Patent Abstract:
polypeptides derived from a proteolytically cleaved portion of the invariant chain of mhc class ii , termed clip , have been found to have immune modulatory properties . depending on the portions of clip administered , immune responses can be either enhanced or suppressed . in addition , these portions can be used to cause weakly immunogenic proteins more strongly immunogenic . the polypeptides can be used directly to modulate the immune response , as can antibodies directed to particular portions of the clip polypeptides . alternatively , polynucleotides encoding either the polypeptides of the antibodies can be administered to cause in situ generation of the immunomodulatory polypeptide or antibodies .

Detailed Description:
it is a discovery of the present inventor that clip polypeptide , a portion from the invariant chain , has dramatic modulatory effects on the immune system of mammals . when contacted with t lymphocytes , clip polypeptide can function as a superantigen , enhancing the activity of cytolytic t cells or b cells . for example , in the context of graft versus host disease ( gvhd ) clip can enhance autoreactive t lymphocyte - mediated tumor cell killing . similarly , clip variants containing the mhc class ii binding domain and the n - terminal flanking region also can enhance tumor cell killing . conversely , clip variants containing the mhc class ii binding domain and the c - terminal flanking region do not have such activity . moreover , it has been found that the clip polypeptide can be used to overcome mhc restriction . chimeric fusion polypeptides which comprise the mhc class ii binding site of clip permit the promiscuous recognition of antigens which are normally not recognized by target autoreactive t cells . thus chimeric fusion polypeptides can be made using clip , or truncated variants thereof , to modulate the immune response to the non - clip fusion partner . thus if an antigen is used , such as a viral antigen or a tumor - associated antigen such as her2 / neu , the immune response to that antigen can be increased . preferably , the clip fusion partner comprises the segment pvsp ( seq id no : 1 ) or pvsk ( seq id no : 11 ), preferably kpvsp ( seq id no : 1 ) or kpvsk ( seq id no : 11 ), and more preferably pksakpvsp ( seq id no : 1 ) or pkppkpvsk ( seq id no : 6 ). typically each fusion partner comprises at least 3 amino acids , and preferably at least 6 amino acids , and more preferably at least 9 amino acids . the fusion polypeptides can be formed by genetic engineering , synthetic chemistry , or by covalent bonding of portions of naturally occurring proteins . by judicious selection of the portion of clip utilized , immune response enhancement or suppression can be effected . it is believed that the n - terminal flanking region of the mhc class ii binding region of clip is stimulatory and the c - terminal region is suppressive . see fig1 . clip and the n - terminal and c - terminal flanking regions of clip from other mammalian species can also be used . polypeptides useful for stimulating or suppressing immune responses need not comprise an antigen . other biologically active proteins may be used as fusion partners , such as toxins , reporter proteins , carrier antibodies , and enzymes . macromolecules , such as polysaccharides , polyacrylamide , solid matrices , radiolabels , and fluorescent labels may also be conjugated or bound to the polypeptides . in addition , polypeptides which comprise all or portions of the naturally occurring clip molecule may be useful as suppressive or stimulatory molecules without attachment to other moieties . the polypeptides of the present invention can be administered to patients to modulate immune responses . preferably the patients are cancer patients . more preferably the patients are bone marrow transplant recipients . more preferably the patients are bone marrow transplant recipients who are also receiving cyclosporin . other patients who require modulation of immune responses , including those with hematological disorders , viral infections , and auto - immune diseases , such as lupus , can also benefit from polypeptide therapy . modulated immune responses include enhancing and suppressing either cell - mediated or humoral responses . the binding of clip to t cells may induce t helper cells which produce cytokines which promote b cells to make antibodies and proliferate . it is believed that the polypeptides of the invention interact with t cells to exert their effect , specifically with cd8 + t cells . such cells can be contacted ex vivo and reinfused to the patient . alternatively the polypeptide can be administered by any means known in the art such that the polypeptide reaches the t cells . this