title: Replacement of the V3 domain in the surface subunit of the feline immunodeficiency virus envelope glycoprotein with the equivalent region of a T cell-tropic human immunodeficiency virus type 1 results in a chimeric surface protein that efficiently binds to CXCR4.
abstract: Feline immunodeficiency virus (FIV) and the T cell-tropic strains of human immunodeficiency virus type 1 (HIV-1) share the use of the chemokine receptor CXCR4 for cell entry. To study this process further we developed a cell surface binding assay based on the expression of a soluble version of the FIV SU C-terminally tagged with the influenza virus hemagglutinin epitope (HA). The specificity of the assay was demonstrated by the following evidence: (1) the SU-HA protein bound to HeLa cells that express CXCR4 but not to MDCK cells that lack this chemokine receptor; and (2) binding of the SU-HA to HeLa cells was blocked by incubation with the CXCR4 antagonist AMD3100 as well as with the anti-CXCR4 monoclonal antibody (MAb) 12G5. Deletion of the V3 region from the FIV SU glycoprotein abolished its ability to bind CXCR4-expressing cells. Remarkably, substitution of the V3 domain of the FIV SU by the equivalent region of the HIV-1 NL4-3 isolate resulted in efficient cell surface binding of the chimeric SU protein to CXCR4. Moreover, transfection of MDCK cells with a plasmid encoding human CXCR4 allowed the association of the chimeric SU-HA glycoprotein to the transfected cells. Interestingly, while cell binding of the chimeric FIV-HIV SU was inhibited by an anti-HIV-1 V3 MAb, its association with CXCR4 was found to be resistant to AMD3100. Of note, the chimeric FIV-HIV Env glycoprotein was capable of promoting CXCR4-dependent cell-to-cell fusion.
authors.affiliation: Laboratorio de Virología, CONICET-Universidad de Belgrano (UB) , Buenos Aires, Argentina .
authors.forename: Silvia A
authors.initials: SA
authors.lastname: González
authors.forename: Juan I
authors.initials: JI
authors.lastname: Falcón
authors.forename: José L
authors.initials: JL
authors.lastname: Affranchino
mesh_terms: D000818:Animals; D002460:Cell Line; D006023:Glycoproteins / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D016089:Immunodeficiency Virus, Feline / Q000235:genetics / Q000502:physiology*; D019718:Receptors, CXCR4 / Q000378:metabolism*; D015728:Receptors, HIV / Q000378:metabolism*; D011995:Recombination, Genetic; D014759:Viral Envelope Proteins / Q000235:genetics*; D053585:Virus Attachment; D054299:env Gene Products, Human Immunodeficiency Virus / Q000235:genetics*
chemical_list: C527276:CXCR4 protein, human; D006023:Glycoproteins; D019718:Receptors, CXCR4; D015728:Receptors, HIV; D014759:Viral Envelope Proteins; D054299:env Gene Products, Human Immunodeficiency Virus; C445079:envelope protein, Feline immunodeficiency virus