Activation of the envelope proteins by a metalloproteinase enables attachment and entry of the hepatitis B virus into T-lymphocyte

Hepatitis B virus replication is upregulated in proliferated peripheral blood lymphocytes

Increasing evidence indicates that the hepatitis B virus (HBV) replicates in peripheral blood mononuclear cells (PBMCs), but at a low level. The present study aimed to establish a reliable and sensitive method that effectively detects HBV viral products for monitoring antiviral therapy, organ transplantation screening, and diagnosing occult HBV infection. In the present study, PBMCs (obtained from six healthy volunteers) were inoculated with HBV, and cultured with phytohemagglutinin (PHA) and interleukin‑2 (IL‑2) to stimulate cell proliferation. PBMCs were harvested, and quantitative detection of HBV DNA in cell suspension and intracellular hepatitis B surface antigen (HBsAg) was conducted on days 0, 1, 6 and 12, respectively. In situ hybridization, immunohistochemistry and reverse transcription‑polymerase chain reaction (RT‑PCR) were performed to analyze the HBV infection. The results demonstrated that HBV DNA increased concurrently with proliferation of PBMCs isolated from three of six healthy volunteers, and the mean number of PBMCs on day 12 was 13.61 times higher than the initially seeded cell number (P<0.01). The mean copies of HBV DNA at day 12 were 2.98 times higher compared with initial levels (P<0.05). Furthermore, intracellular HBsAg levels increased concurrently with proliferation of PBMCs in one group of cultured PBMCs, which was accompanied by increased HBV DNA levels. In addition, HBV nucleic acids were detected in PBMCs using in situ hybridization. Intracellular HBsAg was observed in PBMCs and HBV RNA was also detected by RT‑PCR. The present study demonstrated that HBV replicates in proliferating PBMCs, which were induced by PHA and IL‑2. This method offers a novel investigative tool to detect HBV infection in PBMCs and to monitor the course of HBV infection.

Anti-preS responses influence the anti-HBs response in newborns after vaccination with the third generation Sci-B-Vac vaccine

We analysed the specificity and significance of the antibody response towards the linear preS1 sequence that has been shown to represent the "hepatocyte binding site" comprising amino acids preS1 (21-47) or the specific preS2 (131-140) antibody response to the "polymerised albumin receptor" in relation to the antibody response to hepatitis B surface antigen during immunisation of healthy children with the preS-containing Sci-B-Vac vaccine. Twenty-eight healthy newborns received three doses of the Sci-B-Vac vaccine according to a 0-, 1-, and 6-month scheme. Seventeen (61%) of the 28 newborns had detectable levels of anti-preS1 (21-47) antibodies and 14 (50%) were anti-preS2 (131-140) reactive at 6 and/or 9 months after initiation of the vaccination. The mean levels of anti-HBs were significantly higher in the anti-preS2 (131-140) non-reactive (24580+/-7815IU/l, mean+SEM) compared with the reactive sera (7287+/-2317IU/l, p<0.025). The highest anti-HBs levels were found in newborns who exhibited reactivity towards the aa 21-47 of the preS1 but lacked anti-preS2 (131-140) reactivity.

Sulphated and sulphonated polymers inhibit the initial interaction of hepatitis B virus with hepatocytes

The initial step during hepatitis B virus (HBV) infection is the specific attachment of the virus to the hepatocyte. Here we studied whether the binding of HBV to hepatocytes can, as is the case with most other enveloped viruses, be blocked by polyanionic compounds. Viral particles produced by HepAD38 cells were used as inoculum and HBV-negative HepG2 cells, as well as primary human hepatocytes, as target cells. Three sulphated polymers, that is, PAVAS (a co-polymer of acrylic acid with vinyl alcohol sulphate), heparin and dextran sulphate (DS) (MW 5000), and the sulphonated polymer PAMPS [poly(2-acryl-amido-2-methyl-1-propanesulfonic acid] (MW approximately 7000-12000), proved strong inhibitors of the binding of HBV to HepG2 cells and primary hepatocytes. The 50% effective concentration (EC50) for inhibition of HBV binding to HepG2 cells by PAVAS, heparin, DS and PAMPS was 1.3 microg/ml, 1.6 microg/ml, 1.8 microg/ml and 3.3 microg/ml, respectively, and to primary hepatocytes 1.6 microg/ml (PAVAS), 1.6 microg/ml (heparin), 2.6 microg/ml (DS) and 4.1 microg/ml (PAMPS). These values are in the same range as the concentrations required for these compounds to prevent such viruses as herpesviruses and HIV from binding to cells. These findings may be helpful in elucidating the mechanism of the initial interaction of HBV with hepatocytes.

Limited proteolysis induces woodchuck hepatitis virus infectivity for human HepG2 cells

Previous work from our laboratory has shown that digestion of hepatitis B virus (HBV) with V8 protease rendered the virus infectious for human hepatoblastoma cell line (HepG2). It was hypothesized that the cleavage exposes a 16 amino acid region that includes a consensus 'fusion' motif necessary to mediate infectivity. Since woodchuck hepatitis virus (WHV) and HBV possess significant homology in this region of their envelope proteins, including the V8 protease cleavage site, the possibility that WHV infectivity for HepG2 cells could be induced by V8 digestion was explored. WHV isolated from the serum of chronically infected woodchucks, digested with V8 protease, was shown to loose its preS domain. V8 digested WHV eluted from gel filtration columns with a size similar to that of undigested virus, suggesting that digestion with V8 protease did not cause significant changes in virion size. The amount of progeny virus secreted into the culture medium following infection of HepG2 cells with V8 digested WHV reached 2.5 pg/ml, after 8 days. Moreover, WHV DNA replicative intermediates could be detected in the cells following infection with protease digested, but not undigested, viruses. These data suggest that protease modification of WHV, a non-human virus, induced infectivity for human tissue culture cells. These results are consistent with the hypothesis that exposure of an amino acid region of the envelope polypeptide that contains a consensus fusion motif is important in Hepadnavirus entry.