...Standard & Poor's Ratings Services affirmed its '###' long-term rating on Howard Hughes Medical Institute (HHMI), Md.'s series 2013B taxable bonds. Standard & Poor's also affirmed its '###/A-1+' dual rating on Loudoun County Industrial Development Authority, Va.'s series 2013A multimodal tax-exempt revenue bonds, series 2003A-F variable rate bonds, and 2009B variable rate bonds, issued for HHMI. Standard & Poor's also affirmed its '###/A-1+' rating on Maryland Economic Development Corp.'s series 2008A and 2008B multimodal revenue bonds issued for HHMI. The rating outlook on HHMI remains stable. HHMI is a medical research organization headquartered in Chevy Chase, Md. Although it conducts the majority of its medical research at many host institutions, it also has its own research campus--the Janelia Research Campus in Virginia. HHMI does not receive any federal support or other grant support, nor does it accept donations; it funds its operations almost completely with endowment distributions....