Heparan sulfate proteoglycans are required for cellular binding of the hepatitis E virus ORF2 capsid protein and for viral infection.
The hepatitis E virus (HEV), a nonenveloped RNA virus, is the causative agent of hepatitis E. The mode by which HEV attaches to and enters into target cells for productive infection remains unidentified. Open reading frame 2 (ORF2) of HEV encodes its major capsid protein, pORF2, which is likely to have the determinants for virus attachment and entry. Using an approximately 56-kDa recombinant pORF2 that can self-assemble as virus-like particles, we demonstrated that cell surface heparan sulfate proteoglycans (HSPGs), specifically syndecans, play a crucial role in the binding of pORF2 to Huh-7 liver cells. Removal of cell surface heparan sulfate by enzymatic (heparinase) or chemical (sodium chlorate) treatment of cells or competition with heparin, heparan sulfate, and their oversulfated derivatives caused a marked reduction in pORF2 binding to the cells. Syndecan-1 is the most abundant proteoglycan present on these cells and, hence, plays a key role in pORF2 binding. Specificity is likely to be dictated by well-defined sulfation patterns on syndecans. We show that pORF2 binds syndecans predominantly via 6-O sulfation, indicating that binding is not entirely due to random electrostatic interactions. Using an in vitro infection system, we also showed a marked reduction in HEV infection of heparinase-treated cells. Our results indicate that, analogous to some enveloped viruses, a nonenveloped virus like HEV may have also evolved to use HSPGs as cellular attachment receptors.
Kalia
Manjula
M
Virology Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110 067, India. manjula@icgeb.res.in
Chandra
Vivek
V
Rahman
Sheikh Abdul
SA
Sehgal
Deepak
D
Jameel
Shahid
S
D045744:Cell Line, Tumor; D019812:Heparan Sulfate Proteoglycans / Q000502:physiology*; D016752:Hepatitis E virus / Q000502:physiology*; D006801:Humans; D053667:Syndecans / Q000378:metabolism; D014764:Viral Proteins / Q000378:metabolism*; D014771:Virion / Q000502:physiology
D019812:Heparan Sulfate Proteoglycans; C400971:ORF2 protein, Hepatitis E virus; D053667:Syndecans; D014764:Viral Proteins