 cell lysates expressing both proteins. Based on these results, we speculate that nascent polypeptide-associated complex alpha polypeptide is a functional target of hepatitis B virus preS1 protein in cells.

[Hepatitis B virus surface antigen: a multifaceted protein]

Despite the small size of its genome (3.2 kb) and having only four genes that are encoded within it, the hepatitis B virus (HBV) is one of the most successful viral pathogens in human history. It is estimated that there are about 350-400 million people worldwide who are chronically infected with HBV, and even with the extensive efforts that are being done with preventive vaccination, this malady still remains a clear and present danger to the public health. How is it possible that this small double-stranded DNA virus can escape and outfox the surveillance of the complex human immune system? One explanation is that HBV gene products play multiple roles in infections and throughout the viral life cycle so that the virus can effectively survive under various hostile circumstances. Indeed, the HBV DNA polymerase, for example, exerts several functions such as reverse transcription and RNA degradation, and the HBV X protein not only acts as a transcriptional activator, but it also interferes with the host cells' DNA repair mechanism as well as inducing apoptosis and controlling signal transduction. The HBV surface protein, which is encoded in the env gene, is another intriguing example of such multifunctionality. Thus, our present article overviews and summarizes the multifaceted role of this membrane protein as shown in 1) its role as a structural protein of the virus envelope; 2) its function as the viral ligand for interacting with the viral receptors on host cells; 3) its characteristics as an energy-independent transporter molecule that can mediate the nuclear accumulation of itself and other tagged molecules; 4) its role as a viral transactivator protein that can cause hepatocellular carcinoma; 5) its hypothetical function in viral apoptotic mimicry that results in host anti-inflammatory responses; and last 6) its immunostimulatory property by providing for strong and well-defined B- and T-cell epitopes. Understanding these various functions and the versatility of this single protein will help us decipher and understand the viral- and immuno-pathogenesis of HBV itself.

Superinfection exclusion in duck hepatitis B virus infection is mediated by the large surface antigen

Superinfection exclusion is the phenomenon whereby a virus prevents the subsequent infection of an already infected host cell. The Pekin duck hepatitis B virus (DHBV) model was used to investigate superinfection exclusion in hepadnavirus infections. Superinfection exclusion was shown to occur both in vivo and in vitro with a genetically marked DHBV, DHBV-ClaI, which was unable to establish an infection in either DHBV-infected ducklings or DHBV-infected primary duck hepatocytes (PDHs). In addition, exclusion occurred in vivo even when the second virus had a replicative advantage. Superinfection exclusion appears to be restricted to DHBV, as adenovirus, herpes simplex virus type 1, and vesicular stomatitis virus were all capable of efficiently infecting DHBV-infected PDHs. Exclusion was dependent on gene expression by the original infecting virus, since UV-irradiated DHBV was unable to mediate the exclusion of DHBV-ClaI. Using recombinant adenoviruses expressing DHBV proteins, we determined that the large surface antigen mediated exclusion. The large surface antigen is known to cause down-regulation of a DHBV receptor, carboxypeptidase D (CPD). Receptor down-regulation is a mechanism of superinfection exclusion seen in other viral infections, and so it was investigated as a possible mechanism of DHBV-mediated exclusion. However, a mutant large surface antigen which did not down-regulate CPD was still capable of inhibiting DHBV infection of PDHs. In addition, exclusion of DHBV-ClaI did not correlate with a decrease in CPD levels. Finally, virus binding assays and confocal microscopy analysis of infected PDHs indicated that the block in infection occurs after internalization of the second virus. We suggest that superinfection exclusion may result from the role of the L surface antigen as a regulator of intracellular trafficking.