may be by intraperitoneal , intravenous , subcutaneous , or intramuscular injections . this may be by injestion of oral formulations . this may be by administration to the individual of a recombinant construct which encodes the polypeptide of the present invention . expression in vivo of the polypeptides may prove a more efficient means of delivery . liposomes or other particulate formulations may be used , comprising a carrier molecule , to protect and / or target the polypeptides or polynucleotides to the t cells . cells such as dendritic cells can be transfected ex vivo with such polynucleotides and administered to a patient to obtain expression of the polypeptides of the invention . thus the polypeptides of the present invention when suspended in a pharmaceutically acceptable carrier form a vaccine for inducing an immune response . the vaccine can further comprise immune adjuvants such as bcg which are known in the art . alternatively , the vaccine may be a genetic vaccine which comprises a polynucleotide encoding one or more of the polypeptides of the present invention . having determined the binding of clip polypeptides to α / β chains of the t cell receptor , this interaction can be used as a means of identifying useful drugs . compounds , whether small molecules , polymers , oligonucleotides , peptides , or derivatives of these , can be contacted with a clip polypeptide and an α / β t cell receptor . libraries of such molecules can also be screened . the effect of the compound on the binding interaction can be determined . thus compounds which inhibit , displace , or prevent binding of the two binding partners are candidate immunosuppressants . compounds which increase binding of the two binding partners are candidate immunostimulants . the binding assay can also be performed in the presence of other molecules , particularly mhc class ii molecules . the format of the assay can be varied as is convenient . one binding partner can be attached to a solid support , and the other partner can be labeled , such as with a radiolabel , fluorescent label , etc . the amount of the labeled partner which is found either remaining bound or unbound can be determined . antibodies can be used to quantitate the binding partner which is not attached to the solid support . the solid support may be , for example , a microtiter dish , or beads which are packed in a column . any means known in the art for performing such assays can be utilized . antibody preparations according to the present invention can be monoclonal or polyclonal . preferably they are monospecific and bind only to a portion of clip polypeptide which is either the mhc class ii binding domain , the n - terminal flank , or the c - terminal flank . such antibodies can be used in drug screening assays , for example , to quantitate the amount of binding partners bound . alternatively , such antibodies can be used therapeutically to inhibit the binding of endogenous clip to mhc class ii or to α / β t cell receptor . polynucleotides according to the present invention may have any sequence which encodes the desired polypeptide sequence . the full length clip may be encoded , or portions of clip , or either of those fused to another polypeptide may be encoded . the nucleotide sequence may comprise the natural sequence found in a mammal . see fig4 and 5 , for example . alternatively , any equivalent sequence ( by virtue of the degeneracy of the genetic code ) can be used . the polynucleotides desirably comprise a promoter to render transcription possible , and a translation initiation site . more preferably the promoter is regulatable , such as with an exogenous substance such as tetracycline . the polynucleotides can be present in a vector for introduction into cells . the polynucleotide may be integrated in the genome of cells which will be infused into a patient , for example . because cyclosporin induces the t cell population to which clip binds , clip binding can be used as a method of monitoring cyclosporin therapy , by determining the amount of , or changes in the amount of such t cell populations . t cells can be isolated from a patient receiving cyclosporin therapy and either assayed directly or fractionated to enrich for the population of cd8 + cells . the amount of cells binding to clip can be determined , for example using radiolabeled clip polypeptide . the cells can be incubated with clip polypeptide and the excess non - binding clip polypeptide can be removed . the amount of clip polypeptide bound to the cells can then be determined . alternatively , anti - clip antibodies can be used to label the cells which have clip bound . the labeled cells can be quantitated by any means known in the art . one particular method employs flow