Primary human hepatocytes are susceptible to infection by hepatitis delta virus assembled with envelope proteins of woodchuck hepatitis virus.
ABSTRACT Hepatitis B virus (HBV) and hepatitis delta virus (HDV) share the HBV envelope proteins. When woodchucks chronically infected with woodchuck hepatitis virus (WHV) are superinfected with HDV, they produce HDV with a WHV envelope, wHDV. Several lines of evidence are provided that wHDV infects not only cultured primary woodchuck hepatocytes (PWH) but also primary human hepatocytes (PHH). Surprisingly, HBV-enveloped HDV (hHDV) and wHDV infected PHH with comparable efficiencies; however, hHDV did not infect PWH. The basis for these host range specificities was investigated using as inhibitors peptides bearing species-specific pre-S (where S is the small envelope protein) sequences. It was found that pre-S1 contributed to the ability of wHDV to infect both PHH and PWH. In addition, the inability of hHDV to infect PWH was not overcome using a chimeric form of hHDV containing WHV S protein, again supporting the essential role of pre-S1 in infection of target cells. One interpretation of these data is that host range specificity of HDV is determined entirely by pre-S1 and that the WHV and HBV pre-S1 proteins recognize different receptors on PHH.
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ABSTRACT: A natural subviral agent of human hepatitis B virus (HBV), hepatitis delta virus (HDV) requires only the envelope proteins from HBV in order to maintain persistent infection. HBV surface antigens (HBsAgs) can be produced either by HBV replication, or from integrated HBV DNA regardless of the replication. The functional properties of the integrant-generated HBsAgs were examined using two human HCC-derived cell lines Hep3B and PLC/PRF/5 that contain HBV integrants, but do not produce HBV virions and have no signs of HBV replication. Both cell lines were able to support HDV replication, and assembly/egress of HDV virions. Neither of the cell lines was able to produce substantial amounts of the PreS1-containing HDV particles. HDV virions assembled in PLC/PRF/5 cells were able to infect primary human hepatocytes, while Hep3B-derived HDV appeared non-infectious. These results correlate with the findings that the entire open reading frame (ORF) for the large (L) envelope protein that is essential for infectivity was present on HBV RNAs from PLC/PRF/5 cells, while the L ORF that was truncated and fused to inverted pre-core sequences was found using RNAs from Hep3B cells. This study demonstrated for the first time that at least some of HBV DNA sequences naturally integrated during infection can produce functional small and large envelope proteins capable of the formation of infectious HDV virions. Our data indicated that in vivo chronic HDV infection can persist in the absence of HBV replication (or when HBV replication is profoundly suppressed) if functional envelope proteins are supplied from HBV integrants. The study addresses the unique mechanism of HDV persistence in the absence of ongoing HBV replication; advances our understanding of HDV-HBV interactions; and supports the implementation of treatments directly targeting HDV for HDV/HBV-infected individuals.Journal of Virology 03/2014; 88(10). DOI:10.1128/JVI.00430-14 · 4.65 Impact Factor
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ABSTRACT: Hepatitis B virus (HBV), a major cause of human liver disease worldwide, encodes three envelope proteins needed for the attachment and entry of the virus into susceptible host cells. A second virus, hepatitis delta virus, which is known to enhance liver disease in HBV infected patients, diverts the same HBV envelope proteins to achieve its own assembly and infection. In the lab, lentiviral vectors based on human immunodeficiency virus type 1 can be assembled using the HBV envelope proteins, and will similarly infect susceptible cells. This article provides a partial review and some personal reflections of how these three viruses infect and of how recipient cells become susceptible, along with some consideration of questions that remain to be answered.World Journal of Gastroenterology 10/2013; 19(40):6730-6734. DOI:10.3748/wjg.v19.i40.6730 · 2.43 Impact Factor
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ABSTRACT: The study examined how the envelope proteins of 25 variants of hepatitis B virus (HBV) genotypes A-I support hepatitis delta virus (HDV) infectivity. The assembled virions bore the same HDV ribonucleoprotein and differed only by HBV variant-specific envelope proteins coating the particles. The total HDV yield varied in 122-fold range. A residue Y (374) in the HDV-binding site was identified as critical for HDV assembly. The virions that bind the antibodies, which recognize the region that includes HBV matrix domain and predominantly but not exclusively immunoprecipitate the PreS1-containing virions, were termed as PreS1*-HDVs. Using in vitro infection of primary human hepatocytes (PHH), we measured the specific infectivity (SI), which is a number of HDV genomes/cell produced by infection and normalized by the PreS1*-MOI, which is a multiplicity of infection that reflects a number of PreS1*-HDVs/cell used in inoculum. The SI values varied in 160-fold range and indicated probable HBV genotype-specific trend in supporting HDV infectivity: D>B>E>A. Three variants of genotypes B, C and D supported the highest SI values. We also determined the normalized index of infected PHH (NI), which is the percentage of HDV-infected hepatocytes normalized by the PreS1*-MOI. Comparison of the SI and NI values revealed that while a particular HBV variant may facilitate infection of relatively significant fraction of PHH, it may not always result in a considerable number of genomes that initiated the replication after the entry. The potential implications of these findings are discussed in the context of the mechanism of attachment/entry of HBV and HDV. The study advances the understanding of the mechanisms of (i) the attachment and entry of HDV and HBV; and (ii) transmission of HDV infection/disease.Journal of Virology 03/2014; 88(11). DOI:10.1128/JVI.00346-14 · 4.65 Impact Factor