Pre-s1 antigen-dependent infection of Tupaia hepatocyte cultures with human hepatitis B virus

The susceptibility of the tree shrew Tupaia belangeri to human hepatitis B virus (HBV) has been demonstrated both in vivo and in vitro. In this study, we show that purified HBV infects primary T. belangeri hepatocyte cultures in a very specific manner, as detected by HBV covalently closed circular DNA, mRNA, HBV e antigen, and HBsAg production. A monoclonal antibody (MAb), MA18/7, directed against the pre-S1 domain of the large HBs protein, which has been shown to neutralize infectivity of HBV for primary human hepatocytes, also blocked infection of primary Tupaia hepatocytes. MAbs against the pre-S2 domain of HBs inhibited infection only partially, whereas an S MAb and polyvalent anti-HBs antibodies neutralized infection completely. Thus, both pre-S1 and S antigens are necessary for infection in the tupaia. Using subviral particles, >70% of primary Tupaia hepatocytes are capable of specific binding of pre-S1-rich HBsAg, showing localization in distinct membrane areas. The data show that the early steps of HBV infection in Tupaia hepatocyte cultures are comparable to those in the human system.

[Screening of the genes of hepatitis B virus PreS2 interacting proteins]

OBJECTIVE

To screen and clone the genes of proteins in hepatocytes interacting with hepatitis B virus (HBV) PreS2 by yeast-two hybridization technique.

METHODS

The HBV PreS2 gene was amplified by polymerase chain reaction (PCR) and HBV PreS2 bait plasmid was constructed by using yeast-two hybridization system 3, then transformed into yeast AH109, followed by mating with yeast Y187 containing liver cDNA library plasmid in 2 YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-Ade-His) and synthetic dropout nutrient medium (SD/-Trp-Leu-Ade-His) containing X-alpha-gal for selecting positive blue clones, then amplified by PCR, sequenced, and performed bioinformatics analysis.

RESULTS

HBV PreS2 gene was cloned successfully and expressed in yeast AH109.Twenty-six positive colonies were selected, among them, twelve containing metallothionein 2A, one cytochrome C oxidase II, two cytochrome P450 subfamily IV4F, two cytochrome c oxidase subunit 4 isoform 1, three albumin (ALB), one Na(+)K(+) transporting ATPase beta-1 polypeptide, two prealbumin, one lectin galactoside-binding subunit, and Two new genes with unknown function.

CONCLUSION

Genes of HBV PreS2 interacting proteins have been successfully cloned, which brings some new clues for studying the biological functions of HBV PreS2 and related proteins.

[Regulation of Gal beta 1,3GalNAc alpha 2,3-sialyltransferase (ST3GalI) by hepatitis B virus MHBst/HBx transactivator]

Hepatitis B virus MHBst and HBx fragments were amplified to construct eukaryotic expression vector pCDNA3.1-MHBst and pCDNA3.1-HBx. ST3GalI promoter region was obtained by the method of PCR and GFP report plasmid pEGFP-N1-Psial was constructed. pCDNA3.1-MHBst or pCDNA3.1-HBx with pEGFP-N1-Psial were transiently co-transfected into QGY-7701 cells using calcium phosphate-DNA co-precipitation, respectively. The expressions of Psial-directed GFP were analyzed by FAC-Scalibur. It was found that MHBst/HBx could upregulate ST3GalI promoter activity by 35.2% and 43.8%, respectively. We report the regulation of ST3GalI by MHBst and HBx transactivators. It would be helpful to further investigate the relation between hepatitis B virus infection and sialyltransferase expression.

The PreS2 activator MHBs(t) of hepatitis B virus activates c-raf-1/Erk2 signaling in transgenic mice

The large hepatitis B virus (HBV) surface protein (LHBs) and C-terminally truncated middle size surface proteins (MHBs(t)) form the family of the PreS2 activator proteins of HBV. Their transcriptional activator function is based on the cytoplasmic orientation of the PreS2 domain. MHBs(t) activators are paradigmatic for this class of activators. Here we report that MHBs(t) is protein kinase C (PKC)-dependently phosphorylated at Ser28. The integrity of the phosphorylation site is essential for the activator function. MHBs(t) triggers PKC-dependent activation of c-Raf-1/Erk2 signaling that is a prerequisite for MHBs(t)-dependent activation of AP-1 and NF-kappaB. To analyze the pathophysiological relevance of these data in vivo, transgenic mice were established that produce the PreS2 activator MHBs(t) specifically in the liver. In these mice, a permanent PreS2-dependent specific activation of c-Raf-1/Erk2 signaling was observed, resulting in an increased hepatocyte proliferation rate. In transgenics older than 15 months, an increased incidence of liver tumors occurs. These data suggest that PreS2 activators LHBs and MHBs(t) exert a tumor promoter-like function by activation of key enzymes of proliferation control.