cytometry , as shown in fig2 . other methods can be used as is convenient . recent studies in our laboratory suggest that there are subsets of cells that can be separated based on their dependency for either the n - terminus or c - terminus of clip . thus , cells can be separated using clip polypeptides which have either the n - or , c - terminal portions . for example , such portions can be attached to a solid support and used to pan cells from a mixture of cells . this may be useful diagnostically to determine the status of a patient &# 39 ; s immune response . it may also be useful preparatively , to obtain relatively homogenous populations of t cells . the antitumor effect which has been observed using clip polypeptides alone , or fused to tumor antigens , appears to be enhanced by the administration of recombinant γ - interferon . on the other hand , α - interferon , although less effective than γ - interferon , also potentiates the antitumor activity of autologous gvhd . 24 such cytokines can be administered with clip polypeptides or polynucleotides encoding clip , simultaneously or sequentially . the polynucleotide of the present invention may be dna or rna , and may further comprise a sequence which directs the secretion of the encoded polypeptide from the cell . when the polynucleotide is dna , it can also be a dna sequence which is itself non - replicating , but which can be inserted into a replicating plasmid vector . the polynucleotide may be engineered such that it is not integrated into the host cell genome . alternatively , the polynucleotide may be engineered for integration into the chromosome , preferably the expression of the polypeptide will be regulatable . such regulatable gene expression systems having in vivo applicability are known in the art , and may be used in the present invention . for example , selective killing of transfected cells may be mediated by including in the polynucleotide or vector a gene sequence encoding a protein , such as hsv thymidine kinase . the thymidine kinase gene acts as a suicide gene for transfected cells if the patient is exposed to gancyclovir . thus , if expression of the encoded peptides of the invention is too high , gancyclovir may be administered to reduce the percentage of cells expressing the peptides . depending on the compound contained in the pharmaceutical compositions of the present invention , the length of the administration term may vary . for example , if the pharmaceutical composition comprises a naked dna sequence operatively encoding the polypeptide , cells incorporating the polynucleotide may produce the polypeptide for at least one month . alternatively , if transitory expression of the polypeptide is preferred , the composition of the invention may include a dna or rna sequence operatively encoding the polypeptide , whereby cells containing the dna or rna produce the polypeptide for less than about 20 days , usually less than about 10 days , and often less than 3 or 5 days ( felgner et al ., u . s . pat . no . 5 , 589 , 466 ). preferably , the compounds of the present invention are polypeptides . the polypeptides are preferably 30 amino acids or less , more preferably 20 amino acids or less , and comprise amino acid sequences derived from either the mhc class ii invariant chain or seb that enable the peptide to interact with both mhc class ii molecules and the t cell α / β receptor . as one of ordinary skill in the art is aware , conservative substitutions may be made in the amino acid sequence of the disclosed peptides without losing functionality . these substitutions are well known and are based upon the charge and structural properties of each amino acid . 22 such functionally equivalent peptides are also encompassed in the present invention . desirably the core amino acid sequence for modulating the immune response is not changed . in the instance that the pharmaceutical composition comprises a nucleic acid , it is also well known to those skilled in the art that , due to the degeneracy of nucleolide coding sequences , a number of different nucleic acid sequences may encode the same peptide . the nucleotide sequences of the present invention may also be altered by mutations such as substitutions , additions or deletions that provide for functionally equivalent peptide sequences . functionality can be determined as shown in fig1 for example . the compounds of the present invention can be synthesized by any means known in the art . for instance , both dna and rna can be prepared directly using automated nucleic acid synthesis equipment , pcr , cloning , or any combination of such techniques . when the polynucleotide is rna , it can be readily prepared from the corresponding dna template using an in vitro expression system known in the art . the present peptides may also be prepared using recombinant dna technology from the corresponding nucleic acids . alternatively , the peptides of the invention may be prepared using chemical synthesis . a helpful review of known peptide synthesis protocols and factors to consider when synthesizing a peptide for treatment purposes is given in u . s . pat . no . 