Patent Application
20130142864
The invention described herein relates generally to the composition of preparations for the targeting of membrane-associated antigen (Ag) to dendritic cells (DCs) in order to modulate immune responses, either for disease prevention or for therapeutic purposes. More particularly, the invention relates to a method of modifying Ag-containing membranes, to enable engraftment and/or incorporation of targeting molecules and immunomodulatory factors, allowing the modified membranes to be targeted to DCs in vivo and potently induce, or suppress, immune responses. Even more particularly, the invention relates to a composition that can be used to modify Ag-containing membrane structures, such as liposomes or plasma membrane vesicles (PMVs), to enable the membranes to be targeted effectively to DCs in vivo, thereby modulating immunity, and enabling them to be used either as vaccines or vaccine-like agents in immunotherapies to prevent or treat disease in humans and animals.
Dendritic cells (DCs) are a rare population of antigen presenting cells (APCs) uniquely capable of stimulating primary immune responses, and a strong interest has developed in their use in cancer immunotherapies.1 Attempts to harness the capacity of DCs to stimulate potent immune responses have hitherto focused primarily on procedures involving the manipulation of DCs ex vivo. This approach often requires that DCs be isolated from a patient, expanded in numbers, loaded with antigen (Ag) (ref's 2-5), and then be re-introduced into the patient. While this procedure is simple in principle, there are difficulties associated with isolation and culture of such a rare cell population.6,7 Clearly, strategies that deliver Ags directly to DCs in vivo, and that can elicit an appropriate immune response, have enormous clinical potential.
DCs originate from progenitors in the bone marrow and migrate as immature cells to peripheral tissues where they internalise Ag and undergo a complex maturation process. Ag is internalised via a number of surface receptors, including the complement receptors (e.g., CD11c/CD18) and the endocytic receptors (e.g., DEC-205, DC-SIGN and Toll-like receptors). During Ag acquisition, immature DCs also may receive “danger signals”, in the form of pathogen-related molecules such as bacterial cell wall lipopolysaccharide (LPS), or inflammatory stimuli via cytokines such as IFN-γ. DCs then migrate to the secondary lymphoid organs, maturing to become competent APCs.8 Receptors such as CD11c/CD18, DEC-205, DC-SIGN and Toll-like receptors play a crucial role in the process of Ag capture and presentation, and are expressed primarily on DCs. It is conceivable, therefore, that these receptors also could be used for targeting Ag directly to DC in vivo. Consistent with this notion, fusion proteins composed of Ag and single chain antibodies (ScFvs) to DEC-205 have been shown to target to DCs in vivo, inducing T cell activation when co-administered with inflammatory stimulators such as anti-CD40 antibody.9,10 In contrast, in the absence of such inflammatory stimulators, antigen targeted to DCs via the ScFv induced T cell unresponsiveness.
Synthetic liposomes have the potential to deliver large quantities of Ags to DCs (Ref. 11), but to date their targeting to specific DC surface molecules has been difficult to achieve in practice.12,13 Clearly, an effective strategy that combines the Ag carrying capacity of liposomes and the specificity of molecular recognition to target multiple Ags either with or without “danger signals” directly to DCs in vivo, would have enormous potential in simplifying DC immunotherapies, particularly for cancer, infections, and autoimmune diseases.
In International Application No. PCT/AU00/00397 (Publication No. WO 00/64471) there is described a method of modifying biological or synthetic membranes or liposomes for the purposes of altering immunity, or for the targeting of drugs and other agents to a specific cell type or tissue when the modified biological or synthetic membranes or liposomes are administered in vivo. Modification of the membranes or liposomes is achieved by the incorporation or attachment of metal chelating groups, thereby allowing engraftment of one or more targeting molecules possessing a metal affinity tag. However, the nature of the immune response induced by targeting Ag to DCs is critically dependent on the presence of specific immunomodulatory factors such as cytokines or “danger” signals, and there is no disclosure or suggestion in PCT/AU00/00397 of the membrane modification that is required, or the immunomodulatory factors that are needed, to elicit an appropriate immune response in vivo.
An object of the invention the subject of this application, is to provide a composition for the in vivo targeting to DCs, of Ag-containing liposomes and PMV, by modifying the said membranes through incorporation of an appropriate immunomodulatory factor, or “danger signal”, and the engraftment of a ligand, that can target the modified membranes to receptors on the surface of DCs, and hence elicit an appropriate immune response. The composition can be used as vaccines or in immunotherapies, either to potentiate immunity for preventing or treating diseases such as various cancers and infections, or to suppress immunity to a specific self Ag in a way that can be used to treat or prevent transplant rejection, or the effects of autoimmune diseases such as type I diabetes, rheumatoid arthritis, systemic lupus erythematosus and multiple sclerosis.
Further objects of the invention are to provide a process for preparing suitable compositions, and methods of treatment utilising the compositions.
