Patent Abstract:
a method for constructing stable bioactive fusion proteins of the difficult to express tum or necrosis factor superfamily , and particularly members cd40l and rankl / trance , with collectins , particularly pulmonary surfactant protein d is described . single trimers of these proteins lack the full stimulatory efficacy of the natural membrane forms of these proteins in many cases . the multimeric nature of these soluble fusion proteins enables them to engage multiple receptors on the responding cells , thereby , mimicking the effects of the membrane forms of these ligands . for cd40l - spd , the resulting protein stimulates b cells , macrophages , and dendritic cells , indicating its potential usefulness as a vaccine adjuvant . the large size of these fusion proteins makes them less likely to diffuse into the circulation , thereby limiting their potential systemic toxicity . this property may be especially useful when these proteins are injected locally as a vaccine adjuvant or tumor immunotherapy agent to prevent them from diffusing away . in addition , these and other tnfsf - collectin fusion proteins present new possibilities for the expression of highly active , multimeric , soluble tnfsf members .

Detailed Description:
multimeric : as used herein the term multimeric refers to a multimer of a polypeptide that is itself a trimer ( i . e ., a plurality of trimers ). functional equivalent : herein refers to a sequence of a peptide or polypeptide that has substantial structural similarity and functional similarity to another such sequence . modifications : herein refers to point changes involving single amino acids , wherein the functionality is altered , without appreciably altering the primary sequence or primary structure of a peptide or polypeptide . amino acid : all amino acid residues identified herein are in the natural l - configuration . in keeping with standard polypeptide nomenclature , j . biol . chem . 243 : 3557 - 59 , ( 1969 ), abbreviations for amino acid residues are as shown in the following table of correspondence : it should be noted that all amino acid residue sequences are represented herein by formulae whose left to right orientation is in the conventional direction of amino - terminus to carboxy - terminus . furthermore , it should be noted that a dash at the beginning or end of an amino acid residue sequence indicates a bond to a radical such as h and oh ( hydrogen and hydroxyl ) at the amino - and carboxy - termini , respectively , or a further sequence of one or more amino acid residues up to a total of about fifty residues in the polypeptide chain . base pair ( bp ): a partnership of adenine ( a ) with thymine ( t ), or of cytosine ( c ) with guanine ( g ) in a doable stranded dna molecule . constitutive promoter : a promoter where the rate of rna polymerase binding and initiation is approximately constant and relatively independent of external stimuli . examples of constitutive promoters include the cauliflower mosaic virus 35s and 19s promoters described by poszkowski et al ., embo j ., 3 : 2719 ( 1989 ) and odell et al ., nature , 313 : 810 ( 1985 ). enzyme : a protein , polypeptide , peptide rna molecule , or multimeric protein capable of accelerating or producing by catalytic action some change in a substrate for which it is often specific . expression vector : a dna sequence that forms control elements that regulate expression of structural genes when operatively linked to those genes . expression : the combination of intracellular processes , including transcription and translation undergone by a structural gene to produce a polypeptide . insert : a dna sequence foreign to the rdna , consisting of a structural gene and optionally additional dna sequences . nucleotide : a monomeric unit of dna or rna consisting of a sugar moiety ( pentose ), a phosphate , and a nitrogenous heterocyclic base . the base is linked to the sugar moiety via the glycosidic carbon ( 1 ′ carbon of the pentose ) and that combination of base and sugar is a nucleoside . when the nucleoside contains a phosphate group bonded to the 3 ′ or 5 ′ position of the pentose it is referred to as a nucleotide . operatively linked or inserted : a structural gene is covalently bonded in correct reading frame to another dna ( or rna as appropriate ) segment , such as to an expression vector so that the structural gene is under the control of the expression vector . polypeptide and peptide : a linear series of amino acid residues connected one to the other by peptide bonds between the alpha - amino and carboxy groups of adjacent residues . promoter : a recognition site on a dna sequence or group of dna sequences that provide an expression control element for a gene and to which rna polymerase specifically binds and initiates rna synthesis ( transcription ) of that gene . inducible promoter : a promoter where the rate of rna polymerase binding and initiation is modulated by external stimuli . such stimuli include light , heat , anaerobic stress , alteration in nutrient conditions , presence or absence of a metabolite , presence of a ligand , microbial attack , wounding and the like . spatially regulated promoter : a promoter where the rate of rna polymerase binding and initiation is modulated in a specific structure of the organism such as the leaf , stem or