IgE production in five inbred rat strains following immunization with alum-precipitated egg albumin

Aluminum hydroxide nanoparticle adjuvants can reduce the inflammatory response more efficiently in a mouse model of allergic asthma than traditional aluminum hydroxide adjuvants

Traditional aluminum hydroxide is widely used as a vaccine adjuvant. Despite its favorable safety profile, it can cause an inflammatory response at the injection sites. However, multiple studies have shown that aluminum hydroxide nanoparticles have more potent adjuvant activity than their traditional aluminum hydroxide counterparts as antigen carriers; it has also been found that the local inflammation caused by aluminum hydroxide nanoparticle adjuvants is milder than that of other adjuvants. The aim of the present study was to compare the degree of inflammatory response between the aluminum hydroxide nanoparticle adjuvants and the traditional aluminum hydroxide adjuvants in the desensitization treatment of a mouse model of house dust mite (HDM)-induced allergic asthma. Mice were sensitized intraperitoneally with HDM. Subcutaneous desensitization was performed with PBS, traditional aluminum hydroxide adjuvants and aluminum hydroxide nanoparticle adjuvants. The mice were challenged and subsequently euthanized. The skin tissue at the local injection sites was assessed and specific indices were measured, such as the response of specific immunoglobulins, the airway hyper-responsiveness (AHR), and the inflammation in the bronchoalveolar lavage and lung tissues. Early hypersensitivity responses were suppressed in mice treated with subcutaneous immunotherapy (SCIT). Both traditional aluminum hydroxide-SCIT and aluminum hydroxide nanoparticle-SCIT could inhibit AHR. However, aluminum hydroxide nanoparticle-SCIT was able to significantly inhibit the secretion of eosinophils in the lung tissue and the production of type 2 cytokine Interleukin (IL)-5 in blood compared with the corresponding effects noted by traditional aluminum hydroxide adjuvants. Moreover, the aluminum hydroxide nanoparticle group reduced the inflammatory response at the local injection site. Collectively, the data indicated that allergen-specific immunotherapy using aluminum hydroxide nanoparticle adjuvants reduces lung and local inflammation compared with traditional aluminum hydroxide adjuvants.

Strain differences in histamine release from peritoneal mast cells in rats

1. Peritoneal mast cells from Brown-Norway (BN) rats were compared with those from Wistar and Sprague-Dawley (SD) rats. 2. Peritoneal mast cells from BN rats showed the smallest values in number, cell diameter and histamine contents compared with those from Wistar and SD rats. 3. BN rat peritoneal mast cells were more sensitive to compound 48/80 and anti-IgE than were those from Wistar and SD rats, and they showed a higher response to A23187 than did cells from Wistar rats. 4. The histamine release from passively sensitized peritoneal mast cells was weaker in BN rats than was that from Wistar and SD rats.

Leflunomide, a novel immunomodulating agent, prevents the development of allergic sensitization in an animal model of allergic asthma

BACKGROUND

Leflunomide is a new anti-inflammatory and immunomodulating agent which is showing promise in several immune disorders, especially rheumatoid arthritis. Its activity profile suggests it may be of use in modulating allergic sensitization.

OBJECTIVE

To investigate the effectiveness of leflunomide in preventing the development of allergic sensitization.

METHODS

Fifty-three brown Norway rats were sensitized by intraperitoneal injection of ovalbumin and adjuvant (ricin) on day 0. To determine the ability of leflunomide to inhibit primary allergic sensitization six rats were treated with A77 1726, the active metabolite of leflunomide, from day 0 through day 5, six were treated from day 5 through day 10, and nine rats acted as controls. On day 14, ovalbumin-specific serum antibody levels and the magnitude of the early-phase airway response (EAR) after inhalation allergen challenge were assessed. To determine the ability of acute topical treatment with leflunomide to inhibit mast cell degranulation, three groups of five animals received either vehicle, 100 microg A77 1726, or 1000 g A77 1726 60 min prior to aerosol allergen challenge. To determine the effects of leflunomide treatment in vivo on mast cell function in vitro, mast cells were obtained by bronchoalveolar lavage from 17 rats (nine treated with leflunomide and eight controls). Allergen-specific and non-specific degranulation (48/80 induced) were studied.

RESULTS

In the leflunomide treated rats both ovalbumin-specific IgE and IgG levels were significantly reduced, and the increases in lung resistance and lung elastance were essentially abolished, compared to those of the control group. Non significant differences were found in any of the parameters between the two leflunomide treated groups. Topical pre-treatment with leflunomide did not prevent the allergen-induced EAR. Treatment with leflunomide in vivo prevented allergen-induced mast cell degranulation in vitro because the mast cells lacked IgE on their surface. Non allergen-specific degranulation was normal and allergen-induced degranulation could be restored by passive sensitization.

CONCLUSIONS

These data suggests that leflunomide can prevent primary allergic sensitization and prevent allergen-induced EAR by inhibiting production of allergen-specific IgE antibodies. Further studies in atopic conditions are warranted.

