Conserved Role of an N-Linked Glycan on the Surface Antigen of Human Immunodeficiency Virus Type 1 Modulating Virus Sensitivity to Broadly Neutralizing Antibodies against the Receptor and Coreceptor Binding Sites

Townsley S, et al., 28;90(2):829-41, J Virol., 2015

Earlier studies have reported that the removal of a potential N-linked glycan (PNLG) site at amino acid residue 197 (N7) in the conserved region of gp120 of HIV-1 envelope glycoprotein (Env) increases neutralization sensitivity of the antibodies directed at CD4 binding site (CD4bs) relative to its wild-type (WT). Described herein is an investigation of the role of N-linked glycan at amino acid position 197 (N7) in modulating the antigenicity of HIV-1 Env pertaining to a panel of HIV-1 strains. Broadly neutralizing antibodies (bNAbs) with defined epitope specificities were used. Binding affinity of N7-glycosylated and deglycosylated gp120 to CD4-IgG2 was tested by Bio-Layer Interferometry. A Pall ForteBio Octet instrument equipped with Anti-Human IgG Fc Biosensor probes were used for the binding assays. CD4-IgG2 immobilized Biosensor tips were dipped in a 2-fold dilution series of gp120. The association rate constant (ka) and the dissociation rate constant (kd) were measured. The KD values were calculated for the binding interactions. The findings of this study revealed a conserved role played by the N7 glycan in masking epitopes present in both CD4bs and variable loops.

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