WO2008150181A1

WO2008150181A1 - Compositions and methods for treating anthrax exposure associated conditions

Info

Publication number: WO2008150181A1
Application number: PCT/NZ2008/000130
Authority: WO
Inventors: Franck B. Gelder; Gillian Alison Webster
Original assignee: Innate Therapeutics Limited
Priority date: 2007-06-05
Filing date: 2008-06-05
Publication date: 2008-12-11

Abstract

The present invention relates to compositions and methods for therapeutic and/or prophylactic treatment of anthrax lethal toxin toxaemia and other conditions arising from anthrax exposure or infection, using a microparticulate immuno stimulatory composition to enhance the innate immune system.

Description

COMPOSITIONS AND METHODS FOR TREATING ANTHRAX EXPOSURE

ASSOCIATED CONDITIONS

TECHNICAL FIELD

The present invention is concerned with compositions and methods for therapeutic and/or prophylactic treatment of anthrax lethal toxin toxaemia and other conditions arising from anthrax exposure or infection in mammals. In particular the present invention is concerned with the use of a microparticulate immuno stimulatory composition to enhance the innate immune system in defence against effects of anthrax exposure. More particularly, the present invention relates to a non-toxic microparticle comprising cross-linked muramyl dipeptide and its use for stimulating the innate immune system in defence against effects of anthrax lethal toxin toxaemia and other conditions associated with anthrax exposure.

BACKGROUND

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

The disease anthrax, caused by the bacteria Bacillus anthracis (B. anthracis), has been recognized since ancient times. It was typically seen in agrarian workers like tanners and wool sorters who had close contact with livestock, the main reservoir for this disease. In more recent times, this endemic pathogen has been developed into one of the most effective biological weapons known to man. The effectiveness of B. anthracis as a weapon is based on its ability to be sporulated and dried, for effective dispersion, combined with significant disease morbidity and mortality. Antibiotics are effective against the bacilli in the early stages of infection but once exotoxin production has begun, antibiotics offer no protection against fatal anthrax toxaemia.

Whereas vaccination against anthrax may be an effective way of protecting individuals against infection, vaccinating the general population may not be cost effective or achievable. Thus, different approaches may also be required to slow or prevent anthrax toxin induced morbidity and mortality. Inhibiting the bacterial infection early or neutralizing lethal toxin, formed by two of the bacteria's three toxin proteins, lethal factor (LF) and protective antigen (PA), may change the course of infection and/or allow time to intervene with specific antibiotic treatments. The military interest in anthrax centres on countermeasures against its use as an inhalation biological weapon although other clinical forms are more common in natural exposure situations. In the event of inhalation exposure to B. anthracis spores, the rapid upregulation of an antimicrobial innate immune response would be highly desirable. The innate immune system provides the first-line of defense against a wide range of micro-organisms without previous exposure and this occurs before the development of adaptive immune responses. The cellular basis for activation of innate immunity is now known to involve the pattern-recognition receptors, which are expressed on both the surface and/or intracellular Iy of all known immune cell subsets. These play a crucial role in initiating the innate immune response by the ability to recognize pathogen associated molecular patterns (PAMP) and subsequently initiate a pro-inflammatory response. This response culminates in the secretion of cytokines, chemokines and broad-spectrum anti-bacterial substances such as defensins, and is the basis for adjuvant activity. There is accelerating interest in the use of non-specific immunostimulants or adjuvants immunostimulatory complexes, as a means of enhancing/inducing nonspecific immunity. The term "adjuvant" is widely used to describe compounds which when administered to an individual or tested in vitro, act by inducing the general upregulation of immune cell-specific immunologic activities. Whilst a great variety of materials have been shown to have adjuvant activity, the only adjuvant licensed for general medical use is Alum, which was first used over 50 years ago. Next to Alum, Freund's complete adjuvant (FCA), containing mineral oil and inactivated tubercle bacillus was initially used widely and was regarded as the 'gold standard' but fell into disuse because it formed a granuloma (Stills, 2005). The identification of immunostimulatory/modulatory properties of murumyl dipeptide (MDP), a dipeptide common to gram-positive and gram-negative classes of bacterial peptidoglycans (Inohara, 2003; Kufer, 2006), led to immunopharmaco logical studies aimed at clinical application of MDP as a chemically defined, fully active immunoadjuvant. These expectations were soon frustrated by the realization that MDP itself is not suitable for clinical use, mainly because of its toxicity and poor pharmacokinetic profile, i.e. the rapid clearance of MDP from the body (Lidgate, 1995; Traub, 2006). Attempts to reduce or eliminate pyrogenicity in turn has led to the formulation of derivatives, some of which have been used in clinical trials in a soluble monomeric form e.g. Murabutide (Audibert, 1984; Bahr, 1995; Vidal, 2001).

