Virus excretion and cell-mediated immunity during cytomegalovirus infection among healthy infants and children.

Specific cell-mediated immunity (CMI) and virus isolation were examined longitudinally to clarify the mechanism of the cessation of virus excretion in inapparent cytomegalovirus (CMV) infection among healthy infants and children. We measured leukocyte procoagulant activity (LPCA) responses to CMV antigen and to a purified protein derivative of tuberculin (PPD), with results expressed as a percentage reduction of recalcification (RC) time. Based on the results in seropositive and seronegative adult control subjects, reductions in RC time of more than 10% were considered indicative of a positive LPCA response. The CMV-specific LPCA response was negative in all infants shedding the virus, despite the presence of circulating antibodies, but were converted from negative to positive when the virus excretion ceased. This suggests that cessation of the virus excretion in inapparent CMV infection among healthy infants and children probably results from the specific CMI.