Ubiquitinated Hepatitis D Antigen-Loaded Microvesicles Induce a Potent Specific Cellular Immune Response to Inhibit HDV Replication in Vivo.

Hepatitis D is the most severe form of human viral hepatitis and currently lacks an efficient therapy. Dendritic cell-derived exosomes (Dexs) have been found to induce immune responses capable of eliminating viruses. However, the therapeutic potential of antigen-loaded exosomes in hepatitis D is still unknown. Recently, we designed exosomes loaded with ubiquitinated hepatitis delta virus (HDV) small delta antigen (Ub-S-HDAg) and then treated mice bearing replicating HDV with these exosomes to explore their antiviral effect and mechanism. Mature dendritic cell-derived exosomes (mDexs) were loaded with Ub-S-HDAg and their antivirus function was evaluated in mice with HDV viremia. Furthermore, the proportion of CD8+ cells, the ratio of Th1/Th2 cells, the postimmunization levels of cytokines were explored, and the Janus kinases (JAK)/signal transducer and activator of transcription (STAT) pathway was evaluated with a JAK2 inhibitor AG490. In Ub-S-HDAg-Dexs group, the HDV RNA viral load was significantly decreased compared with other groups by CD8+ cell enrichment and an increase Th1/Th2 cell ratio. Furthermore, lymphocyte infiltration was increased, while the HDAg level was decreased in mouse liver tissue. However, there were no significant differences in HBV surface antigen (HBsAg), alanine aminotransferase (ALT), or aspartate aminotransferase (AST) levels among the groups. Moreover, p-JAK2, p-STAT1, p-STAT4, STAT1, and STAT4 expression was increased in Ub-S-HDAg-Dexs group. In conclusion, Ub-S-HDAg-Dexs might be a potential immunotherapeutic agent for eradicating HDV by inducing specific cellular immune response via the JAK/STAT pathway. IMPORTANCE Hepatitis D is the most severe viral hepatitis with accelerating the process of liver cirrhosis and increasing the risk of hepatocellular carcinoma. However, there are no effective antiviral drugs. Exosomes derived from mature dendritic cells are used not only as immunomodulators, but also as biological carriers to deliver antigens to induce robust immune response. Based on these properties, exosomes could be used as a biological immunotherapy by enhancing adaptive immune response to inhibit hepatitis D virus replication. Our research may provide a new therapeutic strategy to eradicate HDV in the future.

A Rapid Point-of-Care Test for the Serodiagnosis of Hepatitis Delta Virus Infection.

Hepatitis Delta virus (HDV) is a satellite of the Hepatitis B virus (HBV) and causes severe liver disease. The estimated prevalence of 15-20 million infected people worldwide may be underestimated as international diagnostic guidelines are not routinely followed. Possible reasons for this include the limited awareness among healthcare providers, the requirement for costly equipment and specialized training, and a lack of access to reliable tests in regions with poor medical infrastructure. In this study, we developed an HDV rapid test for the detection of antibodies against the hepatitis delta antigen (anti-HDV) in serum and plasma. The test is based on a novel recombinant large hepatitis delta antigen that can detect anti-HDV in a concentration-dependent manner with pan-genotypic activity across all known HDV genotypes. We evaluated the performance of this test on a cohort of 474 patient samples and found that it has a sensitivity of 94.6% (314/332) and a specificity of 100% (142/142) when compared to a diagnostic gold-standard ELISA. It also works robustly for a broad range of anti-HDV titers. We anticipate this novel HDV rapid test to be an important tool for epidemiological studies and clinical diagnostics, especially in regions that currently lack access to reliable HDV testing.

Innate immune recognition and modulation in hepatitis D virus infection.