In contrast to the MDP formulations mentioned above, an MDP composition was developed which lacks the unwanted side effects attributed to MDP while achieving enhanced immunostimulatory properties (Australian Patent No. 732809). This non-toxic form of MDP (NT-MDP) was originally developed, as were most adjuvants, to enhance specific immune responses to native proteins, recombinant proteins, synthetic peptides and other immunogenic materials, i.e. it was used in conjunction with a relevant antigen as a conventional adjuvant-antigen complex. Traditionally bacterial or other adjuvants are not used for immunotherapy on their own, to boost the non-specific immune system in order to fight infection. In part this is because the prior art adjuvants are not able to specifically activate the relevant immune cell types and hence activate the relevant immune response. Prior art adjuvants induce cytokine production by inappropriate cell types that leads to systemic expression of large amounts of diverse cytokines leading to severe and undesirable side-effects which in turn prevents their use as stand-alone immunotherapeutics.

Thus, there is a need for new and improved first-line non-specific immuno stimulants and immunomodulators, particularly those that drive a broad range of innate immune responses, which may also better facilitate the development of immunotherapeutics for treatment of pre and post exposure to B. anthracis and its products.

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 usefiil alternative.

SUMMARY OF THE INVENTION The present invention relates to methods for, enhancing innate immunity defense mechanisms of humans against infection by the bacterium B. anthracis and the toxaemia caused by the bacteria's production of lethal toxin (LeTx). In accordance with the present invention, innate immunity defenses are enhanced by the administration of a immunomodulatory microparticle comprising muramyl dipeptide (NT-MDP). The administration of this immuno modulator significantly augments the antimicrobial activities of the innate immune system against anthrax infection and the effects of anthrax lethal toxin. Thus, according to the first aspect, the present invention provides an immuno stimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide, for stimulation of the innate immune system in defence against or treatment of exposure to B. anthracis and/or its products. . According to a second aspect, the present invention provides an immunostimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide, for stimulation of the innate immune system in defence against or treatment of exposure to anthrax lethal toxin.

The microparticulate muramyl dipeptide composition of the present invention may be conveniently admixed with any conventional pharmaceutical or veterinary carrier, solvent or excipients (See for example "Remington: The Science and Practice of Pharmacy", 19^th Ed, 1995 (Mack Publishing Co. Pennsylvania, USA), "British Pharmacopoeia", 2000, and the like).

Preferably the microparticulate muramyl dipeptide has a particle size of about 0.1 to about 0.2 microns. However it will be understood that somewhat smaller or considerably larger particle sizes may also be useful in the methods of the present invention. For example, the particle size may be in the range of from 0.01 to 2.0 microns or in the range of 0.01 to 1.0 microns. Other suitable particles size ranges are 0.01 to 0.2 microns, 0.01 to 0.1 microns, 0.01 to 0.5, 0.05 to 1 or 0.1 to 0.5 microns diameter.

According to a third aspect, the present invention provides an immunostimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide and one or more other therapeutic agents effective in the treatment of B. anthracis and/or its products and/or anthrax lethal toxin. According to a fourth aspect, the present invention provides a pharmaceutical composition comprising an immunostimulatory composition according to any one of the first to third aspects, for stimulation of the innate immune system in defence against or treatment of exposure to B. anthracis and/or its products.

According to a fifth aspect, the present invention provides a pharmaceutical composition comprising an immunostimulatory composition according to any one of the first to third aspects, for stimulation of the innate immune system in defence against or treatment of exposure to anthrax lethal toxin. According to a sixth aspect, the present invention provides a pharmaceutical composition comprising an immunostimulatory composition according to any one of the first to third aspects and one or more other therapeutic agents effective in the treatment of B: anthracis and/or its products and/or anthrax lethal toxin. According to a seventh aspect, the present invention provides a method for prophylactic or therapeutic treatment of exposure to B. anthracis and/or its products comprising the administration to a subject requiring such treatment, a composition according to the first to sixth aspects.

According to an eighth aspect, the present invention provides a method for prophylactic or therapeutic treatment of exposure to, or effects of, anthrax lethal toxin comprising the administration to a subject requiring such treatment, a composition according to the first to sixth aspects.

The methods of the present invention may further comprise the administration of one or more other therapeutic agents, vaccines and other treatments effective in combating B. anthracis infection or the effects of exposure to anthrax lethal toxin. For example the compositions of the present invention may be used in conjunction with conventional antibiotic therapy or vaccination. The various treatments may be administered simultaneously or sequentially, depending on the need and availability. However, preferably the compositions comprising NT-MDP of the present invention are intended for initial administration, as the first-line defence against the effects of anthrax lethal toxin and other conditions associated with B. anthracis exposure.

