Non-A, non-B hepatitis. II. Experimental transmission, putative virus agents and markers, and prevention

Taming a beast: lessons from the domestication of hepatitis C virus

"What I cannot create, I do not understand." Richard Feynman may have championed reasoning from first principles in his famous blackboard missive, but he could just as well have been referring to the plight of a molecular virologist. What cannot be grown in a controlled laboratory setting, we cannot fully understand. The story of the laboratory domestication of hepatitis C virus (HCV) is now a classic example of virologists applying all manner of inventive skill to create cell-based models of infection in order to clarify prospective drug targets. In this review, we highlight key successes and failures that were instructive in achieving cell-based models for HCV studies and drug development. We also emphasize the lessons learned from the ∼40 year saga that may be applicable to viruses yet unknown and uncultured.

Morphology of hepatitis C and hepatitis B virus particles as detected by immunogold electron microscopy

We performed indirect immunogold electron microscopy (EM) for immunological identification and characterization of hepatitis C virus (HCV). To clarify the morphology of HCV, an indirect immunogold EM of two plasma samples from patients with high HCV RNA titers was carried out using antibodies specific for the putative HCV envelope protein (E) 1. Spherical virus particles 55-65 nm in diameter with delicate spike projections were detected in the 1.14-1.16 g/ml fractions after sucrose density gradient centrifugation. Polyclonal and monoclonal antibodies to the putative HCV E1 specifically recognized these particles. In addition, immunogold EM of the samples was also performed to uncover the morphology of HCV core particles. Spherical particles 33-40 nm in diameter (average, 37 nm) were detected in the 1.22- to 1.25-g/ml fractions by conventional EM after sucrose density gradient centrifugation. Immunogold EM using rabbit polyclonal antibody (RR8) specific for the putative HCV core protein and colloidal gold-labeled goat antirabbit IgG showed binding of the gold particles with RR8. Some of the HCV core particles showed icosahedric morphology. Optical rotation technique showed that the HCV core particles exhibit sixfold symmetry and that the length of the regular hexagon side is approximately 20 nm, suggesting that they have an icosahedric structure. Further, the detection limit of the indirect immunogold EM was evaluated in 11 plasma samples from chronic hepatitis B patients with different degrees of hepatitis B virus (HBV) DNA titers using antihepatitis B surface antigen antibody. The study showed that the detection limit of virus using this method is 10(7) virions/ml.

Cell-based and animal models for hepatitis B and C viruses

Reliable cell-based assays and animal models have been developed for evaluating agents against hepatitis B virus. Although much progress has been made, in vitro and in vivo assays for hepatitis C virus are still on the horizon. Advances towards establishing inexpensive and reliable experimental models have accelerated the development of therapeutic modalities for these life-threatening viral infections. The characterization of well-defined viral targets coupled with improved molecular diagnostic technologies have illuminated this field.

Hepatitis C virus: a historical perspective

Identification and diagnosis of the infecting agent responsible for hepatitis C have only recently occurred. Recognition of an infecting agent distinct from that resulting in hepatitis A or B was made approximately 50 years ago. However, the ability to screen and detect this agent was possible only after molecular biology studies which led to the cloning of parts of the hepatitis C virus (HCV) and the development of a diagnostic antibody test reported by Michael Houghton and colleagues in 1989. The discovery and cloning of HCV has led to a greater understanding of its relationship to acute and chronic hepatitis, cirrhosis, primary liver cancer, and extrahepatic conditions including essential cryoglobulinemia, glomerulonephritis, and serum autoantibody positivity. New antibody tests and quantitation of HCV-RNA have allowed better diagnosis of infectivity and monitoring of treatment effects. HCV genotypes are being related to the natural history of the disease and the effects of treatment. Research continues on HCV hepatitis and other newly identified viral hepatitis agents.

Serological pattern of hepatitis C virus recurrence after liver transplantation

BACKGROUND/AIMS

Hepatitis C infection is characterized by a high incidence of liver cirrhosis, frequently requiring liver transplantation. After orthotopic liver transplantation, recurrence of hepatitis C virus infection is common, but often difficult to differentiate from allograft rejection. In this context the role and diagnostic value of hepatitis C virus-associated markers like the anti-GOR response have not yet been determined. In this study we analyzed the time course of hepatitis C virus recurrence in hepatitis C virus-infected patients who underwent liver transplantation because of end-stage cirrhosis or acute liver failure.

METHODS

We evaluated the serological pattern and diagnostic significance of anti-HCV, anti-HCV-IgM, anti-HCV-core, anti-HCV-core 5-27, anti-GOR, anti-GOR-IgM and HCV-RNA in serial serum samples during hepatitis C virus recurrence with or without allograft rejection up to 5-64 months after orthotopic liver transplantation. For comparison, we also studied these markers in serial serum samples from previously uninfected patients who acquired hepatitis C virus-infection during or shortly after orthotopic liver transplantation. Hepatitis C virus-infected patients who had undergone orthotopic liver transplantation were identified by screening pre-transplant sera from 235 patients for the presence of anti-HCV (2nd generation ELISA) and serum HCV-RNA (reverse transcription polymerase chain reaction).

