S100B and HIV infectious disease: While HIV infection has been reported by others to be associated with increased expression of ULBP-1, ULBP-2, and ULBP-3, Nef expression is associated with the downregulation of NKG2D ligands and expression of ULBP-1, ULBP-2 and MIC-A increases more dramatically in cells infected with Nef-deficient virus [52,55].