5 , 589 , 458 ( jameson et al . ), which is herein incorporated by reference . the present invention provides pharmaceutical compositions that comprise the compounds of the invention and pharmaceutically acceptable carriers or diluents . suitable pharmaceutical carriers are described in remington &# 39 ; s pharmaceutical sciences , a . osol , a standard reference text in this field . the peptides of the present invention may be administered alone or in combination with other diagnostic , therapeutic or additional agents . therapeutic agents may include cytokines or lymphokines , such as il - 2 , α - interferon and interferon - γ . additional agents may include excipients such as flavoring , coloring , stabilizing agents , thickening materials , osmotic agents and antibacterial agents . the treatments of the present invention may be combined with conventional therapies , which may be administered sequentially or simultaneously . the pharmaceutical compositions of the present invention may be administered by any means that enables the active agent to reach the targeted cells . because peptides are subject to digestion when administered orally , parenteral administration , i . e ., intravenous , subcutaneous , intramuscular , would ordinarily be used to optimize delivery . the formulation of the present pharmaceutical composition will depend on the route of administration . aerosol medicaments may be used for intranasal or inhalation administration . in some cases , topical administration may be desirable . liposomal formulations may also be used . when the compound is a nucleic acid , the pharmaceutical composition may be injected directly into a target tissue as described in u . s . pat . no . 5 , 589 , 466 . alternatively , various strategies developed to accomplish cell or receptor - specific targeting of nucleic acids or vectors may also be used . the dosage of compound administered will vary depending upon pharmacodynamic characteristics of the compound , its mode and route of administration , the age , health , and weight of the recipient , the nature and extent of the cancer , and any concurrent treatments . usually , the dosage of peptide will be about 1 to 3000 milligrams per 50 kilograms of body weight ; preferably 10 to 1000 milligrams per 50 kilograms of body weight ; more preferably 25 to 800 milligrams per 50 kilograms of body weight . an effective dna or mrna dosage will generally be in the range from about 0 . 05 μg / kg to about 50 mg / kg . however , this dosage will vary in a manner apparent to these of skill in the art according to the activity of the peptide encoded by the nucleic acid and the efficiency of nucleic acid targeting and expression . other issues pertaining to dosage and administration will be apparent to one skilled in the art in view of the present disclosure . the above disclosure generally describes the present invention . a more complete understanding can be obtained by reference to the following specific examples which are provided herein for purposes of illustration only , and are not intended to limit the scope of the invention . truncated peptides from the rat mhc class ii invariant chain v 0 : ( sequence aa 82 - 103 pksakpvspmrmatpllmrpls ( seq id no : 1 )), v1 : aa 90 - 104 ( seq id no : 2 ), v2 : 86 - 100 ( seq id no : 3 ), v3 : 90 - 100 ( seq id no : 4 ) were synthesized by quality controlled biochemicals co . ( hopkinton , ma .) and purified by hplc . 15 , 23 the peptides (& gt ; 92 % purity ) were dissolved in rpmi 1640 prior to use . force loading of clip was accomplished by incubating the cells in 10 μm of the peptide for 1 hr . at 4 ° c . dose response studies revealed that maximal enhancement of lytic activity was achieved by pretreating the target cells with 1 - 10 μm of peptide . antibody was prepared to the clip peptide by quality controlled biochemicals co . the peptides were conjugated to keyhole limpet hemocyanin ( klh ). rabbits were immunized with the peptide - klh conjugate . the antibody was affinity purified using peptide conjugated sepharose matrix columns . truncated peptides from the human mhc class ii invariant chain ( human sequence aa 82 - 103 : pkppkpvskmrmatpllmqalp ( seq id no : 6 )) and the truncated variant containing the mhc class ii binding domain ( aa 91 - 101 : mrmatpllmqa ( seq id no : 8 )) were synthesized by quality controlled biochemicals co . ( hopkinton , ma .) and purified by hplc . 