It will be understood that the compositions of the present invention may be equally effectively used in pharmaceutical formulations intended for human administration and in formulations intended for veterinary applications. Preferably the formulations of the present invention are intended for human use.

According to a ninth aspect, the present invention provides use of an immunostimulatory composition comprising a cross-linked microparticle form of muramyl dipeptide, for the manufacture of a medicament for the treatment of exposure to B. anthracis and/or its products. According to a tenth aspect, the present invention provides use of an immunostimulatory composition comprising a cross-linked microparticle form of muramyl dipeptide, for the manufacture of a medicament for the treatment of exposure to, or effects of anthrax lethal toxin.

DEFINITIONS

The term "muramyl dipeptide", as used in the context of the present invention, encompasses any natural or synthetic source of muramyl dipeptide.

In the context of the present invention the terms "MDP-microparticle", "NT-MDP" or "non-toxic muramyl dipeptide" or "cross-linked microparticle form of muramyl dipeptide may be used interchangeably".

Exposure to B. anthracis may lead to infection or alternatively may be merely exposure to the bacterium or its products.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". BRIEF DESCRIPTION OF THE FIGURES

Figure 1 : Induction of cytokine production by NT-MDP in whole blood leucocytes

Figure 2: Internalisation of NT-MDP by PMN and monocytes

Figure 3: Induction of IL-8 in PMN by exposure to NT-MDP

Figure 4: Neutrophil responses to NT-MDP: Figure 4a - NT-MDP induced shedding of CD62-L and upregulation of CDl Ib; Figure 4b - NT-MDP upregulation of CD66b.

Figure 5: Induction of TNF-α by monoyctes in response to NT-MDP

Figure 6: Anthrax lethal toxin study in mice

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is motivated by the need for effective, non-toxic, rapid- response immuno stimulants and immunomodulators that can up-regulate the nonspecific (innate) immune response in subjects following exposure to an infective agent such as B. anthracis, or in situations where effective therapy is not available or co- therapy could provide a better outcome. The present invention is based on observations made through detailed studies on immunostimulatory and immunomodulatory activity of a non-toxic micro particulate consisting of cross-linked muramyl dipeptide (NT-MDP), as described hereinafter. NT-MDP is known to be effective at stimulating the host's adaptive immune responses against proteins and peptides via interaction with immune cells such as antigen presenting cells. What was discovered through present experimental studies is that NT-MDP is a selective immune cell stimulant, stimulating only the desirable and relevant immune cell types, thus avoiding unwanted side-effects and promoting therapeutically relevant innate immune responses in a subject, but perhaps more importantly and unexpectedly, the compositions of the present invention were found to be protective against the effects of anthrax lethal toxin.

Thus, compositions of the present invention are useful as possible first-line defence against anthrax infection or as non-specific immuno therapeutics for administration prior to potential exposure to anthrax, for which effective first-line therapy is not available.

Extensive animal studies have established a strong safety profile for NT-MDP without reducing its immuno stimulatory properties. NT-MDP is able to achieve 5 to 10 fold greater induction of therapeutically relevant cytokines than measured for native monomeric MDP. NT-MDP is not immunogenic and allows repeat dosing and re- treatment without triggering an anti-MDP immune response. This contrasts with several other immunomodulators that have been developed and tested.

Not wishing to be bound by theory or be limited by any particular mechanism of action, the ability of NT-MDP compositions of the present invention to rapidly stimulate relevant immune cells, such as neutrophils and monocytes, underpins its activity and usefulness as an effective non-specific immunotherapeutic. NT-MDP's properties associated with a rapid up regulation of innate immune responses while being non-toxic and producing no appreciable side-effects, positions it as a first-line therapeutic immune modulator for preventing and/or treating anthrax infection associated conditions, including anthrax lethal toxaemia. The compositions of the present invention, administered at or about the time of exposure to B.anthracis will enhance innate immune responses resulting in inhibition of bacterial infection and treatment of fatal toxaemia. The compositions of the present invention may be used in conjunction with other anthrax therapies such as antibiotic treatment or vaccination. The initial administration of NT-MDP compositions of the present invention to a subject exposed to, or infected by, B. anthracis will delay the adverse effects of anthrax lethal toxin, thus allowing the affected subject more time to gain access to other available anthrax therapies. By way of example, the data shown demonstrate that NT-MDP stimulation of whole blood leucocytes results in the induction of cytokines that are known to mobilize the innate arm of the immune response. One important aspect of anti-microbial immunity that is induced is neutrophil granulocyte activation. As an example, NT-MDP is shown to be taken up by, and directly activate neutrophil granulocytes to synthesise IL8, which is a cytokine known to act in an autocrine or paracrine manner on monocytes and neutrophil granulocytes and induce degranulation. As another example, NT-MDP is also taken up by, and directly activates monocytes to synthesise TNF-α, a cytokine which is known to enhance neutrophil and monocyte-mediated bacterial killing, in part by enhancing the production of reactive oxygen species following phagocytosis of pathogens. The ability of NT-MDP to inhibit or significantly delay fatal anthrax toxaemia is demonstrated in a mouse anthrax lethal toxin challenge model. Pharmaceutical compositions and their use:

