Interference with dendritic cell (DC) maturation and function is considered to be central to measles virus (MV)-induced immunosuppression. Temporally ordered production of chemokines and switches in chemokine receptor expression are essential for pathogen-driven DC maturation as they are prerequisites for chemotaxis and T cell recruitment. We found that MV infection of immature monocyte-derived DCs induced transcripts specific for CCL-1, -2, -3, -5, -17 and -22, CXCL-10 and CXCL-11, yet did not induce and CCL-20 at the mRNA and protein level. Within 24 h post-infection, T cell attraction was not detectably impaired by these cells. MV infection failed to promote the switch from CCR5 to CCR7 expression and this correlated with chemotactic responses of MV-matured DC cultures to CCL-3 rather than to CCL-19. Moreover, the chemotaxis of MV-infected DCs to either chemokine was compromised, indicating that MV also interferes with this property independently of chemokine receptor modulation.
Hallmarks of measles virus (MV)-induced immuno-suppression include lymphopenia and proliferative unresponsiveness of peripheral blood lymphocytes to mitogens (Griffin et al., 1994;Schneider-Schaulies & ter Meulen, 2002). The ability of myeloid dendritic cells (DCs) to both initiate T cell activation and mediate viral transport to secondary lymphatics has determined that they are central to MV-specific immunity and immunosuppression (Pollara et al., 2005;Steinman et al., 2003). MV targets CD150 + haematopoetic cells (Condack et al., 2007; de Swart et al., 2007), and in experimentally infected macaques, mucosal DCs replicate MV in vivo (de Swart et al., 2007). DCs are generated from precursors and they mature upon MV exposure in vitro (Dubois et al., 2001;Fugier-Vivier et al., 1997;Grosjean et al., 1997;Kaiserlian et al., 1997;Schnorr et al., 1997;Servet-Delprat et al., 2000), this involves toll-like receptor (TLR) signalling and type I interferon (IFN) (Minagawa et al., 2001;Schnorr et al., 1997;Servet-Delprat et al., 2000;Shingai et al., 2007). MV-matured DCs (MV-DCs) fail to promote allogenic T cell expansion, which results from signalling by the viral glycoproteins expressed on the DC surface to T cells (Kerdiles et al., 2006;Schneider-Schaulies & Dittmer, 2006;Schneider-Schaulies et al., 2003;Servet-Delprat et al., 2003).Maturing DCs change their responsiveness from initially pro-inflammatory to lymphoid-type chemokines (reflected by a switch from CCR5 to CCR7 surface expression) which allows egress from peripheral sites where they respond to CCR5-binding chemokines, such as CCL-3, and migration towards secondary lymphatics in response to CCR7-binding chemokines, such as CCL-19 (Caux et al., 2002;Sallusto et al., 1998;Sozzani et al., 1998); alterations in chemokine release also occur (Piqueras et al., 2006). DC chemotaxis is targeted during immune evasion by vaccinia virus, human cytomegalovirus (HCMV), herpes simplex virus (HSV) and influenza A virus (Humrich et al., 2007;Moutaftsi et al., 2004;Prechtel et al., 2005;Salentin e...