BACKGROUND ART Allergy is a clinical syndrome affecting about one third of the population, manifest as rhinitis, asthma, eczema or food hypersensitivity. Although target tissue changes play a role in determining the pattern of disease, the central abnormality (known as atopy) is the genetically influenced propensity to develop an IgE antibody response following antigen exposure. Increasingly it is recognised that the characteristics of the gut bacterial flora may drive IgE-promoting immunological mechanisms possibly by affecting the cytokine balance produced by CD4+ T lymphocytes. Modification of the gut flora may modulate the balance of this T cell response, and indeed differences in faecal quantitative bacteriology have been described within populations of children who differ in their incidence of asthma. A means by which to achieve a reduction in the level of IgE is desirable.

The literature that exists describes the use of yoghurt which contains certain potentially beneficial bacteria but the content of such bacteria in yoghurt is relatively low (usually 105 to 10'organisms) and is largely unknown. Further, many studies show that commercially produced yoghurts contain large numbers of other, not necessarily beneficial bacteria, and often only dead bacteria. Such food products are consumed in an ad hoc and uncontrolled manner. There is no indication or suggestion of how such products, or how much. should be consumed to achieve beneficial effects.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION It has unexpectedly been found that certain bacterial species when introduced live into the digestive system in sufficient quantity have the capacity to downregulate IgE antibody, and thus prevent and/or treat allergic disease. Further, the timing of

administration of the bacteria in relation to antigen/allergen exposure may also be of significance in certain circumstances.

According to a first aspect. the present invention provides a method of lowering IgE levels by administration of a therapeutically effective amount of live probiotic bacteria, or a live probiotic bacteria-containing composition, to a subject in need thereof.

According to a second aspect there is provided a method of prophylactic or therapeutic treatment of allergy by administration to a subject requiring such treatment a therapeutically effective amount of live probiotic bacteria, or a live probiotic bacteria- containing composition..

Preferably, the probiotic bacteria is, or the probiotic bacteria-containing composition includes. Lactobacillus.. Most preferably, the Lactobacillus is Lactobacillus acidophilus and/or Lactobacillus casei.

Preferably, IgE is lowered from elevated levels induced by an allergen or as a consequence of an allergic disorder.

Preferably, the probiotic bacteria, or a probiotic bacteria-containing composition. is administered at the time of exposure to an allergen or shortly thereafter.

In the context of the present invention the term"exposure"with reference to an antigen or allergen includes natural exposure such as for example day-to-day contact with or ingestion of food products and the like, or seasonal exposure or re-exposure to allergens such as pollen or other air-borne allergens or by contact with skin and other body surfaces which may involve contact with synthetic materials or natural substances.

In these circumstances the probiotic bacteria or compositions containing such bacteria are preferably administered at the time of exposure to the antigen/allergen or shortly thereafter. In seasonal exposure or re-exposure to allergens, the treatment is preferably commenced at the beginning of the season or shortly thereafter. However, the term "exposure"when used with reference to antigen/allergen also includes artificial exposure or administration such as for example the injection of antigen/allergen in desensitisation procedures or under-tongue administration of antigen/allergen. In these circumstances the antigen/allergen is preferably co-administered (co-presented) with the probiotic bacteria or a composition containing them. However, probiotic bacteria may also be administered shortly after administration of the antigen/allergen.

Preferably, the subject in need thereof is selected from the group consisting of high risk infants; those subjected to high risk occupational exposure to allergens; those exposed to high risk allergens; those having recognised allergy to specific allergens; and those prone to anaphylaxis. Preferably, the high risk infants are children of parents who both have allergic disease. Preferably, those subject to high risk occupation exposure to allergens are selected from the group consisting of aluminium smelter workers, woodworkers, chemical factory workers, and those working with latex-containing materials, especially gloves. Preferably, those exposed to high risk allergens are exposed to bee venom. Preferably, exposure to high risk allergens is parenteral exposure.

Preferably, in those having recognised allergic disease to specific allergens, the specific allergens are present in the pre-pollen season, foods or latex-containing materials.

Preferably, in those prone to anaphylaxis, the trigger for the allergic response is insect envenomation, and food and drug sensitivities.

Preferably, the probiotic bacteria or probiotic bacteria-containing composition is in tablet or capsule form. However, it will be clear to those skilled in the art that the probiotic bacteria may be present in a food source such as a yoghurt or other dairy product.

