Epstein-Barr virus infectious mononucleosis in children. II. Heterophil antibody and viral-specific responses.

An investigation was performed to address the need to establish the rate of positive heterophil antibody responses, oropharyngeal isolation of Epstein-Barr virus (EBV), and the evolving pattern of EBV-specific antibody responses among children with documented EBV-infectious mononucleosis. Findings showed that the rate of heterophil antibody responses appeared to increase progressively with advancing age from infancy up to 4 years, after which the rates approached values similar to that reported in young adult patients. The rapid slide test detected a heterophil antibody response as frequently as the Paul-Bunnell-Davidsohn horse cell test, except in children less than 4 years old. The decreased sensitivity found with the rapid slide test in the very young was associated with their less intense heterophil response. The younger group of children also developed a lower acute mean titer and, as a result, a decreased persistence of immunoglobulin M antibody to EBV-capsid antigen, whereas they had more frequent responses to EBV-early antigen directed to restricted component than both the older subjects and adults reported elsewhere. Antibodies to EBV-nuclear antigen, characteristically a late-onset antibody, tended to develop earlier than noted in adult patients. In contrast, the prevalence and continued excretion of EBV from oropharyngeal secretions was similar to that reported in adult patients. It is speculated that these age-related differences in host responses are associated with the ontogeny of the immunologic system.