Hepatitis D virus (HDV) is a global health threat with more than 15 million humans affected. Current treatment options are largely unsatisfactory leaving chronically infected humans at high risk to develop liver cirrhosis and hepatocellular carcinoma. HDV is the only human satellite virus known. It encodes only two proteins, and requires Hepatitis B virus (HBV) envelope protein expression for productive virion release and spread of the infection. How HDV could evolve and why HBV was selected as a helper virus remains unknown. Since the discovery of Na+-taurocholate co-transporting polypeptide as the essential uptake receptor for HBV and HDV, we are beginning to understand the interactions of HDV and the immune system. While HBV is mostly regarded a stealth virus, that escapes innate immune recognition, HBV-HDV coinfection is characterized by a strong innate immune response. Cytoplasmic RNA sensor melanoma differentiation antigen 5 has been reported to recognize HDV RNA replication and activate innate immunity. Innate immunity, however, seems not to impair HDV replication while it inhibits HBV. In this review, we describe what is known up-to-date about the interplay between HBV as a helper and HDV's immune evasion strategy and identify where additional research is required.

Hepatitis Delta: Prevalence, Natural History, and Treatment Options.

Half a century after its discovery, hepatitis delta remains a pertinent global health issue with a major clinical impact in endemic regions and an underestimated prevalence worldwide. Hepatitis delta virus infection follows a challenging clinical course and is responsible for significant liver-related morbidity. Although the only currently available treatment (pegylated interferon) does not provide consistent results, emerging therapeutic options are promising. This article explores the epidemiology, natural history, as well as current and potential therapeutic options for hepatitis delta virus infection.

Hepatitis Delta Virus histone mimicry drives the recruitment of chromatin remodelers for viral RNA replication.

Hepatitis Delta virus (HDV) is a satellite of Hepatitis B virus with a single-stranded circular RNA genome. HDV RNA genome synthesis is carried out in infected cells by cellular RNA polymerases with the assistance of the small hepatitis delta antigen (S-HDAg). Here we show that S-HDAg binds the bromodomain (BRD) adjacent to zinc finger domain 2B (BAZ2B) protein, a regulatory subunit of BAZ2B-associated remodeling factor (BRF) ISWI chromatin remodeling complexes. shRNA-mediated silencing of BAZ2B or its inactivation with the BAZ2B BRD inhibitor GSK2801 impairs HDV replication in HDV-infected human hepatocytes. S-HDAg contains a short linear interacting motif (SLiM) KacXXR, similar to the one recognized by BAZ2B BRD in histone H3. We found that the integrity of the S-HDAg SLiM sequence is required for S-HDAg interaction with BAZ2B BRD and for HDV RNA replication. Our results suggest that S-HDAg uses a histone mimicry strategy to co-activate the RNA polymerase II-dependent synthesis of HDV RNA and sustain HDV replication.

Hepatitis D Virus-Specific CD8+ T Cells Have a Memory-Like Phenotype Associated With Viral Immune Escape in Patients With Chronic Hepatitis D Virus Infection.

BACKGROUND & AIM: Hepatitis D virus (HDV) superinfection of patients with chronic HBV infection results in rapid progression to liver cirrhosis. Little is known about HDV-specific T cells and how they contribute to the antiviral immune response and liver disease pathogenesis. METHODS: We isolated peripheral blood mononuclear cells from 28 patients with chronic HDV and HBV infection, identified HDV-specific CD8+ T-cell epitopes, and characterized HDV-specific CD8+ T cells. We associated these with HDV sequence variations and clinical features of patients. RESULTS: We identified 6 CD8+ T-cell epitopes; several were restricted by multiple HLA class I alleles. HDV-specific CD8+ T cells were as frequent as HBV-specific CD8+ T cells but were less frequent than T cells with specificity for cytomegalovirus, Epstein-Barr virus, or influenza virus. The ex vivo frequency of activated HDV-specific CD8+ T cells correlated with transaminase activity. CD8+ T-cell production of interferon gamma after stimulation with HDV peptides correlated inversely with HDV titer. HDV-specific CD8+ T cells did not express the terminal differentiation marker CD57, and fewer HDV-specific than Epstein-Barr virus-specific CD8+ T cells were 2B4+CD160+PD1+, a characteristic of exhausted cells. Approximately half of the HDV-specific CD8+ T cells had a memory-like PD1+CD127+TCF1hiT-betlow phenotype, which associated with HDV sequence variants with reduced HLA binding and reduced T-cell activation. CONCLUSIONS: CD8+ T cells isolated from patients with chronic HDV and HBV infection recognize HDV epitopes presented by multiple HLA molecules. The subset of activated HDV-specific CD8+ T cells targets conserved epitopes and likely contributes to disease progression. The subset of memory-like HDV-specific CD8+ T cells is functional but unable to clear HDV because of the presence of escape variants. ClinicalTrials.gov, Numbers: NCT02511431, NCT00023322, NCT01495585, and NCT00001971. GenBank accession, Number: MK333199-333226.

