Strong response of T cells in infants with dual infection by Epstein-Barr virus and cytomegalovirus.

Abstract

Although a reversed CD4/CD8 ratio and increased proportion of CD8+ HLA-DR+ T cells are well known as the characteristic immune response in infectious mononucleosis (IM), it has not been elucidated whether these immune responses are affected by patient age and pathogenetic viruses. T cell subsets were analyzed by two-color flow cytometry using fluorescein isothiocyanate- and phycoerythrin-conjugated monoclonal antibodies in 115 infants and children aged from 4 months to 10 years with IM due to Epstein-Barr virus (EBV), cytomegalovirus (CMV) and dual infection with both viruses. A reversed CD4/CD8 ratio and increased proportions of CD4+/HLA-DR+ T cells, CD8+ T cells and CD8+/HLA-DR+ T cells became more prominent as the age of the patients became older. No differences were observed in proportions of T cell subsets between EBV- and CMV-infection among patients aged from 6 to 17 months. Although the responses of these T cells were weak in infants with single virus infection by EBV and CMV, markedly strong T cell responses comparable with those in older children were observed in infants with EBV/CMV dual infection. Clinical symptoms were more severe in patients with EBV/CMV dual infection than those with EBV or CMV alone. The manner of these T cell responses in the acute phase of IM was considered to be age dependent, although strong T cell responses and severe disease were observed in EBV/CMV dual infection irrespective of patient age.