Delta Antigen Research Articles

Hepatitis delta virus infection in French male HBsAg-positive homosexuals.

The prevalence and serological features of hepatitis delta virus infections were studied in a French population of chronic, non-drug addict, hepatitis B surface antigen carriers: 42 male homosexual patients were compared to 30 nonhomosexuals (20 who evidently had not been exposed to any of the usual hepatitis B virus-hepatitis delta virus risk factors and 10 hemodialyzed patients or kidney allograft recipients). Six of the 42 male homosexuals (14.3%) had at least one serological marker of hepatitis delta virus infection (hepatitis delta antigen, total and/or IgM anti-hepatitis delta antibodies). Serological follow-up was obtained for five of these patients over several months and confirmed the chronicity of the delta infection in at least four of the five subjects. Hepatitis delta antigen and hepatitis delta virus RNA were found in the liver and in the serum, respectively, of four of the five tested patients. Hepatitis B virus DNA was negative in the serum of five of the six hepatitis delta virus-positive homosexuals vs. only eight of 35 hepatitis delta virus-negative homosexuals (p less than 0.02). Human immunodeficiency virus was negative in all of the nonhomosexuals; its prevalence did not differ between the hepatitis delta virus-positive and -negative homosexuals: three were human immunodeficiency virus-positive among the six former vs. 15 among the 36 latter. Human immunodeficiency virus positivity was without obvious influence on hepatitis B virus replication, since among 35 hepatitis delta virus-negative homosexuals hepatitis B virus DNA was found in 80% of the human immunodeficiency virus-positive individuals and 70% of those who were human immunodeficiency virus-negative.

Hepatitis delta virus in homosexual men in Sydney.

In countries not generally endemic for hepatitis B, homosexual men who are carriers of hepatitis B surface antigen (HBsAg) have to date largely been spared additional delta virus infection. A focus of homosexually acquired delta has, however, recently been identified in California. To assess the prevalence and risk factors for delta virus infection in homosexual men in Sydney, we tested the sera of 204 homosexual men with acute or chronic hepatitis B infection for total antibody to delta and delta antigen. Total antibody to delta was detected in eight men and delta antigen in one other (4.4% of the total). All men with antibody or antigen had intravenous drug use as a risk factor. Overall nine of 22 (40.9%) male homosexual intravenous drug users had serological evidence of delta infection. Delta positive patients tended to be younger, to have engaged in prostitution, to have more severe chronic liver disease, to be more likely to have a symptomatic acute illness, and to be less likely to express hepatitis Be antigen (HBeAg) in their sera. Though the homosexual transmission of delta infection cannot be concluded from this study, the detection of delta markers in nine homosexual men (including four prostitutes) suggests considerable potential for dissemination of this virus homosexually.

Detection of Hepatitis Delta Virus in Serum and Liver Tissue by Molecular Hybridization: Validation of a Rapid Spot-Hybridization Technique

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

Serological and histological follow up of chronic hepatitis B infection.

In order to study the clinical, serological, and morphological evolution of chronic hepatitis B virus infection in childhood, a prospective study has been carried out. A total of 90 children with a chronic infection were followed up for a mean (SD) of 3 (1.8) years. At the beginning of the study, 61 children were asymptomatic and 77 were household contacts of chronic carriers. Serologically 77 were hepatitis B e antigen (HBeAg) positive and 71 of them were positive to hepatitis B virus DNA. The mean alanine aminotransferase activities were higher among HBeAg positive patients than in antihepatitis B e (anti-HBe) positive ones. The most severe histological damage was also found among HBeAg positive patients. The annual seroconversion rate was 14%. A significant increase in the alanine aminotransferase activity was observed 13 (5.6) months before appearance of anti-HBe in the 85% of cases. Among anti-HBe positive patients, the alanine aminotransferase activities were normal in all except three (19%), two of whom had intrahepatic delta antigen. An increase in the histological activity was observed among patients who maintained HBeAg presence while an amelioration of liver damage was observed in anti-HBe carriers.