14 - 17 the peptides (& gt ; 92 % purity ) were dissolved in rpmi 1640 prior to use . force loading of clip was accomplished by incubating the cells in graded concentrations of the peptide for 2 hours at 4 ° c . dose response studies revealed that maximal enhancement of lytic activity was achieved by pre - treating the target cells with ≧ 1 μm of peptide . binding was confirmed by flow cytometry using the rabbit anti - human clip antibody . antibody was prepared to the clip peptide by quality controlled biochemicals co . the peptides were conjugated to keyhole limpet hemocyanin ( klh ). rabbits were immunized with the peptide - klh conjugate . the antibody was affinity purified using peptide conjugated sepharose matrix columns . fab fragments from the affinity purified antibody were prepared by limited papain digestion and sephadex g - 200 column chromatography . 19 the specificity of the affinity purified polyclonal antibody was confirmed by enzyme - linked immunosorbent assay ( elisa ) comparing its ability to recognize the longer truncated clip ( v 00 , seq id no : 5 ) and three shorter variants ( v1 , aa 82 - 103 ( seq id no : 6 ), v2 , aa 90 - 110 ( seq id no : 7 ) and v3 , aa 91 - 101 ( seq id no : 8 )) containing either flanking region or just the mhc class ii binding domain . the polyclonal antibody recognized both flanking regions and the mhc class ii binding domain but did not recognize an irrelevant peptide . moreover , addition of free excess clip or the variants but not the irrelevant peptide inhibited the elisa . murine monoclonal antibody to human clip was also obtained from dr . peter cresswell , yale university ( new haven , conn .). this monoclonal antibody recognized the n - terminal flanking region ( aa 81 - 87 ) on clip . 20 , 21 expression of mhc class ii determinants and clip were assessed flow cytometrically . the cells were stained with either murine anti - human mhc class ii antibodies or the rabbit anti - clip antibody for 1 hr . at 4 ° c ., washed 2 × in phosphate buffered saline and counter stained with fitc conjugated sheep anti - mouse igg ( absorbed with rat igg ; sigma chemical co ., st . louis , mo .) or fitc conjugated goat anti rabbit igg ( sigma chemical co .) for 1 hr at 4 ° c . as previously described . 13 , 18 as controls , the cells were incubated with normal mouse serum or rabbit prebleed igg followed by counter staining with the fitc conjugated secondary reagents . after washing 2 × in phosphate buffered saline , the cells were analyzed on an coulter epics 752 flow cytometer . we first evaluated whether clip in rats is recognized by the autoreactive t cells associated with csa - induced syngeneic gvhd by comparing the lysis of target cells after various pretreatment conditions . pretreatment of the pha lymphoblast target cells with antibody to clip completely blocked lysis mediated by the csa induced autoreactive t cells ( table 1 ). moreover , forced loading of clip onto the target cells markedly enhanced their susceptibility to recognition and lysis . purification of the cd8 + vβ8 . 5 + effector t - cell subset yielded comparable results . spleen cells from control , non csa - treated animals did not mediate significant lysis even when clip loaded target cells were used ( data not shown ). since clip contains an mhc class ii binding domain and flanking regions that extend beyond the peptide binding groove of mhc class ii molecules , a series of studies was undertaken evaluating truncated variants of rat clip . 15 , 23 as shown in fig5 force loading variant 2 ( seq id no : 3 ) containing the flanking regions defined by amino acids 86 - 91 markedly increased the susceptibility of the target cells to lysis mediated by the csa induced autoreactive t lymphocytes . force loading variant 1 ( seq id no : 2 ) containing flanking region defined by amino acids 99 - 104 inhibited recognition of the target cells presumably due to the displacement of endogenously expressed native clip . force loading variant 3 ( seq id no : 4 ) that primarily contains the mhc class ii binding domain modestly inhibited lysis of the target cells . although the unfractionated effector t cells appeared to preferentially recognize variant 2 , clonal analysis by limiting dilution cultures revealed that in addition to cd8 + vβ8 . 5 + t cells ( confirmed by rt - pcr 18 ) that preferentially recognized clip variant 2 , a subpopulation of autoreactive t cells could be isolated that selectively recognized variant 1 . the autoreactive t cells are highly restricted to a vβ tcr element ( vβ8 . 5 ) that , in mice , defines a population of cells that is responsive to the superantigen staphylococcal enterotoxin β ( seb ) ( table 2 ). 