According to a first embodiment of the invention, there is provided a composition for modulating immunity by the in vivo targeting of an antigen to dendritic cells, the composition comprising:
a preparation of antigen-containing membrane vesicles or antigen-containing liposomes having on the surface thereof a plurality of metal chelating groups; and
a ligand for a receptor on said dendritic cells, said ligand being linked to a said metal chelating group via a metal affinity tag on said ligand; wherein,
said antigen-containing vesicles or liposomes include an immunomodulatory factor.
According to a second embodiment of the invention, there is provided a process for preparing a composition for modulating an immune response by the in vivo targeting of an antigen to dendritic cells, the process comprising the steps of:
According to a third embodiment of the invention, there is provided a method of modulating an immune response in a subject, the method comprising administering to said subject a composition according to the first embodiment.
According to a fourth embodiment of the invention, there is provided a method of preventing or treating a tumour in a subject, the method comprising administering to the subject a composition according to the first embodiment, wherein said antigen included in said antigen-containing membrane vesicles or antigen-containing liposomes is a tumour antigen.
According to a fifth embodiment of the invention, there is provided a method of preventing or treating an infection in a subject, the method comprising administering to the subject a composition according to the first embodiment, wherein said antigen included in said antigen-containing membrane vesicles or antigen-containing liposomes is an antigen from an agent causing the infection.
According to a sixth embodiment of the invention, there is provided use of a composition according to the first embodiment in the preparation of a medicament for modulating an immune response in a subject.
According to a seventh embodiment of the invention, there is provided use of a composition according to the first embodiment in the preparation of a medicament for preventing or treating a tumour in a subject.
According to an eighth embodiment of the invention, there is provided use of a composition according to the first embodiment in the preparation of a medicament for preventing or treating an infection in a subject.
Other embodiments of the invention will become apparent from a reading of the following detailed description of the invention, in which description there will be reference to the accompanying drawings briefly described hereafter.
The following abbreviations are used herein:
The term “antigen” is used herein to denote any molecule which can be taken up, internalised and processed by DCs, for presentation to the immune system.
The term “ligand” is used herein to denote any molecule which can specifically bind in vivo to markers/receptors on the surface of DCs. The term includes whole antibodies, and antibody fragments such as ScFvs and domain antibodies.
The term “immunomodulatory factor” is used herein to denote any “danger signal”, cytokine or molecule that can modulate the course or outcome of an immune response.
The term “receptor” is used herein to denote a receptor molecule on the surface of a DC, and is the entity on the DC surface with which a liposome- or membrane vesicle-engrafted ligand can interact.
The term “tumour” is used herein to denote benign and malignant solid tumours as well as solid and non-solid cancers.
With regard to the first embodiment defined above, the antigen-containing membrane vesicles are typically PMVs but can be formed from any biological membrane or biological structure. The PMVs are advantageously tumour-derived PMVs. The PMVs can also be lymphocyte-derived PMVs or leucocyte-derived PMVs. The PMVs can be furthermore membranous preparations of bacteria, protozoa, viruses or fungi. With regard to the antigen-containing liposomes, these include stealth liposomes (SLs) which can be produced from different mixtures of lipids. Such vesicles and liposomes can be prepared as described in references 14, 16, 17 and 28, the entire contents of which are incorporated herein by cross-reference.
The Ag of the compositions can be any Ag, or DNA encoding an Ag, against which an immune response is desired. A composition can comprise a plurality of different antigens which may be from the same or a different source. That is, a composition comprising tumour antigens may include antigens from different tumours.
The metal chelating groups on the surface of the vesicles and liposomes exist as headgroups of amphiphilic molecules present within the phospholipids and/or lipids comprising the vesicles and liposomes. The amphiphilic molecule is advantageously nitrilotriacetic acid ditetradecylamine (NTA-DTDA) or nitrilotriacetic acid phospha-tidylethanolamine (PE-NTA), but compositions can include any molecule containing any metal binding or chelating moiety that can be incorporated into lipid membranes. Compositions can furthermore comprise mixtures of amphiphilic molecules.
As will be explained in greater detail below, a preferred amphiphilic molecule is (NTA)3-DTDA (tri(nitrilotriacetic acid) ditetradecylamine). The related molecule NTA-DTDA, together with other amphiphilic molecules and vesicles and liposomes containing the same, are described in greater detail in International Application No. PCT/AU00/00397 (Publication No. WO 00/64471), the entire content of which is incorporated herein by cross-reference.
The ligand linked to the metal chelating groups on the membrane vesicles and liposomes can be any metal-affinity tagged molecule that can bind specifically to any DC surface marker. A preferred metal-affinity tag is hexahistidine. In examples below, hexahistidine-tagged forms of ScFv against the DC surface molecules CD11c and DEC-205 (CD205) are used. Other examples include any histidine-tagged ligand such as an antibody or antibody fragment that can bind to DC surface markers such as DC-SIGN (CD209), CD206 and CD207.