Influence of HDV infection on clinical, biochemical and histological presentation of HBsAg positive chronic hepatitis.

In an attempt to identify some characteristics of HDV infection in the different forms of HBsAg positive chronic hepatitis (CH), we evaluated numerous clinical, biochemical and histological aspects in 203 consecutive HBsAg positive CH patients. The presence of hepatitis delta antigen (HD-Ag) in the liver tissue was the criterion used to identify HDV infection. HD-Ag was observed in none of the 7 patients with non-specific reactive hepatitis, in 14.6% of the 48 with chronic persistent hepatitis (CPH), in 36.4% of the 44 with chronic lobular hepatitis (CLH), in 36% of the 25 with mild chronic active hepatitis (CAH), in 52% of the 36 with severe CAH and in 30.2% of the 43 with inactive or moderately active cirrhosis. Compared with the 139 HD-Ag negative patients in this study, the 64 HD-Ag positive patients more frequently had severe CAH (29.7 vs. 12.2%, p less than 0.01) and less frequently CPH (10.9 vs. 29.5%, p less than 0.01). Of the 139 HD-Ag negative patients, 80 were anti-HD positive and 59 anti-HD negative. The 59 patients with no HD-Ag or anti-HD showed severe CAH less frequently than the 64 HD-Ag positive patients (6.8 vs. 29.7, p less than 0.01) and CPH more frequently (44.1 vs. 10.9, p less than 0.001). Both in CPH and CLH the presence of HD-Ag in the hepatocytes identified subgroups of patients who frequently showed high serum levels of aminotransferases and gammaglobulins and more extended areas of circumscribed lobular necrosis. HD-Ag positive CAH was characterized by a more frequent occurrence of eosinophilic degeneration of hepatocytes without peripolesis (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatitis B-DNA replication and histological patterns in liver biopsy specimens of chronic HBsAg positive patients with and without hepatitis delta virus superinfection.

The role of active hepatitis B virus (HBV) infection in chronic HBsAg positive hepatitis with and without hepatitis delta virus (HDV) superinfection was analysed in percutaneous liver biopsy specimens from 50 patients. Each specimen was divided into two--one part for histological evaluation and for the detection of HBcAg and delta antigen; the other part was tested for HBV-DNA using Southern blotting. Ten cases were of chronic lobular hepatitis, 10 of chronic persistent hepatitis, and 30 of chronic active hepatitis. Ten cases were delta antigen positive and showed high grade lobular activity but no evidence of HBV-DNA episomal forms or HBcAg reactivity. Twenty one cases showed HBV-DNA replicative intermediate forms; 19 had high grade lobular activity, which occurred in five cases without evidence of free viral DNA. Of the 21 biopsy specimens with HBV-DNA episomal forms, 14 were positive for HBcAg; only one of the 19 cases without detectable viral DNA was positive for such antigen. These data indicate that the presence of HBV or HDV active infection correlates with the histological finding of prominent lobular necrosis. Moreover, intrahepatic HBV-DNA seems to be a more sensitive marker than the presence of viral antigens for indicating HBV replication.

Electron microscopy of ribonucleic acid in nuclear particulate aggregates of hepatitis D using nuclease-gold complexes.

The ultrastructural localization of hepatitis delta antigen (HDAg) and ribonucleic acid (RNA) was investigated by immunoperoxidase electron microscopy and by enzyme electron microscopy of RNase-gold complexes on liver biopsies from seven patients with hepatitis D. HDAg was localized mainly in the nucleus and sometimes in the cytoplasm of hepatocytes. Ultrastructurally, intranuclear HDAg was found on nuclear particulate structures measuring 20 to 30 nm in diameter. Intranuclear RNA visualized with gold particles was found in high amounts in the nucleolus, to a small extent in the chromatin area, and also on nuclear particulate structures. These findings suggest that intranuclear aggregates of irregular granular particulate structures in hepatitis D are the internal component of hepatitis delta virus (HDV) particles in blood.