Preferably the amount of probiotic bacteria administered to a human subject is at least 10'° live bacteria. More preferably the amount administered is from about 10'° to about 1012 live bacteria.

The required dosage amount will vary according to the severity of the allergic condition, the nature of the allergic condition, age of the subject and other standard clinical parameters. These parameters as well as the required dosage can be easily assessed by those skilled in the art.

In human subjects it is preferred that the probiotic bacteria or a composition containing them be administered daily.

According to a third aspect the present invention provides the use of live probiotic bacteria for the manufacture of a medicament for lowering IgE levels.

According to a fourth aspect the present invention provides use of live probiotic bacteria for the manufacture of a medicament for treating allergy.

According to a fourth aspect, the present invention provides a method of identifying a bacterial species capable of lowering IgE levels in a mammal including:

a) administration of the bacterial species to a mammal; b) administration of an allergen (antigen) to the mammal; and c) determination of the IgE antibody level in the mammal after treatment with the bacterial species and comparison with a control mammalian which a bacterial species was not administered, wherein steps (a) and (b) can be performed consecutively in any order or simultaneously.

Preferably, the bacterial species is a Lactobacillus species and most preferably it is Lactobacillus acidophilus or Lactobacillus casei.

The animal model for identifying useful probiotic bacteria preferably makes use of the mouse. However other animal models may be developed on the same principle as disclosed herein.

In the animal model the bacterial species is preferably administered orally however it may also be administered intraperitoneally and other means. Most preferably, the bacterial species is administered in an amount of 108 to 10"bacteria, and more preferably, in an amount of 0.6 to 1.0 x 10'° bacteria. Preferably, 1 to 20 oral doses are administered prior to administration of the antigen and most preferably 4 to 8 oral doses are administered prior to administration of the antigen. Preferably, administration of the oral doses is at 1 to 5 day intervals and, most preferably, at 2 day intervals. Preferably, administration is over a I to 3 week period and, most preferably, over a 1 to 2 week period.

The preferred antigen/allergen used in the animal model is egg albumin (OVA) however it will be clear to those skilled in the art that other antigens can be used as allergens in this model should that be required. Preferably, the antigen is administered at a dose of 4 to 10 ug, and most preferably, at a dose of 8 ag. Preferably, the antigen is administered intraperitoneally. Preferably, the bacterial species is administered at the same time or 1 day after administration of the antigen/allergen. However, in certain embodiments the antigen/allergen can be administered after the bacterial species and in such circumstances the antigen/allergen is administered preferably 1 day after the administration of 4 to 8 oral doses of bacteria.

Preferably, administration of the bacteria species is continued after administration of the antigen. Most preferably, approximately 8 oral doses of bacteria are administered.

Preferably, the bacteria are administered at 2 day intervals.

Preferably, the IgE antibody is obtained from serum. Preferably, the serum is collected approximately 14 days after administration of the antigen. Most preferably, the IgE antibody level is determined using an ELISA assay. However, the skilled addressee will recognise that other IgE antibody assays may also be used.

Preferably, the allergic disease is selected from the group consisting of asthma, eczema, hayfever and food allergy.

According to a fifth aspect, the present invention provides a bacterial species identified by the method of the fourth aspect.

According to a sixth aspect, the present invention provides a composition including a bacterial species according to the fourth aspect.

Preferably the composition is in the form of a capsule or tablet or similar formulation however it may also be in the form of a food product.

According to a seventh aspect there is provided a pharmaceutical composition including an effective amount of live bacterial species according to the fourth aspect, together with a pharmaceutically acceptable carrier, adjuvant, solvent or excipient.

Preferably the bacterial species is L. acidophilus.

According to an eighth aspect there is provided a method of assessing efficacy of treatment with live probiotic bacteria or with a composition having live probiotic bacteria, including the steps of : a measuring the level of salivary immunoglobulin subclass in a sample obtained before commencement of treatment, b measuring the level of salivary immunoglobulin subclass in a sample obtained after commencement of treatment c comparing the levels of salivary immunoglobulin subclass in a) and b), wherein the change in immunoglobulin subclass level is indicative of effective treatment.

Preferably the immunoglobulin subclass is IgG1 or IgG2 and it will be understood that equivalent subclasses in various species can also be advantageously used.

