Induction of IgE and allergic-type responses in fur mite-infested mice

Evaluating a Reduction in Treatment Duration of Ivermectin Diet for Fur Mite (Radfordia affinis) Eradication in Mice

Murine fur mites are commonly excluded in modern research animal programs, yet infestations continue to persist due to challenges in detection and control. Because all diagnostic methods and treatment options have limitations, programs must make many operational decisions when trying to eradicate these ectoparasites. The primary aim of this study was to assess various durations of treatment time with an ivermectin-compounded diet in eliminating Radfordia affinis in mice as determined by PCR testing and pelt examination. A shorter treatment duration would be highly advantageous as compared with the current regimen of 8 wk as it would minimize cost and time for animal management programs, impediments to research, and ivermectin drug effects on infested animals. Five experimental groups of R. affinis -positive mice received dietary ivermectin for 0, 2, 4, 6, or 8 wk. A fur mite-negative, naïve mouse was added to each group every 8 wk to perpetuate the infestation and amplify any remaining populations of fur mites. At 16 wk after the respective treatment end, PCR testing was performed for all treated groups in conjunction with the positive control group (no treatment). Visual examination of pelts for mites and eggs via direct microscopy was also performed at each time point. All treated mice were free of R. affinis at 16 wk after the end of treatment as confirmed by both PCR testing and pelt examination. These findings indicate that a dietary ivermectin treatment duration of as little as 2 wk is effective in eliminating R. affinis, making successful eradication initiatives more achievable.

Assembly of a Draft Genome for the Mouse Ectoparasite Myocoptes musculinus

Myocoptes musculinus is a common ectoparasite of wild mice and is occasionally found on research mice. Infestations of research mice are often subclinical but can cause severe dermatitis. Perhaps more importantly, infestations can cause immunologic reactions that may alter research outcomes, and most animal research facilities strive to prevent or eliminate mites from their mouse colonies. M. musculinus infestations are currently detected by using microscopic evaluation of the fur and skin and PCR assays of pelt swabs targeting the rRNA genes of this mite. In our facility, we encountered multiple, false-positive 18S rRNA PCR results from a closed mouse colony. We could not identify the source of the false positives even after performing PCR analysis of other Myocoptes gene targets using assays developed from the few other target genomic sequences available for M. musculinus or Myocoptes japonensis in public databases. This situation highlighted the limited genetic resources available for development of diagnostic tests specific for this ectoparasite. To expand the available genetic resources, we generated a metagenome of M. musculinus derived by sequencing from fur plucks of an infected mouse. We also determined the completeness of this metagenome and compared it with those of related mites.

Notch dimerization and gene dosage are important for normal heart development, intestinal stem cell maintenance, and splenic marginal zone B-cell homeostasis during mite infestation

Cooperative DNA binding is a key feature of transcriptional regulation. Here we examined the role of cooperativity in Notch signaling by CRISPR-mediated engineering of mice in which neither Notch1 nor Notch2 can homo- or heterodimerize, essential for cooperative binding to sequence-paired sites (SPS) located near many Notch-regulated genes. Although most known Notch-dependent phenotypes were unaffected in Notch1/2 dimer-deficient mice, a subset of tissues proved highly sensitive to loss of cooperativity. These phenotypes include heart development, compromised viability in combination with low gene dose, and the gut, developing ulcerative colitis in response to 1% dextran sulfate sodium (DSS). The most striking phenotypes-gender imbalance and splenic marginal zone B-cell lymphoma-emerged in combination with gene dose reduction or when challenged by chronic fur mite infestation. This study highlights the role of the environment in malignancy and colitis and is consistent with Notch-dependent anti-parasite immune responses being compromised in Notch dimer-deficient animals.