Delta hepatitis in homosexual men in the united states

To assess the incidence and prevalence of delta hepatitis in homosexual men, we tested serum specimens for delta markers in participants in two previous studies: a hepatitis B vaccine trial among homosexual men conducted in the early 1980's and the Centers for Disease Control sentinel counties hepatitis study for 1983-1984. In the vaccine trial, men found to be hepatitis B surface antigen positive at the time of enrollment and those men who had serologic evidence of new hepatitis B virus infection during follow-up were tested. In the sentinel counties study that determined risk factors for viral hepatitis in reported cases, all homosexual men with acute and chronic hepatitis B virus infections were tested for delta markers. Specimens were tested for delta antigen and IgM and total delta antibody. In seven different cities, among 321 men found to be HBsAg positive at the time of screening, eight (2%) were positive for any delta marker. Among 290 men with new hepatitis B virus infections during follow-up, three (two coinfections, one superinfection) had serologic evidence of delta hepatitis. In the sentinel counties study, 0/63 acute hepatitis B virus infections in homosexual men were associated with delta hepatitis. This study indicates that the delta agent is an infrequent cause of viral hepatitis in homosexual men in the United States.

Initiation of replication of the human hepatitis delta virus genome from cloned DNA: role of delta antigen.

Beginning with three partial cDNA clones of the RNA genome of human hepatitis delta virus (HDV), we assembled the complete 1,679-base sequence on a single molecule and then inserted a trimer of this into plasmid pSLV, a simian virus 40-based eucaryotic expression vector. This construct was used to transfect both monkey kidney (COS7) and human hepatocellular carcinoma (HuH7) cell lines. In this way we obtained replication of the HDV RNA genome and the appearance, in the nucleoli, of the delta antigen, the only known virus-coded protein. This proved both that the HDV genome could replicate in nonliver as well as liver cells and that there was no requirement for the presence of hepatitis B virus sequences or proteins. When the pSVL construct was made with a dimer of an HDV sequence with a 2-base-pair deletion in the open reading frame, genome replication was reduced at least 40-fold. However, when we cotransfected with a plasmid that expressed the correct delta antigen, the mutated dimer achieved a level of genome replication comparable to that of the nonmutated sequence. We thus conclude that the delta antigen can act in trans and is essential for replication of the HDV genome.

TCR3: a third T-cell receptor in the chicken.

Avian homologues of mammalian gamma delta and alpha beta T-cell antigen receptors, TCR1 and TCR2, have been identified with monoclonal antibodies. These TCR isotypes are associated with the avian CD3 proteins on the T-cell surface. During chick development, T-cell subpopulations bearing CD3/TCR1 or CD3/TCR2 receptor complexes are generated sequentially in the thymus and seeded to the periphery in the same order. In this study, we used two-color immunofluorescence to identify the subsequent development of a third subpopulation of T cells, provisionally named TCR3. These CD3+ cells, which expressed neither TCR1 nor TCR2, were first detected in the blood 1 week after hatching and increased numerically as a function of age to account for approximately 15% of the circulating T-cell pool in adults. Most (greater than 80%) of the TCR3 cells expressed the CD4 accessory molecule. The relative incidence of the TCR3 subpopulation increased dramatically as a consequence of embryonic treatment with anti-TCR2 antibody and thymectomy after hatching. Two disulfide-linked polypeptides, of Mr 48,000 and 40,000, were associated with the CD3 complex on the TCR3 cells. Examination of the TCR protein backbones and peptide mapping of the TCR chains after partial proteolysis indicated that the TCR3 heterodimer differs from both TCR1 and TCR2. These results suggest the existence of a third class of T-cell receptors in birds.