Amino Acid Substitutions within HLA-B*27-Restricted T Cell Epitopes Prevent Recognition by Hepatitis Delta Virus-Specific CD8+ T Cells.

Virus-specific CD8 T cell response seems to play a significant role in the outcome of hepatitis delta virus (HDV) infection. However, the HDV-specific T cell epitope repertoire and mechanisms of CD8 T cell failure in HDV infection have been poorly characterized. We therefore aimed to characterize HDV-specific CD8 T cell epitopes and the impacts of viral mutations on immune escape. In this study, we predicted peptide epitopes binding the most frequent human leukocyte antigen (HLA) types and assessed their HLA binding capacities. These epitopes were characterized in HDV-infected patients by intracellular gamma interferon (IFN-γ) staining. Sequence analysis of large hepatitis delta antigen (L-HDAg) and HLA typing were performed in 104 patients. The impacts of substitutions within epitopes on the CD8 T cell response were evaluated experimentally and by in silico studies. We identified two HLA-B*27-restricted CD8 T cell epitopes within L-HDAg. These novel epitopes are located in a relatively conserved region of L-HDAg. However, we detected molecular footprints within the epitopes in HLA-B*27-positive patients with chronic HDV infections. The variant peptides were not cross-recognized in HLA-B*27-positive patients with resolved HDV infections, indicating that the substitutions represent viral escape mutations. Molecular modeling of HLA-B*27 complexes with the L-HDAg epitope and its potential viral escape mutations indicated that the structural and electrostatic properties of the bound peptides differ considerably at the T cell receptor interface, which provides a possible molecular explanation for the escape mechanism. This viral escape from the HLA-B*27-restricted CD8 T cell response correlates with a chronic outcome of hepatitis D infection. T cell failure resulting from immune escape may contribute to the high chronicity rate in HDV infection.IMPORTANCE Hepatitis delta virus (HDV) causes severe chronic hepatitis, which affects 20 million people worldwide. Only a small number of patients are able to clear the virus, possibly mediated by a virus-specific T cell response. Here, we performed a systematic screen to define CD8 epitopes and investigated the role of CD8 T cells in the outcome of hepatitis delta and how they fail to eliminate HDV. Overall the number of epitopes identified was very low compared to other hepatotropic viruses. We identified, two HLA-B*27-restricted epitopes in patients with resolved infections. In HLA-B*27-positive patients with chronic HDV infections, however, we detected escape mutations within these identified epitopes that could lead to viral evasion of immune responses. These findings support evidence showing that HLA-B*27 is important for virus-specific CD8 T cell responses, similar to other viral infections. These results have implications for the clinical prognosis of HDV infection and for vaccine development.

Development and performance of prototype serologic and molecular tests for hepatitis delta infection.

