Delta virus hepatitis

Journalof Hepatology, 1986;3:419-423 Elsevier

419

HEP 00248

Conference Report

Delta Virus Hepatitis Delta virus was first described by Rizzetto and colleagues in 1977 when Delta antigen was found in the hepatocyte nuclei of HBsAg-positive patients. It is a defective virus depending on HBsAg for its replication. It is highly infectious and can induce hepatitis in an HBsAg-positive host. At first, Delta infection was described in HBsAg carriers from Southern Italy, many of them drug abusers, but now it is being detected worldwide, in all categories of HBsAg-positive patients. A conference on the hepatitis Delta virus was held in Saint Vincent (Aosta, Italy), on June 19th and 20th, 1986, organised by Mario Rizzetto and the Ospedale Maggiore San Giovanni Battista of the City of Turin. Delta virus hepatitis is not of recent origin. It has been present for as long as stored sera are available. It has been found in blood bank specimens collected between 1962 and 1965 and even in one unit of plasma obtained in 1944 from an U.S. army source (J. Maynard). It has been found in 1967 in specimens from Los Angeles (D. de Cock), in 1971 from Australia (I. Gust) and, in 1974, from Italy (E. Sagnelli). The Delta agent has similarities to plant satellite viruses (T.O. Diener, U.S. Department of Agriculture). These single stranded RNA particles alter the pathogenicity of other viruses. They have no capsule, and provide one of the most extreme forms of parasitism known. Delta hepatitis can be transmitted to animals who carry hepatitis B-like viruses. These include chimpanzees (R.H. Purcell, National Institute of Health); woodchucks and Peking ducks (A. Ponzetto, Turin).

Molecular biology The RNA genome of the virus has been cloned by

several groups. It is a single-stranded circular antisense RNA of 1.75 Kb size. It has an intense secondary structure forming rod-like structures with base pairing between the majority of the two sides of the rod and 'loop outs' where there are anti-complementary regions. Houghton (U.S.A.) reported the complete sequence and noted areas of homology to the satellite plant viruses and viroids. He described five open-reading frames on the anti-genomic strand of the cDNA that he had prepared. When these were expressed, one was shown to encode for a protein identifiable with anti-Delta-positive human serum. Yas reported data which suggest that the virus replicates by a method similar to the 'rolling circle' strategy proposed by Sanger for the bacteriophage OX 174. The anti-genomic strand may be three or more times the length of the viral genome and must be cut up by cellular or viral enzymes before packaging into virus particles. Delta hepatitis shares features with non-A, non-B virus infection. Electron microscopy shows tubular structures in the hepatocyte cytoplasm similar to those described by Y.K. Shimizu (Tokyo) in hepatocytes infected with non-A, non-B (Strain F). G. Kojima (Leuven), using immune electron microscopy noted similar changes in nuclear chromatin in Delta and non-A, non-B infected chimpanzee hepatocytes. Delta antigen, however, was associated with ribosomes possibly indicating the result of transcription of the Delta messenger. Monoclonal antibodies produced by EBV transformation of the peripheral blood lymphocytes of chimpanzees recovered from non-A, non-B hepatitis, bind not only to microtubular structures in the cytoplasm of non-A, non-B infected chimpanzees and humans but also to HDV superinfected HBV carriers (Y.K. Shimuzu, Tokyo).

0168-8278/86/$03.50© 1986Elsevier SciencePublishers B.V. BiomedicalDivision)

420 The absence of nucleic acid homology between HDV and non-A, non-B suggests that this antigen similarity relates to induction by these viruses of a common host component rather than structural similarities of the two agents. In the chimpanzee, both non-A, nonB and Delta show lack of solid, long-term (two year) cross-immunity to reinfection, and the size of the two agents differs. The Delta virus is probably between 30 and 15 A in size, whereas the non-A, non-B virus lies between 50 and 30 A (R.H. Purcell). A further area of interest stems from the presence of a wide variety of autoantibodies in sera of HDV superinfected HBV carriers, including those against the basal cell layer of the rat forestomach (E. Pisi, Bologna) and thymic epithelial cells (L. Magnius, Stockholm). These autoantibodies are of unknown significance.

