Cytomegalovirus-specific T cells are detectable in early childhood and allow assignment of the infection status in children with passive maternal antibodies.

Serological identification of the cytomegalovirus (CMV) status in children less than 18 months of age is complicated by the variable persistence of maternal antibodies. As T cells are not passively transferred, we attempted to assess whether CMV-specific cellular immunity may be superior to determine the actual CMV status; we also performed a functional characterization of T-cell immunity in childhood. Antibodies from 59 mothers and 168 children were determined, and specific CD4(+) T cells were identified by induction of IFN-γ, IL-2, TNF-α, IL-4, and IL-17 after CMV-specific and polyclonal stimulation. Agreement between both tests was perfect for mothers and children more than 18 months. Among infants less than 18 months, 17/30 were concordantly negative. Interestingly, 8/13 seropositive children had detectable CMV-specific T cells, whereas only 5/13 were T-cell negative, indicating passive immunity. CMV-specific T cells from young infants differed in cytokine profiles from that of older age groups, and polyclonal effector T-cell frequencies were higher in young infants with detectable CMV-specific T cells compared with those without. In conclusion, the majority of young infants with CMV-specific antibodies show evidence of true infection, which indicates that passive immunity is overestimated. Our data may have important implications for improved risk stratification and CMV management in infants in the setting of transplantation.