Compounds that induce autoimmunity in the brown Norway rat sensitize mast cells for mediator release and interleukin-4 expression

Brown Norway (BN) rats given mercuric chloride (HgCl2), gold (Au) salts or D-penicillamine develop a T helper 2 (Th2) cell-mediated autoimmune syndrome. The recent observation of tissue injury within 24 h of HgCl2 treatment suggested the involvement of a non-T cell. We therefore examined the effect of these compounds on rat mast cells in vitro. Incubation of BN rat peritoneal mast cells with HgCl2 enhanced the release of serotonin in response to IgE cross-linking agents. Mast cells from Lewis rats, a strain not susceptible to the autoimmune syndrome in vivo, were affected to a lesser extent. The effect was observed with purified BN mast cells, suggesting a direct action. Similar effects were seen with D-penicillamine in the presence of copper ions, a combination that produces hydrogen peroxide, and Au. HgCl2 caused significant induction of interleukin (IL)-4 mRNA in mast cells from BN, but not Lewis rats. The data demonstrate a novel enhancing effect of a number of compounds on mast cell mediator release, and an inducing effect of HgCl2 on mast cell IL-4, expression. These findings are consistent with our hypotheses that mast cells may contribute to early tissue injury, and also, via production of IL-4, may initiate and/or augment, the Th2 response in the BN rat model of chemical-induced autoimmunity.

Model of bronchial allergic inflammation in the brown Norway rat. Pharmacological modulation

Exposure of non-sensitized Brown Norway (BN) rats to a 10%-ovalbumin aerosol induced an increase in the number of neutrophils in the broncho-alveolar lavage (BAL) fluid 3 and 6 h later but with no change in number of cells at 24 h. When the BN rats were actively sensitized (i.m. injection of 10 mg/kg ovalbumin and i.p. injection of killed Bordetella pertussis) and exposed 12-14 days later to a 10%-ovalbumin aerosol there was an increase in the number of eosinophils in the BAL fluid, maximal 24-48 h after the anaphylactic reaction. The increase in the number of neutrophils in the bronchial lumen 3 and 6 h after the anaphylactic reaction was larger than that obtained in non-specific inflammation and in contrast to this was still present 24-48 h after ovalbumin exposure. In passively sensitized BN rats exposed to ovalbumin aerosol, no inflammation appeared in the BAL fluid 24 h after the anaphylactic reaction. Various drugs, administered twice, 5 min and 5 h after the anaphylactic reaction, have been evaluated for their effects on the 24-h inflammation obtained in actively sensitized rats. Dexamethasone acetate (0.08 mg/kg i.p.) and theophylline (50 mg/kg i.p.) decreased the number of eosinophils and neutrophils. Ketotifen fumarate (12.5 mg/kg), cetirizine dihydrochloride (12.5 mg/kg), salbutamol (2 mg/kg), disodium cromoglycate (50 mg/kg) all given intraperitoneally, reduced the number of eosinophils. Tioxamast decreased the number of eosinophils at 12.5 mg/kg i.p. and by the oral route.(ABSTRACT TRUNCATED AT 250 WORDS)

Late airway responses to antigen challenge in sensitized inbred rats

We studied the magnitude and the time course of changes in pulmonary resistance (RL) after aerosol challenge with chicken ovalbumin (OA) of 15 sensitized, highly inbred Brown-Norway (BN) rats. Animals were actively sensitized and 2 wk later were challenged through the airways. Airway responses of sensitized animals were compared to those of 6 control animals challenged with sufficient methacholine (MCh) to at least double RL and to 4 unsensitized control rats challenged with OA. Ten of 15 rats in the experimental group displayed an early response (ER), defined as an increase in RL of at least 50% within 1 h of challenge. A late response (LR) was considered to have occurred when the value of RL exceeded the mean plus 2 standard deviations of all the measurements taken from 1 h after challenge to the end of the experiment. Two rats died less than 240 min after OA challenge with RL greater than 200% baseline. The remaining 13 were studied for a total duration that ranged from 390 to 720 min and of these animals 10 demonstrated LRs. Maximal RL during the LR after OA was 287 +/- 49% (SE) baseline (range, 129 to 760) versus 115 +/- 15% (75 to 176) for control animals after MCh (p less than 0.01) and 52 +/- 3% (51 to 142; p less than 0.01) for unsensitized control animals after OA. There was no correlation between the magnitude of ER and LR; 3 LRs occurred in the absence of detectable ERs. The median time to the peak of the LR was 450 min; median duration of LRs was 90 min (range, 30 to 135 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunomodulation by nematodes: a review

There is current evidence that infections with Trichinella spiralis, Ascaris suum, Nippostrongylus brasiliensis, Nematospiroides dubius (syn. Heligmosomoides polygyrus) and diverse filariae affect the immune responsiveness of their hosts. T. spiralis, or its extracts, can depress or enhance the heterologous humoral or cell-mediated immunities, and affect macrophage activity or the response to other invaders. These effects are induced by products of the migratory and early muscle larvae and appear to obey more than one single-mechanism. A suum acute infections or extracts depress responses involving T cell activity, but stimulate polygonal expansion of B-cells. Nippostrongylus brasiliensis causes polyclonal stimulation of IgE-producing cells, enhances immune responses during the first week of infection and inhibits them later on. Nematospiroides dubius depresses homologous and heterologous immunity and facilitates the permanence of other intestinal nematodes. Filarial worms appear to depress the homologous cell-mediated immunity and the heterologous humoral response by induction of suppressor cells and humoral factors. These phenomena are probably the result of evolutionary pressures on the parasites that facilitate their survival. In the host, they are likely to aggravate the homologous infection, facilitate intercurrent conditions and interfere with immunoprophylaxis procedures.