Mite Burden and Immunophenotypic Response to Demodex musculi in Swiss Webster, BALB/c, C57BL/6, and NSG Mice

Detection methods for Demodex musculi were historically unreliable, and testing was rarely performed because its prevalence in laboratory mice was underestimated. Although infestations are unapparent in most mouse strains, D. musculi burdens are higher and clinical signs detected in various immunodeficient strains. The parasite's influence on the immune system of immunocompetent mice is unknown. We characterized mite burden (immunocompetent and immunodeficient strains) and immunologic changes (immunocompetent strains only) in naïve Swiss Webster (SW; outbred), C57BL/6NCrl (B6; Th1 responder), BALB/cAnNCrl (BALB/c; Th2 responder) and NOD. Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG; immunodeficient) mice after exposure to Demodex-infested NSG mice. Infested and uninfested age-matched mice of each strain (n = 5) were euthanized 14, 28, 56, and 112 d after exposure. Mite burden was determined through PCR analysis and skin histopathology; B-cell and CD4+ and CD8+ T-cell counts and activation states (CD25 and CD69) were evaluated by using flow cytometry; CBC counts were performed; and serum IgE levels were measured by ELISA. Mite burden and PCR copy number correlated in NSG mice, which had the highest mite burden, but not in immunocompetent strains. Infested immunocompetent animals developed diffuse alopecia by day 112, and both BALB/c and C57BL/6 mice had significantly increased IgE levels. These findings aligned with the skewed Th1 or Th2 immunophenotype of each strain. BALB/c mice mounted the most effective host response, resulting in the lowest mite burden of all immunocompetent strains at 112 d after infestation without treatment. Clinically significant hematologic abnormalities were absent and immunophenotype was unaltered in immunocompetent animals. Topical treat- ment with imidacloprid-moxidectin (weekly for 8 wk) was effective at eradicating mites by early as 7 d after treatment. IgE levels decreased substantially in infested BALB/c mice after treatment. These findings demonstrate a need for D. musculi surveillance in mouse colonies, because the infestation may influence the use of infested mice in select studies.

Regulatory T Cells Control Th2-Dominant Murine Autoimmune Gastritis

Pernicious anemia and gastric carcinoma are serious sequelae of autoimmune gastritis (AIG). Our study indicates that in adult C57BL/6-DEREG mice expressing a transgenic diphtheria toxin receptor under the Foxp3 promoter, transient regulatory T cell (Treg) depletion results in long-lasting AIG associated with both H(+)K(+)ATPase and intrinsic factor autoantibody responses. Although functional Tregs emerge over time during AIG occurrence, the effector T cells rapidly become less susceptible to Treg-mediated suppression. Whereas previous studies have implicated dysregulated Th1 cell responses in AIG pathogenesis, eosinophils have been detected in gastric biopsy specimens from patients with AIG. Indeed, AIG in DEREG mice is associated with strong Th2 cell responses, including dominant IgG1 autoantibodies, elevated serum IgE, increased Th2 cytokine production, and eosinophil infiltration in the stomach-draining lymph nodes. In addition, the stomachs exhibit severe mucosal and muscular hypertrophy, parietal cell loss, mucinous epithelial cell metaplasia, and massive eosinophilic inflammation. Notably, the Th2 responses and gastritis severity are significantly ameliorated in IL-4- or eosinophil-deficient mice. Furthermore, expansion of both Th2-promoting IFN regulatory factor 4(+) programmed death ligand 2(+) dendritic cells and ILT3(+) rebounded Tregs was detected after transient Treg depletion. Collectively, these data suggest that Tregs maintain physiological tolerance to clinically relevant gastric autoantigens, and Th2 responses can be a pathogenic mechanism in AIG.

Steady-state production of IL-4 modulates immunity in mouse strains and is determined by lineage diversity of iNKT cells

Invariant natural killer T cells (iNKT cells) can produce copious amounts of interleukin 4 (IL-4) early during infection. However, indirect evidence suggests they may produce this immunomodulatory cytokine in the steady state. Through intracellular staining for transcription factors, we have defined three subsets of iNKT cells (NKT1, NKT2 and NKT17) that produced distinct cytokines; these represented diverse lineages and not developmental stages, as previously thought. These subsets exhibited substantial interstrain variation in numbers. In several mouse strains, including BALB/c, NKT2 cells were abundant and were stimulated by self ligands to produce IL-4. In those strains, steady-state IL-4 conditioned CD8(+) T cells to become 'memory-like', increased serum concentrations of immunoglobulin E (IgE) and caused dendritic cells to produce chemokines. Thus, iNKT cell-derived IL-4 altered immunological properties under normal steady-state conditions.