Compositions can include a plurality of ligands for different markers/receptors on DCs. For example, a composition can comprise as ligands an ScFv against DEC-205 in combination with an ScFv against DC-SIGN.
As indicated above, the metal affinity tag of a ligand is typically a hexahistidine moiety covalently linked at a convenient site on the ligand. For example, the hexahistidine can be linked to a protein antigen at the N- or C-terminal thereof. Other metal affinity tags include any moiety or amino acid sequence that can chelate metals and that can be covalently attached to a convenient site on the ligand.
The immunomodulatory factors of compositions according to the first embodiment include compounds or molecules that can enhance or modify the response of DCs to antigens. Such compounds include “danger signals” (e.g., bacterial lipopolysaccharide), cytokines (e.g., interferon-γ, interleukin-2, interleukin-4, interleukin-10, interleukin-12 and transforming growth factor-(β), as well as chemokine, hormonal and growth factor-like molecules, or DNA encoding such molecules. A composition can include more than one immunomodulatory factor.
Concerning the second embodiment of the invention, suitable processes for the preparation of membrane vesicles or liposomes with ligand entrapped thereon are described in the international application (No. PCT/AU00/00397) referred to above.
With regard to step (i) of the second embodiment process, the membrane vesicles are typically PMVs but can be formed from any biological membrane or biological structure. The liposomes include SLs. The Ag of the membrane vesicles and liposomes can be protein, glycoprotein, peptide or polysaccharide, or DNA encoding an antigen, or combinations thereof, to be delivered to the DCs.
In step (ii) of the second embodiment process, as with the first embodiment composition, the immunomodulatory factor can be a “danger signal” (e.g., a bacterial lipopolysaccharide), a cytokine (e.g., interferon-γ, interleukin-2, interleukin-4, interleukin-10, interleukin-12 and transforming growth factor-β), or DNA encoding such factors.
The immune response modulation of the method according to the third embodiment has application in the prevention or treatment of conditions which include transplant rejection, or the effects of autoimmune diseases such as type I diabetes, rheumatoid arthritis, systemic lupus erythematosus and multiple sclerosis. In the case of transplant patients, this involves the administration of PMVs from donor leukocytes that are targeted to the DCs of the transplant recipient. The immunomodulatory factor in this instance can be, for example, a cytokine such as interleukin-10 or transforming growth factor-β. However, the immunomodulatory factor can be any molecule that has the ability to generate tolerogenic DCs.
The method of the fourth embodiment can be used in the treatment of any tumour including, but not limited to, melanoma, and cancers of the prostate, bowel, breast and lung. The method can also be used in the treatment of leukaemia and lymphomas. The method can be used to treat tumours in any mammalian animal but is particularly suited for treating tumours in humans.
The amount of modified Ag-containing membrane vesicles or liposomes to be delivered to a subject and the administration regime can be established by the clinician after assessment of the subject in the light of the tumour under treatment.
Those of skill in the art will immediately recognise that the method according to the fourth embodiment provides an effective alternative to the ex vivo manipulation of DCs for use in cancer immunotherapy.
With regard to the fifth embodiment, the method can be used to prevent or treat any infection including infections caused by bacteria, mycobacteria, viruses and fungi in order to enhance immunity to the agent responsible for the infection and/or for use in the treatment of an infection. In a similar fashion to the example given above for the prevention of transplant rejection, all that is required to provide an efficacious method is to prepare PMVs or liposomes that include at least one antigen from the infectious agent. That antigen can be, for example, envelope proteins of viruses (e.g., HIV, hepatitis B and C) or cell wall components of bacteria (e.g., Mycobacteria), fungi (e.g., Candida) and protozoa (e.g., malaria).
Administration of compositions to a subject in accordance with the third to fifth embodiments of the invention can be by any of the methods known to those of skill in the art. Compositions are typically administered intravenously or subcutaneously.
The subject of the methods of the third to fifth embodiments is typically a mammalian subject. The methods are particular suited for use with a human subject.
Those of skill in the art will appreciate that a medicament according to the sixth to eighth embodiment of the invention will also include at least a carrier for the composition. The carrier can be any solution with which PMVs and liposomes are compatible. Typical carriers are saline and buffered saline such as PBS.
Medicaments can include further active agents consistent with the intended use of the medicament. For example, a medicament according to the seventh embodiment can include other anti-tumour agents while a medicament according to the eighth embodiment can include other agents with anti-bacterial, anti-protozoan, anti-viral or anti-fungal activity as appropriate for the target infection. Such additional agents will be known to those of skill in the art.
