Human Cytomegalovirus Alters Localization of MHC Class II and Dendrite Morphology in Mature Langerhans Cells

Abstract

Hemopoietic stem cell-derived mature Langerhans-type dendritic cells (LC) are susceptible to productive infection by human CMV (HCMV). To investigate the impact of infection on this cell type, we examined HLA-DR biosynthesis and trafficking in mature LC cultures exposed to HCMV. We found decreased surface HLA-DR levels in viral Ag-positive as well as in Ag-negative mature LC. Inhibition of HLA-DR was independent of expression of unique short US2-US11 region gene products by HCMV. Indeed, exposure to UV-inactivated virus, but not to conditioned medium from infected cells, was sufficient to reduce HLA-DR on mature LC, implicating particle binding/penetration in this effect. Reduced surface levels reflected an altered distribution of HLA-DR because total cellular HLA-DR was not diminished. Accumulation of HLA-DR was not explained by altered cathepsin S activity. Mature, peptide-loaded HLA-DR molecules were retained within cells, as assessed by the proportion of SDS-stable HLA-DR dimers. A block in egress was implicated, as endocytosis of surface HLA-DR was not increased. Immunofluorescence microscopy corroborated the intracellular retention of HLA-DR and revealed markedly fewer HLA-DR-positive dendritic projections in infected mature LC. Unexpectedly, light microscopic analyses showed a dramatic loss of the dendrites themselves and immunofluorescence revealed that cytoskeletal elements crucial for the formation and maintenance of dendrites are disrupted in viral Ag-positive cells. Consistent with these dendrite effects, HCMV-infected mature LC exhibit markedly reduced chemotaxis in response to lymphoid chemokines. Thus, HCMV impedes MHC class II molecule trafficking, dendritic projections, and migration of mature LC. These changes likely contribute to the reduced activation of CD4+ T cells by HCMV-infected mature LC.

The Human Cytomegalovirus Protein TRS1 Inhibits Autophagy via Its Interaction with Beclin 1

“…The efficacy of inactivation was tested by immunofluorescence staining of MRC5 cells infected with UV-HCMV using anti-immediate-early antigens (IEAs) monoclonal antibody (MAb) and pp65 MAb (see below), followed by a secondary fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse antibody (data not shown). Successful inactivation was ensured through abrogation of IE antigen expression, whereas pp65 tegument protein detection was comparable to cell infection with nonirradiated virus by using methods previously described (13,34).…”

Inhibition of IFN-γ-Induced STAT1 Tyrosine Phosphorylation by Human CMV Is Mediated by SHP2

“…Mechanisms are targeted to various steps within the same pathway, presumably leading to greater efficiency. For example, inhibition of constitutive MHC II expression, which results in decreased CD4 ϩ T cell recognition, has been reported to result from altered localization of constitutive MHC II (23)(24)(25). Other mechanisms have involved either degradation or inhibition of assembly of MHC II by US2 and US3 proteins (26).…”

Immunomodulatory Properties of a Viral Homolog of Human Interleukin-10 Expressed by Human Cytomegalovirus during the Latent Phase of Infection

“…Maturation of DCs leads to phenotypic changes including upregulation of the costimulatory and adhesion molecules CD40, CD80, CD83, and CD86, which are involved in T-lymphocyte activation, and increased MHC-I and -II expression on the surface of maturing DCs (3,43,62). A number of studies have demonstrated that productive HCMV infection interferes with the maturation of DCs and their antigen-presenting function by inhibiting the expression of these immune molecules (4,18,30,38,51). Furthermore, Chang et al (9) and Raftery et al (46) showed that stimulation of immature DCs to mature in the presence of cmvIL-10 results in the functional paralysis of DCs (9,46).…”