The serology of delta hepatitis and the detection of IgM anti-HD by EIA using serum derived delta antigen

A sensitive and specific capture assay for IgM antibody to hepatitis D virus (HDV) was developed employing serum-derived delta antigen (HDAg). In a retrospective and prospective study of an outbreak of hepatitis B (HB), 135 hepatitis B surface antigen (HBsAg) positive drug-abusers with acute hepatitis and 18 HBsAg carriers, attending various hospitals and clinics in Dublin, were found to be infected with HDV. Serological follow-up was available from 24 of those with acute hepatitis allowing a comparison of the duration and level of IgM anti-HD with the more commonly used markers, HDAg and anti-delta (anti-HD), and an assessment of the usefulness of each. HDV and HB serology was grossly altered by human immunodeficiency virus (HIV) in two patients, with severe clinical manifestation in one. All 135 patients with HDV co-infection had delta antigenaemia. In co-infections with optimum sampling times, the mean duration of delta antigenaemia was 21 days. IgM anti-HD was always found between HDAg and sero-conversion to anti-delta and was the only ‘window’ marker present in five cases. The mean duration of IgM anti-HD was four weeks (optimum at 2.8 weeks) and was of moderate or low titre and occurred simultaneously with HDAg in 78%. In HDV-infected HBsAg carriers, high-litre IgM anti-HD ( > 1 10000 ) persisted for the duration of the study and is a useful indicator of chronic HDV infection. IgM anti-HD was not found in 202 random blood donors nor in 205 patients with non-B hepatitis or other disorders. Total (IgG) anti-HD persisted in all patients (except the two reactivations) at titres of less than 1 1000 in co-infections and greater than 1 5000 in carriers, for the duration of follow-up. We conclude that HDAg is singly the best marker of HDV co-infection and. where only late specimens are available. IgM anti-HD is also useful. IgM anti-HD will also distinguish between chronic HDV infection and previous exposure.

An Ultraviolet-Sensitive RNA Structural Element in a Viroid-Like Domain of the Hepatitis Delta Virus

The RNA genome of the hepatitis delta virus (HDV) appears to be made up of two parts: a small domain with a high degree of sequence conservation and structural features likely to promote replication; plus a second, larger domain that is less conserved and encodes the delta antigen. This report focuses on one of the several sets of data that have led to the proposal of this model: the existence of a novel structural element in HDV genomic RNA. This structural element lies within the highly conserved domain of HDV RNA and may be related to the local tertiary structure previously mapped to the central conserved region of the plant viroid genome. Both elements occur in regions with no apparent coding capacity and are distinctively responsive to ultraviolet (UV) light. Transcripts containing partial and full-length genomic sequences of HDV readily undergo a UV-induced crosslinking reaction, which establishes a covalent bond between two noncontiguous segments. By locking two segments of the overall structure into place, this crosslink has permitted the unbranched, rodlike model of HDV RNA to be examined and confirmed in the portion of the RNA analyzed. The clustering of the novel tertiary structure and the recently discovered self-cleavage sites into a highly conserved, but apparently noncoding, portion of the genome defines a viroid-like domain in HDV RNA and raises questions about the possible events leading up to the association of free-living RNAs with messenger RNAs and other RNA molecules.

Delta virus hepatitis.

The Hepatitis Delta Virus (HVD) occupies a unique niche in humai virology. At variance with conventional animal viruses, it cannot replicate autonomously but requires the presence of the Hepatitis B Virus (HBV) to initiate infection. It behaves like a defective interfering agent, in that it ihibits the synthesis of the competent HBV helper once its infection is established. This cooperation is reflected in the HD virion, a 36 nm spherical particle formed by an envelope of HBV-derived surface antigen (HBsAg), which encloses the genome and a specific delta antigen (HD-Ag) (1).KeywordsFulminant HepatitisHepatitis Delta VirusHelper VirusWoodchuck Hepatitis VirusDefective VirusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Evidence for replication of hepatitis delta virus RNA in hepatocyte nuclei after in vivo infection