In a prototype study, the inventors have found that the chelator-lipid (NTA)3-DTDA can be used to anchor His-tagged ScFv onto either tumour-derived plasma membrane vesicles (PMV) or onto tumour antigen-containing stealth liposomes for the targeting of DCs. Targeting of Ag directly to DCs in this way elicited a strong anti-tumour response.
Liposomes have been hailed as having high therapeutic potential, but their use has been hampered by a lack of a simple method for attachment of targeting molecules.13 The novel chelator-lipid, (NTA)3-DTDA (
Initially, the ability of engrafted PMV and SL to stimulate functional responses in assays of DC-initiated Ag presentation was examined. Our studies show that ScFv-engrafted PMV and Ag-containing SL are significantly more effective than control PMV and SLs at inducing DCs to stimulate T cell proliferation (
Evidence suggests that “danger” signals are important in the maturation and migration of DCs after Ag exposure, and can avoid induction of tolerance to the presented Ag.9,10,18 Notably, “danger” signals were not required in the in vivo Ag presentation assays (
An examination of the ability of ScFv-engrafted PMV and SL containing Ag to induce DCs to initiate CTL responses revealed that, compared to control cells, T cells from animals immunised with ScFv-engrafted PMV or Ag bearing SL exhibit an increased ability, following in vitro restimulation, to lyse B16-OVA target cells in vitro (
A finding of paramount importance in this work was our observation that syngeneic animals immunised with CD11c-ScFv- and DEC-205-ScFv-engrafted PMV had a significantly lower number of tumour metastases in the lungs compared to controls, after challenge with the B16-OVA melanoma. Similarly, syngeneic animals immunised with ScFv-engrafted SL containing OVA and either LPS or IFN-γ had a lower number of metastases (
A particular intriguing aspect of this study is that the apparent generation of CTL activity against the B16-OVA melanoma was not associated with tumour protection. This point is particularly evident with the SIINFEKL-SL vaccine that would be expected to generate only a CD8+ CTL response against OVA produced by the B16-OVA tumour cells. Despite the vaccine inducing a strong in vitro recall CTL response against B16-OVA tumour cells, no in vivo protection against the tumour was afforded by the immunisation. It is known that the B16-OVA melanoma line expresses very low levels of MHC class I, and consequently, is resistant to CTL lysis unless high avidity CTLs are used.14 The fact that splenocytes from mice immunised with DC targeting preparations of PMV or SL could lyse B16-OVA tumour cells after restimulation with tumour cells in vitro implies that high avidity CTLs can be generated against this tumour cell line. Presumably, such CTLs are either not generated, or are not effective in vivo. In fact, previous studies indicate that CD4+ rather than CD8+ T cells are effective against B16-OVA metastases, with CD4+ T cells with a cytokine profile characteristic of T helper 2 (Th2) cells being particularly effective.14 Furthermore, eotaxin dependent recruitment of eosinophils into the tumours was essential for tumour regression to be observed.14 To explore a possible role of CD4+ T cells-mediated eosinophil recruitment in the anti-tumour effects observed in this study, eotaxin knockout mice were immunised with ScFv-engrafted PMV. Our results show that compared to controls, eotaxin knockout mice exhibit a markedly reduced ability to inhibit the growth and metastasis of the B16-OVA tumour (
The modified PMV and SL system described herein offers a number of advantages over current strategies using DCs for tumour immunotherapy. Firstly, the system can deliver Ags directly to DCs in vivo, thus eliminating the need to isolate DCs from patients and to manipulate the cells ex vivo for use in immunotherapies. Secondly, a targeted or active liposome-mediated delivery of Ag to DC has the potential to deliver more Ag, and/or several different Ags, simultaneously, potentially stimulating a more effective immune response. The same approach could potentially deliver to DCs any Ag or immunostimulatory agent, such as “danger” signals, RNA, DNA, and cytokines, or combinations thereof, which cannot be easily achieved using Ags fused to DC targeting proteins.9,10 Thirdly, the approach is versatile and would be convenient to use clinically since potentially any DC targeting protein(s) possessing a histidine tag can be engrafted onto the modified PMV or SL to deliver specific tumour Ags or other agents to enhance tumour immunity in patients.
Having broadly described the invention and particular application thereof in the foregoing prototype studies, specific examples will now be given after detailing the materials and methods used therein. It will be understood by those of skill in the art that these examples are for illustrative purposes only and do not in any way limit the scope of the invention.