In one embodiment, the present invention provides pharmaceutical compositions containing NT-MDP of the present invention and a pharmaceutically acceptable carrier, solvent or excipient. NT-MDP is present in a therapeutically effective amount, which is the amount of NT-MDP required to achieve the desired effect in terms of treating or preventing conditions associated with anthrax exposure by enhancing innate immunity. The compositions of the present invention are administered alone, i.e., without a co -administered antigen, to potentate the immune system in the treatment of exposure to anthrax.

Amounts effective for this use will depend on, e.g., the particular composition administered, the manner of administration, the stage and severity of the disease being treated, level of exposure, the weight and general state of health of the patient, and the judgment of the prescribing physician.

The immunostimulatory compositions of the present invention may be used in a dosage range of about 1, 5, 50, 500, or 5000 μg of NT-MDP composition and preferably in a dose range of 5 μg to 500 μg NT-MDP composition. Dosage values for a human typically range from about 10 μg to about 100 μg per 70 kilogram patient. The maximum dose expected to be given to a human may be up to 1 mg per 70 kilogram, however those skilled in the art will recognize that dose will be dependent on immunogenic ity, severity of condition, other patient factors, and will vary to achieve the desired effect. While any suitable carrier known to those of ordinary skill in the art may be employed in the immunostimulatory compositions of this invention, the type of carrier will typically vary depending on the desired mode of administration. Compositions of the present invention may be formulated for any appropriate manner of administration, including for example, topical, oral, nasal, intravenous, intracranial, intraperitoneal, intradermal, subcutaneous or intramuscular administration. For parenteral administration, such as subcutaneous injection, the carrier will often comprise water, saline, alcohol, a fat, a wax or a buffer. For oral administration, the above carriers are often used, or a solid carrier such as mannitol, lactose, starch, magnesium stearate, sodium saccharine, talcum, cellulose, glucose, sucrose, and magnesium carbonate, can also be employed.

The compositions can also comprise buffers (e.g. neutral buffered saline, phosphate buffered saline or phosphate buffers without saline), carbohydrates (e.g., glucose, mannose, sucrose or dextrans), mannitol, proteins, polypeptides or amnino acids such as glycine, antioxidants, bacterio stats, chelating agents such as EDTA or glutathione, adjuvants (e.g., aluminum hydroxide), solutes that render the formulation isotonic, hypotonic or weakly hypertonic with the blood of a recipient, suspending agents, thickening agents and/or preservatives. Alternatively, compositions of the present invention may be formulated as a lyophilizate. The compositions can also be encapsulated within liposomes using well known technology. The compositions of the present invention can be aqueous formulations comprising an effective amount of one or more surfactants. For example, the composition can be in the form of a micellar dispersion comprising at least one suitable surfactant, e.g., a phospholipid surfactant. Illustrative examples of phospholipids include diacyl phosphatidyl glycerols, such as dimyristoyl phosphatidyl glycerol (DPMG), dipalmitoyl phosphatidyl glycerol (DPPG), and distearoyl phosphatidyl glycerol (DSPG), diacyl phosphatidyl cholines, such as dimyristoyl phosphatidylcholine (DPMC), dipalmitoyl phosphatidylcholine (DPPC), and distearoyl phosphatidylcholine (DSPC); diacyl phosphatidic acids, such as dimyristoyl phosphatidic acid (DPMA), dipalmitoyl phosphatidic acid (DPPA), and distearoyl phosphatidic acid (DSPA); and diacyl phosphatidyl ethanolamines such as diimyristoyl phosphatidyl ethanolamine (DPME), dipalmitoyl phosphatidyl ethanolamine (DPPE) and distearoyl phosphatidyl ethanolamine (DSPE).

. Suitable formulation protocols and excipients can be found in standard texts such as "Remington: The Science and Practice of Pharmacy", 19^th Ed, 1995 (Mack Publishing Co. Pennsylvania, USA), "British Pharmacopoeia", 2000, and the like.

In other embodiments, the composition is an emulsion, such as a water-in-oil emulsion or an oil- in water emulsion. Such emulsions are generally well known to those skilled in this art.