Adjuvants that enhance priming of cytotoxic T cells to a Kb-restricted epitope processed from exogenous but not endogenous hepatitis B surface antigen

Intramuscular (i.m.) or s.c. injection of plasmid DNA encoding hepatitis B small surface antigen (HBsAg) primes potent MHC I-restricted cytotoxic T lymphocyte (CTL) responses in H-2(d) (BALB/c) and H-2(b) (C57BL/6) mice. In contrast, i.m. or s.c. injection of exogenous HBsAg particles without adjuvants primes CTL responses in 'high responder' H-2(d) but not 'low responder' H-2(b) mice. We have shown that processing of exogenous but not endogenous HBsAg generates the Kb-binding S208-215 peptide ILSPFLPL. This system allowed us to optimize conditions for stimulating murine CTL responses to exogenous antigen by identifying adjuvants that facilitate priming of Kb-restricted CTL by injecting recombinant HBsAg particles into 'low responder' H-2(b) mice. Synthetic oligodeoxynucleotides with immunostimulating sequences or the recombinant cytokine IL-12 efficiently enhanced priming of CTL to exogenous HBsAg. Hence, the adjuvanticity of DNA sequences that induce Th1 cytokines facilitate priming of MHC I-restricted T cell responses to exogenous antigen and are therefore of potential value in formulating vaccines designed to enhance CTL priming to exogenous antigen.

Infection process of the hepatitis B virus depends on the presence of a defined sequence in the pre-S1 domain

During the life cycle of hepatitis B virus (HBV), the large envelope protein (L) plays a pivotal role. Indeed, this polypeptide is essential for viral assembly and probably for the infection process. By performing mutagenesis experiments, we have previously excluded a putative involvement of the pre-S2 domain of the L protein in viral infectivity. In the present study, we have evaluated the role of the pre-S1 region in HBV infection. For this purpose, 21 mutants of the L protein were created. The entire pre-S1 domain was covered by contiguous deletions of 5 amino acids. First, after transfection into HepG2 cells, the efficient expression of both glycosylated and unglycosylated L mutant proteins was verified. The secretion rate of envelope proteins was modified positively or negatively by deletions, indicating that the pre-S1 domain contains several regulating sequences able to influence the surface protein secretion. The ability of mutant proteins to support the production of virions was then studied. Only the four C-terminal deletions, covering the 17 amino acids suspected to interact with the cytoplasmic nucleocapsids, inhibited virion release. Finally, the presence of the modified pre-S1 domain at the external side of all secreted virions was confirmed, and their infectivity was assayed on normal human hepatocytes in primary culture. Only a short sequence including amino acids 78 to 87 tolerates internal deletions without affecting viral infectivity. These results confirm the involvement of the L protein in the infection step and demonstrate that the sequence between amino acids 3 and 77 is involved in this process.

DNA-mediated immunization to hepatitis B virus envelope proteins: preS antigen secretion enhances the humoral response

In order to design optimized DNA vectors as genetic vaccines against infections with the hepatitis B virus (HBV) we investigated if secretion or retention of the viral antigens has an influence on the quality and quantity of the humoral immune response. Intramuscular injection of plasmid DNA encoding the HBV large L envelope protein, known to be retained within host cells, induced only a weak response in mice whereas a vector expressing the secretion-competent small S envelope protein elicited strong and sustained immunity. Immunization with rearranged envelope genes further demonstrated that secretion affects the magnitude of the immune response. In situ expression of modified small and middle envelope genes carrying C-terminally attached epitopes are derived from the preS1 region of L generated high titers of preS1- and preS2-specific antibodies, unless antigen secretion was blocked. Accessibility of preS antigens to B-cells that can be achieved by generating extracellular forms of the envelope proteins is thus critical to elicit humoral responses. Such DNA constructs carrying preS1 determinants are promising candidates for the development of multivalent HBV vaccines.