RESULTS

Of 218 patients transplanted for end-stage liver cirrhosis, 65 (30%) were anti-HCV positive and 33 (15%) were HCV-RNA positive, while only one of 17 patients (6%) transplanted for acute liver failure was found to be anti-HCV positive without detectable HCV-RNA. Fifty-two hepatitis C virus-infected patients were studied serially before and after liver transplantation: 46 patients (89%) showed recurrent anti-HCV antibodies within 3 months and 51 patients (98%) within 42 months after orthotopic liver transplantation. Serum HCV-RNA was detected in 39 patients (75%) within 3 months and in 44 patients (85%) within 42 months after orthotopic liver transplantation. In the patients studied serially during hepatitis C virus-recurrence, anti-GOR antibodies displayed the same serological profile as hepatitis C virus antibodies, i.e. a decrease after orthotopic liver transplantation and slowly rising titers when HCV-RNA became detectable again. De novo infection with hepatitis C virus as studied in four patients produced a significant peak of anti-HCV titers accompanied or followed by an increase in anti-GOR titers, indicating that the immune response to GOR-autoantigen is triggered by the hepatitis C virus. No significant diagnostic difference between anti-GOR and anti-HCV was noted during hepatitis C virus recurrence and allograft rejection.

Hepatitis C virus: historical perspective and current concepts

Over the past 30 years, hepatitis C has emerged from shadowy enigma to important public health problem. The existence of the etiological agent of this disease was first appreciated two decades ago but significant progress in its understanding had to await its molecular characterization within the past 5 years. The virus is a member of the family Flaviviridae and is the cause of approximately 20% of clinical viral hepatitis in the United States. While the control of the transmission of hepatitis C virus in blood and blood products has been nothing less than spectacular, the control of community-acquired hepatitis C will be a major challenge to the scientific and medical communities.

Intrahepatic mononuclear cell populations and MHC antigen expression in patients with chronic hepatitis C [correction of B]: effect of interferon-alpha

Twenty-four subjects with chronic HCV infection were treated with IFN for six months. Liver biopsies were obtained before and after therapy. The number of mononuclear cells staining for CD3, CD4, CD8, 3G8, and the number of mononuclear cells, liver cells, and bile duct cells staining for class I and II MHC antigens in the biopsies was determined. NK cells increased from 16 +/- 3 to 28 +/- 3 cells per 5 high-power fields (HFP) (P < or = 0.03). The number of bile duct cells expressing class I and II MHC Ag and liver cells expressing class II MHC Ag increased (all P < or = 0.03). The only parameter that distinguished responders from nonresponders was the number of NK cells. Following IFN withdrawal, expression of these antigens declined. Based upon these data, it is concluded that IFN treatment of HCV increases: (1) the NK cells number; (2) the expression of class I MHC Ag on bile duct cells and the expression of class II MHC Ag on liver and bile duct cells; and (3) with IFN withdrawal, these changes disappear.

Treatment of chronic sporadic-type non-A, non-B hepatitis with lymphoblastoid interferon: gamma GT levels predictive for response

The aim of this study was to evaluate the efficacy of human lymphoblastoid interferon-alpha treatment in chronic sporadic-type non-A, non-B hepatitis. We also aimed to determine if histological or liver function data could predict either response or relapse. Sixty patients with chronic sporadic-type non-A, non-B hepatitis were randomized in two groups of 30. One group was treated with interferon-alpha (3 MU thrice weekly) for one year; the other group was untreated controls. The treated group was followed for another year after interferon withdrawal. Liver function tests were performed during treatment. Liver biopsy was carried out before and a year after randomization. We evaluated rate of response [normalization of alanine aminotransferase (ALT) levels for at least three consecutive months] and rate of relapse (ALT rebound after therapy suspension). We also looked at possible predictive factors for response and relapse. In the treatment group the rate of response was 55% (16/29). No control patient exhibited ALT normalization. Among the responders, 31% (5/16) relapsed after interferon withdrawal. Low gamma GT and female sex are positive predictive factors of response (P < 0.01 and P < 0.02 respectively). Presence of portal and periportal inflammation at the second liver biopsy was correlated with relapse (P < 0.05). In conclusion, human lymphoblastoid interferon-alpha treatment for one year is beneficial in patients suffering from chronic sporadic-type non-A, non-B hepatitis. Low pretreatment gamma GT levels and female sex are positive predictors of response in this patient population.(ABSTRACT TRUNCATED AT 250 WORDS)