Immunological memory ≠ protective immunity

So-called 'immunological memory' is, in my view, a typical example where a field of enquiry, i.e. to understand long-term protection to survive reexposure to infection, has been overtaken by 'l'art pour l'art' of 'basic immunology'. The aim of this critical review is to point out some key differences between academic text book-defined immunological memory and protective immunity as viewed from a co-evolutionary point of view, both from the host and the infectious agents. A key conclusion is that 'immunological memory' of course exists, but only in particular experimental laboratory models measuring 'quicker and better' responses after an earlier immunization. These often do correlate with, but are not the key mechanisms of, protection. Protection depends on pre-existing neutralizing antibodies or pre-activated T cells at the time of infection-as documented by the importance of maternal antibodies around birth for survival of the offspring. Importantly, both high levels of antibodies and of activated T cells are antigen driven. This conclusion has serious implications for our thinking about vaccines and maintaining a level of protection in the population to deal with old and new infectious diseases.

Oligonucleotide based-strategies for allergy with special reference to siRNA

BACKGROUND

Allergic diseases are a significant global health care problem. Current pharmacological approaches address symptoms but do not alter the underlying immune dysregulation. Current allergen-specific immunotherapy has several drawbacks. Therefore, approaches that attenuate allergic responses safely and effectively at the level of upstream causative events are desirable. Oligonuleotide-based therapies [CpG DNA, antisense oligonucleotides, and small interfering RNA (siRNA)] are promising approaches.

OBJECTIVE/METHODS

We review developments in oligonucleotide-based therapies and the potential of siRNA for treating allergy.

RESULTS/CONCLUSIONS

Strategies with oligonucleotides basically aim to reduce T helper type 2 (Th2) responses. It is controversial whether the reduction of Th2 responses does, in fact, attenuate allergic diseases. Increased understanding of allergic mechanisms will enhance the efficacy of oligonucleotide-based therapy.

Inhibition of allergic responses by CD40 gene silencing

BACKGROUND

Gene silencing using small interfering RNA (siRNA) is a potent method of specifically knocking down molecular targets. Small interfering RNA is therapeutically promising, however, treatment of allergic diseases with siRNA has not been explored in vivo. The aim of this study was to evaluate therapeutic effects of CD40 siRNA on inhibition of allergic responses.

METHODS

Mice sensitized with ovalbumin (OVA) and alum were treated with CD40 siRNA, scrambled siRNA, or phosphate buffer saline (PBS) alone, and then challenged intranasally with OVA.

RESULTS

A significant reduction in nasal allergic symptoms was observed in the CD40 siRNA treated OVA-allergic mice compared to the controls of scrambled siRNA and PBS alone, which is correlated with the decrease of local eosinophil accumulation. CD40 siRNA treatment knocked down CD40 expression on dendritic cells (DCs) in vivo and impaired their antigen presenting function. Treatment with CD40 siRNA resulted in inhibition of OVA-specific T cell response and decrease of interleukin-4 (IL-4), IL-5, and interferon-gamma production from T cells stimulated with OVA. Administration of CD40 siRNA also suppressed CD40 expression on B cells, resulting in down-regulation of OVA-specific immunoglobulin E (IgE), IgG1, and IgG2a levels. Additionally, increased regulatory T cells were observed in the CD40 siRNA treated mice.

CONCLUSIONS

The present study demonstrates a novel therapeutic use for siRNA in allergy. CD40 siRNA attenuated allergy through inhibition of DC and B cell functions and generation of regulatory T (Treg) cells.

Serum and monoclonal immunoglobulin E antibodies from NC/Nga mice with severe atopic-like dermatitis recognize an auto-antigen, histone H3

BACKGROUND

NC/Nga mice are known to show a spontaneous outbreak of atopic-like dermatitis accompanied by a marked elevation in serum IgE levels when reared in a conventional environment. The specific effects of such a strong serum IgE response on the development of the dermatitis and specific antigens recognized by the IgE antibodies are still uncertain.

OBJECTIVE AND METHODS

To characterize the IgE of NC/Nga mice, we established IgE-secreting hybridoma clones from spleen cells of NC/Nga mice spontaneously developing dermatitis and identified variable-region genes and specific antigens of the IgE monoclonal antibodies (mAbs). Serum polyclonal IgE, as well as IgG1 and IgG2a, specific for the identified antigen were also analysed.

