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. 2005 Apr;73(4):2452-60.
doi: 10.1128/IAI.73.4.2452-2460.2005.

Human Leukocyte antigen-DQ8 Transgenic Mice: A Model to Examine the Toxicity of Aerosolized Staphylococcal Enterotoxin B

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Human Leukocyte antigen-DQ8 Transgenic Mice: A Model to Examine the Toxicity of Aerosolized Staphylococcal Enterotoxin B

Chad J Roy et al. Infect Immun. .
Free PMC article

Abstract

Staphylococcal enterotoxins (SEs) belong to a large group of bacterial exotoxins that cause severe immunopathologies, especially when delivered as an aerosol. SEs elicit the release of lethal amounts of cytokines by binding to major histocompatibility complex (MHC) class II and cross-linking susceptible T-cell receptors. Efforts to develop effective therapeutic strategies to protect against SEs delivered as an aerosol have been hampered by the lack of small animal models that consistently emulate human responses to these toxins. Here, we report that human leukocyte antigen-DQ8 (HLA-DQ8) transgenic (Tg) mice, but not littermate controls, succumbed to lethal shock induced by SEB aerosols without potentiation. Substantial amounts of perivascular edema and inflammatory infiltrates were noted in the lungs of Tg mice, similar to the pathology observed in nonhuman primates exposed by aerosol to SEB. Furthermore, the observed pathologies and lethal shock correlated with an upsurge in proinflammatory cytokine mRNA gene expression in the lungs and spleens, as well as with marked increases in the levels of proinflammatory circulating cytokines in the Tg mice. Unlike the case for littermate controls, telemetric evaluation showed significant hypothermia in Tg mice exposed to lethal doses of SEB. Taken together, these results show that this murine model will allow for the examination of therapeutics and vaccines developed specifically against SEB aerosol exposure and possibly other bacterial superantigens in the context of human MHC class II receptors.

Figures

FIG. 1.
FIG. 1.
Aerosol exposure to SEB is lethal to HLA-DQ8/human CD4 transgenic mice. HLA-DQ8/human CD4 transgenic mice were exposed to 5, 30, 60, 120, 240, or 310 μg of aerosolized SEB per kg. All mice were monitored for illness for 21 days after SEB challenge. Results are plotted on Kaplan-Meier survival curves as percent survival for each group over time (n = 10 to 20 per group). The data presented are a compilation of those from two to four experiments with each dose of SEB.
FIG. 2.
FIG. 2.
Aerosol exposure to SEB induces pathological lesions in HLA-DQ8 transgenic mice. (A) Lung from a normal HLA-DQ8/human CD4 mouse. (B) Lung from an HLA-DQ8/human CD4 mouse 3 days after exposure by aerosol to 120 μm of SEB per kg. (C) Lung from a normal rhesus monkey. (D) Lung from an SEB-exposed rhesus monkey 4 days postchallenge with 5 to 7 LD50 of SEB delivered by aerosol. Hematoxylin and eosin staining was used. Magnification, ×200. These data are representative of findings from two animals, and the experiment was repeated twice with similar results.
FIG. 3.
FIG. 3.
Exposure of HLA-DQ8 mice to aerosolized SEB induces cytokine mRNA changes in the lungs. Total RNA was isolated from the lungs of HLA-DR2β/IEα (unfilled bars) or HLA-DQ8 (filled bars) mice exposed by aerosolization to 120 μg of SEB per kg after 4, 10, and 24 h. RNAs from three to five animals were pooled, reverse transcribed, and cDNA amplified for IL-2, IL-4, IL-6, IFN-γ, TNF-α, or β-actin. RT-PCR products were resolved on an ethidium bromide-stained agarose gel. The data are expressed as the relative abundance of each cytokine mRNA, which was determined by comparing the signal of the RT-PCR product for the cytokine mRNA with that of the loading control of β-actin. These data are representative of those from three experiments with a similar design and outcome.
FIG. 4.
FIG. 4.
Exposure of HLA-DQ8 mice to aerosolized SEB induces cytokine mRNA changes in the spleen. Total RNA was isolated from the spleens of HLA-DR2β/IEα (unfilled bars) or HLA-DQ8 (filled bars) mice exposed by aerosolization to 120 μg of SEB per kg after 4, 10, and 24 h. RNAs from three to five mice were pooled, reverse transcribed, and cDNA amplified for IL-2, IL-4, IL-6, IFN-γ, TNF-α, or β-actin. RT-PCR products were resolved on an ethidium bromide-stained agarose gel. The data are shown as the relative abundance of each cytokine mRNA, which was determined by comparing the signal of the RT-PCR product for the cytokine mRNA with that of the loading control of β-actin. These data are representative of those from three experiments with a similar design and outcome.
FIG. 5.
FIG. 5.
Exposure to SEB aerosols increases serum cytokine levels in HLA-DQ8 mice. Circulating cytokine levels in HLA-DR2β/IEα (unfilled bars) or HLA-DQ8 (filled bars) mice were measured at 4, 10, or 24 h after exposure to aerosolized SEB (120 μg/kg). The levels of IL-2, IL-6, IFN-γ, and TNF-α were determined by ELISA. The bars indicate the means for four animals, and the error bars indicate the standard deviations. These data are representative of those from three experiments with a similar design and outcome.
FIG. 6.
FIG. 6.
Exposure of HLA-DQ8 mice to aerosolized SEB results in dramatic decreases in body temperature. Mice were implanted with telemetric chips to measure their body temperature. HLA-DRβ/IEα (open circles) or HLA-DQ8 (filled circles) transgenic mice were exposed to 120 μg of SEB per kg. The body temperatures of the mice were monitored after exposure. The results are plotted as the mean of the body temperature (n = 5 per group, except at time points beyond 120 h, when the SEB-treated HLA-DQ8 mice began to succumb to toxic shock). The error bars indicate the standard deviations of the group means. These data are representative of those from three experiments with a similar design and outcome.

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