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Characterization of intestinal dendritic cells in murine norovirus infection - PubMed

Characterization of intestinal dendritic cells in murine norovirus infection

Xiuxu Chen et al. Open Immunol J. 2011.

Abstract

We have shown that respiratory viral infections drive allergic disease through dendritic cells, whether gastrointestinal viruses induce allergies is not known. Norovirus infections are a major cause of gastroenteritis in humans. We used murine norovirus (MNV) to explore the effect of MNV infection on gastrointestinal conventional DCs (cDCs) and plasmacytoid DCs (pDCs). MNV infection induced disparate effects on cDCs and pDCs in lymphoid tissues of the small intestine and draining mesenteric lymph nodes. FcεRI was transiently expressed on lamina propria cDCs, but not on pDCs. In addition, feeding ovalbumin during the viral infection led to a modest, brief induction of anti-ovalbumin IgE. Together, these data suggest that like with a respiratory viral infection, an intestinal viral infection may be sufficient to induce changes in DCs and the generation of food-specific IgE. Whether this represents a novel mechanism of food allergy remains to be determined.

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Conflict of interest statement

Conflict of interest: MHG has received research support from Genentech and the NIH. The other authors declare no competing financial interests.

Figures

Figure 1
Figure 1. The frequency of lamina propria conventional dendritic cells (LP-cDC) is reduced after MNV infection

LP-cDC were identified by CD11c expression in the lamina propria of frozen sections from small intestine of C57BL/6 mice. Mice were inoculated by oral gavage with PBS (A), MNV-CW1 (MNV; 5×105 pfu per mouse) (B, D, F), or ultraviolet light-inactivated MNV (UV-MNV) (C, E, G). Sixteen hours post inoculation (p.i.), mice were sacrificed and cryosections from the proximal 1/3 (A, B, C), middle 1/3 (D, E) and distal 1/3 (F, G) of the small intestine were stained with PE-labeled rat anti-mouse CD11c monoclonal antibody or isotype rat IgG control (red) and DAPI (blue), and visualized by epi-fluorescence microscope. Frequency of CD11c+ LP-cDCs in the vili of the small intestine was analyzed by Zeiss LSM software. Representative images from three independent experiments of 2 mice per experiment are shown. Ah IgG = Armenian hamster IgG control.

Figure 2
Figure 2. Effect of MNV infection on cDCs from the Lamina Propria (LP), Peyer’s Patch (PP), and mesenteric lymph node (MLN)

(A) Gating strategy for flow cytometry. Single cell suspensions were made from lamina propria (LP), Peyer’s Patches (PP) and mesenteric lymph nodes (MLN) and then stained with DAPI and various cell surface markers, as shown. Frequencies of CD11c-expressing cells (cDCs) or pDCA-1-expressing cells (pDCs) were analyzed by gating first on cellular events based on forward and side scatter, and then excluding DAPI positive cells (dead cells). Cells were then quantified as the percentage of cells in this gate that expressed the specific markers. (B) Time course of CD11c-expressing cDCs in different tissue compartments after MNV (filled circle), UV-MNV (open circle) or PBS (“x”) inoculation. Data are shown as mean frequency ± sem of cells at the indicated time p.i. and are from 3 independent experiments of 2–8 mice/experiment. *p < 0.05 versus pre-inoculation value (day 0). Frequency of cells were determined as indicated in (A). (C) cDC subsets in LP, MLN or PP after UV-MNV or MNV inoculation. Sixteen hours after MNV or UV-MNV inoculation, the frequency of cDC’s expressing CD11b, CD103, CD4, or CD8α were determined by flow cytometry. Data representative from 3 independent experiments of 2 mice per experiment. *p < 0.05 versus UV-MNV treated.

Figure 3
Figure 3. MNV infection increases pDC frequencies in the PP and MLN but not in the LP

Data was collected and analyzed similar to figure 2. (A) Frequencies of pDCA-1+ cells in different tissues on the given days p.i. MNV (filled circle), UV-MNV (open circle), or PBS (“x”). *p < 0.05 versus day 0 (pre-inoculation value). Data compiled from 3 independent experiments of 2–8 mice per experiment. (B) Frequency of pDC subsets in LP, MLN and PP after UV-MNV or MNV inoculation. Plasmacytoid DC were identified as shown in figure 2C and the frequency of pDC expressing CD11b, CD103, CD4, or CD8α determined 16 hours p.i. MNV or UV-MNV. Data are representative from 3 independent experiments of 2 mice per experiment. No differences were found to be statistically significant.

Figure 4
Figure 4. MNV infection transiently increases receptors for IgE on LP-cDCs and drives a modest IgE response against non-viral antigens

(A) Expression of high-affinity (FcεRIα) and low-affinity (CD23) IgE receptors was determined on LP-cDCs and LP-pDCs by flow cytometry at the indicated days p.i. MNV. UV-MNV inoculation led to no increase in expression of these proteins at any of the time points examined (data not shown). Data shown as net mean ± sem percent of LP-cDCs or LP-pDCs expressing the given marker, and are from 3 independent experiments, with 2 mice per experiment. *p < 0.05 versus pre-inoculation value (day 0). (B) Oral exposure to ovalbumin (OVA) during MNV infection is sufficient to induce production of anti-OVA IgE. Mice were inoculated with either MNV or UV-MNV and 5 days later gavaged with OVA or PBS. One-week later serum was collected and levels of anti-OVA IgE determined by ELISA. Data are presented as mean ± sem fold increase of anti-OVA IgE over pre-inoculation values for mice given OVA or PBS at day 5 p.i. Data from 2 experiments with 3 mice per group. *p < 0.05 versus both UV-MNV and baseline values.

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