RESULTS

Four IgE-producing hybridoma clones were established. Variable-region nucleotide sequences of the IgE mAbs showed that these clones did not necessarily share common germline gene segments (V, D or J) for each variable region, and several somatic mutations had occurred in the V gene segments. Through antigen screening, histone H3 was identified to be an auto-antigen recognized by three of the four IgE mAbs. Serum IgE as well as IgG1 specific for histone H3 were almost undetectable in 6-week-old mice, but rapidly increased by 10-12 weeks of age. This age-dependent increase in the serum anti-histone H3 IgE was roughly in parallel with the onset of dermatitis, and slightly preceding total IgE elevation. The serum-specific IgE level correlated well with a dermatitis-severity score of each mouse at 12-16 weeks of age, and weakly with the severity of ear erosion of each mouse over 28 weeks of age. Furthermore, immunologically detectable histone-H3 antigens were observed in skin tissue sections from the dermatitis sites.

CONCLUSION

In NC/Nga mice, anti-histone H3 auto-antibodies may contribute, at least in part, to the considerably elevated serum IgE and might play some roles in the development and exacerbation of dermatitis.

Novel vaccination for allergy through gene silencing of CD40 using small interfering RNA

Small interfering RNA (siRNA) is a potent means of inducing gene-specific silencing. Gene silencing strategies using siRNA have demonstrated therapeutic benefits in animal models of various diseases, and are currently in clinical trials. However, the utility of gene silencing as a treatment for allergic diseases has not yet been reported. In this study, we report a novel therapy for allergy through gene silencing of CD40, a critical costimulatory molecule and a key factor in allergic immune responses. Silencing CD40 resulted in generation of immunoregulatory dendritic cells (DCs). Administration of CD40 siRNA remarkably reduced nasal allergic symptoms and local eosinophil accumulation in the OVA-induced allergic mice. The OVA-specific T cell response was inhibited after the CD40 siRNA treatment. Additionally, anti-OVA specific IgE and production of IL-4 and IL-5 of T cells stimulated by OVA were significantly decreased in CD40 siRNA-treated mice. Furthermore, we demonstrated that the therapeutic effects by CD40 siRNA were associated with impaired Ag-presenting functions of DCs and B cells, and generation of regulatory T cells. The present study highlights a therapeutic potential of siRNA-based treatment for allergic diseases.

How long do the systemic and ventilatory responses to toluene diisocyanate persist in dermally sensitized mice?

BACKGROUND

Years after removal from exposure, workers with occupational asthma still show respiratory symptoms and airway hyperresponsiveness on re-exposure to the offending agent.

OBJECTIVE

We investigated the persistence of the respiratory responsiveness to toluene diisocyanate (TDI) in a mouse model.

METHODS

BALB/C mice received dermal applications of TDI on days 1 and 8, and a single intranasal instillation of TDI on day 10, 15, 20, 25, 30, 40, 50, 60, or 90. After instillation, early (1 hour) changes in ventilatory function and methacholine responsiveness (22 hours) were assessed. Cell counts and macrophage inflammatory protein 2 were measured in bronchoalveolar lavage. Total serum IgE, IgG(1), and IgG(2a) were quantified. Lymphocyte subpopulations were assessed in auricular and cervical lymph nodes, and release of IL-4 and IFN-gamma by these lymph node cells was measured.

RESULTS

Toluene diisocyanate-treated mice showed immediate ventilatory changes, increased methacholine reactivity, and an influx of neutrophils and macrophage inflammatory protein 2 in bronchoalveolar lavage as long as 50 days after initial treatment. These mice also showed a relative increase in CD19(+) cells and a decrease in CD4(+) and CD8(+) cells in auricular lymph nodes. Increased release of IL-4 and IFN-gamma in auricular lymph node cells was observed only until 20 days after sensitization. Total serum IgE, IgG(1), and IgG(2a) remained significantly elevated in TDI-sensitized mice until 90 days after dermal sensitization.

CONCLUSION

Ventilatory and lung inflammatory responses decrease with increasing delay between sensitization and challenge, despite persistent humoral signs of sensitization.