QUANTIFICATION OF LOW-FREQUENCY WHITE BLOOD-CELLS EXPRESSING HUMAN CYTOMEGALOVIRUS ANTIGEN BY IMAGE CYTOMETRY

Human cytomegalovirus (HCMV) infections cause considerable morbidity a nd mortality in immunocompromized patients. During HCMV infection, leu kocytes appear in the circulation in low frequencies that express the HCMV pp65 protein antigen. Since there is evidence that changes in the frequency of antigen-positive cells in the early phase of the infecti on have prognostic value, we applied automated image cytometry to quan tify these antigen-positive cells. For this purpose weekly peripheral blood leukocyte samples of 80 kidney transplant recipients were visual ly examined for the presence of antigen-positive cells using an immuno cytochemical detection method. Seventeen patients, who reacted positiv e with this assay, were identified. Next, automated image cytometry wa s applied to quantitate the frequency of antigen-positive cells in seq uential blood samples from the 17 patients. Patients who developed a p eriod of HCMV viremia had a significantly longer antigenemic period an d a significantly higher frequency of antigen-positive cells than pati ents with a HCMV infection who remained non-viremic. Therefore, automa ted image immunocytometry based screening can be used to distinguish p atients at risk for the development of a HCMV viremia. Moreover, autom ated quantitation reveals prognostic information about the HCMV infect ion at a more sensitive level than other HCMV detection techniques. (C ) 1994 Wiley-Liss, Inc.