Overview: diagnostic tests for viral infections transmitted by blood

The risk of transmitting viral infections by transfusion today is quite remote. The many, sensitive, diagnostic tests in place, when applied to the blood of volunteer, unpaid (unremunerated), unpressured donors who are also carefully evaluated at the time of donation, make blood and blood component transfusions very safe. A number of sensitive laboratory tests are performed on each unit of donated blood and plasma to reduce the risk of transmission of hepatitis viruses and retroviruses from asymptomatic donors to transfusion recipients. With the tests, we hope to catch otherwise undetectable individuals who may be carrying these viruses yet appear healthy and deny risk factors for their carriage. However, the laboratory tests in use in blood banks were designed to aid in the diagnosis of patients with viral diseases. Therefore, a reactive test, even if reproducible, on a sample from a healthy blood donor is more apt to be falsely than truly positive. An ideal microbiologic test is one which is one hundred percent sensitive, i.e., it will identify every person with an infectious disease (including asymptomatic carriers). In addition, a perfect test would have one hundred percent specificity, i.e., it would not be reactive in anyone without the infectious agent. The decision point or "cutoff" for an ideal test would be above the (negative) results for all normal and uninfected samples, but below that for all (positive) infectious ones. In reality, there is an overlap between some of the results on normals and those on diseased individuals, including persons who are carrying an infectious agent. When we try to obtain maximal sensitivity, e.g., to detect all asymptomatic carriers of a virus, the assay cutoff is set very low for tests applied to blood donors; but this approach will compromise the specificity of a test. The net effect is that many normal people donating blood are said to have "abnormal" test results which, among other things, necessitates the loss of their blood and plasma. In addition, we must follow up the reactive results by enzyme linked immunoassays (EIA or ELISA) or radioimmunoassays (RIA) used to screen or preliminarily test blood from donors with supplemental or confirmatory tests to verify whether the initial test is a true positive or a false positive one. Trying to explain the significance of a false positive test for AIDS or hepatitis to a healthy donor often causes fear, concern and/or anger. Thus, the use of very sensitive tests on blood donors will increase the safety of transfusion for recipients but result in loss of some donors and discard of many blood components unnecessarily. Despite the problems in applying sensitive tests to asymptomatic individuals who are not patients, the assays in place in blood banks have, nonetheless, resulted in remarkably small risks of virus transmission by transfusions. Currently, the risk of HCV infection following a transfusion is about 1 in 3,300 per unit transfused. This is an enormous improvement compared to the risks of what was called non-A, non-B hepatitis in the 1970s and 1980s before the use of the test for antibodies to HCV. For HTLV-1 (and, potentially, HTLV-II) the risk of transfusion transmission is about 1 in 50,000 per unit of screened blood. Using blood which is anti-HIV-1/2 non-reactive, the risk is about 1 in 225,000 units of transmitting HIV. The risk of transfusion associated AIDS is thus quite remote in 1993. For hepatitis B virus, only about 1 in 200,000 units of blood transmit this virus now. In sum, only about 3 units of blood per 10,000 of those collected from acceptable, volunteer donors are currently likely to transmit a serious or fatal transfusion-transmitted viral infection. In contrast, in America, about 6 out of every 1,000 patients hospitalized will die from an accidental or preventable cause other than the underlying disease for which he/she was hospitalized. (ABSTRACT TRUNCATED)

The declining risk of post-transfusion hepatitis C virus infection

BACKGROUND

The most common serious complication of blood transfusion is post-transfusion hepatitis from the hepatitis C virus (HCV). Blood banks now screen blood donors for surrogate markers of non-A, non-B hepatitis and antibodies to HCV, but the current risk of post-transfusion hepatitis C is unknown.

METHODS

From 1985 through 1991, blood samples and medical information were obtained prospectively from patients before and at least six months after cardiac surgery. The stored serum samples were tested for antibodies to HCV by enzyme immunoassay, and by recombinant immunoblotting if positive.

RESULTS

Of the 912 patients who received transfusions before donors were screened for surrogate markers, 35 seroconverted to HCV, for a risk of 3.84 percent per patient (0.45 percent per unit transfused). For the 976 patients who received transfusions after October 1986 with blood screened for surrogate markers, the risk of seroconversion was 1.54 percent per patient (0.19 percent per unit). For the 522 patients receiving transfusions since the addition in May 1990 of screening for antibodies to HCV, the risk was 0.57 percent per patient (0.03 percent per unit). The trend toward decreasing risk with increasingly stringent screening of donors was statistically significant (P less than 0.001). After we controlled for the method of donor screening, the risk of seroconversion was strongly associated (P less than 0.001) with the volume of blood transfused, but not with the use of particular blood components.

CONCLUSIONS

The incidence of post-transfusion hepatitis C has decreased markedly since the implementation of donor screening for surrogate markers and antibodies to HCV. The current risk of post-transfusion hepatitis is about 3 per 10,000 units transfused.

