Failure to detect nucleic acid homology between some non-A, non-B viruses and hepatitis B virus DNA

Geographical variation in prevalence of hepatitis B virus DNA in HBsAg negative patients

AIMS--To study the geographical variation of the prevalence of hepatitis B virus (HBV) DNA in hepatitis B surface antigen (HBsAg) negative subjects. METHODS--A nested polymerase chain reaction (PCR) assay was used to amplify the core region of HBV. The assay was able to detect 10 molecules of a full length HBV plasmid. RESULTS--When applied to HBsAg negative paraffin wax embedded liver samples from Italy, Hong Kong, and the United Kingdom, a geographical variation in the prevalence of HBV-DNA positivity was noted. Two of 18 (11%) of Italian samples and 2/29 (6.9%) of Hong Kong samples were positive for HBV-DNA while none of the 70 cases from the United Kingdom was positive by nested PCR. Contamination by plasmid DNA was excluded using a novel method based on heteroduplex formation. One HBV-DNA positive case had idiopathic chronic active hepatitis, but the diagnoses in the other three HBV-DNA positive cases did not suggest any aetiological connection between HBV-DNA positivity and liver pathology. CONCLUSIONS--HBV-DNA could be detected in the liver tissues of a proportion of HBsAg negative subjects. The prevalence of such cases is related to the endemic rate of a geographical region. The use of HBV PCR on paraffin wax embedded tissues will be valuable for future studies on the molecular epidemiology of HBV.

In vitro amplification of hepatitis B virus sequences from liver tumour DNA and from paraffin wax embedded tissues using the polymerase chain reaction

A 185 base pair fragment from the core-polymerase overlap region of the hepatitis B virus (HBV) genome was amplified using the polymerase chain reaction (PCR). The results were compared with those of Southern blotting on extracted DNA from eight hepatocellular carcinomata. The data agreed with those of Southern blotting in six cases (two positive, four negative) but in two other positive cases PCR failed to amplify HBV sequences. This suggests deletion or mutation, or both, of this viral region in these cases. PCR was also used to amplify HBV sequences from formalin fixed, paraffin wax embedded tissue. Tissue inhibition of PCR occurred which increased with the number of tissue sections. It was present in tissues from different organs and species and fixed by different procedures, thus highlighting the need for a positive control during amplification. Use of formalin fixed Alexander cells, however, showed a sensitivity of one viral copy per 5000 cells. Confirmation of the identity of the PCR products was carried out using PCR-generated biotinylated probes, and suggested the insertion of extra nucleotide sequences or infection with an HBV variant in one case.

Non-A, non-B hepatitis

Diagnosis of non-A, non-B hepatitis (NANB) is made after exclusion of other known causes of hepatitis. Parenterally spread non-a, non-B hepatitis (PNANB) and enterally transmitted non-A, non-B hepatitis (ENANB) almost certainly appear to be two different diseases. The definite causative agents have not hitherto been identified. Much of our knowledge of NANB is based on (i) experimental studies on chimpanzees; and (ii) epidemiological studies. Parenterally spread non-A non-B hepatitis caused by whole blood transfusion and blood-product infusion has different incubation periods and may be caused by different agents. It is a mild disease clinically, and the majority of the patients are asymptomatic. It can be prevented only by judicious use of blood transfusion. Whenever possible, blood/blood products should be derived from individual volunteer donors who are anti-HBc sero-negative and have serum alanine transaminase of under 45 IU/l. Enterally-transmitted non-A non-B hepatitis is endemic in the Indian subcontinent, South-East Asia, North and East Africa and Latin America. Epidemic NANB is usually transmitted by water supply contaminated with feces. ENANB has a predilection for young adults. The disease is usually mild, except in pregnant women, who have a high case-fatality rate from fulminant hepatic failure. Control measures include provision of clean water supplies, safe disposal of human excreta and sound personal and food hygiene practices.

