Mapping the Domains of CD134 as a Functional Receptor for Feline Immunodeficiency Virus

Abstract

The feline homologue of CD134 is the primary binding receptor for feline immunodeficiency virus (FIV), targeting the virus preferentially to activated CD4؉ helper T cells. However, strains of FIV differ in utilization of CD134; the prototypic strain PPR requires a minimal determinant in the first cysteine-rich domain (CRD1) of feline CD134 to confer near-optimal receptor function, while strains such as GL8 require additional determinants in the CD134 CRD2. We map this determinant to a loop in CRD2 governing the interaction between the receptor and its ligand; the amino acid substitutions S78N-S79Y-K80E restored full viral receptor activity to the CDR2 of human CD134 in the context of feline CD134, with tyrosine-79 appearing to be the critical residue for restoration of receptor function.The initial event in the process of virus entry into a target cell is the interaction between the virus and its cellular receptor; the specificity of this interaction determines both the cell tropism and the pathogenicity of the virus. The primary receptor for feline immunodeficiency virus (FIV) is CD134 (OX40) (13), a member of the tumor necrosis factor receptor (TNFR)/ nerve growth factor receptor family of molecules. CD134 expression is greatest on activated CD4 ϩ T-helper cells (7); thus, infection results in a progressive depletion of T-helper cells and AIDS-like illness. Primary isolates of FIV use CD134 as the binding receptor in conjunction with the chemokine receptor CXCR4 as a cofactor for infection (11,13,15). FIV binds specifically to CD134-expressing cells (13); FIV Env interacts directly with CD134 (4), and pretreatment of virus with soluble CD134 facilitates infection of CD134 Ϫ /CXCR4 ϩ cells (3). The binding site for the PPR strain of FIV has been mapped to the first cysteine-rich domain (CRD1) (3); human CD134 is not a functional receptor for FIV (13), and substitution of CRD1 of human CD134 with that of feline CD134 renders the molecule functional as a receptor for the PPR strain of FIV. However, expression of feline CD134 CRD1 in the context of human CD134 is insufficient to confer receptor function on many primary strains of FIV; additional determinants in CRD2 of feline CD134 are required to restore function (16), indicating differential utilization of CD134 by diverse strains of FIV (16). In order to map the determinants in CRD2, we compared the amino acid sequences of the CRD2s of feline and human CD134 (previously we identified the fragment spanning amino acids 65 to 82 as containing the critical determinant [s] [16]) and identified amino acid sequence differences (Fig. 1B). Next, using the human CRD2-containing chimera FFHH as our template, we proceeded to mutate the remaining amino acids in CRD2 from the human sequence to the feline sequence by PCR amplification from the FFHH template by using a mutagenic internal oligonucleotide (3Ј) carrying a BsrGI restriction site and a nonmutagenic external flanking (5Ј) primer carrying a BamHI restriction site. The following mutations were introduced: R66L-P67Q (...

Central and peripheral reservoirs of feline immunodeficiency virus in cats: a review

“…Furthermore, CD134 domains required for FIV Env binding and infection with more pathogenic FIV strains were mapped to two cysteine-rich domains (CRD1 and CRD2), whereas less pathogenic strains only required binding to CRD1 based on in vitro analyses. These findings agreed with evidence for FIV Env-CD134 binding patterns changing over time in individually infected animals, which may ultimately influence viral cell surface affinity due to nucleotide base changes in env and reflect isolates sensitive to circulating anti-CD134 autoantibodies [44][45][46]. Recent studies further [47].…”

“…Early reports showed that different CD134 binding-domain patterns may be viral strain-dependent [35,44,45]. Furthermore, CD134 domains required for FIV Env binding and infection with more pathogenic FIV strains were mapped to two cysteine-rich domains (CRD1 and CRD2), whereas less pathogenic strains only required binding to CRD1 based on in vitro analyses.…”

Mapping of the CXCR4 Binding Site within Variable Region 3 of the Feline Immunodeficiency Virus Surface Glycoprotein

“…Recent studies have indicated the involvement of additional residues in domain 2 in binding of certain other strains of FIV (49). For SU interaction with its entry receptor, CXCR4, involvement of the second extracellular loop of CXCR4 has been reported (5,47).…”

Feline Immunodeficiency Virus and Its Receptors

“…CD134 was primary described as MRC OX-40, an antigen expressed on activated rat CD4 + T belonging to tumor necrosis factor receptor/nerve growth factor receptor (TNFR/NGFR) superfamily (Mallett et al 1990, Paterson et al 1987. The SU of FIV, gp95, binds to alone is enough to confer nearly optimal receptor function for infection with strains such as PPR, subtype A, and B2542, subtype B, although pathogenic primary strains of virus, such as GL8, subtype A, GPGammer, subtype C, and NCSU1, subtype B, need extra determinants, the second cysteine-rich domain, CRD2, in the CD134 and at that rate the CD134 form a functional receptor (Willett et al 2006a, Willett et al 2006b). …”