 - No history of human immunodeficiency virus HIV, active or chronic hepatitis B, hepatitis C or human T-cell lymphotropic virus HTLV-I infection; NOTE: a positive hepatitis B serology indicative of previous immunization i.e., hepatitis B surface antibody HBsAb positive and hepatitis B core antibody HBcAb negative, or a fully resolved acute hepatitis B virus HBV infection is not an exclusion criterion 