The compositions of the present invention can be administered together with other immunomodulators and immunostimulants. By way of illustration, immunomodulators and immunostimulants can include oil-based adjuvants (for example, Freund's Complete and Incomplete), liposomes, mineral salts (for example, aluminium compounds and salts, silica, alum, kaolin, and carbon), polynucleotides (for example, poly IC and poly AU acids), polymers (for example, non-ionic block polymers, polyphosphazenes, cyanoacrylates, polymerase-(DL-lactide-co-glycoside), among others, and certain natural substances (for example, lipid A and its derivatives, wax D from Mycobacterium tuberculosis, as well as substances found in Corynebacterium parvum, Bordetella pertussis, and members of the genus Brucella), bovine serum albumin, diphtheria toxoid, tetanus toxoid, edestin, keyhole-limpet hemocyanin, Pseudomonal Toxin A, choleragenoid, cholera toxin, pertussis toxin, viral proteins, and eukaryotic proteins such as interferons, interleukins, or tumor necrosis factor. Such proteins may be obtained from natural or recombinant sources according to methods and commercially available kits well known to those skilled in the art. When obtained from recombinant sources, the adjuvant may comprise a protein fragment comprising at least the immunostimulatory portion of the molecule. Other known immunostimulatory macro molecules which can be used in the practice of the invention include, but are not limited to, polysaccharides, tRNA, non-metabolizable synthetic polymers such as polyvinylamine, polymethacrylic acid, polyvinylpyrrolidone, mixed polycondensates (with relatively high molecular weight) of 4',4-diaminodiphenylmethane-3,3'- dicarboxylic acid and 4-nitro-2-amino benzoic acid (See SeIa, M., Science 166:1365 1374 (1969)) or glycolipids, lipids or carbohydrates.

EXAMPLES

Experimental models used in the studies described hereinafter were chosen to demonstrate the type of immune response that is required and anticipated to be effective in combating anthrax infection and effects of anthrax lethal toxin. •

Example 1: Preparation and Characterization of the Biochemical and Conformational Requirements of NT-MDP.

A multiple repeat of muramyl dipeptide (MDP) isolated from Propionibacterium acini, formed the core structure of the MDP microparticle complex of this example. The chemical composition of the monomeric subunit is as below.

CH ₂ OH

CH₃CH-CO-NH-CH-CO-NH-CH-CONH₂ CH₃ (CH₂)₂

COOH

Muramyl dipeptide may also be synthesised from the individual components, glutamine, alanine and muramic acid. These may be used to make other muramyl dipeptides including muramyl-L-alanine-L -isoglutamine, or muramyl-d-alanine-d- isoglutamine. The prefered synthetic monomeric subunit is muramyl-L-alanine-D- iso Glutamine.

To date, both MDP isolated from natural sources and synthetic MDP have been associated with significant toxicity when administered to mammals. This toxicity has limited the effectiveness of MDP as an immunostimulant.

A method for the isolation of MDP free from toxic components is provided herein. Propionibacterium acnes was grown to a mid-stationary growth phase and washed to remove contaminants of bacterial culture origin, employing techniques well known to those in the art. Hydrophobic components contained in the cell walls and cytoplasm were sequentially extracted by successive washes with increasing .. concentrations of ethanol/isopropano I/water (10%:10%:80%, 25%:25%:50% and 40%:40%:20%) at elevated temperatures. The isopropyl alcohol was then removed with successive washes with decreasing concentrations (80%, 50%, 40% and 20%) of ethanol at elevated temperatures. The resulting MDP micro particle was then suspended in 20% ethanol and its concentration was measured by relating its absorbance at 540 run to the absorbance of turbidity standards. The concentration of the MDP micro particle was adjusted to 10 mg/ml for storage and later use.

Analysis of this preparation demonstrated muramyl dipeptide extensively crosslinked, having an average microparticle size of 0.1 to 0.2 micron. The terminal dipeptide amino-linked L-alanine-D-isoglutamine corresponded to the monomeric structure shown above. It is well known that there can be differences between bacterial strains and these differences can result in differences in peptide composition, such as terminal peptides with five or more amino acids, changes in dipeptide amino acid composition, in particular L-alanine-L-isoglutamine, and sites where O-acylated beta myristate groups have been incorporated. These are not desirable and account for toxicity and poor adjuvant properties of MDP isolated from natural sources. In a preferred embodiment, the MDP microparticles have amino-linked L-alanine-D- isoglutamine dipeptide. Such a microparticle can be isolated from natural sources, as above, or synthesized using well known synthetic procedures. Particle size ranges that can be obtained and may be suitable include the ranges of about 0.1 to 0.2 microns, 0.01 to 2.0 microns or 0.01 to 1.0 microns. Other suitable particles size ranges are about 0.01 to 0.2 microns, 0.01 to 0.1 microns, 0.01 to 0.5, 0.05 to 1 or 0.1 to 0.5 microns diameter.