Epidemiology There are wide variations in the prevalence of Delta infection throughout the world. Figures differ whether acute hepatitis or chronic liver disease is being studied. In Southern Italy about 30% of acute hepatitis B is associated with Delta infection (E. Sagnelli, Naples). Delta is found in between 26 and 46% of patients with chronic active hepatitis and cirrhosis. In Greece, Delta is found in 2.4% of the general population and in 12% of those with chronic liver disease (G. Papaevangelou). Reports from Roumania show a fantastic association of Delta with chronic liver disease, 228 of 373 patients (83.3%) with chronic active hepatitis, chronic persistent hepatitis and hepatocellular carcinoma being Delta positive (D. Tapalaga, Bucharest). The carrier rate of the hepatitis-B in Saudi Arabian males is 11.2% and 53% of those with chronic active hepatitis are Delta-positive (O. Shobokshi, Saudi Arabia). The carriage rate of HBsAg in Ethiopian army recruits is 10.9% and 5.6% of these have serum Delta antibodies (M. Rapicella, Ethiopia,). The Delta antibody was found in 31 of 131 patients with acute hepatitis B in Bombay (D.D. Banker, India), but on the whole the frequency is low in North India. The overall carriage rate of HBsAg in the Far East is 15%. yet there is little Delta infection. This is

S. SHERLOCK and H.C. THOMAS particularly so in Hong Kong. However, 15.6% ol patients with hepatitis B-related chronic active hel~. titis patients have positive serum anti-Delta (Bea~ ley). In Taiwan, 25% of acute hepatitis in adult chronic B-carriers, is associated with superadded Delta infection (Y.F. Liaw, Taiwan). In Australia, 8.6% of patients with acute hepatitis B have Delta in. fection (I. Gust, Melbourne). Drug abuse accounts for 60% of acute hepatitis B, and of these, 13.4e/¢ have Delta. In Japan, Delta infection is found in only 0.8% of patients with B-related chronic liver disease (R.P. Beasley, Taiwan). The prevalence is low in Chile (J. Maynard), Argentina (O. Fay) and Brazil (J.C. Fonseca). Delta infection does not, so far, seem to have reached the Eskimos, or the North American Indians (J. Maynard). Epidemiological studies show great variation not only from country to country, but in the same country. Thus in the U.S.S.R., Delta carriage is 3.3% in the 'European' parts but 14.4% in the 'middle' areas of Atne, Ata and Tashkent (Ketiladze, U.S.S.R.). It is found in 2% of patients with acute hepatitis B in Moscow. Similarly, in China, the distribution varies from 9% in inner Mongolia to zero in Shanghai (M. Roggendorf, F.R.G.). In the Pacific islands generally, despite the high prevalence of carriage of HBsAg, there is no Delta. There are, however, exceptions in Nauru (31.4%), Numea (28.6%) and Western Somoa (25%) (Gust). The Delta agent must have arrived before the tourists and how it reached such remote islands remains a mystery. In South America. too, there are differences between the Amazon basin areas of Brazil, Colombia and Venezuela, where 23-26% of hepatitis B carriers are hepatitis Deltapositive, and Rio de Janeiro where the mean is 0.5% (1.2-2.8). The prevalence of hepatitis Delta infection may also vary from year to year. In Naples, the overall Delta infection in acute hepatitis is 29%. but this can vary from 20 to 45% according to the year (E, Sag. nello). The patient groups are very similar to those affected by hepatitis B. They include drug abusers and homosexuals (K. de Cock). Blood transfusion is particularly important in areas with high carrier rates ~f

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hepatitis B and where facilities are not available for screening donor blood. Large pool commercial products are particularly liable to be infectious and 40% of samples can be positive for Delta (G. Saracco, Turin). Thus, 50% of hepatitis B-positive thalassaemics in Greece are positive for Delta, compared with 35% in drug abusers and 2.4% in the general population (G. Papaevangelou). Intra-family spread is probably more important as shown in a multicentre study from Italy (F. Bonino, Turin). The Greek island of Archangelos, where drug abuse and homosexuality are virtually unrecognised, has 4 100 inhabitants, 10.7 HBsAg-positive and 27.3% of these carry Delta infection. This compares with figures of 4.1 and 0% Delta carriage in a neighbouring village (S. Hadzyannis, Athens). Intra-familial (horizontal) spread is also likely in Saudi Arabia (F. Shoborshi, Jeddah).

ular probes for the detection of serum and liver H D V - R N A . This was found in the serum of patients with both acute and chronic Delta infection. The majority of patients with IgM anti-Delta are HDV-RNA-positive in serum. The use of RNA probes (riboprobes) may give more sensitivity and might be valuable for epidemiological studies, particularly in identifying carriers.

