Hepatitis B virus, hepatitis non-A, non-B virus and hepatitis delta virus in lyophilized antihemophilic factor: relative sensitivity to heat

The chimpanzee model for hepatitis B virus infection

Even before the discovery of hepatitis B virus (HBV), it was known that chimpanzees (Pan troglodytes) are susceptible to human hepatitis viruses. The chimpanzee is the only primate animal model for HBV infections. Much like HBV-infected human patients, chimpanzees can develop acute and chronic HBV infections and consequent hepatitis. Chimpanzees also develop a cellular immune response similar to that observed in humans. For these reasons, the chimpanzee has proven to be an invaluable model for investigations on HBV-driven disease pathogenesis and also the testing of novel antiviral therapies and prophylactic approaches.

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: 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.

Lack of protective immunity against reinfection with hepatitis C virus

Some individuals infected with hepatitis C virus (HCV) experience multiple episodes of acute hepatitis. It is unclear whether these episodes are due to reinfection with HCV or to reactivation of the original virus infection. Markers of viral replication and host immunity were studied in five chimpanzees sequentially inoculated over a period of 3 years with different HCV strains of proven infectivity. Each rechallenge of a convalescent chimpanzee with the same or a different HCV strain resulted in the reappearance of viremia, which was due to infection with the subsequent challenge virus. The evidence indicates that HCV infection does not elicit protective immunity against reinfection with homologous or heterologous strains, which raises concerns for the development of effective vaccines against HCV.

A second group of hepatitis C viruses

cDNA clone 11-7 was isolated by immunoscreening a cDNA library that was prepared from a pooled plasma of non-A non-B hepatitis (NANBH) patients using expression vector lambda gt11. This cDNA corresponds to known nucleotide positions 3983-4745 of the genome of hepatitis C virus (HCV). This clone was used as a probe for screening the HCV-related cDNAs in a cDNA library similarly prepared by using lambda gt10. As a result, six more cDNA clones were isolated and analyzed for their nucleotide sequences. The results strongly suggested that there are at least two groups of HCV, group I and group II. According to our classification, the prototype HCV and clone 11-7 belong to group I HCV, and their nucleotide and deduced amino acid sequences were diverged from those of group II HCV. Genetic variation observed in the nucleotide and the amino acid sequences between the two groups resembles that in the NS3 region of the genome between Japanese encephalitis virus and West Nile fever virus. Polypeptides produced in Escherichia coli carrying a clone 11-7 or a group II cDNA clone E reacted with antibodies in the blood of 12 or 4 out of 14 individual chronic NANBH patients, respectively. Our data clearly indicate the existence of a second group of HCV.

Inactivation of lipid-enveloped viruses in proteins by caprylate

The use of caprylate for the inactivation of lipid-enveloped viruses in biologically active proteins both plasma derived and produced by cell culture was evaluated. Viruses consisted of herpes simplex virus type I, vesicular stomatitis virus, vaccinia virus, and Sindbis virus. Utilizing the dissociation reaction and varying the concentration of the ionized form of caprylate, a specific amount of the nonionized form of caprylate was maintained over a wide pH range. Virus-spiked protein solutions contacted with caprylate provide rapid virus inactivation under a variety of conditions while maintaining the integrity of the respective protein or activity. With the exception of coagulation factor AHF, protein and biological activity yield were essentially quantitative. Caprylate is removed after treatment by size exclusion chromatography or anion/cation exchange adsorption of the protein, followed by buffer wash.

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)

Hepatitis C virus shares amino acid sequence similarity with pestiviruses and flaviviruses as well as members of two plant virus supergroups

Hepatitis C virus (HCV) is an important human pathogen that is associated with transfusion-related non-A, non-B hepatitis. Recently, HCV cDNA was cloned and the nucleotide sequence of approximately three-quarters of the virus genome was determined. A region of the predicted polyprotein sequence was found to share similarity with a nonstructural protein encoded by dengue virus, a member of the flavivirus family. We report here that HCV shares an even greater degree of protein sequence similarity with members of the pestivirus group (i.e., bovine viral diarrhea virus and hog cholera virus), which are thought to be distantly related to the flaviviruses. In addition, we find that HCV shares significant protein sequence similarity with the polyproteins encoded by members of the picornavirus-like and alphavirus-like plant virus supergroups. These data suggest that HCV may be evolutionarily related to both plant and animal viruses.

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.

Hepatitis delta virus (HDV) infection and disease

The conformational and biologic properties of the hepatitis delta virus (HDV), a defective RNA hepatotropic pathogen dependent on obligatory helper functions provided by the hepatitis B virus (HBV), are different from the properties of conventional RNA animal viruses but resemble in many aspects the characteristics of the satellite RNAs and satellite viruses of higher plants. The HBsAg coat provided to HDV by HBV makes the defective virus transmissible via the vectors and modes of transmission of the ubiquitous helper; alike HBV, HDV is prevalent in tropical and subtropical areas and in the Mediterranean basin. In contrast to HBV, HDV is highly pathogenic and its infection aggravates the underlying HBV infection upon which it thrives. The defective pathogen has been recognized worldwide as a major cause of fulminant hepatitis and of severe chronic hepatitides leading to cirrhosis and liver failure. There is yet no established therapy for this ominous disease.