The PreS2 activators of the hepatitis B virus: activators of tumour promoter pathways

In addition to causing acute and chronic hepatitis, hepatitis B virus (HBV) is considered to be a major cliological factor in the development of human hepatocellular carcinoma (HCC). Epidemiological studies have demonstrated an approximately 10-fold increase in the relative risk of HCC among HBV carried compared to noncarriers. Almost all HBV-associated HCCs studied so far harbor chromosomally integrated HBV DNA. Integrated viral DNA can encode two types of transcriptional activators, the HBx protein and the PreS2 activators [the large surface proteins (LHBs) and truncated middle surface proteins (MHBs)]. The activator function of the PreS2 activators is based on the cytoplasmic orientation of the PreS2 domain. The PreS2 domain is PKC-dependent phosphorylated. Moreover, the PreS2 domain binds of PKC alpha/beta and triggers a PKC-dependent activation of the c-Raf-1/MAP2-kinase signal transduction cascade, resulting in an activation of transcription factors such as AP-1 and NF-kB. Furthermore, by activation of this signaling cascade, the PreS2 activators cause an increased proliferation rate of hepatocytes. According to the two-step model of carcinogenesis (initiation/promotion), the PreS2 activators could exert a tumour-promoter-like function by activation of the PKC/c-Raf-1/MAP2-kinase signaling cascade: cells harboring critical mutations (initiation) may be positively selected (promotion). Such a multistep process may account for the long latency period in HCC development, but it also leads to the hypothesis that each tumor reflects an individual case.

Role of the pre-S2 domain of the large envelope protein in hepatitis B virus assembly and infectivity

Among the three viral proteins present in the hepatitis B virus (HBV) envelope, both the small and large polypeptides, but not the middle polypeptide, are necessary for the production of complete viral particles. Whereas it has been established that the C-terminal extremity of the pre-S1 region is required for HBV morphogenesis, whether the pre-S2 region of the large surface protein plays a critical role remains questionable. In the present study, we have analyzed the role of the large-polypeptide pre-S2 region in viral maturation and infectivity. For this purpose, mutants bearing contiguous deletions covering the entire pre-S2 domain were generated. First, the efficient expression of all the mutant large envelope proteins was verified and their ability to substitute for the wild-type form in virion secretion was tested. We found that distinct deletions covering the domain between amino acids 114 and 163 still allowed virion production. In contrast, the polypeptide lacking the first 5 amino acids of pre-S2 (amino acids 109 to 113) was unable to support viral secretion. This result shows that the domain of the large surface protein, required for this process, must be extended to the N-terminal extremity of pre-S2. We then demonstrated that all the mutants competent for virion release were able to infect normal human hepatocytes in primary culture. Taken together, these results indicate that only 10% of the large-protein pre-S2 region at its N-terminal extremity is essential for virion export and that the remaining part, dispensable for viral secretion, is also dispensable for infectivity.

The hepatitis B virus MHBst167 protein is a pleiotropic transactivator mediating its effect via ubiquitous cellular transcription factors

C-terminally truncated surface proteins of hepatitis B virus (HBV) are frequently translated from genomically integrated viral sequences. They may be relevant for hepatocarcinogenesis by stimulating gene expression. First, we examined the transactivating potential of middle hepatitis B surface protein truncated at amino acid (aa) position 167 (MHBst167) on the HBV regulatory element. In transient cotransfection assays using Chang liver or HepG2 cell lines and chloramphenicol acetyltransferase (CAT) reporter constructs only the HBV enhancer I, but no other HBV regulatory elements like the X promoter, the S1 or S2 promoter or the enhancer II/core promoter could be stimulated by MHBst167. Since there is no evidence for a direct interaction of MHBst167 with DNA, we subsequently analysed whether cellular transcription factors were involved in mediating transactivation. This was tested both with isolated transcription-factor-binding sites and in the natural context of viral and cellular promoter elements. Deletion analysis and electrophoretic mobility shift assays revealed that Sp1, AP1 and NF-kappa B can mediate transactivation by MHBst167. No involvement of CREB, NF1 or the liver-specific factor C/EBP was found. These data indicate that MHBst167 is a pleiotropic, non-liver-specific transactivator which exerts its effect via ubiquitous cellular transcription factors that are also involved in the regulation of expression of cellular genes relevant for proliferation and inflammation.

