VIRUS-SPECIFIC CD8(+) CELLS CAN SWITCH TO INTERLEUKIN-5 PRODUCTION AND INDUCE AIRWAY EOSINOPHILIA

Virus infections of the lung are thought to predispose individuals to asthma, a disease characterized by eosinophil infiltration of the airways. CD8(+) T cells are an important part of the host response to virus infection, however, they have no reported role in eosinophil recruitment. We developed a mouse model of virus peptide-stimulated CD8(+) T cell immune responses in the lung. We found that bystander CD4(+) T helper cell type 2 immune responses to ovalbumin switched the virus peptide-specific CD8(+) T cells in the lung to interleukin (IL) 5 production. Furthermore, when such IL-5-producing CD8 T cells were challenged via the airways with virus peptide, a significant eosinophil infiltration was induced. In vitro studies indicated that IL-4 could switch the virus-specific CD8(+) T cells to IL-5 production. These results could explain the link between virus infection and acute exacerbation of asthma and, perhaps more importantly, they indicate an IL-4-dependent mechanism that would impair CD8(+) T cell responses and delay viral clearance from the host.