Hepatitis transmission by blood products

The main causes of hepatitis transmission by blood products are hepatitis B and non A non B hepatitis (NANB). A reduction in hepatitis transmission has been achieved by screening blood donors for hepatitis B surface antigen, but it is not known what the effectiveness of screening donors for raised plasma alanine aminotransferase levels or hepatitis B core antibody will be. Attempts to reduce NANB hepatitis transmission have mainly focussed on heat treatment of factor VIII and IX concentrations, and preliminary data suggests that under certain heating conditions inactivation of the NANBvims occurs. Although albuminoid preparations are known not to transmit hepatitis, three immunoglobulin preparations for intravenous administration (IV IgG) have transmitted hepatitis, suggesting that the inclusion of a terminal virucidal step is essential.

Inactivation of lipid-enveloped viruses in labile blood derivatives by unsaturated fatty acids

Virus sterilization of blood plasma derivatives by addition of several naturally occurring fatty acids was evaluated using vesicular stomatitis virus and Sindbis virus as markers for lipid-enveloped virus inactivation and human immunodeficiency virus (HIV). Inactivation of greater than or equal to 10(4) tissue culture infectious doses (TCID50) of marker viruses added to antihemophilic factor (AHF) concentrates, with 60-100% retention of AHF activity, was achieved with oleic, 11-eicosenoic, linoleic, linolenic, palmitoleic and arachidonic acids. Elaidic, gamma-linolenic, palmitic, and arachidic acids and another fat-soluble compound previously reported to inactivate virus, butylated hydroxytoluene, were less effective. A long chain mono- but not a di- or triglyceride also displayed virucidal properties. Evaluation of the inactivation of HIV added to an immune globulin solution on exposure to 0.033% sodium oleate for 20 min indicated inactivation of greater than or equal to 10(3.4) TCID50. The degree of virus inactivation depended on the sample composition. A favorable balance was achieved between degree of virus inactivation and retention of protein function for AHF concentrate, prothrombin complex concentrate, antithrombin III concentrate, and immune globulin solution on incubation with 0.033% (w/v) sodium oleate at 24 degrees C for 4-6 h. Virus inactivation in whole plasma and plasma cryoprecipitate was not complete despite use of higher concentrations of sodium oleate and/or incubation at 37 degrees C. Reduced virus kill in these less purified derivatives probably is a consequence of their endogenous lipid and/or albumin.

Hepatitis delta (delta) cDNA clones: undetectable hybridization to nucleic acids from infectious non-A, non-B hepatitis materials and hepatitis B DNA

Hepatitis Delta (delta) cDNA clones were hybridized to RNA extracted from livers of chimpanzees infected with the blood-borne Non-A, Non-B hepatitis (NANBH) agent(s) and to total nucleic acids extracted from chimpanzee plasma containing a high titer of these NANBH agent(s). Since no hybridization was observed, the data suggests that the hepatitis Delta viral genome is not closely related to the genome(s) of the NANB agent(s). Our studies, in which the Hepatitis B virus genomic DNA was hybridized to hepatitis Delta cDNA clones, also confirm and extend previous studies [Hoyer et al, 1983], which report a lack of detectable homology between the hepatitis Delta genome and HBV DNA.

Hepatitis B vaccination of 113 hemophiliacs: lower antibody response in anti-LAV/HTLV-III-positive patients

One-hundred thirteen adults and children with hemophilia or other congenital bleeding disorders were vaccinated against the hepatitis B virus. Each patient was given three subcutaneous injections of the vaccine at monthly intervals and then a fourth booster dose 14 months after the first. The vaccine was highly immunogenic, since 111 of 113 patients (98%) produced anti-HBs (10 mIU/ml or more). After the first three vaccine doses and after the booster dose, ten anti-LAV/HTLV-III-positive hemophiliacs produced anti-HBs but had a lower average titer than anti-LAV/HTLV-III-negative hemophiliacs. Of the 23 patients treated with concentrates in the 15 month postvaccination period only, none acquired HBV infection. Of the 50 patients treated with concentrates also in the 6 month prevaccination period, one developed hepatitis B. In summary, the vaccine was highly immunogenic in both children and adults with hemophilia; anti-LAV/HTLV-III-positive patients responded to the vaccine, but the average anti-HBs response was lower; no case of hepatitis B occurred in patients treated with concentrates only in the postvaccination period.

Further studies by immunofluorescence of the monoclonal antibodies associated with experimental non-A, non-B hepatitis in chimpanzees and their relation to D hepatitis

To further investigate the specificity of the monoclonal antibodies (48-1 and S-1) associated with non-A, non-B hepatitis, extensive immunofluorescence studies were performed on liver biopsy specimens from chimpanzees with experimental hepatitis A, B, non-A, non-B or delta, or from normal chimpanzees. Both 48-1 and S-1 antibodies reacted in the same manner with liver biopsy specimens from 47 of 50 (94%) chimpanzees with acute or chronic non-A, non-B hepatitis and 15 of 18 (83%) chimpanzees with type D hepatitis. Examinations of serial liver biopsy specimens revealed that the duration of expression of the antigen reacting with the antibodies in hepatocytes of chimpanzees infected with non-A, non-B viruses appeared to be longer than that of chimpanzees infected with the hepatitis delta-virus. By thin-section electron microscopy, the presence of the microtubular aggregates, identical to those previously described for chimpanzees with non-A, non-B hepatitis and shown by immunoelectron microscopy to react with the antibodies, was noted in hepatocytes during the acute phase of hepatitis delta-virus. The antibodies did not react with liver biopsy specimens from chimpanzees acutely or chronically infected with hepatitis B virus or hepatitis A virus, or from normal chimpanzees. The present results confirm our previous observations with the 48-1 and S-1 antibodies. Furthermore, the finding that these two antibodies were also associated with hepatitis D would support the possibility that non-A, non-B agents and the hepatitis delta-virus may have a similar nature or may elicit a similar host response.