Prevalence of hepatitis C virus antibody in a liver transplantation population

The development of a serologic assay to detect antibodies directed at an antigen (C-100-3) of the hepatitis C virus (anti-HCV) has been a major breakthrough in the long search for causative agents of non-A, non-B (NANB) hepatitis. The frequency of HCV in those who have end-stage liver disease is not known. Moreover, the rate of recurrence after liver transplantation (OLTx) and the rate of acquisition of new HCV infection as a result of the OLTx experience is as yet unknown. This study was performed in an attempt to answer these questions. The prevalence of HCV in 372 patients undergoing OLTx at the University of Pittsburgh was determined. Those transplanted for HBV-related liver disease with hepatoma had the highest rate of HCV antibody positivity (45.4%) followed by those with metabolic liver disease (42.5%), putative NANB liver disease (41.4%), and cryptogenic cirrhosis (20.9%); those with cholestatic liver disease exhibited the lowest rate (16.2%). HCV antibody was positive in only 26.3% of patients with hepatoma. Of those patients who were negative prior to transplantation, 12.2% acquired HCV antibody post-OLTx. In the putative NANB group, no difference was detected in the AST and ALT prior to transplantation in either the HCV antibody-positive or -negative patients. In patients with cryptogenic cirrhosis, those who were positive for HCV antibody had higher transaminase levels prior to transplantation than did those patients who were HCV antibody negative.

Antibodies against synthetic oligopeptides deduced from the putative core gene for the diagnosis of hepatitis virus infection

Immunoassays were developed to detect antibodies against oligopeptides deduced from the putative core gene of hepatitis C virus, and their performances were compared with that of the commercial immunoassay for antibodies against the product of nonstructural regions of hepatitis C virus (anti-C100-3). A 19-mer oligopeptide (CP10) and a 36-mer oligopeptide (CP9) were chemically synthesized, which represented hydrophilic regions of the product of the hepatitis C virus core gene. They were used to capture corresponding antibodies, anti-CP10 and anti-CP9, by enzyme-linked immunosorbent assay in sera from patients with acute or chronic non-A, non-B liver disease and in blood donations. At the onset of acute non-A, non-B hepatitis, anti-CP10 was detected in 15 of 20 patients (75%), and anti-CP9 was detected in 14 patients (70%). This was more frequent than anti-C100-3, which was found in only 9 patients (45%). In 186 patients with chronic non-A, non-B liver disease, anti-CP9, anti-CP10 or both were detected in 170 patients (91%). This was more frequent than anti-C100-3, which was found in 138 patients (74%). Blood with anti-CP10 as the single serological marker for hepatitis C virus infection transmitted non-A, non-B hepatitis by needlestick exposure. In sera from 558 apparently healthy blood donors, anti-CP10 was detected in 55 donors (9.9%), anti-CP9 was detected in 26 donors (4.7%) and anti-C100-3 was detected in 7 donors (1.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of the hepatitis C virus genome in acute and chronic experimental infection in chimpanzees

In order to gain an understanding of the relationship of various markers of hepatitis C virus (HCV) infection in acute and chronic cases of the disease, serial blood samples obtained from chimpanzees before and after infection with HCV were analyzed for the presence of the HCV genome by using polymerase chain reaction (PCR) amplification of cDNA (cDNA PCR) synthesized from plasma- and serum-derived RNA. In a chimpanzee with acute hepatitis C, signals detectable by cDNA PCR appeared 1 week before characteristic ultrastructural changes visualized by electron microscopy, persisted throughout the peak alanine aminotransferase levels, and diminished with the disappearance of alterations visualized by electron microscopy. This was in contrast to the results obtained from chimpanzees with chronic HCV infection, in which the HCV genome was consistently detectable for up to 10 years after infection. The results indicate the usefulness of detection of HCV RNA by cDNA PCR as a sensitive and semiquantitative method for monitoring the course of HCV infection and as a potential marker for differentiating between chronic and acute cases of disease.

Post-transfusion hepatitis

Prospective international studies have shown the incidence of post-transfusion hepatitis in the 1980s to vary between 2% and 31%. Rare cases of hepatitis B continue to occur despite donor screening for the hepatitis B surface antigen, but most are of the non-A, non-B type. Non-A, non-B hepatitis is typically mild and often subclinical in the acute phase but has a tendency to become chronic in about half the affected subjects. The recently characterised hepatitis C virus has been shown to cause most, if not all, transfusion associated non-A, non-B hepatitis. Hepatitis C seropositivity seems to be associated with viraemia and infectivity among blood donors, and donor screening for these antibodies has now been instituted in many countries. New assays now being developed are improving the sensitivity and specificity of this screening, which is estimated to prevent most cases perhaps 70 to 80% of post-transfusion hepatitis.