Hepatitis B virus replication and mutation are autoregulated by interactions between surface antigen and HBeAg and the HBV DNA polymerase: a functional model with therapeutic implications

Infection with hepatitis B virus can result in asymptomatic seroconversion with viral clearance, fulminant hepatic failure and death, or chronic, typically lifelong, transmissible infection. The mechanism(s) of viral persistence are poorly understood but viral clearance and fulminant hepatic failure are generally thought to result from co-ordinated and effective and abnormally vigorous immune responses, respectively, whereas viral persistence results from immunological failure in addition to poorly characterized viral factors promoting persistence. This paper proposes (1) that the predominant viral factor(s) promoting persistence of hepatitis B virus are homeostatic mechanism(s) responsible for modulating its replication and mutation and (2) that chronic hepatitis B results when these mechanisms are successful and other outcomes occur when these homeostatic mechanism(s) fail. Furthermore, it is proposed that seroconversion (e.g. from HBsAg to anti HBsAg positivity), when it occurs, is a consequence facilitated by restricted viral antigenic diversity and reduced viral replication rather than a proximate cause of it. The specific homeostatic mechanisms proposed--negative feedback inhibition of hepatitis B virus DNA polymerase/reverse transcriptase mediated by HBs antigen and a hepatitis B virus DNA polymerase fidelity modulating function of HBeAg--are consistent with the available data and resolve many paradoxical clinical observations. But, more importantly, this model has clear implications for therapy, including the rational design of drugs and therapeutic vaccines.

Protease-activated lymphoid cell and hepatocyte recognition site in the preS1 domain of the large woodchuck hepatitis virus envelope protein

A site capable of strictly host- and cell type-specific recognition was identified in the preS1 domain of woodchuck hepatitis virus (WHV) through the use of antipeptide antisera generated against the extreme N-terminal fragment of the large virus envelope protein. The crucial determinant of this binding site was mapped to amino acids 10-13. Although a synthetic analogue of the site was highly immunogenic, natural WHV envelope did not display the site activity unless it was modified by proteolysis or acidic pH treatment, indicating an internal location of the determinant in viral envelope. Synthetic peptides encompassing the sequence of this site bound woodchuck lymphoid cells and hepatocytes in a species-restricted manner which followed characteristics of a specific ligand-receptor interaction, although their ability to interact with lymphoid cells was considerably greater than that for hepatocytes. In WHV-infected animals, a natural antibody to the identified cryptic cell-binding site arose independently of that directed against epitopes of unmodified virus envelope and its appearance constituted the earliest immunovirological indicator of virus invasion. Our results demonstrated that the preS1 domain of the large WHV envelope protein is endowed with the species- and cell type-specific recognition site which is protected against antibody surveillance by the natural tertiary structure of the protein and we suggest that proteolytic cleavage is required to induce the binding activity.

Fibronectin of human liver sinusoids binds hepatitis B virus: identification by an anti-idiotypic antibody bearing the internal image of the pre-S2 domain

Anti-idiotypic antibodies (anti-Ids) have been successfully used to characterize and isolate receptors of several cell ligands. To prepare an immunological probe for identification of cellular components interacting with the hepatitis B virus (HBV), polyclonal antisera against a panel of five HBV-specific monoclonal antibodies (MAbs) were produced in syngeneic BALB/c mice. MAbs to HBV used for immunization (Ab1) recognized biologically important and potentially neutralizing epitopes, located in the pre-S1, pre-S2, or S region-encoded domains of HBV proteins. All the anti-Ids (Ab2) were specific to idiotopes of the homologous Ab1 and inhibited their interaction with the corresponding viral epitopes, suggesting that they recognized unique determinants on the paratope of each immunizing Ab1. Therefore, all five generated polyclonal anti-Ids were of the Ab2 beta type and could represent internal images of viral epitopes. Ab2 raised against the pre-S2 region-specific MAb F124 bound to the extracellular matrix fibronectin of human liver sinusoids. Immunohistochemical studies demonstrated the attachment of viral and recombinant (S, M) hepatitis B surface antigen particles with the pre-S2 region-encoded epitopes to the fibronectin of human liver sinusoids. In contrast, recombinant (S, L*) hepatitis B surface antigen particles, in which the epitope recognized by F124 MAb was not expressed, did not show any binding capacity. These findings suggest that human liver fibronectin may bind HBV in vivo by the pre-S2 region-encoded epitopes in a species-restricted manner. Furthermore, binding of the circulating virus to liver sinusoids could facilitate its subsequent uptake by hepatocytes.

