Quantitation of human cytomegalovirus DNA in peripheral blood leukocytes of heart transplant recipients: relationship with pp65 antigenernia and with antiviral therapy

Abstract

OBJECTIVE: To retrospectively determine DNA levels in blood polymorphonuclear leukocytes (PMNLs) of 21 heart transplant patients who suffered from HCMV infection and who were monitored by the antigenemia assay (pp65 test) during follow-up, by use of a quantitative competitive polymerase chain reaction (PCR) assay for human cytomegalovirus (HCMV) DNA. METHODS: Quantitation of HCMV DNA by PCR was expressed as genome equivalents (GE) per 200 000 PMNLs. RESULTS: Ten patients experienced symptomatic HCMV infection (five primary infections and five reactivations) with mild symptoms and received ganciclovir treatment, whereas 11 asymptomatic HCMV infections were not treated. Therapy was discontinued when a 90% reduction of the pretreatment antigenic load was achieved in a symptomless patient. The mean HCMV DNA and antigenic loads were significantly higher in symptomatic than in asymptomatic patients: 4.6 x 105 plus minus 4.7 x 105 GE and 1.1 x 104 GE (p<0.0001) and 390 plus minus 350 versus 25 plus minus 12 pp65-positive PMNLs (p<0.0001), and in primary than in secondary infections (583 plus minus 403 pp65-positive PMNLs versus 85 plus minus 111, p=0.002 and 5.2 x 105 plus minus 5.2 x 105 GE instead of 1.5 x 105 plus minus 3.2 x 105 GE, p=0.02). A single course of 14--21 days of ganciclovir caused a marked decrease of HCMV DNA and antigenemia in eight of 10 patients in whom a 90% reduction of the antigenic load correlated with a 98% DNA reduction of the pretreatment levels. In two primary infections, a 90% antigenic reduction was achieved by 21 days of ganciclovir treatment, but those data only correlated with a DNA load reduction of 28% and 60% of the pretreatment levels. Fifteen and 12 days later, respectively, the two patients relapsed and underwent a second ganciclovir course, at the end of which a 90% reduction of the antigenic load correlated with a >98% DNA drop. GCV was discontinued and the patients recovered completely. In those two patients we retrospectively found persistent high DNA levels before the second ganciclovir course, whereas the antigenic load slowly increased after an apparent reduction. CONCLUSIONS: Our data suggest that: (1) DNA levels have the same trend as the pp65 antigen test---they are significantly higher in symptomatic and in primary HCMV-infected patients than in asymptomatic patients and those with secondary infection; (2) a 90% antigenic load reduction from the pre-treatment level may be a less reliable predictor of the efficacy of anti-HCMV therapy than DNA load, at least in primary infection, in which a much higher viral load and much more severe disease are present; and (3) a DNA load reduction of >98% of the pretreatment value is required for therapeutic success.