Transmission of hepatitis C virus by organ transplantation

BACKGROUND

Liver disease is a frequent and major complication after organ transplantation. We sought to determine whether hepatitis C virus (HCV) is transmitted by organ transplantation and whether it causes post-transplantation liver disease.

METHODS

Serum samples from all cadaver organ donors to the New England Organ Bank between 1986 and 1990 were screened retrospectively for antibodies to HCV (anti-HCV) by enzyme-linked immunosorbent assay (ELISA). We reviewed the hospital records of all recipients of organs from anti-HCV-positive donors for evidence of liver disease. Serum samples from recipients obtained before transplantation and during follow-up were analyzed for anti-HCV.

RESULTS

Of 716 organ donors, 13 (1.8 percent) were positive for anti-HCV. Their organs (19 kidneys, 6 hearts, and 4 livers) went to 29 recipients. Non-A, non-B hepatitis developed after transplantation in 14 of the 29 (48 percent), for a prevalence 7.4 times the 6.5 percent prevalence after transplantation from untested donors that was previously reported by two institutions in the organ bank (P less than 0.0001). The liver disease began a mean of 3.8 months after transplantation and became chronic in 12 patients; the other 2 had subfulminant hepatic failure. Liver disease was more frequent in the patients who had received antilymphocyte preparations (P = 0.04). HCV was the cause of the post-transplantation liver disease in 12 of the 13 recipients (92 percent) for whom serum samples were available. Anti-HCV was detected by ELISA in eight and enzyme immunoassay in one; in three others, HCV RNA was detected by polymerase chain reaction in serum samples obtained after transplantation.

CONCLUSIONS

Organ transplantation can transmit hepatitis C. This raises serious questions about the continued acceptance of organs from donors positive for anti-HCV.

Antibodies to hepatitis C virus in community-acquired acute non-A, non-B hepatitis

Circulating antibodies to the recently identified hepatitis C virus (anti-HCV) have been investigated by ELISA in a series of 129 adult Italian patients with acute, community-acquired non-A, non-B hepatitis. Anti-HCV was detected in 50 (38%) cases with a prevalence rate which increased from 19%, in sera taken during the first 2 weeks of illness to 52% in samples obtained 5-6 weeks after onset, indicating a rather late appearance of the antibody. Anti-HCV positivity was independent of risk factors in the clinical history, but correlated with the outcome of the disease. Eighteen (26%) of 68 patients who recovered were anti-HCV positive compared to 10 of 14 (71%) who progressed to chronicity (p less than 0.01). In this latter group the antibody persisted for more than 12 months after the onset of the illness. Conversely, in 12 (85%) of 14 serially tested patients who recovered, anti-HCV positivity was transient, lasting from a few weeks to a few months. These findings indicate that HCV is implicated in a consistent proportion of acute community-acquired non-A, non-B hepatitis cases, particularly cases which progress to chronicity. A large proportion of cases remained unclassified, however, and it will be important to define whether they represent cases of HCV infection with poor serologic response, or are due instead to other, as yet unidentified, non-A, non-B agents.

Hepatitis C virus

HepCV is the major cause of NANB PT hepatitis and is also implicated as the cause in a large proportion of sporadic cases of NANBH. Chronic infection with HepCV has also been linked to the development of hepatocellular carcinoma. Chimpanzees and marmosets are the only animals found to be experimentally infectable and the virus has not been propagated in any cell culture system. HepCV is an enveloped virus with a diameter of 30-60 nm and a 10-kb positive-stranded RNA genome. Its genome organization resembles that of the flaviviruses and pestiviruses. A 5'-untranslated segment of 341 nucleotides precedes a continuous ORF of 9030/9033 nucleotides which is followed by a 54 nucleotides long 3'-non-coding segment. Further work is required to resolve the question of whether the genomic RNA possesses a 3'-poly(U) or poly(A) tail. The genome also carries an internal poly(A) segment towards the 5'-end of its ORF. Genomic RNA is probably translated into a single polyprotein of 3010/3011 amino acids which is processed into functional proteins. The viral proteins have not been identified, but on the basis of the predicted amino acid sequences, hydrophobicity plots, location of potential glycosylation sites and similarities of these properties to those of pesti- and flaviviruses, the following genome organization has been predicted. The predicted viral structural proteins, a nucleocapsid protein and two envelope glycoproteins are located at the amino-terminal end of the polyprotein. They are followed by a highly hydrophobic protein and proteins that exhibit proteinase, helicase and replicase domains and thus are probably involved in RNA replication and protein processing. The replicase domain is located close to the carboxy terminus of the polyprotein. Although the overall nucleotide and amino acid homologies between HepCV and pestiviruses are low, a number of similarities exist that point to a closer ancestral relationship to the latter than the flaviviruses. First, the 5'-untranslated segment of the HepCV genome resembles that of the pestivirus genomes in size and presence of several short ORFs and it contains several segments with high nucleotide homology. Second, the two putative envelope glycoproteins of HepCV resemble two of the three putative envelope glycoproteins of the pestiviruses. Because its genome organization and predicted virion structure closely resemble those of the flaviviruses and pestiviruses, HepCV has been proposed to be placed in the family Flaviviridae.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical, virological and epidemiological basis for the treatment of chronic non-A, non-B hepatitis