Renal transplantation in asymptomatic carriers of hepatitis B surface antigen

The aim of the present study was: (a) to assess the effect of HBsAg on the survival of both renal grafts and patients, and (b) to determine the outcome of HBV chronic infection after renal transplantation. Fourteen patients seropositive for HBsAg but asymptomatic before renal transplantation (group A) were included in the study. The results were compared to those of 14 transplanted patients (group B) seronegative for HBsAg with similar age and immunosuppressive treatment. Four patients received a graft from a living-related donor and 10 patients from a cadaver donor in each group. Eight of 14 patients of group A showed, after renal transplantation, chronic hepatitis, which was not observed in any of the group B patients (p < 0.01). The rate of acute rejection episodes was significantly greater (p < 0.05) in group B than in group A. The graft survival was found to be similar in both groups at the 1st year, but significantly less (p < 0.01) in group B than in group A at the 5th year after transplantation. The survival of patients was found to be significantly less in group A than in group B at the 1st (p < 0.05) and 5th years (p < 0.01) after transplantation. In 2 patients of group A and 1 of group B anti-HCV was found, while HDAg plus anti-HD was found in 1 patient of group B. The HBV-DNA was found in 4 of 8 alive patients of group A.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of hepatitis C virus in fulminant viral hepatitis in an area with endemic hepatitis A and B

BACKGROUND/AIMS

The role of hepatitis C virus in fulminant hepatitis remains controversial and needs further investigation. The aim of this study was to examine the role of hepatitis C virus in fulminant hepatitis in an area with endemic hepatitis A and B.

METHODS

Serological markers of hepatitis C virus were studied in 62 adults from Taiwan with fulminant viral hepatitis.

RESULTS

Of 62 patients, 5 (8.1%) were infected with acute type B hepatitis, 11 (17.7%) were infected with acute non-A, non-B hepatitis, and the remaining 46 (74.2%) were hepatitis B surface antigen (HBsAg) positive but immunoglobulin M (IgM) antibody to hepatitis B core antigen negative. Of the latter, 11 (23.9%) were IgM antibody to hepatitis D virus positive, 16 (34.8%) had high-titered serum hepatitis B virus DNA (> 1000 pg/mL) and were suspected to have hepatitis B virus reactivation, and the other 19 (41.3%) had no identified causes. Serum hepatitis C virus RNA was found in 5 (45.5%) of 11 patients with fulminant non-A, non-B hepatitis, 3 (27.3%) of 11 HBsAg carriers with delta superinfection, and 6 (31.6%) of 19 HBsAg carriers with fulminant hepatitis of undetermined cause.

CONCLUSIONS

Nearly half of fulminant non-A, non-B hepatitis and about 20% of HBsAg carriers with superimposed fulminant hepatitis in Taiwan could be attributed to hepatitis C virus infection.

Human non-hepatocytes support hepadnaviral replication and virion production

The competence of non-hepatocytes to support hepatitis B virus (HBV) gene expression and replication was studied by transient transfection of various human cell lines with a head-to-tail dimer of HBV DNA. Independent of their neuroectodermal, mesenchymal or epithelial origin, all non-hepatocyte cell lines tested synthesized and secreted hepatitis B surface antigen (HBsAg) and hepatitis B core/e antigen (HBc/eAg). Further analyses of two of these cell lines (LS 180 and COLO 320) identified the two major HBV transcripts of 3.6 and 2.2/2.4 kb length, respectively. LS 180 cells were permissive for HBV and duck hepatitis B virus (DHBV) DNA replication and secretion of infectious virions. COLO 320 cells also supported HBV DNA replication, but did not appear to export complete viral particles. These findings provide direct evidence that both HBV and DHBV can replicate in non-hepatic tumour cell lines, one of which is shown also to produce infectious virions.

