Adenovirus infection in paediatric stem cell transplant recipients: increased risk in young children with a delayed immune recovery.

Adenovirus (HAdV) infections are a frequent cause of morbidity and mortality after allogeneic human stem cell transplantation (HSCT). We report a retrospective single-centre study on 328 consecutive paediatric recipients of an allogeneic HSCT. During the first 6 months after HSCT, HAdV infection occurred in 37 children (cumulative incidence 12%). The highest incidence was found in young children up to 5 years of age, transplanted after 1994, with >2 log T-cell depletion of a graft of another than an HLA-genotypically identical related donor (actuarial frequency at 6 months 84%). Persistence of HAdV and spreading of the virus over multiple sites showed a trend towards the development of HAdV disease or death, but did not reach significance. Recovery of immunity after HSCT, that is, serum concentrations of IgM and peripheral blood counts of T cells and subsets, was delayed in children with an HAdV infection compared with noninfected children. In seven out of seven patients with HAdV DNA in serum and decreasing lymphocyte counts, the infection had a fatal course. Manipulation of cellular immunity either by tapering of immunosuppression, infusion of donor lymphocytes or immunotherapy using HAdV-specific T cells should be considered in graft recipients at risk for a severe HAdV infection.