School of Health and Rehabilitation Sciences, Division of Medical Laboratory Science, Ohio State University, Columbus, OH, USA. National Heart, Lung, and Blood Institute, Bethesda, MD, USA. Division of Infectious Diseases, Johns Hopkins University, Baltimore, MD, USA. Brigham and Women's Hospital/Harvard Medical School, Boston, MA, USA. Center for AIDS Research, Division of Infectious Diseases and HIV Medicine, Department of Medicine, Case Western Reserve University/University Hospitals Case Medical Center, Cleveland, OH, USA.