18 based on the fact that clip can modify the t cell response to this superantigen , 17 seb was assessed for its ability to inhibit the recognition of target cells by syngeneic gvhd autoreactive lymphocytes . pretreatment of the effector t lymphocytes with seb for one hour at 4 ° c . completely inhibited their ability to recognize and lyse the target cells . comparatively , pretreatment of the target cells with this superantigen was ineffective at preventing recognition and lysis . studies were undertaken to characterize the effector cell population that mediated the autocytotoxicity . the results showed that depletion of cells expressing the α / β t cell receptor and the cd8 cell surface determinant eliminated the ability of pbmc from patients with autologous gvhd to lyse pretransplant lymphoblasts . depletion of the cd4 subset of cells had only a minimal effect . in one patient , however , autocytoxic function was significantly eliminated (& gt ; 70 %) when the pbmc were depleted of either cd4 or cd8 cells . these results suggest either both cd4 + and cd8 + were required for killing or that the effector cell in this single patient expressed both cell surface accessory molecules . a series of antibody blocking studies was also performed in order to identify the antigen or restricting element recognized on the target cell by the autoreactive lymphocytes . the pretransplant lymphoblasts and the t47d breast cancer cell line were pretreated with 51 cr and monoclonal antibodies to either mhc class i or mhc class ii determinants for one hour at 4 ° c . the cells were washed in rpmi 1640 prior to use as targets in the 51 cr release assay . the results detailed in table 3 show that pre - treatment of both target cells with antibody to mhc class ii determinants significantly blocked lysis mediated by the pmbc from patients with autologous gvhd . on the other hand , mhc class i antibodies were ineffective . a series of studies was undertaken to determine whether clip was involved in the recognition of mhc class ii determinants by the autologous gvhd effector t cells . initially , the affinity purified antibody to clip was assessed for its ability to block lysis mediated by the autoreactive t cells derived from patients with autologous gvhd . pretransplant lymphoblasts and t47d cells were labeled with 51 cr and with ( 1 . 5 μg ) rabbit antibody to clip ( fab ) or prebleed igg for 1 hr at 4 ° c . prior to use as targets in a 51 cr release assay ( table 4 ). in every patient tested , lysis of pretransplant lymphoblasts and the t47d cell line was completely blocked by pretreatment of the target cells with the affinity purified anti - clip antibody . blocking of lysis (& gt ; 95 % reduction ) was confirmed in three patients using a murine monoclonal antibody to human clip that recognizes the n - termal flanking region ( aa 81 - 87 ). 20 , 21 moreover , addition of free excess clip ( 10 μm ) but not an irrelevant peptide to the assay specifically inhibited the antibody from blocking recognition ( data not shown ). on the other hand , anti - clip antibody pretreatment of target cells did not block lysis mediated by allospecific cytolytic t cells sensitized in a mixed lymphocyte response ( n = 3 , mean ± s . d . 27 . 3 ± 6 . 2 % specific lysis of control mouse ig treated target cells versus 25 . 9 ± 5 . 4 % specific lysis of anti - clip treated target cells at a 75 : 1 effector : target ratio ). expression of clip and mhc class ii determinants on the lymphoblasts and on the human t47d tumor cell line was assessed flow cytometrically . as shown in fig2 approximately 25 % of the mhc class ii positive lymphoblasts expressed significant levels of clip as detected by staining with the anti - clip antibody . the remainder of the lymphoblasts showed minimal staining with the anti - clip antibody indicating low expression of clip . forced loading of clip ( 1 μm ) not only resulted in an increase in the relative intensity of staining of the population but also led to a two to threefold increase in the number of cells that intensely stain with the anti - clip antibody ( data not presented ). comparatively , the t47d cells which also expressed mhc class ii determinants , showed significant staining with the anti - clip antibody . clip expression on the tumor cell line as detected flow cytometrically , was more homogeneous compared to the lymphoblasts . since only a fraction of the autologous pha blast cells expressed significant levels of clip , studies were undertaken to assess whether force loading of this peptide onto the target cells enhances their ability to be recognized and lysed by the autoreactive t lymphocytes . pretransplant lymphocytes stimulated with pha were incubated for 2 hours at 4 ° c . with 1 μm of clip and washed three times in rpmi 1640 prior to use as target cells in a 5 cr release assay . the results in table 5 show that force loading of clip onto the pha lymphoblast target cells significantly enhanced their susceptibility to lysis mediated by the autologous gvhd associated effector t cells . lysis was enhanced two - fold after force loading of clip . similarly , as shown in table 5 , lysis of the human t47d cell line by the autologous gvhd effector t cells was also enhanced by force loading of clip . in contrast , loading an irrelevant mhc class ii binding peptide did not enhance lysis . recent studies in our laboratory show sgvhd effector cells in rats have antitumor activity in vivo , achieving about a 1 - 2 log kill of crl1662 myeloma cells . thus , the magnitude of the immunologic antitumor activity generated by sgvhd appears to be similar to that produced by allogeneic gvhd . 26 since sgvhd has little toxicity , enhancement the antitumor activity of this syndrome was examined for potential increases in therapeutic efficacy in vivo . nylon wool nonadherent spleen cells ( 50 × 10 6 ) from lou m animals with syngeneic gvhd were adoptively transferred into secondary lou m recipients ( irradiated , bone marrow reconstituted ) challenged with 2 . 5 × 10 4 crl 1662 myeloma cells . animals were treated with gamma - interferon ( 50 , 000 u / d ), il - 2 ( 10 , 000 u / d ), or a combination for ten days . survival was assessed and log tumor cell kill was estimated from dose response studies ( see table 6 ). one approach therefore was to amplify the autoreactive effector cells by the administration of il - 2 . in fact , high - dose il - 2 ( 50 , 000 - 100 , 000 u / d ) markedly exacerbates the clinical autoimmune syndrome in animals , leading to the death of all the animals treated with csa and il - 2 . 27 , 28 on the other hand , both interferon - γ 25 and interferon - α enhance the antitumor effect of sgvhd by 1 - 2 logs in the rat model , with cure of about half of animals given 5 × 10 3 tumor cells . this activity of the interferons in sgvhd appears to be mediated through increasing the expression of mhc class ii determinants on the tumor , as the interferons have no direct activity on their own in this animal model . moreover , resolution of the tumor was associated with the development of tumor - specific immunity as the rats were immune to rechallenge with the tumor after resolution of the sgvhd . although high - dose il - 2 ( 50 - 100 , 000 u / d ) markedly augments the severity of sgvhd , the addition of low - dose il - 2 to interferon produces significant enhancement of antitumor activity without an apparent increase in toxicity . 27 , 28 low - dose ( 5 - 10 , 000 units / d ) il - 2 alone has no immunomodulatory effects on csa - induced sgvhd . this dose of il - 2 , however , appears to have an additive effect when used in combination with interferon - γ , increasing the tumor cell kill by 1 - 2 logs compared to interferon - γ alone . these data suggest that the antitumor activity of csa - induced sgvhd can be enhanced by amplifying the autoreactive effector t cells and by upregulating the target antigen ( mhc class ii determinants ) on the tumor cells , thereby potentiating tumor cell recognition and destruction . we characterized the regions of clip that are required for the promiscuous recognition of mhc class ii determinants . the results from our studies reveal several important concepts . first , promiscuous recognition of mhc class ii determinants occurs at the clonal level and is critically dependent on clip . pretreating both syngeneic and mhc disparate target cells with antibodies to mhc class ii determinants ( but not mhc class i antigens ) or to clip blocked killing of the target cells mediated by vβ8 . 5 + cd8 + t cell clones established from animals with auto gvhd . second , recognition of the mhc class ii determinants by the autoreactive t cells requires both the mhc class ii binding domain and the n - terminal flanking region of clip . this n - terminal flanking region extends beyond the open termini of mhc class ii molecules and appears to interact near the staphylococcal enterotoxin b ( seb ) binding site of the vβ segment of the t cell receptor ( tcr ). this interaction strengthens the tcr - clip - mhc class ii complex , decreasing the off time , thus , maximizing recognition and lysis . our results also explain the restriction of the t cell repertoire to lymphocytes expressing the vβ8 . 5 tcr segment . third , vβ8 . 