Simian Immunodeficiency Virus SIVmac239, but Not SIVmac316, Binds and Utilizes Human CD4 More Efficiently than Rhesus CD4

Abstract

Rhesus macaques are used to model human immunodeficiency virus type 1 (HIV-1) infections, but they are not natural hosts of HIV-1 or any simian immunodeficiency virus (SIV). Rather, they became infected with SIV through cross-species transfer from sooty mangabeys in captivity. It has been shown that HIV-1 utilizes rhesus CD4 less efficiently than human CD4. However, the relative ability of SIV envelope glycoproteins to bind or utilize these CD4 orthologs has not been reported. Here we show that several SIV isolates, including SIVmac239, are more efficiently neutralized by human CD4-Ig (huCD4-Ig) than by the same molecule bearing rhesus CD4 domains 1 and 2 (rhCD4-Ig). An I39N mutation in CD4 domain 1, present in human and sooty mangabey CD4 orthologs, largely restored rhCD4-Ig neutralization of SIVmac239 and other SIV isolates. We further observed that SIVmac316, a derivative of SIVmac239, bound to and was neutralized by huCD4-Ig and rhCD4-Ig with nearly identical efficiencies. Introduction of two SIVmac316 CD4-binding site residues (G382R and H442Y) into the SIVmac239 envelope glycoprotein (Env) markedly increased its neutralization sensitivity to rhesus CD4-Ig without altering neutralization by human CD4-Ig, SIV neutralizing antibodies, or sera from SIV-infected macaques. These changes also allowed SIVmac239 Env to bind rhCD4-Ig more efficiently than huCD4-Ig. The variant with G382R and H442Y (G382R/H442Y variant) also infected cells expressing rhesus CD4 with markedly greater efficiency than did unaltered SIVmac239 Env. We propose that infections of rhesus macaques with SIVmac239 G382R/H442Y might better model some aspects of human infections. IMPORTANCE Rhesus macaque infection with simian immunodeficiency virus (SIV)has served as an important model of human HIV-1 infection. However, differences between this model and the human case have complicated the development of vaccines and therapies. Here we report the surprising observation that SIVmac239, a commonly used model virus, more efficiently utilizes human CD4 than the CD4 of rhesus macaques, whereas the closely related virus SIVmac316 uses both CD4 orthologs equally well. We used this insight to generate a form of SIVmac239 envelope glycoprotein (Env) that utilized rhesus CD4 more efficiently, while retaining its resistance to antibodies and sera from infected macaques. This Env can be used to make the rhesus model more similar in some ways to human infection, for example by facilitating infection of cells with low levels of CD4. This property may be especially important to efforts to eradicate latently infected cells.KEYWORDS CD4, SIVmac239, SIVmac316, human immunodeficiency virus, rhesus macaques, simian immunodeficiency virus

eCD4-Ig Limits HIV-1 Escape More Effectively than CD4-Ig or a Broadly Neutralizing Antibody

“…eCD4-Ig escape, results in a substantial drop in infectivity that can be partially rescued by changes in the V3 base region and/or the V2 apex region. Modest differences between HOS and Cf2Th cells may reflect the relatively higher levels of CD4 on the latter cells (34) or differences in CCR5 expression between these cell lines.…”

“…Expi293 cells were grown in Expi293 expression medium (Thermo Fisher Scientific). Plasmids encoding CD4-Ig, eCD4-Ig, and tyrosylprotein sulfotransferase 2 (TPST2) have been described previously (30,34 (59,60). Vectors expressing 447-52D were provided by Meredith Davis-Gardner.…”

“…HIV-1 pseudoviruses were generated as described above except that pNL4-3.Luc.R Ϫ E Ϫ was used as the HIV-1 expression vector (64). The generation of Cf2Th-CCR5 cells stably expressing rhesus CD4 has been described before (34). HOS CD4 ϩ CCR5 ϩ cells and Cf2Th-CCR5 cells stably expressing rhesus CD4 were harvested, diluted to 100,000 cells/ml in DMEM with 10% FBS, and incubated with virus dilutions at 37°C.…”

AAV-delivered eCD4-Ig protects rhesus macaques from high-dose SIVmac239 challenges

“…rh-eCD4-Ig I39N uses rhesus CD4 domains 1 and 2 modified with an asparagine at residue 39 to better emulate the potency of human eCD4-Ig. As previously reported, this human CD4-derived residue improves binding to both HIV-1 and SIV Env proteins (29,30). In this study, we examined the efficacy of AAV-expressed eCD4-Ig to protect rhesus macaques from SIVmac239 challenges.…”

Potent suppression of HIV-1 cell attachment by Kudzu root extract

“…To investigate whether Kudzu was targeting gp120 directly, we first assessed its ability to interfere with the interaction between gp120 and CD4. For this, we coated monomeric recombinant gp120 on an ELISA plate and measured its interaction with CD4-Ig (as in [ 34 ]), in the presence of increasing concentrations of Kudzu (Fig. 4 d).…”