Worldwide, an estimated 5% of hepatitis B virus (HBV) infected people are coinfected with hepatitis delta virus (HDV). HDV infection leads to increased mortality over HBV mono-infection, yet HDV diagnostics are not widely available. Prototype molecular (RNA) and serologic (IgG) assays were developed for high-throughput testing on the Abbott m2000 and ARCHITECT systems, respectively. RNA detection was achieved through amplification of a ribozyme region target, with a limit of detection of 5 IU/ml. The prototype serology assay (IgG) was developed using peptides derived from HDV large antigen (HDAg), and linear epitopes were further identified by peptide scan. Specificity of an HBV negative population was 100% for both assays. A panel of 145 HBsAg positive samples from Cameroon with unknown HDV status was tested using both assays: 16 (11.0%) had detectable HDV RNA, and 23 (15.7%) were sero-positive including the 16 HDV RNA positive samples. Additionally, an archival serial bleed panel from an HDV superinfected chimpanzee was tested with both prototypes; data was consistent with historic testing data using a commercial total anti-Delta test. Overall, the two prototype assays provide sensitive and specific methods for HDV detection using high throughput automated platforms, allowing opportunity for improved diagnosis of HDV infected patients.

Prokaryotic Expression, Purification and Immunogenicity in Rabbits of the Small Antigen of Hepatitis Delta Virus.

Hepatitis delta virus (HDV) is a viroid-like blood-borne human pathogen that accompanies hepatitis B virus infection in 5% patients. HDV has been studied for four decades; however, the knowledge on its life-cycle and pathogenesis is still sparse. The studies are hampered by the absence of the commercially-available HDV-specific antibodies. Here, we describe a set of reproducible methods for the expression in E. coli of His-tagged small antigen of HDV (S-HDAg), its purification, and production of polyclonal anti-S-HDAg antibodies in rabbits. S-HDAg was cloned into a commercial vector guiding expression of the recombinant proteins with the C-terminal His-tag. We optimized S-HDAg protein purification procedure circumventing a low affinity of the His-tagged S-HDAg to the Ni-nitrilotriacetyl agarose (Ni-NTA-agarose) resin. Optimization allowed us to obtain S-HDAg with >90% purity. S-HDAg was used to immunize Shinchilla grey rabbits which received 80 µg of S-HDAg in two subcutaneous primes in the complete, followed by four 40 µg boosts in incomplete Freunds adjuvant. Rabbits were bled two weeks post each boost. Antibody titers determined by indirect ELISA exceeded 107. Anti-S-HDAg antibodies detected the antigen on Western blots in the amounts of up-to 100 pg. They were also successfully used to characterize the expression of S-HDAg in the eukaryotic cells by immunofluorescent staining/confocal microscopy.

Expression and Purification of Recombinant Hepatitis Delta Virus (HDV) Antigen for Use in a Diagnostic ELISA for HDV Infection Using the High-Density Fermentation Strategy in Escherichia coli.

OBJECTIVE: Hepatitis Delt a Virus (HDV) antigen is widely used as a capture antigen in ELISAs for the identification of HDV infection; large amounts of recombinant HDV antigen with active antigenicity are required for this purpose. METHODS: Reconstruct the gene of HDV antigen based on the bias code of Escherichia coli, the recombinant protein expresses by high-density fermentation with fed-batch feeding strategy, and purify by immobilized metal chromatography. The sensitivity and specificity of this antigen detect by ELISA method. RESULTS: The expression of HDV antigen can reach 20% of the total cell mass in the soluble form. The recombinant HDV antigen can be conveniently purified (98%) by immobilized metal ion affinity chromatography (IMAC) using the interaction between a His-tag and nickel ions. Production of recombinant HDV antigen can reach 0.5 g/L under conditions of high-density cell fermentation. Applied to the diagnostic ELISA method, the recombinant HDV antigen shows excellent sensitivity (97% for IgM and 100% for IgG) and specificity (100% for IgG and IgM) for the detection of anti-HDV antibodies. CONCLUSION: Expression and purification the recombinant HDV antigen as a candidate protein for application in a diagnostic ELISA for HDV infection. Large-scale production of the protein can be achieved using the high-density fermentation strategy.

Protein-peptide arrays for detection of specific anti-hepatitis D virus (HDV) genotype 1, 6, and 8 antibodies among HDV-infected patients by surface plasmon resonance imaging.