Examination of a naturally infected human liver and experimentally infected chimpanzee and woodchuck livers by in situ hybridization showed that hepatitis delta virus (HDV) RNA was restricted to hepatocytes. Genomic RNA was 20–30 times more abundant than antigenomic RNA and was predominantly single-stranded while antigenomic RNA was predominantly double-stranded. In acute delta hepatitis, viral RNA was a more reliable marker of virus infection in single cells than hepatitis delta antigen (HDAg) while in chronic hepatitis both markers were usually present in the same cell. In all cases, viral antigen and RNA were localized predominantly to the nuclei of infected cells. Thus, replication of HDV RNA is closely associated with HDAg expression at the cellular and intracellular level and it is likely that this new class of defective animal RNA viruses replicates in the nucleus of the infected cells.

Serial passage of hepatitis delta virus in chronic hepatitis B virus carrier chimpanzees.

Five consecutive passages of hepatitis delta virus in hepatitis B virus carrier chimpanzees were performed in order to further characterize the infectious and pathogenic nature of this naturally occurring defective virus. Three animals received identical inocula at fourth passage in order to assess individual animal variation as a factor in the course of infection and disease. Acute hepatitis delta virus infection occurred in all hepatitis B virus carrier chimpanzees as demonstrated by coincident intrahepatic hepatitis delta antigen, serum hepatitis delta antigen and serum hepatitis delta virus RNA followed by seroconversion to antibody to hepatitis delta antigen. In all animals, acute hepatitis was temporally associated with hepatitis delta virus infection and was self-limited. The incubation period to hepatitis shortened with passage, whereas biochemical and histologic evidence of liver diseases increased. The marked increase in liver disease with passage was not associated with increasing markers of hepatitis delta virus replication or expression, thus indicating that adaptation to the chimpanzee by serial passage resulted in increased hepatitis delta virus virulence. The duration of hepatitis due to hepatitis delta virus infection in three chimpanzees which received the same inoculum varied from 1 to 8 months. The observations of passage adaptation and individual host variation in this experimental model of hepatitis delta virus disease parallel known pathogenic variations in human hepatitis delta virus infection.

Influence of hepatitis delta virus superinfection on the clearance of hepatitis B virus (HBV) markers in HBV carriers in Japan.

To elucidate the influence of hepatitis delta virus (HDV) superinfection on the clearance of hepatitis B virus (HBV) associated antigens in HBV carriers, we examined for antibody to hepatitis delta antigen (anti-HD) serial sera collected from 1,029 HBV carriers in Kure, Japan. Of the 242 HBV carriers with hepatitis B e antigen (HBeAg), 28 became seropositive for anti-HD, of whom 18 (64.3%) cleared HBeAg; 214 did not become seropositive for anti-HD, of whom 70 (32.7%) cleared HBeAg. Thus, HBeAg clearance was observed in a significantly higher proportion of HDV-superinfected carriers as compared with carriers without HDV infection (P less than 0.005). In the 56 HBV carriers who cleared hepatitis B surface antigen (HBsAg), anti-HD was detected in three cases with increased serum alanine aminotransferase activity preceding HBsAg clearance. The duration of anti-HD seropositive state was less than 5 years, and the titer of anti-HD was relatively low in every case. These data suggest that the HDV infection rate in Japan is higher than previously reported, that HDV superinfection can be one of the factors that induce the HBeAg clearance and HBsAg clearance in HBV carriers, and also that the most likely outcome of HDV superinfection in HBV carriers in Japan may be acute self-limited infection.