[3H]-Thymidine and 51Cr (Na51CrO4) were obtained from Amersham (Buckingham-shire, United Kingdom). Palmitoyl-oleoyl-phosphatidyl-choline (POPC), OVA (Grade II, purified by FPLC), LPS (from Escherichia coli serotype 0111:B4), Isopaque, Ficoll and β-mercaptoethanol were supplied by Sigma-Aldrich (Castle Hill, New South Wales, Australia). Phosphotidylethanolamine-polyethylene glycol-2000 (PE-PEG2000) was obtained from Avanti Polar Lipids Inc. (Alabaster). 2-(4,4-difluoro-5octyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero 3-phosphocholine (PC-BODIPY) and 5-(and -6)-carboxyfluorescein diacetate, succinimidyl ester, mixed isomers (CFSE) were purchased from Molecular Probes (Eugene, Oreg.). The chelator-lipid (NTA)3-DTDA, consisting of three nitrilotriacetic acid (NTA) head groups covalently linked to two ditetradecylamine (DTDA) chains was synthesized essentially as described,27 but with additional steps to covalently couple a NTA group onto each carboxyl group of the NTA-DTDA, to produce (NTA)3-DTDA. NiSO4 was used for all additions of Ni2+ to buffers.
Murine CD56 (clone 42.18, rat IgG2a) mAb was from the 6th Human NK Cell Workshop and the murine CD3 mAb (clone 145-2C11, Armenian hamster IgG) was purchased from PharMingen (San Diego, Calif.). Recombinant murine IFN-γ and GM-CSF were supplied by PeproTech Inc (Rockey Hill, New Jersey). Recombinant ScFv antibodies N418 (anti-CD11c) and NLDC145 (anti-DEC-205), each with a hexahistidine (6H) tag at the carboxy terminal and denoted CD11c-ScFv and DEC-205-ScFv, respectively, were produced using the baculovirus protein expression system and purified as described.16,28 Peptides were synthesised by the Biomolecular Resource Facility, John Curtin School of Medical Research (JCSMR), ANU, Canberra. The L2 peptide (GHHPHGHHPH), a sequence of ten amino acids found in the plasma protein histidine-rich glycoprotein, was used routinely to engraft control PMV and SL since it binds to Ni-(NTA)3-DTDA with high avidity and can block its non-specific binding to cells. The peptide SIINFEKL-6H, representing the immunodominant CTL epitope of OVA in H-2b mice (OVA residues 257-264), with hexahistidine tag attached was used for peptide Ag delivery to DCs.
Female or male C57BL6 mice (H-2b) 6-8 weeks of age were supplied by the Animal Breeding Establishment, (JCSMR, ANU), and C57BL6 eotaxin knockout mice (H-2b) (eotaxin−/−) were a gift from Dr Paul Foster, Division of Biochemistry and Molecular Biology (JCSMR), and were used to obtain lymphoid cells for in vitro assays, and in tumour growth studies in vivo. The highly metastatic murine B16-OVA melanoma [C57BL6 (H-2b)], an OVA-secreting tumour cell line was cultured at 37° C. in an atmosphere of 5% CO2 in RPMI 1640 medium (Gibco-BRL, Invitrogen, Melbourne, Australia) containing 10% fetal calf serum (FCS, Trace Biosciences, Noble Park, Victoria, Australia) and 0.5 mg/mL Geneticin (Invitrogen). Murine Foetal Skin Dendritic Cells (FSDC) [C57BL6-DBA/2J F1 (H-2b/d)] were cultured in the same medium but without Geneticin. Murine Long Term Culture Dendritic Cells (LTC-DC) [B10.A(2R) (H-2k/b)], isolated and cultured as described,29 were a gift from Dr H. O'Neill (School of Biochemistry and Molecular Biology, ANU).
Murine DC and T cells were isolated from the spleens of C57BL/6 mice. Briefly, splenocytes were isolated by digestion with Collagenase IV (Boerhringer Mannheim), followed by isolation of low density splenocytes by density gradient centrifugation using an Isopaque-Ficoll gradient. DCs were isolated by plastic adherence as described31 and then suspended in complete RPMI 1640 growth medium containing 10% FCS, 5×10−5 M β-mercaptoethanol, 100 IU/ml penicillin, 100 μg/ml neomycin, and 10 mM HEPES. For isolation of T cells, the spleens were dissociated into single cell suspensions, and after removing red cells by hypotonic lysis, the T cells were isolated using a nylon wool column.32
PMV from cultured cells were prepared by sucrose gradient centrifugation,30 and modified essentially as outlined.16,17 Liposomes used to modify PMV were prepared as follows: ethanolic solutions of POPC, (NTA)3-DTDA, LPS and PC-BODIPY (molar ratio 94:2:2:2); or POPC, (NTA)3-DTDA and PC-BODIPY (molar ratio 96:2:2), were mixed, dried under a stream of N2, then rehydrated in 100 μl PBS containing 60 μM Ni2+. Where indicated, as an alternative to LPS, either IFN-γ or GM-CSF (50 ng) was included in the rehydration buffer. Hydrated mixtures were sonicated (three times, 15 sec bursts) using a TOSCO 100 W ultrasonic disintegrator (Measuring and Scientific Ltd., London, UK) at maximum amplitude. Liposomes (100 μl) were mixed with 100 μl of B16-OVA cell-derived PMV (1×108 cell equivalents), before adding 15% PEG400 and diluting 10 times with PBS. The (NTA)3-DTDA- and cytokine-containing PMV were purified by size-exclusion chromatography,17 before engrafting with the appropriate ScFv.
