TT virus loads and lymphocyte subpopulations in children with acute respiratory diseases

Abstract

TT virus (TTV) produces chronic plasma viremia in around 90% of healthy individuals of all ages and has, therefore, been proposed as a commensal human virus. We recently demonstrated that in children hospitalized for acute respiratory diseases high TTV loads were associated with severe forms of disease. Here, we report that in such children TTV loads showed an inverse correlation with the percentage of circulating total T and helper T cells and a direct correlation with the percentage of B cells. Thus, florid TTV replication might contribute to lymphocyte imbalances and, possibly, immunosuppressive effects, thus resembling related animal viruses.

FIG. 1.

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.