Non-A, non-B hepatitis is the most common serious complication of blood transfusion and also occurs in a sporadic form whose routes of transmission are currently unknown. While generally mild in its acute presentation, non-A, non-B hepatitis frequently progresses to chronic hepatitis which may eventuate in cirrhosis and hepatocellular carcinoma. The disease is caused by a small, enveloped RNA virus now designated hepatitis C virus, which has similarities to the flaviviruses. Studies using the recently developed antibody assay have indicated that hepatitis C virus is the predominant agent of both transfusion-associated and sporadic non-A, non-B hepatitis. In 50-85% of transfusion-associated cases, a donor can be found who is positive for antibodies to the hepatitis C virus. Current data indicate that these antibodies are present in approx. 0.5% of blood donors in the United States and Europe, 1.5% in Japan and 6% in Africa, as well as in 60-80% of haemophiliacs and intravenous drug abusers and approx. 20% of dialysis patients. With changes in donor selection and transfusion practices, the incidence of transfusion-associated non-A, non-B hepatitis has declined from rates of 5-10% prior to 1985 to estimated current rates of 2-4%. The introduction of the anti-HCV test should effect an additional 50% reduction in transfusion-associated non-A, non-B hepatitis. In addition to these preventive measures, effective therapy now appears at hand in the form of alpha-interferon. The efficacy of other antiviral agents and the potential for combination therapies also need to be explored.

Cloning of a cDNA associated with acute and chronic hepatitis C infection generated from patients serum RNA

In order to clone hepatitis C (blood-borne non-A, non-B hepatitis) virus, lambda gt11-cDNA library was constructed from RNA extracted from 100 liters serum collected from 1,047 donors with elevated ALT levels and negative for hepatitis B virus-DNA. The library was immunoscreened on Y1090 cells with pooled serum obtained from patients with acute hepatitis C or chronic hepatitis C. By screening 29 clones specific for Japanese hepatitis C infection were isolated. The specificity of these clones for hepatitis C infection was determined by panels constructed in 3 laboratories. Of these, 12 clones were specific for American hepatitis C infection as well. The nucleotide sequence (201 bp) of one of them was determined to be unique compared to known human viruses including hepatitis A virus, hepatitis B virus and hepatitis D virus. Southern blot analysis showed the absence of the sequence of the human genome in the clone. The predicted amino acid sequence is rich in residues of lysine, arginine, glutamic acid and asparagine, while lacking leucine, cysteine and methionine.

Blood transfusion and hepatitis: still a threat?

The incidence of post-transfusion hepatitis (PTH) in recipients of blood products is reviewed. PTH was observed in 10%-12% of recipients of blood products in the United States, 2%-4% in northern Europe and 15%-20% in southern Europe. All studies indicate that 80%-90% of all PTH cases are attributed to non-A/non-B. At least 40% of the patients with PTH non-A/non-B will develop chronic hepatitis or cirrhosis. No specific tests for the detection of the non-A/non-B agent(s) exist. However, several independent studies indicate that part of the donors carrying the infectious non-A/non-B agent have increased levels of alanine amino transferase (ALT). When donors are excluded with elevated ALT values, it is estimated that about 30% of the PTH non-A/non-B cases would be prevented. Some studies indicate that anti-hepatitis B core (anti-HBc) positive donors may carry an increased risk to transmit the non-A/non-B agent, but more recent studies do not confirm this. There is hope that a specific non-A/non-B test will be developed soon.

Transmission of hepatitis B from hepatitis-B-seronegative subjects

The polymerase chain reaction (PCR) was used to identify and characterise serum HBV DNA sequences in 3 patients negative for all HBV serological markers. HBsAg determinants were detected in 1 individual by monoclonal anti-HBsAg immunoradiometric assay. By use of sets of primers on the S and pre-S parts of the HBV genome the presence of HBV DNA was demonstrated in the serum of all 3 patients. Inoculation of human sera to 2 chimpanzees induced acute hepatitis in both animals; 1 became positive for HBsAg and anti-HBcAg and the other only for anti-HBsAg. Cloning of DNA sequences from viral isolates from 1 chimpanzee and 1 patient was accomplished after amplification of the 3' region of the S gene. Comparison of the partial nucleotide sequence with that of known HBV subtypes showed 0 and 1 point mutation, respectively, in the highly conserved 3' end of the S gene. Therefore the results show that PCR with HBV primers may unambigously identify HBV infectious particles among non-A, non-B viruses and is a potentially useful diagnostic test for detection of HBV DNA sequences in serum.