Example 2: Characterisation of the NT-MDP pro-inflammatory response in human whole blood in vitro stimulation assays. The ability of NT-MDP to stimulate human pro-inflammatory cytokines was tested as follows. Whole human anti-coagulated venous blood was diluted 1/10 into warm complete medium (Hepes-buffered RPMI, 10% v/v heat inactivated FBS and penicillin/streptomycin antibiotics (Invitrogen). Diluted blood was cultured in 24 well tissue culture plate (1 ml/well) with 20 and 5 μg/ml of NT-MDP. Phytohaemaglutinin lectin from Phaseolus vulgaris (PHA, Sigma) served as an assay positive control. The samples were incubated for 72 hr (humidified, 37⁰C, 5%CO₂) and cell-free supernatant were collected for cytokine content analysis. Supernatants were analysed for IL-8, TNF- α, and IFN-γ content using flow cytometric bead array technology, commercially available as a kit for the detection of multiple cytokine simultaneously (Bender MedSystem FlowCytomix human ThI /Th2 cytokine multiplex kit).

The results show (Figure 1) that NT-MDP induced the secretion of cytokines known to be associated with the general immunostimulation, recruitment and degranulation of neutrophils.

Example 3: Whole blood neutrophil granulocytes rapidly internalise fluorescent Alexa-488 labelled NT-MDP.

To determine whether monocytes and neutrophil granulocytes (PMN) are involved in the uptake of NT-MDP, fluorescently labelled NT-MDP was prepared for cell tracing studies. To achieve this, NT-MDP was labelled with the fluorescent dye Alexa-Fluor-488 ™ (AF-488). This was accomplished using a commercial kit (Invitrogen), which irreversibly attaches the dye via amine groups on the NT-MDP. The ratio for coupling was 9.5 μg free dye per 1 mg NT-MDP. To perform the cellular uptake study, 100 μl of whole human heparinised blood was incubated with serial dilutions of AF-488-NT-MDP in 12 x 75 mm polypropylene tubes for 60 min (humidified, 37⁰C, 5%CO₂). Fluorescent monoclonal antibodies (Becton Dickinson) against CD45 (common leucocyte antigen) and CD 14 (monocytes), were added directly to the tubes, and the samples were incubated for a further 20 min in the dark at 4⁰C. Red blood cells were lysed by the addition of 0.75 ml of FACSLyse (Becton Dickinson) per tube, followed by incubation at room temperature in the dark. The samples were analysed by flow cytometry (Becton Dickinson LSR II). PMN were identified based on CD45 expression concomitant with high side scatter signal. Monocytes were identified based on CD45 and CD 14 fluorescence. The proportion of PMN and monocytes showing positivity for AF-488-NT-MDP was then determined. The results, shown in Figure 2, demonstrate that PMN and monocytes rapidly internalize NT-MDP in a dose- responsive fashion.

Example 4: NT-MDP directly activates neutrophil granulocyte IL-8 secretion, a cytokine involved in activation and degranulation. 0.5 ml of whole human heparinised blood from two donors were each incubated with l Oμg/ml NT-MDP in 15 ml conical polypropylene tubes for 5 hours (humidified, 37⁰C, 5%CO₂). At 2 hours into the stimulation, Brefeldin A protein transport inhibitor (Golgi-plug™, Becton Dickinson) was added at 1/1000 dilution. At the end of the incubation period, red blood cells were then lysed by the addition of 4.5 ml of FACSLyse (Becton Dickinson) per tube, followed by incubation at room temperature in the dark for 10 minutes. The lysed samples were stored at -80⁰C until subsequent intracellular cytokine analysis. For analysis of intracellular IL-8, samples were thawed and 0.2 ml of cells were washed into FACS staining buffer (FSB; PBS/1% BSA/0.09% sodium azide) and labeled with the fluorescent antibodies (Becton Dickinson) CD45- PacBlue and CD14-FITC for 20 mins (room temperature, in the dark) then washed once more in FSB. Cell pellets were fixed and permeabilised (Cytofix/Cytoperm, Becton Dickinson) for 20 min (4⁰C, in the dark) then washed twice in FSB supplemented with 5% w/v non-fat milk powder and 0.5% v/v saponin (milk-SAP-FSB). Cells were resuspended in 0.2 ml of milk-SAP-FSB and incubated with fluorescent antibody against IL-8 (IL-8-PE; Becton Dickinson) and incubated for a further 20 min (4⁰C, in the dark). Cells were washed twice more in MILK-SAP-FSB and then were analysed by flow cytometry (Becton Dickinson LSR II). PMN were identified based on CD45 expression concomitant with high side scatter signal and exclusion of monocytes based on CD 14 fluorescence. The proportion of PMN showing positivity for IL-8-PE was then determined, as shown in Figure 3. The results clearly show that short-term exposure of PMN to NT-MDP induces IL-8 secretion in the majority of cells.

