Emergence and prevalence of cytomegalovirus UL97 mutations associated with ganciclovir resistance in AIDS patients

Objectives: To evaluate the prevalence of the most common cytomegalovirus (CMV) UL97 mutations associated with ganciclovir resistance directly in polymorphonuclear leukocytes (PMNL) of patients with AIDS and CMV retinitis. Also to correlate the presence (or absence) of these mutations with the systemic CMV viral load and the ophthalmologic outcome of these subjects. Methods: Monthly blood samples were obtained from 19 patients with AIDS and CMV retinitis who had been treated with systemic ganciclovir for greater than or equal to 2 months. Detection of CMV UL97 mutations was done using nested PCR amplification followed by restriction enzyme analysis. The viral load was assessed with a polymerase chain reaction-based assay and non-isotopic hybridization detection. Results: CMV UL97 mutations were detected in PMNL of four of 13 (30.8%) patients who had been treated with ganciclovir for greater than or equal to 3 months but in none of six patients who had been treated for < 3 months. All four patients with detectable UL97 mutations were presenting evidence of retinitis progression at the time those mutations were first detected (mean, 145.7 days of ganciclovir) and three of four patients had a viral DNA load > 10 000 copies per 10(5) PMNL contrasting with the copy numbers in the 15 subjects without mutations (mean, 492.9 copies per 10(5) PMNL after a mean of 146.8 days of ganciclovir). Conclusions: The prevalence of the most common CMV UL97 mutations associated with ganciclovir resistance in PMNL of patients with AIDS treated for greater than or equal to 3 months (30.8%) appears to be higher than the rate of emergence of ganciclovir-resistant CMV isolates as previously reported using phenotypic assays (about 8%). Moreover, the detection of these mutations is associated with a considerable increase in the CMV DNA load in the blood as well as with progression of CMV retinitis during ganciclovir therapy.