Delta and non-A, non-B hepatitis viruses

A review is given on the current knowledge of the hepatitis delta virus (HDV), the only hepatotropic non-A and non-B (NANB) virus characterized, although the infection it causes requires infection with hepatitis B virus (HBV). Studies in chimpanzees have provided the most data now available on the putative NANB agents. Histologic and electron microscopic changes occurring in HDV and NANB hepatitis have been shown to be comparable, and some biologic, epidemiologic and clinical features are similar. However, the lack of cross-protection between NANB and HDV hepatitis in cross-challenge transmission experiments and the lack of hybridization between HDV-RNA and nucleic acids from NANB material indicate that HDV and the putative NANB agents are minimally, if at all, related.

Viral hepatitis

Recent research has led to a greater understanding of the mechanisms and management of the various forms of viral hepatitis. The clinician can rapidly arrive at a precise diagnosis using serologic markers to complement epidemiologic data. In addition, effective immunoprophylaxis is possible; thus, disease spread can be minimized.

Lack of reverse transcriptase activity in serum in sporadic post-transfusional and presumed epidemic or water-borne forms of severe non-A, non-B hepatitis

Reverse transcriptase (RT) activity was not detected in any serum sample taken from 22 patients with mainly severe non-A, non-B hepatitis (NANBH), using two assays selected to cover the range of known human and animal retroviruses. The study included patients with fulminant and sub-acute hepatic failure, which was was attributed to sporadic, post-transfusional, and presumed epidemic or water-borne epidemiological forms of NANBH. Although we cannot exclude the possibility that some of the agents implicated in NANBH are retroviruses, our negative findings suggest that other agents may be involved at least in the severe forms of NANBH.

Viral hepatitis

Recent research has led to a greater understanding of the mechanisms and management of the various forms of viral hepatitis. The clinician can rapidly arrive at a precise diagnosis using serologic markers to complement epidemiologic data. In addition, effective immunoprophylaxis is possible; thus disease spread can be minimized.

Post-transfusion non-A, non-B hepatitis: significance of raised ALT and anti-HBc in blood donors

The FDA has recommended that all blood collected in the USA should be screened for antibody to hepatitis B core antigen (anti-HBc) and for raised alanine aminotransferase (ALT) as possible indicators of non-A, non-B hepatitis carriage. As part of an assessment of the medical and economic implications of such a screening programme, we have screened 1,742 regular blood donors for ALT and 2,086 (including the same 1,742) for anti-HBc. 42 (2.4%) of the 1,742 donors had ALT levels above 45 units/l. Clinical assessment of 33 of these revealed that 26 exceeded their ideal body weight by more than 10% and 15 by more than 20%. 11 admitted to an alcohol intake of over 40 g daily. In all, 82% of donors with raised ALT had a 'non-viral' clinical explanation for this abnormality. Anti-HBc was detected in 42 (2.0%) of the 2,086 donors screened. 27 (64%) also had anti-HBs, and 11 (26%) had anti-HBe. There was no overlap between donors with raised ALT and those with anti-HBc. Combined screening would lead to a loss of at least 4.4% of donations in the population studied. In view of the medical and economic implications of the introduction of these screening tests, and the poverty of data on the clinical significance of post-transfusion non-A, non-B hepatitis, we conclude that such a screening programme cannot be justified at present. Further studies are required, including a prospective controlled trial of the effects of screening.

Spumaviruses isolated from sources containing agents of non-A, non-B (NANB) hepatitis do not cause NANB hepatitis

Serum and liver tissue containing infective non-A, non-B hepatitis virus were shown to contain a retrovirus-like agent that replicated when inoculated into chimpanzee liver cell cultures in vitro. The virus appeared to assemble its core particles in association with tubular structures reminiscent of those characteristically seen in non-A, non-B hepatitis virus-infected chimpanzee liver in vivo, and produced syncytial cytopathic effects in a number of continuous and a primary mammalian liver cells. The agents were neutralized by acute and convalescent sera from human and chimpanzee cases of non-A, non-B hepatitis, as well as by antisera against simian spumavirus type 7, but not type 6. Aluminum chloride failed to abolish viral infectivity. There was no evidence of virus replication or hepatitis in chimpanzees inoculated with a seventh passage of one of the isolates. Thus the data suggest that the isolates are not causally related to non-A, non-B hepatitis, as was previously postulated.

