Impact of CMV Reactivation, Treatment Approaches, and Immune Reconstitution in a Nonmyeloablative Tolerance Induction Protocol in Cynomolgus Macaques.

BACKGROUND: Cytomegalovirus (CMV) infection is a serious complication in immunosuppressed patients, specifically transplant recipients. Here, we describe the development and use of an assay to monitor the incidence and treatment of CMV viremia in a Cynomolgus macaque model of bone marrow transplantation (BMT) for tolerance induction. We address the correlation between the course of viremia and immune reconstitution. METHODS: Twenty-one animals received a nonmyeloablative conditioning regimen. Seven received cyclosporine A for 28 days and 14 received rapamycin. A CMV polymerase chain reaction assay was developed and run twice per week to monitor viremia. Nineteen recipients were CMV seropositive before BMT. Immune reconstitution was monitored through flow cytometry and CMV viremia was tracked via quantitative polymerase chain reaction. RESULTS: Recipients developed CMV viremia during the first month post-BMT. Two animals developed uncontrollable CMV disease. CMV reactivation occurred earlier in cyclosporine A-treated animals compared with those receiving rapamycin. Post-BMT, T-cell counts remained significantly lower compared with pretransplant levels until CMV reactivation, at which point they increased during the viremic phase and approached pretransplant levels 3 months post-BMT. Management of CMV required treatment before viremia reached 10 000 copies/mL; otherwise clinical symptoms were observed. High doses of ganciclovir resolved the viremia, which could subsequently be controlled with valganciclovir. CONCLUSIONS: We developed an assay to monitor CMV in Cynomolgus macaques. CMV reactivation occurred in 100% of seropositive animals in this model. Rapamycin delayed CMV reactivation and ganciclovir treatment was effective at high doses. As in humans, CD8 T cells proliferated during CMV viremia.

Distinctive Leukocyte Subpopulations According to Organ Type in Cynomolgus Macaques.

Cynomolgus macaques (CYNO; Macaca fascicularis) are a well-established NHP model used for studies in immunology. To provide reference values on the baseline cell distributions in the hematopoietic and lymphoid organs (HLO) of these animals, we used flow cytometry to analyze the peripheral blood, bone marrow, mesenteric lymph nodes, spleen, and thymus of a cohort of male, adult, research-naïve, Mauritian CYNO. Our findings demonstrate that several cell distribution patterns differ between CYNO and humans. First, the CD4(+):CD8(+) T-cell ratio is lower in CYNO compared with humans. Second, the peripheral blood of CYNO contains a population of CD4(+)CD8(+) T cells. Third, the CD31 level was elevated in all organs studied, suggesting that CD31 may not be an accurate marker of recent thymic emigrants within the CD4(+) T cells of CYNO. Finally the B-cell population is lower in CYNO compared with humans. In summary, although the majority of immune cell populations are similar between cynomolgus macaques and humans, several important differences should be considered when using CYNO in immunologic studies. Our current findings provide valuable information to not only researchers but also veterinarians working with CYNO at research centers, in zoos, or in the wild.