Objective: The aim of this study was to assess the consequence of sequence variations in HLA-C*03:04-presented HIV-1 p24 Gag epitopes on binding of the inhibitory natural killer (NK) cell receptor KIR2DL2 to HLA-C*03:04.
Design: HIV-1 may possibly evade recognition by KIR+ NK cells through selection of sequence variants that interfere with the interactions of inhibitory killer cell immunoglobulin-like receptors (KIRs) and their target ligands on HIV-1 infected cells. KIR2DL2 is an inhibitory NK cell receptor that binds to a family of HLA-C ligands. Here, we investigated whether HIV-1 encodes for HLA-C*03:04-restricted epitopes that alter KIR2DL2 binding.
Methods: Tapasin-deficient 721.220 cells expressing HLA-C*03:04 were pulsed with overlapping peptides (10mers overlapped by nine amino acids, spanning the entire HIV-1 p24 Gag sequence) to identify peptides that stabilized HLA-C expression. The impact that sequence variation in HLA-C*03:04-binding HIV-1 epitopes has on KIR2DL2 binding and KIR2DL2+ NK cell function was determined using KIR2DL2-Fc constructs and NK cell degranulation assays.
Results: Several novel HLA-C*03:04 binding epitopes were identified within the HIV-1 p24 Gag consensus sequence. Three of these consensus sequence peptides (Gag144–152, Gag163–171 and Gag295–304) enabled binding of KIR2DL2 to HLA-C*03:04 and resulted in inhibition of KIR2DL2+ primary NK cells. Furthermore, naturally occurring minor variants of epitope Gag295–304 enhanced KIR2DL2 binding to HLA-C*03:04.
Conclusion: Our data show that naturally occurring sequence variations within HLA-C*03:04-restricted HIV-1 p24 Gag epitopes can have a significant impact on the binding of inhibitory KIR receptors and primary NK cell function.