According to a ninth aspect there is provided a method of assessing efficacy of treatment with live probiotic bacteria or with a composition having live probiotic bacteria, including the steps of: a measuring the level of IL-4 or IFN-y in a sample obtained before commencement of treatment, b measuring the level of IL-4 or IFN-y in a sample obtained after commencement of treatment c comparing the levels of IL-4 or IFN-y in a) and b), wherein the change in IL-4 or IFN-y level is indicative of effective treatment.

It will be clear however that any know cytokine marker for the Thl or the Th2 response will be suitable in place of IFN-y or IL-4.

BRIEF DESCRIPTION OF DRAWINGS Figure 1: Suppression of IgE antibody response in mice fed probiotic bacteria.

Figure 2: Suppression of IgE response to OVA by L acidophilus before/after allergen sensitisation Figure 3: Dose dependency of suppression of IgE response to OVA by L. acidophilus Figure 4: Suppression of IgE response to OVA by live and killed L acidophilus s Figure 5: Suppression of IgE response to OVA, and cytokine and IgG antibody subclass response, by L acidophilus DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the invention will now be described by way of example only.

A mouse animal model was developed which enabled identification of probiotic bacteria capable of downregulating the IgE response to an antigen/allergen. Typically the animal used is a mouse (for example C57BL/6). The animals are fed the candidate bacterial species (alive, dose 108-10", frequency every 1-5 days, for 1-3 weeks). In certain advantageous embodiments the animals are fed the bacteria at the same time as the antigen was being introduced or shortly thereafter, for example the following day.

Mice were immunised intraperitoneally with antigen (for example ovalbumin) at an appropriate dose (eg 4-1out, preferably 8llg), with specific and total IgE measured in serum (eg. at 14 days after immunisation). In certain examples feeding with test bacteria

continues throughout the experiment (see examples). In other examples comparisons are made with killed organisms and dose-response is estimated. In yet other examples the timing of administration of probiotic bacteria in relation to antigen/allergen challenge is examined. The examples demonstrate: (i) that frequent dosage with live probiotic bacteria at an appropriate does can reduce the IgE response to antigen/allergen.

(ii) that not all probiotic bacteria have the same capacity to reduce the IgE response-thus the model can be used to select candidate bacteria for human use in management or prevention of allergic disease.

(iii) Lactobacillus acidophilus is particularly effective in blunting the IgE response to novel antigens.

(iv) that oral administration of the bacterial species affects the systemic IgE antibody response (following injected antigen) and thus may be of value in subjects who have anaphylaxis (eg insect envenomation, and food and drug sensitivities).

(v) probiotic bacteria can downregulate IgE production following antigen administration or exposure to antigen-thus continuous oral ingestion of appropriate doses of live bacteria selected by this method may be of value in the ongoing management of allergic disease.

(vi) administration of live probiotic bacteria is particularly effective (vii) co-administration of probiotic bacteria with the antigen/allergen, or administration of probiotic bacteria shortly after the antigen/allergen challenge is particularly effective (viii) to be effective doses of probiotic bacteria in excess of those found in conventional food sources are usually required The bacterial species identified by the method are useful (1) for the prevention of allergic disease (a) in high risk infants (eg those with both parents with allergy) (b) in those subjected to high risk occupation exposure (eg aluminium smelter workers, woodworkers, chemical factory workers and those working with latex-containing material, especially gloves) (c) following parenteral exposure to high risk allergens, eg bee venom

(d) in subjects having recognised allergy to specific allergens (eg pre-pollen season, foods, latex, etc) (2) for the suppression of established allergic disease such as asthma, eczema, hayfever and food allergy.

The probiotic bacteria can be formulated into various compositions and preferably the compositions are pharmaceutical compositions in the form of capsules, tablets, powders and the like. Such formulations can be prepared by known means, using pharmaceutically acceptable carriers, excipients, solvents or adjuvants. Such procedures and ingredients are well know and amply described in standard texts and manuals, for example"Remington: The Science and Practice of Pharmacy", 1995, Mack Publishing Co. Easton, PA 18042, USA, which is incorporated herein by reference.

The probiotic bacteria may also be formulated into food products by the usual well known means.

The invention will now be described more particularly with reference to non- limiting examples.

EXAMPLES Example 1: Suppression of IgE antibody response to OVA following oral administration of Lactobacillus.

Bacteria (Lactobacillus acidophilus or Lactobacillus casei) were grown in MRS agar petri dishes (3.8% w/v, Oxoid, Basingstoke, UK). Plates were incubated in 5% COi and air in a humid atmosphere at 37°C for 48 hours.