Antigenomic RNA of human hepatitis delta virus can undergo self-cleavage

The structure and replication of the single-stranded circular RNA genome of hepatitis delta virus (HDV) are unique relative to those of known animal viruses, and yet there are real similarities between HDV and certain infectious RNAs of plants. Therefore, since some of the latter RNAs have been shown to undergo in vitro site-specific cleavage and even ligation, we tested the hypothesis that similar events might also occur for HDV RNA. In partial confirmation of this hypothesis, we found that in vitro the RNA complementary to the HDV genome, the antigenomic RNA, could undergo a self-cleavage that was not only more than 90% efficient but also occurred only at a single location. This cleavage was found to produce junction fragments consistent with a 5'-hydroxyl and a cyclic 2',3'-monophosphate. Since the observed cleavage was both site-specific and occurred only once per genome length, we propose that the site may be relevant to the normal intracellular replication of the HDV genome. Because the site is located almost adjacent to the 3' end of the delta antigen-coding region, the only known functional open reading frame of HDV, we suggest that the cleavage may have a role not only in genome replication but also in RNA processing, helping to produce a functional mRNA for the translation of delta antigen.

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

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

Kinetics of delta antigen and delta antibody in acute delta hepatitis: evaluation with different enzyme immunoassays.

The kinetics of delta antigen (HDAg) and anti-delta antibody (anti-HD) was analyzed in 22 acute delta hepatitis infections (11 coinfections and 11 superinfections), with an enzyme immunoassay developed by Organon Teknika and with two commercially available assays: Deltassay, a test for HDAg from Noctech and Abbott anti-delta enzyme immunoassay, a test for anti-HD from Abbott Laboratories. In seven cases, HDAg was detected with the Organon assay but not with Deltassay. These discrepancies were not related to the type of hepatitis delta virus infection. All samples from these patients taken beyond week 4 of illness were found anti-HD positive with both the Organon and Abbott anti-HD assays. These data reflect the lack of sensitivity of Deltassay. In no instance were HDAg and anti-HD present simultaneously when tested with the Organon assays. On the contrary, 10 sera among the 28 that were HDAg positive with the Organon assay also were found anti-HD positive with the Abbott test. We suspected that the test procedure recommended by Abbott (a one-step competitive assay) may have yielded false-positive anti-HD results when HDAg present in the sera reacted with peroxidase-labeled anti-HD of the kit. To determine the specificity of the simultaneous presence of HDAg and anti-HD, these 10 sera were retested with the Abbott anti-HD assay, but by a modified two-step procedure that avoided contact between sera and labeled antibody. For six sera a negative result was obtained with the second procedure, suggesting that a false anti-HD reaction occurred with the standard test procedure. For four sera a positive result with both procedures was indicative of the simultaneous presence of HDAg and anti-HD. In conclusion, assay for HDAg was found very convenient for the early diagnosis of acute hepatitis delta virus infections. Seroconversion to anti-HD could be used for a late diagnosis 2 to 5 weeks after the beginning of illness. However, anti-HD results obtained with one-step competitive assays have to be interpreted carefully in HDAg-positive sera.

Intranuclear inclusion bodies in liver of chronic hepatitis B with delta infection.

Seventy-two patients with HBsAg-positive chronic hepatitis were studied for serum antibody to delta antigen (anti-HD) by radioimmunoassay. Delta antigen (HDAg) in liver of the 72 patients was also studied immunohistochemically using peroxidase-labeled anti-HD. In one of the 72 patients, high titers of anti-HD and intrahepatic HDAg were detected. In this patient, HDAg was localized mainly in nuclei and occasionally in the cytoplasm of hepatocytes. By immunoelectron microscopy, HDAg was observed diffusely in some hepatocytic nuclei, but their nucleoli, perichromatin and heterochromatin were devoid of HDAg. Occasionally, inclusion body-like ring-shaped or irregularly shaped aggregates of HDAg were observed in nuclei. At higher magnification, these aggregates consisted of an HDAg-positive amorphous substance and microtubular structures. In their vicinity, scattered HDAg-positive granules were also present. By conventional electron microscopy, similar inclusion bodies composed of a clustered amorphous substance and microtubular structures 10-20 nm in diameter, together with 20-30 nm irregular granules were observed in hepatocyte nuclei, but no core of Dane particles were found. These novel intranuclear structures were not observed in other patients with chronic hepatitis B. It is suggested that they may represent the characteristic ultrastructure associated with delta infection.