Small-form hepatitis B surface antigen is sufficient to help in the assembly of hepatitis delta virus-like particles

Hepatitis delta virus (HDV) has an envelope composed of large-, middle-, and small-form hepatitis B surface antigens (HBsAgs) provided by the helper hepatitis B virus (HBV). In order to examine the roles of individual HBsAgs in HDV assembly, we constructed plasmids containing each specific HBsAg gene and then cotransfected each plasmid with HDV cDNA into a permissive human hepatoma cell line (HuH-7) to examine the effects on HDV production. Results indicated that the plasmids containing only the HBsAg genes were able to complement HDV cDNA as efficiently as the plasmid containing the complete HBV genome in generating HDV-like particles. Moreover, the small-form HBsAg alone was sufficient for HDV packaging. The particles produced from the cotransfection experiments have density and protein composition characteristics similar to those of naturally occurring HDV. With the electron microscope, they were identified as 36- to 38-nm-diameter particles. It was concluded that only the HBsAgs were able to help in the assembly of HDV-like particles.

Three envelope proteins of hepatitis B virus: large S, middle S, and major S proteins needed for the formation of Dane particles

The infectious particles of hepatitis B virus are called Dane particles and consist of viral nucleic acid encapsulated within a core particle that is enveloped by virus-coded surface proteins. The major S protein constitutes a significant fraction of these surface proteins. In addition, there are two other related proteins (large S and middle S), but their role in envelope formation has not yet been elucidated. We modified the translation initiation codon ATG of each of the envelope proteins by site-directed mutagenesis and found that mutant genomes that did not produce one or two of these proteins were unable to form Dane particles. The particles released into the culture medium by such mutants did not carry DNA. Synthesis of virus-coded RNA still occurred normally, and core particles carrying DNA accumulated intracellularly. The DNA in such core particles was mostly in the double-stranded open circular form, in contrast to the normal situation in which the particles contain mostly RNA and its complementary single-stranded DNA or else contain linear DNA that is partially single stranded and otherwise duplex. The role of the large S and middle S proteins in the formation of Dane particles is discussed.

Delta hepatitis. The disease and the virus

Delta hepatitis virus is a new human pathogen always found associated with hepatitis B virus (HBV) causing both fulminant hepatitis and the accelerated progression of pre-existing HBV hepatitis. The virus is coated in HBsAg and contains circular single stranded RNA genome with very high intramolecular base-pairing, similar to the genomes of plant viroids, and the HDV antigen, a specific marker of HDV infection also found in the nuclei of infected hepatocytes. The genome is about 1700 nucleotides long and of minus polarity with a major constant antigenomic Open Reading Frame (ORF) which codes for the antigen. Replication of viral RNA appears to proceed by a rolling circle mechanism and specific self-cleavage and self-ligation of both genomic and antigenomic HDV RNA strands has been demonstrated in vitro. HDV appears to require HBsAg for its propagation and hepatotropism but not to depend on HBV for replication.

Effect of the N-terminal hydrophobic sequence of hepatitis B virus surface antigen on the folding and assembly of hybrid beta-galactosidase in Escherichia coli

To investigate the mechanism of inclusion body formation and the effect of a hydrophobic sequence on the in vivo polypeptide folding, the aggregation caused by recombinant fusion beta-galactosidase in Escherichia coli was examined. Two plasmids were constructed: pTBG(H-) carried only the preS2 sequence of the hepatitis B virus surface antigen (HBsAg) in front of the beta-galactosidase gene (lacZ) while pTBG(H+) carried an additional sequence encoding the amino-terminal hydrophobic sequence of the S region of HBsAg between preS2 and lacZ. Unlike cells expressing the fusion protein not containing the hydrophobic sequence, E. coli JM109/pTBG(H+) exhibited temperature-sensitive production of beta-galactosidase. As the culture temperature increased the activity decreased dramatically. This decrease in activity was not due to a decrease in fusion polypeptide production, but rather the fusion polypeptides containing the hydrophobic sequence aggregated within the cells at high temperature. However once the fusion polypeptides folded into proper conformation at low temperature, they maintained the activity even at high temperature. The results indicate that aggregation is a consequence of incorrect folding and assembly of the polypeptides, and is not derived from the native structure. The aggregates of the pTBG(H+)-encoded fusion polypeptides did not revert to active form when the culture temperature was lowered.