5 + cd8 + clones requiring this interaction were the pathogenic t cells in vivo confirmed in a local gvhr foot pad assay . injection of these cells in vivo resulted in histological changes ( dyskeratosis ) consistent with gvhd . we have identified the amino acid sequence on clip responsible for the interaction with vβ segment of the tcr . our studies reveal the sequence to be - kpvsp - ( residues 5 - 9 of seq id no : 1 ), although vsp is sufficient , and - pksakpvsp - ( residues 1 - 9 of seq id no : 1 ) works even better . target cells were loaded with the clip variants ( 10 um ) and evaluated for their ability to be lysed by syngeneic gvhd effector t cells . lytic activity was compared to control diluent treated target cells with enhancement representing at least a & gt ; 25 % increase in specific killing . r = mrmatplllmr ( residues 10 - 19 of seq id no : 1 ) which is the # rat mhc class ii binding domain . the corresponding human sequence is r = mrmatpllmq ( residues 10 - 19 seq id no : 5 ). the human corresponding n - flanking region is pkppkpvsk ( residues 1 - 9 of seq id no : 6 ). the human c - terminal flanking region is alpmgalpqg ( residues 20 - 29 of seq id no : 5 ). the rat c - terminal flanking region is plsmdnmlqa ( residues 20 - 29 of seq id no : 1 ). studies to evaluate the ability of peptides from the mhc class ii invariant chain to augment tumor cell recognition in the auto gvhd setting were initiated . our results clearly indicate that clip can enhance autoreactive t lymphocytes mediated tumor cell kill . following induction of auto gvhd , animals were challenged intraperitoneally with 2 . 5 × 10 4 crl1666 tumor cells ( mhc class ii +). subsequently parent clip , or two truncated variants ( v1 : mhc class ii domain plus c - terminal flanking region ; v2 : mhc class ii domain plus n - terminal flanking region ) were administered intraperitoneally ( 100 μg ). animals treated with the parent peptide ( 2 / 3 ) or variant v2 ( 3 / 3 ) survived beyond 50 days . in contrast , animals receiving the control diluent or variant v1 all succumbed to tumor growth by day 25 . previous tumor cell dose response studies suggest our results are consistent with an additional 1 - 2 log tumor cell kill . importantly , these peptides did not significantly enhance the clinical manifestations of auto gvhd . interestingly , the activity of the peptides in the tumor model paralleled the clip specificity of the effector t cells summarized above . we evaluated whether addition of the - kpvsp - peptide fragment could potentiate the recognition of target cells expressing another mhc class ii binding peptide by the syngeneic gvhd effector t cells . the bn allopeptide ( sequence identified in fig3 ( seq id no : 14 )) from bn strain rats that binds to lewis rat mhc class ii antigens was modified by the addition of the kvsp fragment ( seq id no : 1 ). the bn allopeptide ( derived from mhc class i molecules ) is one of the peptides conferring allorecognition of bn rats by lewis strain animals . lewis target cells were loaded with either the parent bn allopeptide or the chimeric construct and evaluated for their susceptibility to killing mediated by 15 syngeneic gvhd effector clones . as shown in fig3 there was minimal to no recognition of target cells loaded with the unmodified bn allopeptide . in contrast target cells loaded with the chimeric peptide were effectively lysed by the autoreactive t cell clones . addition of the kpvsp ( seq id no : 1 ) fragment potentiated recognition of the target cells overriding restriction normally conferred by the mhc class ii allopeptide complex animals were immunized ( 2 ×, subcutaneous ) with the chimeric construct . the animals received bn skin grafts . control animals receiving diluent rejected the bn skin grafts were a survival of 13 days . skin graft survival , however , was only 8 - 9 days in the animals immunized with the chimeric construct suggesting that immunity was heightened . 1 . hess , a . d . syngeneic / autologous graft - vs - host disease : mobilization of autoimmune mechanisms as antitumor immunotherapy . cancer control 1 : 201 , 1994 . 2 . hess , a d . autologous graft - versus - host disease : a novel approach for antitumor immunotherapy . human immunology 34 : 219 , 1992 . 3 . jones r j , vogelsang g b , hess a d , farmer e r , mann r b , geller r b , piantadosi s . santos , g w . induction of graft - versus - host disease after autologous bone marrow transplantation . lancet 1 : 754 , 1989 . 4 . hess a d , horwitz l r , beschorner w e , santos g w . development of gvhd - like syndrome in csa - treated rats after syngeneic bmt . j . exp . med . 161 : 718 , 1985 . 5 . jenkins m k , schwartz r h , pardoll d m . effects of cyclosporine a on t cell development and clonal deletion . science 241 : 1655 , 1988 . 6 . geller r b , esa a h , beschorner w e , frondoza c g , santos g w , hess a d . successful in vitro graft - 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