The effect of Helicobacter hepaticus infection on immune responses specific to herpes simplex virus type 1 and characteristics of dendritic cells

Abstract

Infection of mice with Helicobacter hepaticus is common in research colonies, yet little is known about how this persistent infection affects immunologic research. The goal of this study was to determine whether H. hepaticus infection status can modulate immune responses specific to herpes simplex virus type 1 (HSV1) and the phenotypic and functional characteristics of dendritic cells (DC) of mice. We compared virus-specific antibody and T cell-mediated responses in H. hepaticus-infected and noninfected mice that were inoculated intranasally with HSV1. The effect of H. hepaticus on the HSV1-specific antibody and T cell-mediated immune responses in superficial cervical and tracheobronchal lymph nodes (LN) did not reach statistical significance. Surface expression of the maturation-associated markers CD40, CD80, CD86, and MHC II and percentages of IL12p40- and TNFalpha-producing DC from spleen and colic LN in H. hepaticus-infected mice and noninfected mice were measured in separate experiments. Expression of CD40, CD86, and MHC II and percentages of IL12p40- and TNFalpha-producing DC from colic LN were decreased in H. hepaticus-infected mice. In contrast, H. hepaticus infection did not reduce the expression of these molecules by splenic DC. Expression of CD40, CD80, CD86, and MHC II on splenic DC from H. hepaticus-infected mice was increased after in vitro lipopolysaccharide stimulation. These results indicate that H. hepaticus infection can influence the results of immunologic assays in mice and support the use of H. hepaticus-free mice in immunologic research.

Figure 1.

Quantification of HSV1-specific CD8⁺ T cells in superficial cervical and tracheobronchal LN of H. hepaticus-infected and noninfected mice 1 wk after intranasal HSV1 infection. (A and B) Percentage of gB_498–505-specific CD8⁺ T cells expressed in terms of total population of CD8⁺ T cells and (C and D) absolute numbers of gB_498–505-specific CD8⁺ T cells. Data (mean ± SE) were normalized to the percentage or absolute number of gB_498–505-specific CD8⁺ T cells in LN from noninfected mice within each experiment (n = 5 mice per group). Results were combined from 2 independent experiments. P value was determined by using the unpaired t test.

Figure 2.

Quantification of IFNγ-producing, HSV1-specific CD8⁺ T cells in the superficial cervical and tracheobronchal LN of H. hepaticus-infected and noninfected mice after in vitro stimulation with either OVA_257–264 or gB_498–505 peptide. (A and B) Percentage of IFNγ-producing, CD8⁺ T cells expressed in terms of total population of CD8⁺ T cells and (C and D) absolute number of IFNγ-producing CD8⁺ T cells. Data (mean ± SE) were normalized to the percentage or absolute number of IFNγ-producing CD8⁺ T cells after gB_498–505 peptide stimulation of lymphoid cells from noninfected mice within each experiment (n = 5 mice per group). Results were combined from 2 independent experiments. P value was determined by using the unpaired t test.

Figure 3.

Quantification of HSV1-specific CD107⁺CD8⁺ cytotoxic T cells in the superficial cervical and tracheobronchal LN of H. hepaticus-infected and noninfected mice after in vitro stimulation with OVA_257–264 or gB_498–505 peptide. (A and B) Percentage of CD107⁺CD8⁺ T cells expressed in terms of total population of CD8⁺ T cells and (C and D) absolute number of CD107⁺CD8⁺ T cells. Data (mean ± SE) were normalized to the percentage or absolute number of CD107⁺CD8⁺ T cells after gB_498–505 peptide stimulation of lymphoid cells from noninfected mice within each experiment (n = 5 mice per group). Results were combined from 2 independent experiments. P value was determined by using the unpaired t test.

Figure 4.

Expression of maturation-associated surface markers on DC derived from colic LN. (A) Geometric mean (± SE) fluorescence intensity (GMFI) was normalized to the level of surface expression on DC from noninfected mice (% baseline GMFI) within each experiment (n = 5 to 6 mice per group). Results were combined from 3 independent experiments. (B) Representative histograms depicting the staining profile for surface markers on DC of H. hepaticus-infected (bold line) and noninfected (shaded area) mice. Dotted line represents unstained control. *, significant difference (P < 0.05) between indicated groups.

Figure 5.

Intracellular proinflammatory cytokine expression by DC in the colic LN of H. hepaticus-infected and noninfected mice after in vitro exposure to medium or lipopolysaccharide (LPS). (A) The percentage (mean ± SE) of cytokine-producing DC was normalized to the percentage of cytokine-producing cells from noninfected mice after incubation with medium within each experiment (n = 5 or 6 mice per group). Results were combined from 3 independent experiments. (B) Representative dot plots depicting the intracellular staining profile for IL12p40 and TNFα in CD11c⁺ DC population. *, significant difference (P < 0.05) between indicated groups.

Figure 6.

Expression of maturation-associated surface markers on DC derived from the spleens of H. hepaticus-infected and noninfected mice after in vitro exposure to medium or lipopolysaccharide (LPS). (A) Geometric mean (± SE) fluorescence intensity (GMFI) was normalized to the level of surface expression on DC from noninfected mice after medium exposure (% baseline GMFI) within each experiment (n = 5 or 6 mice per group). Results were combined from 3 independent experiments. (B) Representative histograms show DC from H. hepaticus-infected (bold line) and noninfected mice (shaded area) after lipopolysaccharide stimulation. Dotted line represents unstained controls. *, significant difference (P < 0.05) between indicated groups.