Liver diseases linked to hepatitis B-hepatitis D virus co- or superinfections are more severe than those during hepatitis B virus (HBV) monoinfection. The diagnosis of hepatitis D virus (HDV) infection therefore remains crucial in monitoring patients but is often overlooked. To integrate HDV markers into high-throughput viral hepatitis diagnostics, we studied the binding of anti-HDV antibodies (Abs) using surface plasmon resonance imaging (SPRi). We focused on the ubiquitous HDV genotype 1 (HDV1) and the more uncommon African-HDV6 and HDV8 genotypes to define an array with recombinant proteins or peptides. Full-length and truncated small hepatitis D antigen (S-HDAg) recombinant proteins of HDV genotype 1 (HDV1) and 11 HDV peptides of HDV1, 6, and 8, representing various portions of the delta antigen were grafted onto biochips, allowing SPRi measurements to be made. Sixteen to 17 serum samples from patients infected with different HDV genotypes were injected onto protein and peptide chips. In all, Abs against HDV proteins and/or peptides were detected in 16 out of 17 infected patients (94.12%), although the amplitude of the SPR signal varied. The amino-terminal part of the protein was poorly immunogenic, while epitope 65-80, exposed on the viral ribonucleoprotein, may be immunodominant, as 9 patient samples led to a specific SPR signal on peptide 65 type 1 (65#1), independently of the infecting genotype. In this pilot study, we confirmed that HDV infection screening based on the reactivity of patient Abs against carefully chosen HDV peptides and/or proteins can be included in a syndrome-based viral hepatitis diagnostic assay. The preliminary results indicated that SPRi studying direct physical HDAg-anti-HDV Ab interactions was more convenient using linear peptide epitopes than full-length S-HDAg proteins, due to the regeneration process, and may represent an innovative approach for a hepatitis syndrome-viral etiology-exploring array.

Characterization of hepatitis delta virus in sub-Saharan Africa.

Hepatitis D virus (HDV) is a satellite of hepatitis B virus (HBV), and infection with this virus aggravates acute and chronic liver disease. While HBV seroprevalence is very high across sub-Saharan Africa, much less is known about HDV in the region. In this study, almost 2,300 blood serum samples from Burkina Faso (n=1,131), Nigeria (n=974), Chad (n=50), and the Central African Republic (n = 118) were screened for HBV and HDV. Among 743 HBsAg-positive serum samples, 74 were positive for HDV antibodies and/or HDV RNA, with considerable differences in prevalence, ranging from <2% (pregnant women from Burkina Faso) to 50% (liver patients from Central African Republic). HDV seems to be much more common in chronic liver disease patients in the Central African Republic (CAR) than in similar cohorts in Nigeria. In a large nested mother-child cohort in Burkina Faso, the prevalence of HDV antibodies was 10 times higher in the children than in their mothers, despite similar HBsAg prevalences, excluding vertical transmission as an important route of infection. The genotyping of 16 full-length and 8 partial HDV strains revealed clade 1 (17/24) in three of the four countries, while clades 5 (5/24) and 6 (2/24) were, at least in this study, confined to Central Nigeria. On the amino acid level, almost all our clade 1 strains exhibited a serine at position 202 in the hepatitis D antigen, supporting the hypothesis of an ancient African HDV-1 subgroup. Further studies are required to understand the public health significance of the highly varied HDV prevalences in different cohorts and countries in sub-Saharan Africa.

[Gene optimization, protein expression, purification and characterization of the HDV antigen for diagnosis].

OBJECTIVE: To prepare HDAg with biological activities as a candidate of diagnostic reagent. METHODS: To synthesize HDV gene fragment after codon optimization. To construct a thio-fused recombinant plasmid based on M48 expression vector. To express in E. coli induced by IPTG. To purify the protein by affinity chromatography followed by characterization in ELISA: RESULTS: Plasmid construction was verified by enzyme digestion. SDS-PAGE indicated the molecular weight of the protein was the same as we expectation. ELISA proved its affinity with HDV antibodies. CONCLUSION: HDAg was obtained successfully and it will pave the road to the research of HDV diagnostic reagent.