Review of hepatitis non-A, non-B: the potential hazards in dental care

Several of the common viral agents that can cause hepatitis have been detected in body fluids, including saliva and blood, which may both form important routes for transmission of disease. The viruses most commonly implicated include hepatitis A virus (HAV), hepatitis B virus (HBV), cytomegalovirus (CMV), and Epstein-Barr virus. Hepatitis delta virus (HDV) can be found in persons positive for hepatitis B surface antigen (HBsAg) and presumably follows the same routes of transmission as HBV. Herpes simplex and echo viruses can cause hepatitis on rare occasion. Other agents, not yet positively identified but collectively referred to as non-A, non-B are also believed to follow the same routes as HBV and/or HAV. The aim of this reviews is twofold. First, we will discuss hepatotropic viruses other than HBV that may be spread via saliva and blood and, therefore, should be considered along with HBV as a potential health hazard to dental personnel and also to dental patients. The second aim is to highlight the epidemiology and the risk of transmission of these viral infections. The potential hazards are discussed in relation to those associated with HBV and human immunodeficiency viruses (HIV), implicated in the acquired immunodeficiency syndrome (AIDS).

Potential of urinary neopterin excretion in differentiating chronic non-A, non-B hepatitis from fatty liver

Urinary neopterin excretion was measured in 26 patients with histologically proven chronic non-A, non-B hepatitis (16 chronic persistent hepatitis, 10 chronic active hepatitis) and in 16 patients with steatosis. The potential of neopterin levels to discriminate between the two patient groups was compared with that of standard laboratory variables. Neopterin levels and triglycerides were shown to be the best variables for discriminating between the hepatitis and fatty liver patients, neopterin being the more specific of the two. Neopterin excretion in chronic persistent hepatitis was not statistically different from that in chronic active hepatitis. In the absence of specific tests, increased neopterin excretion seems to be a useful marker for diagnosing chronic non-A, non-B hepatitis and particularly in differentiating it from fatty liver.

Microbial structures in a patient with sporadic non-A, non-B fulminant hepatitis treated by liver transplantation

Double-shelled virus-like particles (60 nm) and long cytoplasmic tubular structures were found in the cytoplasm of hepatocytes from areas of collapsed and regenerating areas of hepatectomised liver in a 13-year-old boy who received a liver graft for fulminant hepatitis attributed to sporadic non-A, non-B hepatitis. The patient died on the ninth postoperative day from acute graft failure. Although virus-like particles were not found, instead, gram-negative rods were identified in the necrotic graft and the most likely cause of death was a gram-negative septicaemia with a Shwartzman-like reaction localized to the liver.

Treatment of chronic non-A,non-B hepatitis with recombinant human alpha interferon. A preliminary report

We treated 10 patients who had chronic non-A,non-B hepatitis with recombinant human alpha interferon in varying doses (0.5 to 5 million units) daily, every other day, or three times weekly for up to 12 months. In 8 of the 10 patients, elevated serum aminotransferase levels decreased rapidly during therapy and eventually fell into the normal or nearly normal range. In two of these patients, the interferon therapy was stopped after four months, and in both cases, a prompt return of aminotransferase activities to pretreatment values occurred. Prolonged treatment was associated with a sustained improvement in aminotransferase levels; in three cases, biopsy specimens obtained after one year of therapy showed marked improvement in hepatic histology, even though low doses of alpha interferon had been used. These preliminary findings, although not adequately controlled, suggest that long-term, low-dose alpha interferon therapy may be effective in controlling the disease activity in some patients with chronic non-A,non-B hepatitis. A prospective controlled trial is now needed to assess the role of interferon therapy in this disease.

Clinical approach to viral hepatitis in homosexual men

The prevalence of both hepatitis A and hepatitis B is increased in homosexual men. On an annual basis, 5% to 7% of homosexual men will acquire hepatitis A. Risk factors for HAV infection include length of homosexual activity, number of sexual contacts, and oral--anal sexual contact. The HBsAg carrier rate of homosexual men is 5% to 6%, and another 50% have evidence of previous HBV infection with a positive anti-HBs. HBeAg is present in a higher precentage of HBsAg-positive homosexual men (38% to 75%) than in general population carriers (3% to 30%). The annual incidence for HBV infection in homosexual men is 16% to 28%, higher than that for hepatitis A. Transmission of HBV infection in homosexual men is facilitated by a large number of sexual partners, high HBsAg carrier rate, high infectivity of carriers (positive HBeAg), and the specific sexual practices of oral--anal and anal--genital contact with exposure to HBV on open mucosal surfaces. The prevalence of non-A, non-B and delta infection in homosexual men is probably somewhat increased, but the importance of these viruses in the development of hepatitis in this population remains uncertain. Prevention of hepatitis A and B in homosexual men will ultimately be achieved by vaccination of susceptible individuals, which currently is feasible only for hepatitis B. Appropriate use of immune globulins for postexposure prophylaxis and knowledge of specific sexual practices that transmit disease may reduce the incidence of hepatitis A and B.