Relationship of in vitro immune responses to Epstein-Barr herpesvirus and severity of infectious mononucleosis.

Immune responses to Epstein-Barr herpesvirus (EBV) and EBV-related antigens were studied serially in 18 patients with heterophil antibody-positive infectious mononucleosis and in 18 control subjects. Enhanced cellular immune responses to EBV particles and to EBV intracellular soluble antigens were found in the patients at convalescence, suggesting that the development of specific cellular immune responses was associated with apparent control of the virus infection. In addition, a correlation between severity of disease and specific cellular immune response was found. Patients with severe clinical signs were found to have a more active cellular immune response to EBV intracellular soluble antigens early in the infection compared with patients with mild disease. This suggests that an increased immune reactivity to intracellular antigens during the early part of the illness is related to the severity of clinical manifestations in infectious mononucleosis. Serum antibody to viral capsid antigen and early antigen was not related to the severity of clinical disease.