Diagnosis The course of the disease varies according to whether the hepatitis B and Delta are acquired together (co-infection) or whether Delta infects an established hepatitis B carrier (super-infection). Co-infection is diagnosed by the finding of serum IgM anti-Delta in the presence of high titre IgM antiHBc. These appear at one week and IgM anti-HDV is gone by 5 - 6 weeks, but may last up to 12 Weeks (P. Farci, Cagliari). However, some patients have no serum IgM anti-Delta response. When serum IgM antiDelta disappears, serum lgG anti-Delta appears. There may be a "window' period between the disappearance of one and the detection of the other. Positive diagnosis of acute Delta infection can only be made if several sera are tested for Delta antibodies over several weeks. Super-infection of a B carrier with Delta is marked by the early presence of serum IgM anti-Delta, usually at the same time as early IgG anr!-Delta, and both antibodies persist. These patients are usually IgM anti-HBc-negative but may have low titres of this antibody. 84% of sufferers of chronic Delta infection have a positive serum lgM anti-Delta. This is particularly so in the presence of chronic active hepatitis and active cirrhosis. A. Smedile (Messina) discussed the use of molec-

Clinical aspects The acute attack is marked by dark urine and serum Delta antigenaemia which disappears within 6 days to be followed between 2 and 8 weeks (mean 3 weeks) by the presence of serum Delta antibodies (I. Gust, Melbourne). Co-infection may present as relapsing hepatitis (biphasic course). The maximum interval between the two attacks is 6 weeks; in general, the prognosis of relapse is good (F. Caredda, Milan). Fulminant hepatitis can accompany Delta co-infection or super-infection. E. Sagnelli (Naples) found fluctuations over the years since 1974 with between 46 and 67% of fulminant hepatitis being due to H D V infection, compared with 20-45% of benign cases. In Los Angeles, 1 in 7 cases of Delta infection were fulminant (K. de Cock). This may reflect patient referral to a specialized liver unit. Other groups have not connected Delta infection with a fulminant course. In Milan, F. Caredda found only slightly more fulminant than benign cases with Delta co-infection. In Melbourne 180 cases of acute Delta infection were not associated with more severe disease; no fulminant cases were reported and there were no deaths (Gust). In Greece, post-transfusion studies showed 2 or 90 patients developing benign hepatitis were Delta-positive (G. Papaevangelou, Athens). This compared with 2 Delta-positive patients out of 23 (8.7%) developing fulminant disease. Acute Delta appears to be a less severe infection in Greece and Australia. Chronic B-carriers infected with Delta show a fall in serum markers of hepatitis B replication. Thus, F. Bonino (Turin) noted that serum H B V - D N A was rarely found in anti-HBc-positive patients with chronic Delta infection. Co-infection with Delta and B, may be followed by clearing of B and hence also of Delta. Only 5% develop chronic HBV and BDV in-