Assembly of viral particles in Xenopus oocytes: pre-surface-antigens regulate secretion of the hepatitis B viral surface envelope particle

Infection with hepatitis B virus (HBV) is associated with the production of a viral envelope particle that contains membrane lipids, surface antigen (S), and two presurface-antigens (pre-S) comprised of the entire S moiety with approximately 55 (pre-S2) and 174 (pre-S1) additional NH2-terminal amino acids. We show here that Xenopus oocytes injected with synthetic S mRNA assemble and secrete characteristic 22-nm viral envelope particles. In contrast, pre-S1 and pre-S2 antigens are synthesized but not secreted. By coinjecting mRNAs, we found that synthesis of high levels of pre-S proteins specifically inhibits S antigen secretion. On the other hand, high levels of S synthesis can drive the secretion of small amounts of either pre-S antigen. These observations are consistent with a model for viral envelope assembly in which both S and pre-S proteins are incorporated into a multimeric particle, presumably via interactions between the S protein domains, while the pre-S amino-terminal moieties regulate the secretion of this structure. Our results indicate that Xenopus oocytes will provide a powerful system for studying the morphogenesis of simple structures of viral or cellular origin.

Dane particle-associated hepatitis B e antigen in patients with chronic hepatitis B virus infection and hepatitis B e antibody

A commercial radioimmunoassay was adapted to detect serum Dane particle-associated HBeAg in patients whose sera contained homologous antibody. HBeAg was released from Dane particles with guanidine HCl. Dane particles were separated from anti-HBe by gel-filtration (Sepharose 4B) and ultracentrifugation of the eluate. Dane particle-HBeAg was tested in 45 HBsAg carriers with anti-HBe and was present in 8 (18%) carriers, all of whom had chronic liver disease. By contrast, HBeAg was not found in 10 carriers with normal liver histology. Serum or liver HBcAg was found in 6 of 8 patients with Dane particle-HBeAg. None of the carriers without Dane particle-HBeAg had other markers of hepatitis B virion synthesis. We conclude that Dane particle-HBeAg provides a sensitive index of active hepatitis B virus replication, a guide to the presence of chronic hepatitis in HBsAg carriers with anti-HBe, and a noninvasive method to follow infection in these patients.

Light microscopic localization of hepatitis B virus antigens in the human pancreas. Possibility of multiplication of hepatitis B virus in the human pancreas

Hepatitis B virus has been considered to be strictly organotropic and to infect and multiply only the hepatocytes of humans and chimpanzees. The localization of hepatitis B surface antigen in extrahepatic tissues has been regarded as due to deposition or phagocytosis of hepatitis B surface antigen circulating in the blood. In the present study, however, we demonstrated hepatitis B virus antigens in the pancreases of autopsied subjects with hepatitis B surface antigenemia by Shikata's orcein stain, and immunoperoxidase, immunofluorescent studies; hepatitis B surface antigen and hepatitis B virus core antigen were localized within the cytoplasm of pancreatic acinar cells in 18 and 6 cases, respectively, out of 30 cases studied. In contrast, 25 autopsy cases with no hepatitis B surface antigenemia failed to stain hepatitis B surface antigen or hepatitis B core antigen in the pancreas and liver. Therefore, it may be reasonable to assume that hepatitis B virus can infect and replicate in the human pancreatic acinar cells; however no convincing hepatitis B virus-associated ultrastructures were detected in the present study. Although there were some cases demonstrating chronic inflammatory reaction or fatty necrosis, or both, in the pancreas with hepatitis B virus antigens, the causal relationship between these pathologic changes and hepatitis B virus infection awaits further clarification.