Example 5: Neutrophil granulocytes respond to NT-MDP stimulation by modulation of migration/adhesion molecules L-Selectin (CD62-L) and CDl Ib as well as upregulation of markers associated with degranulation (CD66b).

To determine the effect of NT-MDP on key PMN adhesion molecules, 100 μl of whole human heparinised blood was incubated with 10 μg/ml NT-MDP in 12_.x 75 mm polypropylene tubes for 30 min (humidified, 37⁰C, 5%CO₂). As a positive control, TNF- α (R & D systems) was included at 10ng/ml. At the end of the incubation, the fluorescent monoclonal antibodies (Becton Dickinson) CD45-FITC, CD62L-PE and CDl Ib-APC were added directly to the tubes, and the samples were incubated for a further 20 minutes in the dark at 4⁰C. Red blood cells were lysed by the addition of 0.75 ml of FACSLyse (Becton Dickinson) per tube, followed by incubation at room temperature in the dark for 10 min. The samples were analysed by flow cytometry (Becton Dickinson LSR II). PMN were identified based on CD45 expression concomitant with high side scatter signal. CD62-L and CDl Ib co-expression analysis was performed to reveal that NT-MDP induced shedding of CD62-L concomitant with upregulation of CDl Ib, both of which are hallmarks of PMN activation and extravation (migration) (Figure 4a).

To directly measure the effect of NT-MDP on PMN degranulation, whole blood PMN were purified using a standard density gradient separation procedure (PolymorphPrep, Axis). 5x10⁶ PMN were resuspended in 1 ml of Krebs PBS (PBS supplemented with 1 mM Ca²⁺, 1.5 mM Mg²⁺ and 5.5 mM glucose, pH 7.2) and incubated for 3 hours with a dose-response of NT-MDP (humidified, 37⁰C, 5%CO₂). At the end of the incubation cell- free supernatants were harvested and stored at -8O⁰C for analysis of secreted defensins. For analysis of degranulation, the PMN were washed into FSB and cells were labelled with the fluorescent antibodies (Becton Dickinson) CDl Ib-APC and CD66b-FITC for 20 min (4⁰C, in the dark). Cells were the analysed by flow cytometry (Becton Dickinson LSR II). PMN were identified based on CDl Ib expression concomitant with high side scatter signal. CD66b co-expression analysis was performed to reveal that NT-MDP stimulation caused upregulation of the intensity of CD66b, as shown by increased mean fluorescent intensity (MFI) of CD66b, a hallmark of PMN degranulation. (Figure 4b).

Example 6: Monocytes respond to NT-MDP stimulation by secretion of TNF-α, a cytokine that is known to activate phagocytes and stimulate micorbicidal activity. 200 μl of human PBMC (10⁶/ml) in complete medium (see example 2) was cultured with NT-MDP at 20, 10, 5 and 1 μg/ml for 22 hr in a 96 well U-bottom tissue culture plate. Protein transport inhibitor brefeldin A (Golgi-plug™, Becton Dickinson) was added at 1/1000 dilution for the last 6 hr of the culture to enable cytokine accumulation. Cells were washed into physiological saline and then labelled with 1/1000 dilution of fixable violet live/dead stain (Invitrogen) for 30 minutes. Free dye was washed out using FSB (see example 4) then cells were fixed and permeabilised using Cytofix/Cytoperm (Becton Dickinson) for 20 minutes (4⁰C, in the dark). Cells were subsequently washed twice in milk-SAP-FSB (see example 4) and then incubated with fluorescent antibody against TNF-α (TNF-α-APC-Cy7; Becton Dickinson) for 20 minutes. Cells were washed twice in FSB and then analysed by flow cytometry (Becton Dickinson LSR II). Viable monocytes were identified based on live/dead dye exclusion combined with FSC vs high SSC gating (See Figure 5A). The proportion of gated viable monocytes expressing TNF-α was determined for each NT-MDP concentration (See Figure 5B). The results, shown in Figure 5B demonstrate that NT-MDP is a potent inducer of monocyte-associated TNF-α.

Example 7: Mouse MDP-Microparticle pre -treatment study

Female Balb/c mice (7 weeks, average weight 17g, Taconic Farms, NY), 3 mice per group, were treated with 500μg NT-MDP on days 0, 10 and 20 via intraperitoneal injection with 500μl total volume.

