Mutations in the gene encoding CCR5 for example, the \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\varDelta$$\end{document} 32 bp deletion, have been associated with either delayed progression to AIDS or resistance to HIV infection [4–9]. The gene discussed is CCR5; the disease is AIDS.