Analytical and biological considerations in the measurement of cell-associated CCR5 and CXCR4 mRNA and protein

The accurate measurement of T cell-associated CC chemokine receptor type 5 (CCR5) and CXC chemokine receptor type 4 (CXCR4) expression, including expression of CCR5 and CXCR4 mRNA as an immune measure of immunologic response to highly active antiretroviral therapy (HAART) and newer agents, including entry inhibitors, is essential. Previous studies have reported alterations in lymphocyte cell membrane CCR5 expression that were related to blood collection and cell separation media. Clinical trials often require the transport of specimens to central laboratories for evaluation, resulting in significant time delays between specimen procurement and analysis. This study shows that CCR5 expression on naïve and memory T cells is influenced by blood collection media and specimen age. Peripheral blood collected in Streck Vacutainer tubes containing a cell stabilizer and fixative was found to improve detection of CCR5 expression compared to specimens collected in K2 EDTA anticoagulant. The selection of flow cytometry gating strategies for the identification of naïve and memory T-helper cells can also significantly influence the sensitivity of detection of CCR5 expression. Procedural methods are described that allow for the optimal measurement of naïve and memory T-helper cell CCR5 and CXCR4 expression as well as the quantitation of CCR5 and CXCR4 mRNA.