Cross-reactive memory CD4+ T cells alter the CD8+ T-cell response to heterologous secondary dengue virus infections in mice in a sequence-specific manner.

Secondary dengue virus (DENV) infection is a major factor contributing to the risk for severe disease, an effect that depends upon the sequence of infection with different DENV serotypes. We previously reported sequence-dependent effects of secondary DENV infection on CD8+ T-cell responses in mice. To further evaluate the effect of infection sequence, we analyzed DENV-specific CD4+ T-cell responses and their relationship to the CD8+ T-cell response. Serotype cross-reactivity of CD4+ T-cell responses also depended upon the sequence of serotypes in this model. Furthermore, adoptive transfer of memory CD4+ T cells altered the response of memory CD8+ T cells to secondary infection. These data demonstrate the interaction of different components of the T-cell response in determining the immunological outcome of secondary DENV infection.