Measles virus infection synergizes with IL-4 in IgE class switching

Increasing evidence suggests that viral infections are associated with the induction and exacerbation of asthma. One characteristic of human asthma is an increase in the levels of circulating IgE, Previous studies have shown that circulating IgE levels are elevated during the early phase of infectio n with measles virus (MV), We have shown previously that one mechanism by w hich viral infections can increase IgE levels is via an induction of IgE cl ass switching through the activation of the antiviral protein kinase (dsRNA -activated protein kinase), leading to the activation of multiple NF-kappa B complexes. Therefore, to determine whether infection with MV can also ind uce IgE class switching, we infected the human Ramos B cell line with the E dmonston strain of MV, Infecting Ramos cells with Rn did not result directl y in either the activation of dsRNA-activated protein kinase or IgE class s witching. However, a synergistic effect on IgE class switching was observed when Ramos cells were infected with MV before IL-4 treatment. Ab cross-lin king of the MV receptor, CD46, mimicked the effects of MV infection in syne rgizing with IL-4 to induce IgE class switching, suggesting that viral hema gglutinin is involved in this synergistic effect. These data provide the fi rst indication of a potential mechanism for MV-induced IgE up-regulation an d suggest a model for a viral-induced exacerbation of IgE:mediated disorder s such as asthma.