422 fection. Delta infection may sometimes terminate HBV infection thereby reducing the sum total of patients with chronic hepatitis B infections (de Cock, Los Angeles). Superinfection with Delta of a patient carrying hepatitis B accelerates the course of the liver disease (A. Carxi, Palermo; F. Caredda, Milan). Delta infection is the major cause of cirrhosis in young people in Italy. 14% of those superinfected die within three years of the acute episode. Death is usually due to bleeding, liver failure or hepato-cellular carcinoma. Such figures emphasise the need for a Delta vaccine for hepatitis B carriers. Those previously, and successfully, vaccinated against hepatitis B will, of course, be immune to Delta infection. A particularly fulminant form of acute Delta infection has been described from the Amazon Basin of Brazil, the Yucpa area of Venezuela and the Santa Marta area of the Sierra Nevada area of Colombia (H. Popper, New York; J. Maynard, Bethesda, U.S.A.). In Brazil it is termed Labrea (acute hepatic failure with black vomit). It affects adolescents and young adults of the indigent population. Liver histology shows small droplet fatty change, eosinophilic necrosis, minimal inflammation with portal lymphocytes and sometimes Morula (plant-like) cells (H. Popper). Delta antigen can be found in hepatocytes in 70-100% of sufferers. The disease existed in South America 50 years ago when viscerotomy specimens of liver were routinely taken after death to exclude Yellow Fever. Examination of these specimens allowed the present identification of acute Delta hepatitis. A similar fulminant picture was reported by C. Trepo (Lyons) from Bangu in Equatorial Africa, where massive steatosis was found in 68% of Deltapositive livers. Treatment There have been limited attempts to treat Delta infection with anti-viral drugs. H.C. Thomas (London) used a 12-week course of 10 megaunits/m 2 of lympho- ' blastoid alpha-interferon given three times a week to treat five patients with Delta infection with chronic active hepatitis or cirrhosis. Three showed a complete response with loss of serum hepatic Delta RNA

S. SHERLOCK and tt.C. IIIOMAS ( H D V - R N A O ) in one the effect was partial with reduction, but not disappearance of HDV-RNA. and in one the treatment failed. Side-effects included fe~. er, lethargy and bone marrow suppression. The el'. fect on the course of the liver disease was variable. J. Hoofnagle (National Institute of Health, U. S.A.) treated six patients with lower doses of daily subcutaneous recombinant human alpha-interferon for four months. Three responded with loss of serum H B V - D N A , but in one it returned later. In three. the treatment failed. F. Rosina (Turin) conducted a controlled clinical trial of 5 megaunits/m 2 of interferon given three times a week for twelve weeks. At the end of therapy, serum H D V - D N A was cleared in six, reduced in one and unchanged in one. Eight patients showed biochemical improvement. However, at 12 months. only one had sustained clinical and virological remission with absence of Delta antigen from the liver Ten had relapsed with rises of serum transaminase.~ and Delta antigen being detected in liver. The twelve control subjects showed no virological or biochemical changes. All three trials indicate that alpha-interferon can inhibit H D V replication but the long-term effects are less clear. Further studies will be needed to determine the optional regimen and the effects on the course of the liver disease. Hepatic transplantation was used to treat three Delta-positive patients in Rome (G. Marinucci). One patient died at three months, when small amounts ol Delta antigen were found in the liver at post mortcm The second died 4 - 5 days post-transplant and. at autopsy, markers of hepatitis B and Delta virus were not found in the liver. The third patient died, at I(I weeks, from fulminant hepatitis; at autopsy, hep:ltitis B core antigen and Delta antigen were found in the transplanted liver. G.M. Vigevani presented the hepatic transplantation results of D.A. Galmarini of Milan. Four Deltapositive patients were transplanted. Two arc alive. six and five months later and both have positive serum anti-Delta tests. Two died at 81 and 15 days after transplant and in both, at autopsy, Delta antigen ~v;l~ found in the transplanted liver.

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Thus, at the present time, hepatic transplantation does not seem to be an effective treatment for chronic liver disease associated with Delta. The chances of infection of the transplanted liver are high, perhaps related to Delta proliferation in extra-hepatic sites, or more likely to ineffective passive immunization procedures with hyperimmune globulin. Pre-transplantation interferon treatment might be useful and lower dose cyclosporin will have to be given after the transplant. Monoclonal antibodies may be needed to neutralise the HBV infection of the transplanted liver.

probably cytopathic and induces changes in the hepatocyte similar to those of non-A, non-B. Retrospective studies show that it has been present for at least 50 years and perhaps much longer. Its effect on the course of HBV infection is important and emphasises the need for effective therapy.

Conclusion Hans Popper made a masterly summary of the meeting. The structure of the Delta virus is now known and we can anticipate rapid progress in our understanding of the strategy of replication and the relationship of Deltas to HBV. The Delta virus is

The proceedings of the conference will be published as a separate issue of Progress in Clinical and Biological Research by the publisher Alan R. Liss, New York. References to the various papers cited above will be found in this book. SHEILA SHERLOCK HOWARD C. THOMAS

Royal Free Hospital, School of Medicine, London NW3 2QG, U.K.