Large hepatitis delta antigen activates STAT-3 and NF-κB via oxidative stress.

Hepatitis delta virus (HDV) coinfection or superinfection in hepatitis B virus (HBV)-infected patients results in a more aggressive liver disease, with more often fulminant forms and more rapid progression to cirrhosis and hepatocellular carcinoma. The mechanism(s) for this pejorative evolution remains unclear. To explore a specific HDV pathogenesis, we used a model of transient transfection of plasmids expressing the small (sHDAg or p24) or the large (LHDAg or p27) delta antigen in hepatocyte cell lines. We found that the production of reactive oxygen species was significantly higher in cells expressing p27. Consequently, p27 activated the signal transducer and activator of transcription-3 (STAT-3) and the nuclear factor kappa B (NF-κB) via the oxidative stress pathway. Moreover in the presence of antioxidants (PDTC, NAC) or calcium inhibitors (TMB-8, BAPTA-AM, Ruthenium Red), p27-induced activation of STAT-3 and NF-κB was dramatically reduced. Similarly, using a mutated form of p27, where the cysteine 211-isoprenylation residue was replaced by a serine, a significant reduction of STAT-3 and NF-κB activation was seen, suggesting the involvement of isoprenylation in this process. Additionally, we show that p27 is able to induce oxidative stress through activation of NADPH oxidase-4. These results provide insight into the mechanisms by which p27 can alter intracellular events relevant to HDV-related liver pathogenesis.

Development of a hepatitis delta virus antibody assay for study of the prevalence of HDV among individuals infected with hepatitis B virus in China.

Co-infection with hepatitis delta virus (HDV) and hepatitis B virus (HBV) has been shown to be associated with a more severe form of acute and chronic hepatitis. Cloning and expression of recombinant HDV antigen (rHDAg) in Escherichiacoli are described. Using purified rHDAg, a cost-effective indirect anti-HDV enzyme-linked immunosorbent assay (ELISA) kit was developed. Direct comparison of 15 known HDV-positive sera and 15 HDV-negative sera showed concordance agreement between the new assay kit and the Abbott Murex Anti-Delta (total) kit. In addition, 1,486 hepatitis B surface antigen (HBsAg) positive blood samples collected from various areas of China were tested using this indirect anti-HDV ELISA. It was found that 1.2% (95% CI: 0.7-1.9%) of the samples were anti-HDAg positive. It is suggested that the prevalence of HDV and HBV co-infection in China is relatively low.

[Investigation of anticardiolipin antibodies in chronic hepatitis B infection together with total anti-delta positivity]. / Kronik hepatit B enfeksiyonu ile birlikte total anti-delta pozitifliginde antikardiyolipin antikorlarinin arastirilmasi.

Anticardiolipin antibodies (ACAs) are formed against phospholipids in various clinical conditions such as autoimmune diseases, malignancy, infectious diseases, alcohol-related and hepatic cirrhosis. The aims of this study were to investigate the presence of ACAs in patients with chronic hepatitis B together with positive total anti-delta antibodies, and to investigate the relationship between age, gender, and some laboratory parameters (ALT, AST, albumin, globulin, platelet number) of patients with chronic hepatitis delta virus (HDV) infection, who were positive or negative for ACAs. A total of 60 patients (43 male, 17 female) with chronic hepatitis D infection [HBsAg positive, HBeAg negative, anti-HBe positive, anti-HBc IgG positive, anti-HBc IgM negative, total anti-delta positive, anti-HCV negative] and 30 patients (21 male, 9 female) without hepatitis D infection [HBsAg positive, HBeAg negative, anti-HBe positive, anti-HBc IgG positive, anti-HBc IgM negative, total anti-delta negative, anti-HCV negative] as control group were included to the study. ACA IgG and IgM were searched by a commercial microELISA kit (Euroimmun, Germany). The statistical evaluation was performed with Pearson's chi-square test, Student's t-test, and Fisher's exact test. Total ACAs positivity rate of 60 patients with chronic HDV infection, was found as 13.3%, in which four of the patients were positive for only ACA IgM, while four was positive for only IgG. Positivity for both ACA IgG and ACA IgM could not be detected in these patients. No patients in the control group had positivity for ACAs (IgG and/or IgM). A statistically significant difference was observed in terms of ACA positivity between patients with and without HDV infection (p< 0.05). After all, there was no statistically significant correlation between ACAs positivity and the age, sex, and laboratory parameters of the patients with chronic HDV infection, except lower serum albumin levels (p= 0.004). Although the data of this study revealed a statistically significant positive correlation between chronic HDV infection and anticardiolipin antibodies, it is clear that there is a need for further studies on this subject.