Search for hepatitis B virus DNA in sera from patients with acute type B or non-A, non-B hepatitis

One hundred and three single sera from adults hospitalized with acute type B (78) or non-A, non-B (25) hepatitis were tested for the presence of hepatitis B virus DNA (HBV DNA). All sera from patients with type B hepatitis were IgM anti-HBc-positive. These patients were classified as benign (47) or fulminant (31) hepatitis. The 25 acute non-A, non-B patients were also classified as benign (21) or fulminant (4) hepatitis and were negative for serologic markers of past HBV infection. Serum HBV DNA was detected with similar frequency in benign (38.5%) and fulminant (FH, 34.6%) HBsAg-positive cases. HBV DNA was not detected in either the 26 acute HBsAg-negative hepatitis B cases who were positive for anti-HBc and anti-HBs or the 25 acute non-A, non-B hepatitis cases. The absence of HBV DNA in 43.8% of benign hepatitis B patients who were positive for HBsAg and HBeAg could possibly be attributed to either low level replication of HBV that was not detectable by the [32P]HBV DNA probe or to a period of delayed clearance of free HBeAg following cessation of HBV replication. Emergence of anti-HBs in the presence of HBsAg did not always correspond to clearance of HBV in fulminant type B cases. However, in acute type B hepatitis, irrespectively of severity, disappearance of HBsAg and appearance of anti-HBs was accompanied by reduction of HBV replication to undetectable levels.

Absence of detectable hepatitis B virus DNA in sera and liver of chimpanzees with non-A, non-B hepatitis

The risk of hepatitis B infections has been reduced by screening of blood donors for hepatitis B surface antigen (HBsAg). However, recipients remain at significant risk of developing post-transfusion hepatitis. Studies have shown that non-A, non-B hepatitis virus(es) are responsible for the majority of post-transfusion hepatitis infections. In spite of many efforts, these non-A, non-B hepatitis viruses have not yet been identified. Epidemiological studies, however, suggest that non-A, non-B hepatitis shares many features with hepatitis B. Recently, Wands et al [1982] showed, in chimpanzees infected with non-A, non-B hepatitis agents, the presence of antigenemia or viremia by radioimmunoassay with monoclonal antibodies directed toward distinct determinants of HBsAg and by molecular hybridization analysis. They suggested that non-A, non-B hepatitis agents may be related, but distinct variant(s) of hepatitis B virus (HBV). In this study, five chimpanzees were inoculated with three different agents that have been shown to transmit non-A, non-B hepatitis. The following inocula were used (I) a factor VIII preparation kindly provided by D.W. Bradley, (II) acute phase serum from a chimpanzee infected with the F strain kindly provided by A.J. Zuckerman, and (III) a DS-antigen serum previously shown by us to transmit non-A, non-B hepatitis [Duermeyer et al, 1983]. All chimpanzees developed a rise in transaminase levels between 8 and 10 weeks after inoculation. None of the chimpanzees was positive for any markers of HBV infection. No evidence was obtained of infection with hepatitis A, cytomegalovirus, or Epstein-Barr virus. One chimpanzee developed chronic liver disease.(ABSTRACT TRUNCATED AT 250 WORDS)

The agents of non-A, non-B viral hepatitis

Recent studies have provided physicochemical and electron microscopic evidence for the existence of two distinct agents of posttransfusion non-A, non-B (NANB) hepatitis. One of these agents is chloroform-resistant and is not associated with the formation of unique ultrastructural structures in infected liver. The other agent is CHCl3-sensitive, induces the formation of characteristic hepatocyte cytoplasmic tubules, and interferes with concurrent HAV or HBV infection in experimentally inoculated chimpanzees. The tubuleforming agent (TFA) has also been shown to pass through an 80 nm capillary pore membrane filter, suggesting that it is a small enveloped (or lipid-containing) virus. The TFA can also be recovered from low titer (less than or equal to 10(5) infectious doses/ml) chronic-phase chimpanzee plasma by use of a multi-step purification procedure that assumes the agent is a small enveloped RNA virus with an approximate buoyant density of 1.24 g/cm3 and a sedimentation coefficient of 200-280 S. The apparent lack of nucleic acid homology between the NANB-TFA and HBV further suggests that the NANB-TFA is either Togavirus-like or belongs to another or as yet undefined class of RNA or DNA virus.