Quantitation of human cytomegalovirus in recipients of solid organ transplants by real-time quantitative PCR and pp65 antigenemia

Abstract

Human cytomegalovirus (HCMV) infections and anti-HCMV treatment are usually monitored by measuring pp65 antigenemia. This method is time-consuming, labour-intensive and requires skilled operators. We have compared results obtained using real-time Light Cycler quantitative PCR (QPCR) and the pp65 antigen assay on serial samples collected from recipients of solid organ transplants. We collected 198 blood samples from 14 solid organ transplant recipients and assayed them for pp65 antigen and with Light Cycler PCR. HCMV DNA was extracted from leukocytes and measured using primers and probe located in the UL83 region. The quantity of HCMV DNA was calculated using a standard curve prepared from a plasmid containing the target sequence. There was a good correlation between the number of pp65-positive cells and the DNA copy number (r = 0.57, P < 0.0001). A clinical threshold of 50 positive polymorphonuclear leukocytes/200,000 cells was equivalent to two log10 genome copies per capillary by Light Cycler PCR. HCMV DNA was detected before pp65 antigen in three patients at a mean time of 10 days, whereas the two tests were positive simultaneously for eight patients. Both the pp65 antigen data and DNA copy number decreased over time during antiviral treatment, although the QPCR was positive 28.2 days after the pp65 antigen assay had become negative. The real-time Light Cycler quantitative PCR assay is a rapid and labour-saving technique. This molecular method could be useful for monitoring infections and antiviral treatment in recipients of solid organ transplants.