Polyclonal IgE increase after HgCl2 injections in BN and LEW rats: a genetic analysis

An autoimmune disease and a dramatic increase in total serum IgE concentration are observed in BN rats that are chronically injected with HgCl2. In contrast, LEW rats do not develop the characteristic glomerulonephritis and are very "low IgE responders". In this study, we examined the genetic control of total serum IgE increase after HgCl2 injection in F1 and F2 hybrids, in both backcrosses between LEW and BN rats, and in LEW.1N congenic rats. Genetic analysis was performed using peak IgE concentrations expressed as log microgram/ml. A high IgE phenotype was found to be dominant. Eighty-five percent of F2 variance was due to genetic factors (VG) while only 15% of this variance was caused by environmental factors (VE). From observations in F2 hybrids and backcrosses, estimations of additive variance (VA) and dominance variance (VD) were made following three different methods. Genetic control by about four loci is demonstrated. One of these genes is RT1-linked. This gene contributes to 25% of the phenotypic difference observed between BN and LEW rats. No correlation was found between the peak total IgE level and autoimmune disease based on IgG deposition in spleen and/or kidney.

Antigen-induced release of histamine from serosal mast cells, lung, and tracheal tissue: variation with tissue and rat strain in relation to serum IgE-antibody level

Rats of the Brown Norway (BN)2, Fischer, PVG and Sprague Dawley (SD) strains were immunized intraperitoneally with graded doses of ovalbumin (OA) together with either alum or Silica gel. At specified times after immunization, in vitro histamine release from serosal mast cells and from chopped lung and tracheal tissue was determined after challenge with OA. The development of the capacity to respond in these tests seemed to vary within strain independently for mast cells, lung, and tracheal tissue with immunization dose of antigen and nature of adjuvant. These variations were not closely correlated to observed variations in serum levels of OA-IgE antibody or ratio OA-IgE to total IgE as determined by radioimmunoassay. Furthermore, variations between strains in response capacity did not correlate to inter strain variation in median serum OA-IgE antibody level. These results do not clearly conform to the possibility that one single class of IgE mediates anaphylactic reactivity of various tissues of the rat.

Stimuli for the production and control of IgE in rats

In Hooded Lister rats IgE responses may be induced by administration of antigen together with one of a number of adjuvants. The primary IgE response may subsequently be enhanced either specifically by a further exposure to antigen (booster response) or non-specifically by infection with helminth parasites (potentiated response). In the latter case the enhanced response is associated with a great increase in total serum IgE. The primary response itself is not significantly influenced by variations in the general theme of conventional immunization, including dose or route of administration of antigen, or the nature of the adjuvant employed. The booster response however is inhibited, a) in rats primed with a 'large' (e.g. greater than 100 microgram EA) dose of antigen and B. pertussis, and b) rats primed with any dose of antigen given in Al(OH)3 or CFA, and c) following repeated booster doses of soluble (i.e. unadjuvanted antigen even at a dosage of a few picogrammes. It is thought that each of the stimuli generate antigen specific suppressor T cells. Live worm parasites selectively, but non-specifically, stimulate heterologous antigen primed IgE responses. The evidence suggests that it may be this non-specific IgE stimulating effect rather than the parasite specific IgE response per se which leads to the great elevation of total serum IgE. Other immunoglobulin classes are not elevated in the same way. The potentiated IgE response is not susceptible to the suppressive influence generated by previous administration of large or repeated doses of the heterologous antigen. On the other hand, a parasite specific regulatory mechanism acts to prevent repotentiation of the heterologous (but not the parasite specific or total IgE) responses following reinfection. These results are discussed in relation to the work of others in rats and other species.

Active bronchial anaphylaxis in the rat: inhibition by tiaramide

Intravenous administration of the benzothiazoline derivative tiaramide hydrochloride, to rats actively sensitized to ovalbumin, inhibited immunologic lung reactions in a dose-related manner. Methysergide also inhibited anaphylactic lung reactions. Serotonin, but not other chemical mediators, produced changes in pulmonary mechanics qualitatively similar to those produced by the sensitizing antigen. The bronchoconstrictive action of serotonin was blocked by methysergide and tiaramide. The latter drug also inhibited bronchoconstriction induced by methacholine. The results implicate serotonin as the primary mediator of the respiratory component of systemic anaphylaxis in the rat: however, the mechanism by which tiaramide inhibits anaphylactic bronchoconstriction remains to be elucidated.