title: Neutralization of hepatitis A virus (HAV) by an immunoadhesin containing the cysteine-rich region of HAV cellular receptor-1.
abstract: Hepatitis A virus (HAV) infects African green monkey kidney (AGMK) cells via the HAV cellular receptor-1 (havcr-1), a mucin-like type 1 integral-membrane glycoprotein of unknown natural function. The ectodomain of havcr-1 contains an N-terminal immunoglobulin-like cysteine-rich region (D1), which binds protective monoclonal antibody (MAb) 190/4, followed by an O-glycosylated mucin-like threonine-serine-proline-rich region that extends D1 well above the cell surface. To study the interaction of HAV with havcr-1, we constructed immunoadhesins fusing the hinge and Fc portion of human IgG1 to D1 (D1-Fc) or the ectodomain of the poliovirus receptor (PVR-Fc) and expressed them in CHO cells. These immunoadhesins were secreted to the cell culture medium and purified through protein A-agarose columns. In a solid-phase assay, HAV bound to D1-Fc in a concentration-dependent manner whereas background levels of HAV bound to PVR-Fc. Binding of HAV to D1-Fc was blocked by treatment with MAb 190/4 but not with control MAb M2, which binds to a tag epitope introduced between the D1 and Fc portions of the immunoadhesin. D1-Fc neutralized approximately 1 log unit of the HAV infectivity in AGMK cells, whereas PVR-Fc had no effect in the HAV titers. A similarly poor reduction in HAV titers was observed after treating the same stock of HAV with murine neutralizing MAbs K2-4F2, K3-4C8, and VHA 813. Neutralization of poliovirus by PVR-Fc but not by D1-Fc indicated that the virus-receptor interactions were specific. These results show that D1 is sufficient for binding and neutralization of HAV and provide further evidence that havcr-1 is a functional cellular receptor for HAV.
authors.affiliation: Laboratory of Hepatitis Viruses, Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
authors.forename: E
authors.initials: E
authors.lastname: Silberstein
authors.forename: G
authors.initials: G
authors.lastname: Dveksler
authors.forename: G G
authors.initials: GG
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003545:Cysteine; D000939:Epitopes; D000072596:Hepatitis A Virus Cellular Receptor 1; D006507:Hepatovirus / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry* / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D009500:Neutralization Tests; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D011961:Receptors, Fc / Q000378:metabolism; D011991:Receptors, Virus / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; C491143:HAVCR1 protein, human; D000072596:Hepatitis A Virus Cellular Receptor 1; D007136:Immunoglobulins; D008562:Membrane Glycoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D011961:Receptors, Fc; D011991:Receptors, Virus; D011993:Recombinant Fusion Proteins; C050855:immunoglobulin D receptor; D003545:Cysteine