Correlation between the percentages of CD3, CD4, and CD19 cells in peripheral blood samples and TTV loads in plasma samples from 40 infants with ARD. TTV load was determined with a universal real-time PCR assay directed to a highly conserved segment of the untranslated region of the viral genome (lower limit of detection, 103 DNA copies per ml). This assay has the potential to detect most if not all genetic forms of TTV hitherto described but not the TTV-like mini virus (5, 6). Total CD3, total CD4, and total CD19 lymphocyte counts were performed by fluorescence-activated cell sorting.