Stealth Liposomes (SL) were prepared as follows: POPC, (NTA)3-DTDA, PE-PEG2000, LPS and PC-BODIPY (molar ratio 96:1:1:1:1); or POPC, (NTA)3-DTDA, PE-PEG2000 and PC-BODIPY (molar ratio 97:1:1:1) dissolved in ethanol were dried under a stream of N2, then rehydrated in 100 μl PBS containing 30 μM Ni2+ (total lipid 1 mM). For mixtures lacking LPS, IFN-γ or GM-CSF (50 ng) was included in the PBS. Lipid mixtures were sonicated and SL purified (as above). For functional studies the PC-BODIPY was omitted from all lipid mixtures.
Encapsulation of the immunodominant epitope of the OVA protein, SIINFEKL, into SL was attempted but proved difficult since this peptide has low solubility at the pH used to produce the SL and to engraft histidine-tagged ScFv (pH 7.4). However, a hexahistidine-tagged form of the peptide, SIINFEKL-6H, permitted efficient encapsulation and/or engraftment of the peptide onto (NTA)3-DTDA-containing SL. Binding studies using FACS analysis showed that CD11c-ScFv- or DEC-205-ScFv-engrafted SL containing SIINFEKL-6H could effectively target receptors on DCs in vitro (not shown). Thus, where indicated, SIINFEKL-6H (2 μM) was included to simultaneously engraft with ScFv. The efficient encapsulation of OVA into SL containing POPC, (NTA)3-DTDA and PE-PEG2000, was achieved by rehydrating the desiccated lipid mixture in PBS containing 0.1 mg OVA (1 mg/ml), followed by brief sonication. The (NTA)3-DTDA-containing PMV and SL were engrafted by incubating with the appropriate ScFv (200 μg/ml) for 1 hr at room temperature. The binding of engrafted PMV and SL to DCs was assessed by flow cytometry as previously described.7
In order to obtain highly fluorescent PMV for tracking studies PMV were reacted with fluorescein-isothiocyanate (FITC, Molecular Probes), engrafted with L2 or ScFv, and then injected into the hind footpad of mice. After 16 hrs the draining popliteal lymph node of each animal was harvested and used either for isolation of lymph node cells for two colour flow cytometric analysis after staining with biotinylated CD11c mAb and streptavidin-phycoerythrin (streptavidin-PE), or for confocal fluorescence imaging. For imaging, lymph nodes were fixed in 10% formalin, then embedded in paraffin, and cut into sections; the sections were then adhered onto slides and de-waxed. Slides were blocked by incubation with PBS plus 20% goat serum (PBS-goat serum) for 30 min at room temperature, before incubating with mAb N418 to CD11c in PBS-goat serum for 1 hr at room temperature. The slides were then washed extensively in water and stained with streptavidin-Rhodamine in PBS-goat serum. After further washing, the slides were analysed for fluorescein and Rhodamine fluorescence using a Radiance 2000 fluorescence confocal microscope (Bio-Rad, Richmond, California). Images were acquired by Kalman averaging of 30 successive laser scans, and processed using Bio-Rad Image software.
DCs were incubated with modified PMV or SL at 37° C. in complete medium for 4 hrs, and then washed to remove unbound PMV or SL, γ-irradiated (5000 rad), and aliquoted in growth medium (2×104 cells/200 μl/well) into a 96-well flat-bottom plate. Syngeneic T cells were added (2×104/well) and the cells co-cultured for 4 days, before assessing proliferation by measuring incorporation of [3H]-thymidine.14 The proportion of proliferating CD4+ and CD8+ T cells in Ag presentation assays was assessed by labelling the T cells with CFSE (5 μM) prior to co-culture with DCs as described.33 After 4 days co-culture cells were washed, stained with anti-mouse CD4 (clone L3T4)-Cy-Chrome (10 μg/ml), and anti-mouse CD8 (clone Ly-2)-PE (10 μg/ml), and analysed for CFSE-, Cy-Chrome-, and PE-fluorescence by flow cytometry.
