We analyzed cytomegalovirus (CMV) infection risk factors and immune reconstitution kinetics in 89 patients after allogeneic stem cell transplantation (allo-SCT). The use of alemtuzumab for in vivo T cell depletion (TCD) had, besides the donor/recipient CMV serostatus, the strongest influence on the CMV infection risk in univariate and multivariate analyses. In comparison to without use of in vivo TCD, the CMV infection risk [hazard ratio (HR)] was 4.82-fold after TCD with alemtuzumab, but only 1.40-fold after TCD with antithymocyte globulin (ATG). Alemtuzumab strongly depressed CD4(+) and CD8(+) T cell reconstitution, whereas ATG only delayed CD4(+) T cell reconstitution. Considering the reconstitution kinetics of CD4(+) and CD8(+) T cells, CMV-specific CD8(+) T cells, NK cells and the IgG concentration, only a low day +60 NK cell count (< or =161 versus >161/microl) was significantly associated with CMV infection development (HR 2.92, p = 0.034). CMV-specific CD8(+) T cells were detected in 57% of patients with a CMV-seropositive donor, but in none of the patients with a CMV-seronegative donor on day +30 (p = 0.01). Our data indicate that the type of in vivo TCD (alemtuzumab or ATG) differentially influences both the CMV infection risk and CD4(+)/CD8(+) T cell reconstitution kinetics in patients after allo-SCT.

We developed a novel algorithm to define the need for high-dose prophylactic i.v. Igs (IVIG) in periods of high risk for CMV to patients after allo-SCT. IVIG were administered only if at least one of the following, monthlyassessed, criteria was fulfilled: (1) IgG concentration o4 g/l, (2) NK (natural killer) cell count o100/ll, (3) CD4 þ cell count o100/ll, (4) acute or chronic GVHD. The primary endpoint was to determine the cumulative incidence of CMV infection in patients who received prophylactic IVIG according to the algorithm (intervention group) and compare it with that of a sequentially assessed control group, to which prophylactic IVIG were not administered. The study included 79 patients (44 in the intervention and 35 in the control group). The estimated cumulative incidence of CMV infection in the intervention and control group did not differ significantly (44 and 36%; P ¼ 0.31). Additionally, prophylactic IVIG did not reduce the frequency of CMV infection episodes. CMV disease was rare in both cohorts (5 and 9%; P ¼ 0.65). We conclude that prophylactic IVIG should not be administered after allo-SCT, even if administered selectively in a high dose to patients with delayed immune reconstitution or GVHD.