On day 35 (15 days following the last boost) mice were challenged with 200μg Anthrax Lethal Toxin (1 :1 PA83 (anthrax antigen) + LF, LeTx) via intraperitoneal injection in 200μl total volume. An additional group of control mice not receiving NT-MDP were also treated with LeTx to serve as a toxicity control. Recombinant PA and LF were obtained from Wadsworth Center of the New York State Department of Health, USA. Anthrax antigens may also be purchased from commercial sources such as Alpha Diagnostics Intl. Inc, San Antonio, Texas, USA.

Mice in the control group all succumbed to LeTx within 24 hours as expected. Mice in the NT-MDP treated group showed a delay in onset of illness with 33% of these mice surviving an additional 72 hours, as compared to the toxicity in control mice, and another 33% surviving for 96 hours. The remainder of mice in the NT-MDP treated group survived until the end of the study and did not exhibit any significant signs of illness or distress.

Consistent with earlier examples, NT-MDP upregulated innate immune responses and elicited protection from anthrax LeTx challenge. This discovery supports the use of NT-MDP in a either a non-vaccinated population, or vaccinate population where the efficacy of the vaccination was unproved, as an immune modulator for delaying or preventing the pathology associated with anthrax exposure or infection. Results of these studies are shown in Figure 6. Although the present invention has been described with reference to certain preferred embodiments and examples, it will be understood that variations and modifications in keeping with the spirit and thrust of the disclosure provided are also within its scope.

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Claims

CLAIMS:

I . Irnmunostimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide, for stimulation of the innate immune system in defence against or treatment of exposure to B. anthracis and/or its products. 2. Irnmunostimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide, for stimulation of the innate immune system in defence against or treatment of exposure to anthrax lethal toxin.

3. Immunostimulatory composition according to claim 1 or claim 2, further comprising one or more pharmaceutical or veterinary excipients, carriers or solvents. 4. Immunostimulatory composition according to any one of claims 1 to 3, wherein the microparticulate form of muramyl dipeptide has a particle size of about 0.01 to about 2 microns diameter.

5. Immunostimulatory composition according to claim 4, wherein the microparticulate form of muramyl dipeptide has a particle size of about 0.01 to about 1 microns.

6. Immunostimulatory composition according to claim 5, wherein the microparticulate form of muramyl dipeptide has a particle size of about 0.01 to about 0.2 microns.

7. Immunostimulatory composition according to claim 6, wherein the microparticulate form of muramyl dipeptide has a particle size of about 0.01 to about 0.1 microns.

8. Immunostimulatory composition according to claim 7, wherein the microparticulate form of muramyl dipeptide has a particle size of about 0.1 to about 0.2 microns. 9. Immunostimulatory composition comprising a cross-linked microparticulate form of muramyl dipeptide and one or more other therapeutic agents effective in the treatment of B. anthracis and/or its products and/or anthrax lethal toxin. 10. Pharmaceutical composition comprising an immunostimulatory composition according to any one of claims 1 to 9, for stimulation of the innate immune system in defence against or treatment of exposure to B. anthracis and/or its products.

I 1. Pharmaceutical composition comprising an immunostimulatory composition according to any one of claims 1 to 9, for stimulation of the innate immune system in defence against or treatment of exposure to anthrax lethal toxin.

12. Pharmaceutical composition comprising an immunostimulatory composition according to any one of claims 1 to 9 and one or more other therapeutic agents effective in the treatment of B. anthracis and/or its products and/or anthrax lethal toxin.

13. Method for prophylactic or therapeutic treatment of exposure to B. anthracis and/or its products comprising the administration to a subject requiring such treatment, a composition according to any one of claims 1 to 12.

14. Method for prophylactic or therapeutic treatment of exposure to, or effects of, anthrax lethal toxin comprising the administration to a subject requiring such treatment, a composition according to any one of claims 1 to 12. 15. A method according to claim 13 or claim 14, further comprising the administration of one or more other therapeutic agents effective in the treatment of B. anthracis infection and/or exposure to anthrax lethal toxin.

16. A method according to claim 15, wherein the one or more other therapeutic agents is a vaccine and/or an antibiotic that is administered simultaneously or sequentially.

17. A method according to any one of claims 13 to 16, wherein the subject is a human.

18. Use of an immunostimulatory composition comprising a cross-linked micro particle form of muramyl dipeptide, for the manufacture of a medicament for the treatment of exposure to B. anthracis and/or its products.

19. Use of an immunostimulatory composition comprising a cross-linked microparticle form of muramyl dipeptide, for the manufacture of a medicament for the treatment of exposure to, or effects of anthrax lethal toxin.