Bacteria were harvested, washed twice in phosphate buffered saline (PBS) and then resuspended to 3-5 x 10'° bacteria per mL in PBS.

Thirty female C57/B 16 SPF mice (Animal Resource Centre, Perth, WA, Australia) were fed with 4 or 8 oral doses of 0.6-1.0 x 10'° L acidophilus or L casei in 0. 2 mL PBS or PBS alone given two days apart.

One day after the last oral dose, mice were injected intraperitoneally with 7 g of egg albumin (ovalbumin, OVA, Sigma-Aldrich, St Loius, Missouri, USA) and 4 mg aluminium hydroxide (Amphojel, Whitehall Laboratories, Sydney, Australia) in 0.2 mL PBS or with PBS alone.

Immunised and control mice were then placed on a feeding regime consisting of 8 oral doses of 0.6-1.0 x 10"'bacteria in PBS or PBS alone given two days apart.

Mice were bled by the saphenous vein 2 days after the last dose and the serum collected for IgE antibody determination using an ELISA assay.

The results are shown in Figure 1. Suppression of IgE antibody response to OVA was observed in mice given oral doses of L acidophilus and L casei compared with immunised mice given PBS. This level of suppression was statistically significant when L acidophilus was used.

Example 2: Suppression of IgE response to OVA by L acidophilus after allergen sensitisation C57/B16 mice were fed 10'° L acidophilus before or 24 hrs after sensitisation with 8 u. ovalbumin (OVA) in alum per mouse. Control mice were sham fed with normal saline. In each group, a total of 10 feeds was administered before they were assessed for levels of OVA-specific IgE antibody and total IgE in serum. L acidophilus was more effective if administered (or co-administered) at the time of exposure to OVA than when administered prior to allergen exposure, as shown by the suppression of OVA-specific IgE antibody and total IgE responses (Figure 2). Data are mean + SEM from 5-10 mice. *, p < 0.05 compared with control values from saline-fed sensitised mice. Baseline variation reflects different experiments and conditions) Example 3: Suppression of IgE response to OVA by L. acidophilus is dose- dependent Mice were fed orally with 108, 10'or 10"L acidophilus before they were sensitised 24 hrs later with OVA in alum. Control mice were sham fed PBS. Each dose was administered 10 times every 2 days for 21 days. One week following the final dose, serum IgE and OVA-specific IgE antibody were measured. A dose-dependent suppression of IgE and OVA-specific IgE antibody was noted with a statistically significant effect with 10'° bacteria (Figure 3). Data are mean + SEM from 10 mice. *, p < 0.05 compared with control values from saline-fed sensitised mice.

Extrapolation to human subjects indicates the requirement for a dose in the range of approximately 10'° to 10''live L acidophilus each day to effectively downregulate IgE antibody-mediated allergic disease. This is considerably in excess of the numbers of live Lactobacilli which can be practically introduced via currently available food products (often about 105-107 per serving).

Example 4: Suppression of IgE response to OVA is dependent on live culture of L acidophilus Mice were fed live or formalin-killed 10'° L acidophilus and then sensitised with OVA as per standard protocol described in Example 3. Figure 4 shows that live bacteria were more effective in suppressing IgE response than killed bacteria. Data are mean + SEM from 5 mice. *, p < 0.05 compared with values from saline-fed sensitised mice.

Example 5: Suppression of IGUE response to OVA by L acidophilus correlates with cytokine and IgG antibodv subclass response Mice fed 10'° L acidophilus produced higher amounts of IFN-y and lower amounts of IL-4 in the spleen, a finding consistent with the suppression of IgE response.

In addition, the contrasting cytokine patterns correlated with the production of salivary IgG subclass antibodies which showed an upregulation of IgG2a antibody and a downregulation of IgG 1, respectively (Figure 5). Data are mean + SEM from 10 mice.

*, p < 0.05; **, p < 0.01 compared with values from saline-fed sensitised mice.

These results indicate that IgG subclass antibody in saliva is an effective surrogate marker for monitoring response of allergic disease to intervention therapy.

Thus measurement of equivalent subclasses in humans would be an appropriate laboratory test for effective desensitisation therapy eg. increase in IgG2 anti-allergen antibody and/or decrease in IgGI antibody in saliva (or other secretions) is indicative of a response to therapy.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. In particular, it will be clear to the skilled addressee that the methods and compositions described above can be applied to any probiotic which can lower IgE levels in a subject.