Comparative analysis of disease activity in patients of chronic hepatitis B virus, with and without superinfection with hepatitis D virus; an experience at tertiary care centre.

BACKGROUND: The hepatitis D virus super-infection contributes significantly to the morbidity and mortality of hepatitis B virus infection. The objectives were to describe the incidence of Hepatitis D virus and comparative analysis of disease activity in patients of chronic hepatitis B virus, with and without super-infection of hepatitis D virus. METHODS: This Cross-sectional comparative study was conducted at Department of Medicine and Gastroenterology Clinic Jinnah Postgraduate Medical Centre, Karachi, Pakistan from February 2007 to July 2007. HBsAg positive patients who attended our Gastroenterology clinic were selected for the study. After screening for Anti-HDV these patients were segregated in to Anti-HDV positive and negative groups. Data was analyzed on SPSS 12. RESULTS: Eighty-four patients were selected. Seventy-three patients who fulfilled the inclusion criteria were enrolled in to the study. Anti-HDV was positive in 23 (31.5%) patients. Among these 23 anti-HDV positive, HDV-RNA was detected in 15 (75%) patients. The differences of age, gender, marital status and area of residence whether rural or urban were not significant between the two groups. HBV-DNA was significantly suppressed in majority of anti-HDV positive patients (p = 0.019). Mean serum ALT levels were significantly higher in patients who had HDV infection (p = 0.014). CONCLUSION: HDV infection was common in this series of patients with a frequency of 31.5%. All patients of chronic HBV should be screened for HDV whether they are asymptomatic HBV carriers or have chronic active hepatitis particularly when they have raised serum ALT.

Characterization of deltoid, a chimeric protein containing the oligomerization site of hepatitis delta antigen.

Both forms of the hepatitis delta antigen (HDAg) encoded by hepatitis delta virus are active only as oligomers. Previous studies showed that quadrin, a synthetic 50-residue peptide containing residues 12-60 from the N-terminus of HDAg, interferes with HDAg oligomerization, forms an alpha-helical coiled coil in solution, and forms a novel square octamer in the crystal consisting of four antiparallel coiled-coil dimers joined at the corners by hydrophobic binding of oligomerization sites located at each end of the dimers. We designed and synthesized deltoid (CH3CO-[Cys23]HDAg-(12-27)-seryl-tRNA synthetae-(59-65)-[Cys42]HDAg-(34-60)-Tyr-NH2), a chimeric protein that structurally resembles one end of the quadrin dimer and contains a single oligomerization site. The 51-residue chain of deltoid contains a seven-residue alpha-hairpin loop in place of the remainder of the quadrin dimer plus Cys12 and Cys31 for forming an intrachain disulfide bridge. Reduced, unbridged deltoid (Tm=61 degrees C, DeltaG(H2O)=-1.7 kcal mol(-1)) was less stable to denaturation by heat or guanidine HCl than oxidized, intrachain disulfide-bridged deltoid (Tm>80 degrees C, DeltaG(H2O)=-2.6 kcal mol(-1)). Each form is an alpha-helical dimer that reversibly dissociates into two monomers (Kd=80 microM).