Kinetics of host immune responses and cytomegalovirus resistance in a liver transplant patient. 
Among solid organ transplant (SOT) recipients, donor-seropositive/recipient-seronegative (D+/R-) cytomegalovirus (CMV) status is associated with the highest risk of ganciclovir-resistant CMV disease, which has been reported for patients receiving oral ganciclovir but not valganciclovir prophylaxis.  We report a case of CMV breakthrough infection in a D+/R- liver transplant patient while he was receiving oral valganciclovir.  Forty samples collected over 6 months were analyzed for the CMV viral load, lymphocyte counts, cytokine levels, and lymphocyte differentiation status.  Genotypic resistance testing of the viral UL97 gene was performed when the patient failed to respond.  CMV viremia occurred on day 50 post-transplant, and 5 samples taken between days 50 and 85 showed the wild-type UL97 genotype.  The appearance of deletion 594-595 was observed from day 114 post-transplant.  Viral loads declined when foscarnet was commenced and remained below 10,000 copies/mL when the lymphocyte count was greater than 1000/microL (P = 0.02).  T cell responses revealed significant expansion of CD8+ terminal effector memory cells.  CD4+ cells were largely populations of naïve and central memory cells.  Circulating interleukin 10 (IL-10) levels correlated with the viral load (P < 0.0001).  Seroconversion occurred on day 230.  The CMV viral load in combination with lymphocyte counts and IL-10 may be a predictive marker for the risk of development of resistant CMV disease in D+/R- SOT patients.