Measles virus hemagglutinin triggers intracellular signaling in CD150-expressing dendritic cells and inhibits immune response.

Measles virus (MV) is highly contagious pathogen, which causes a profound immunosuppression, resulting in high infant mortality. This virus infects dendritic cells (DCs) following the binding of MV hemagglutinin (MV-H) to CD150 receptor and alters DC functions by a mechanism that is not completely understood. We have analyzed the effect of MV-H interaction with CD150-expressing DCs on the DC signaling pathways and consequent phenotypic and functional changes in the absence of infectious context. We demonstrated that contact between CD150 on human DCs and MV-H expressed on membrane of transfected CHO cells was sufficient to modulate the activity of two major regulatory pathways of DC differentiation and function: to stimulate Akt and inhibit p38 MAPK phosphorylation, without concomitant ERK1/2 activation. Furthermore, interaction with MV-H decreased the expression level of DC activation markers CD80, CD83, CD86, and HLA-DR and strongly downregulated IL-12 production but did not modulate IL-10 secretion. Moreover, contact with MV-H suppressed DC-mediated T-cell alloproliferation, demonstrating profound alteration of DC maturation and functions. Finally, engagement of CD150 by MV-H in mice transgenic for human CD150 decreased inflammatory responses, showing the immunosuppressive effect of CD150-MV-H interaction in vivo. Altogether, these results uncover novel mechanism of MV-induced immunosuppression, implicating modulation of cell signaling pathways following MV-H interaction with CD150-expressing DCs and reveal anti-inflammatory effects of CD150 stimulation.