Ag-specific CTL assays were performed similar to those described.34 Syngeneic C57BL6 mice were immunized intravenously (i.v.) with PBS (control), or ScFv-engrafted B16-OVA cell-derived PMV or SL bearing Ag (as indicated). At day 14 after immunization, spleens were removed and T lymphocytes (effector T cells) were isolated as above. The T cells were then suspended in complete growth medium and aliquoted into 24-well flat-bottom plates (ICN Biomedicals) at a concentration of 1×105 cells/well and co-cultured with 1×105 γ-irradiated (5000 rad) B16-OVA cells. After 5 days of co-culture, the cytolytic activity of the T cells was assessed in a standard 51Cr-release assay, as described.16
Mice were immunized by three i.v. tail vein injections given weekly, with PBS (control), or either ScFv-engrafted B16-OVA cell-derived PMV (2×105 cell equivalents), or SL (˜0.16 μg total lipid) bearing associated Ag (˜0.2 μg of OVA or 0.8 ng of SIINFEKL-6H), each suspended in a 200 μl volume of PBS. Two weeks after the last injection, the mice were challenged by the i.v. injection of 3×105 B16-OVA cells. At day 16 the lungs were removed and the number of tumour foci was counted visually under a dissection microscope. Alternatively, mice were immunised with ScFv-engrafted B16-OVA PMV 3, 6 and 9 days after i.v. injection of 1.5×105 B16-OVA cells.
Two types of liposome preparations were used to target tumour Ags to DCs (see
To determine whether liposomes prepared in this manner can be used to target tumour antigens to DCs, we first explored the ability of this system to target Ag to DCs in vitro. In this study we used the highly metastatic melanoma cell line, B16-OVA, as this line secretes low levels of OVA which can be used as a surrogate secreted tumour-specific Ag (Ref. 17), enabling OVA-specific immune responses to be assessed. The B16-OVA tumour line is largely resistant to OVA-specific CTLs unless high avidity CTLs are used.17 PMV (B16-OVA-derived) could be modified to contain incorporated (NTA)3-DTDA by fusion with synthetic liposomes composed of POPC, (NTA)3-DTDA, and PC-BODIPY (molar ratio 96:2:2). Also, (NTA)3-DTDA-containing SLs were produced from an appropriate mixture of lipids: POPC, PE-PEO2000, (NTA)3-DTDA, and PC-BODIPY (molar ratio 96:2:1:1). SLs preparations could be made to contain OVA, or the OVA CTL epitope, SIINFEKL. The (NTA)3-DTDA-containing PMV and SLs were engrafted with either a control hexahistidine-containing molecule (L2 peptide) or a hexahistidine-tagged ScFv against either CD11c or DEC-205. Since the modified membranes also contain PC-BODIPY as a fluorescent tracer, their targeting to DCs can be assessed by flow cytometry.
Incubation of long term culture DC (LTC-DC) with control-modified PMV (PMV-L2) increased the fluorescence intensity of the cells slightly (−2-fold above background), but their fluorescence after incubation with PMV engrafted with CD11c-ScFv (PMV-CD11c), or with DEC-205-ScFv (PMV-DEC-205), was 4-8-fold greater than control cells (
To establish that ScFv-engrafted PMV could target DCs in vivo, we injected mice subcutaneously into the hind footpad with fluorescein-labelled PMV engrafted with ScFv, and then examined cells isolated from the draining popliteal lymph node for fluorescein fluorescence by flow cytometry, or sections of the draining lymph node by confocal scanning laser microscopy, after PE staining each with a CD11c mAb as a DC marker. The results show that the injection of mice with L2-, CD11c-ScFv or DEC-205-ScFv-engrafted PMV results in a high level of CD11c-specific-fluorescence in a relatively small population (2-2.5%) of lymph node cells, thus identifying these as DCs, both by FACS analysis and fluorescence microscopy (
aPMV derived from B16-OVA melanoma cell line.
bSIINFEKL immunodominant class I MHC epitope with H-2b haplotype.
cControl hexahistidine-containing molecule for coupling to liposomes.
To determine whether Ag-bearing PMV and SL targeted to DCs can induce functional Ag presentation to T cells, we initially examined the ability of ScFv-engrafted PMV and SL to stimulate T cell proliferation in an Ag-presentation assay. Splenic DCs isolated from C57BL/6 mice were pulsed separately with B16-OVA-PMV, SL bearing SIINFEKL-6H, or SL bearing OVA, engrafted with either a control histidine-tagged peptide (L2) or with ScFv against CD11c and DEC-205. After the incubation, the cells were co-cultured with purified syngeneic T cells and then pulsed with [3H]-thymidine to assess the rate of T cell proliferation. Compared to control cultures, DCs exposed to PMV or SL (SIINFEKL-6H or OVA bearing) engrafted with CD11c-ScFv induced substantially higher levels of T cell proliferation. Even greater rates of proliferation were seen when the T cells were co-cultured with DC exposed to PMV or SL engrafted with a DEC-205 ScFv (
Interestingly, studies using CFSE-labelled T cells revealed that the ratio of proliferating CD4+ to CD8+ T cells was dependent on the Ag used. Thus, co-cultures of T cells with DCs which had been pulsed with DEC-205-engrafted PMV consisted of ˜60% CD8+ T cells and 40% CD4+ T cells (
Recent studies have demonstrated the importance of danger signals during Ag exposure and DC maturation9,10 in determining the type of immune response initiated by DCs. Although studies showed that liposomes can target Ag to DCs in vitro and induce T cell responses, previous in vivo studies suggest that for this approach to succeed in vivo, the co-delivery of danger signals to DCs is required. Thus, in order to deliver both Ag and inflammatory stimuli to DCs simultaneously, we produced Ag-bearing modified PMV and SL that contained incorporated LPS, IFN-γ, or GM-CSF. We found that up to 1% LPS could be included in the lipid mixture, and that PMV and SL could be made to incorporate the cytokines GM-CSF and IFN-γ with high efficiency, without significantly interfering with the ability of ScFv engrafted SL to target DCs in vitro, as assessed by binding studies using flow cytometry. Moreover, since GM-CSF induces the proliferation of FSDC in serum-free medium, and IFN-γ inhibits their proliferation in complete medium,17 FSDC proliferation assays were used to monitor cytokine entrapment in the SL with >85% of the GM-CSF and >75% of IFN-γ being found to be incorporated (not shown).
