Comparison between canine distemper virus-infected and non-infected cells.

<p>*results of statistical analyses (p-values) at 120 hours post infection; bold values display significant changes compared to control (non-infected cells), ↑ = significantly increased; ↓ = significantly decreased compared to control; ↑* = statistical tendency of increase compared to control; CDV = canine distemper virus; RNA = ribonucleic acid; MHC = major histocompatibility complex; IL = interleukin; TNF = tumor necrosis factor; TGF = transforming growth factor; TCID₅₀ = tissue culture infectious dose 50.</p

Canine Distemper Virus Infection Leads to an Inhibitory Phenotype of Monocyte-Derived Dendritic Cells <i>In Vitro</i> with Reduced Expression of Co-Stimulatory Molecules and Increased Interleukin-10 Transcription

<div><p>Canine distemper virus (CDV) exhibits a profound lymphotropism that causes immunosuppression and increased susceptibility of affected dogs to opportunistic infections. Similar to human measles virus, CDV is supposed to inhibit terminal differentiation of dendritic cells (DCs), responsible for disturbed repopulation of lymphoid tissues and diminished antigen presenting function in dogs. In order to testify the hypothesis that CDV-infection leads to an impairment of professional antigen presenting cells, canine DCs have been generated from peripheral blood monocytes <i>in vitro</i> and infected with CDV. Virus infection was confirmed and quantified by transmission electron microscopy, CDV-specific immunofluorescence, and virus titration. Flow cytometric analyses revealed a significant down-regulation of the major histocompatibility complex class II and co-stimulatory molecules CD80 and CD86 in CDV-infected DCs, indicative of disturbed antigen presenting capacity. Molecular analyses revealed an increased expression of the immune inhibitory cytokine interleukin-10 in DCs following infection. Results of the present study demonstrate that CDV causes phenotypical changes and altered cytokine expression of DCs, which represent potential mechanisms to evade host immune responses and might contribute to immune dysfunction and virus persistence in canine distemper.</p></div

Phenotypic analyses of monocyte-derived dendritic cells by flow cytometry.

<p>Significantly increased (*; p≤0.05) expression of A) CD1a and B) CD14 and up-regulation of co-stimulatory molecules C) CD80 and D) CD86 at day seven compared to cells at day one in culture. Box and whisker plots display median and quartiles with maximum and minimum values. Representative histograms of A’) CD1a, B’) CD14, C’) CD80 and D’) CD86 expression intensity in gated cells. Filled tinted curve = isotype control; thin line = monocytes at day one in culture; thick black line = dendritic cells at seven days in culture.</p

Cytokine expression analyses of canine distemper virus-infected monocyte-derived dendritic cells.

<p>Reverse transcriptase-quantitative polymerase chain reaction revealed a significantly increased (*; p≤0.05) interleukin-10 (IL-10) mRNA-expression and a statistical tendency (*p = 0.058) of an increased interleukin-8 (IL-8) transcription in infected cells compared to non-infected cells at 120 hours post infection. Box and whisker plots display median and quartiles with maximum and minimum values.</p

Phenotypic analyses of canine distemper virus-infected monocyte-derived dendritic cells by flow cytometry.

<p>Significantly decreased (*; p≤0.05) expression of A) CD80, B) CD86 and C) major histocompatibility complex (MHC) class II of infected cells compared to non-infected cells at 120 hours post infection. Box and whisker plots display median and quartiles with maximum and minimum values. Representative histograms of A’) CD80, B’) CD86, C’) MHC class II expression intensity in gated cells. Filled tinted curve = isotype control; thin line = non-infected cells; thick black line = infected cells.</p

Ultrastructural analysis of canine distemper virus-infected monocyte-derived dendritic cells.

<p>Accumulation of viral nucleocapsid in the cytoplasm (arrow). Note also periodical microstructure (arrowhead) and cytoplasmic processes representing features of dendritic cells. Transmission electron microscopy, magnification = 50.000×.</p