To determine whether DC-targeted PMV or Ag-containing SL could generate CTL responses in vivo, we immunised C57BL6 mice with preparations that either lacked or contained danger signals such as LPS, IFN-γ, or GM-CSF. We then isolated splenic T cells, restimulated the cells in vitro with γ-irradiated B16-OVA tumour cells, and assessed their cytolytic activity towards B16-OVA cells in a standard 51Cr-release assay. Representative lytic curves are shown in
For ease of comparison, the cytolytic activity of the various PMV and SL immunisation conditions are presented at the 25:1 effector to target ratio in
Mice immunised with the various B16-OVA preparations were examined for their ability to resist an i.v. challenge of B16-OVA tumour cells, with lung metastases being quantified 16 days following tumour cell injection. Compared to control mice, a much lower number of metastases was observed in mice immunised with PMV or OVA-bearing SL engrafted with ScFv and containing either LPS or IFN-γ (
To explore the effect of vaccination on pre-existing tumours, we injected a group of 6 mice with DEC-205-ScFv-engrafted PMV containing IFN-γ at 3 days after challenge with 1.5×105 B16-OVA tumour cells. Interestingly, vaccinated mice subsequently did not show any signs of tumour development, whereas a group of six control animals had to be euthanised at day 22 due to an increasing tumour burden in the lungs which contained an average of 250±37 tumour foci each.
The high proportion of proliferating CD44 T cells seen in Ag presentation assays (
In this example, we demonstrate that the invention can be used to target antigens of an infectious agent to DCs. BCG is a mycobacterium containing many of the antigens also present in the pathogen Mycobacterium tuberculi which is the cause of tuberculosis in humans. In the example to be described here, BCG mycobacteria were used instead of Mycobacterium tuberculi. BCG mycobacteria were grown in culture, heat-killed, and labelled [by reacting with a tracer 6-(fluoresein-5(and -6)-carboxamido)hexanoic acid succinimidyl ester] to allow tracking, before modifying to permit targeting to DCs. Thus, the heat-killed BCG was mixed with an appropriate amount of Ni-(NTA)3-DTDA, and briefly sonicated to permit incorporation of the chelator lipid into the BCG membrane vesicles containing the BCG antigens. Incorporation of the Ni-(NTA)3-DTDA into the BCG membranes then enabled engraftment of ScFv to either CD11c or DEC-205 to allow specific targeting to the CD11c and DEC-205 markers, respectively, on DCs.
The specific targeting is evident from the graphs comprising
Further experiments were conducted to verify that BCG preparations containing engrafted DC-targeting ScFv also enhance the immune response to BCG antigens when used as vaccines in animals. C57/BL6 mice were vaccinated intravenously with the engrafted BCG preparations using essentially the same vaccination regime as in Example 1 above. After 2-4 weeks the mice were sacrificed, their spleens removed for isolation of T cells and to assay for BCG-specific interferon-γ production. The results of an Elispot assay of interferon-γ production were obtained by culturing the T cells isolated from the spleens of the mice in the presence of heat-killed BCG for a period of three days before assaying the cultures for interferon-γ-producing cells. The results of these experiments are presented in
It can be seen from
It will be appreciated by one of skill in the art that many changes can be made to the methods and compositions exemplified above without departing from the broad ambit and scope of the invention.
The term “comprise” and variants of the term such as “comprises” or “comprising” are used herein to denote the inclusion of a stated integer or stated integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required.
Any reference to publications cited in this specification is not an admission that the disclosures constitute common general knowledge in Australia.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003904513 | Aug 2003 | AU | national |
| PCT/AU04/01125 | Aug 2004 | AU | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10568939 | Jul 2006 | US |
| Child | 13729708 | US |