root . examples of spatially regulated promoters are given in chua et al ., science , 244 : 174 - 181 ( 1989 ). spatiotemporally regulated promoter : a promoter where the rate of rna polymerase binding and initiation is modulated in a specific structure of the organism at a specific time during development . a typical spatiotemporally regulated promoter is the epsp synthase - 35s promoter described by chua et al ., science , 244 : 174 - 181 ( 1989 ). temporally regulated promoter : a promoter where the rate of rna polymerase binding and initiation is modulated at a specific time during development . examples of temporally regulated promoters are given in chua et al ., science , 244 : 174 - 181 ( 1989 ). protein : a linear series of greater than about 50 amino acid residues connected one to the other as in a polypeptide . recombinant dna molecule : a hybrid dna sequence comprising at least two nucleotide sequences not normally found together in nature . selective genetic marker : a dna sequence coding for a phenotypical trait by means of which transformed cells can be selected from untransformed cells . structural gene : a dna sequence that is expressed as a polypeptide , i . e ., an amino acid residue sequence . synthetic promoter : a promoter that was chemically synthesized rather than biologically derived . usually synthetic promoters incorporate sequence changes that optimize the efficiency of rna polymerase initiation . this invention discloses the production of tnfsf proteins as multimeric ( i . e ., many trimers ) ligands fused onto a trimeric , branched protein backbone . collectin molecules are ideal for this purpose because they are formed from many trimeric , collagenous arms linked to a central hub by disulfide bonds . of the collectins , pulmonary surfactant protein d ( spd ) was chosen initially because it is a homopolymer encoded by a single gene , unlike c1q and surfactant protein a , which are composed of two different protein subunits . in addition , recombinant spd has been successfully expressed in vitro in reasonable yield [ crouch , 1994 ], and a peptide containing the “ neck ” region of spd was shown to spontaneously trimerize in solution [ hoppe , 1994 ]. consequently , extracellular domains of human and murine cd40l were substituted for the carbohydrate recognition domain of pulmonary surfactant d ( spd ) to create a four - armed molecule ( three peptide chains per arm ) with cd40l at the end of each arm . this molecule is named cd40l - spd . in addition , because spd tends to stack into higher order aggregates with up to 8 molecules associated at the hub [ crouch ], even greater degree of multimerization can occur [ lu , 1993 ]. cd40l - spd therefore mimics the expression of cd40l by an activated t cell in that it presents a multivalent complex similar to membrane - bound cd40l . while remaining soluble , cd40l - spd equals membrane cd40l in its range of activities . cdnas of exposed human and murine cd40l , removed from cell membranes , were cloned by pcr by well - known methods . murine surfactant protein d was cloned by hemi - nested pcr from murine lung mrna ( clonetech ). cdna was prepared using superscript ii reverse transcriptase ( mmlv reverse transcriptase containing mutations in the rnase h region of the gene , thus eliminating rnase h activity , life technologies , gaithersburg , md .) and random hexamers as primers . pcr primer sequences were as follows ( the underlined bases indicate restriction endonuclease sites for cloning into the vector ): because the murine spd sequence of the 5 ′ untranslated region containing the ribosomal binding site was unknown when this work was started [ motwani , 1995 ], a primer ( rmspd5 ) was designed based on the available rat sequence [ shimizu , 1992 ] which extended the 5 ′ end with rat sequence ( shown in bold ) along with an added nhe i site ( underlined ). to create the cd40l - spd fusions , overlap pcr was used . murine spd was amplified by nested pcr using mspd5 and mspd3ext for the first round of 30 cycles . the product was diluted 1 : 1 , 000 and 1 μl was amplified for another 30 cycles using rmspd5 and cd40l / spd3 , where the 3 ′ half of cd40l / spd3 is a reverse primer for spd c - terminal to the neck region ( deleting the crd ) and the 5 ′ half of cd40l / spd3 contains bases from the n - terminus of the extracellular portion of cd40l ( immediately adjacent to the transmembrane region ). similarly , the cd40l plasmid was amplified with spd / cd40l5 and cd40l3 , which contains a kpn i site ( underlined ). all of these pcrs were performed with pfu cloned polymerase ( stratagene ,) using hot start ( ampliwax , wax beads for hot start pcr , perkin - elmer ) and the thermocycling program : 94 ° c . for 2 . 5 min ; then 30 cycles of 94 ° c . for 10 sec , 43 ° c . for 30 sec , and 75 ° c . for 7 min . to form the chimeric construct , 1 μl of a 1 : 1 , 000 dilution of gel - purified products from the above reactions was combined and amplified with rmspd5 and cd40l3 . because pfu polymerase did not consistently yield the expected 1 . 62 kb overlap product , accutaq la dna polymerase ( a mixture of taq polymerase and a polymerase with 3 ′-& gt ; 5 ′ exonuclease activity for proofreading , sigma ) was used for this pcr , using the thermocycling program : 94 ° c . for 2 . 5 min ; then 30 cycles of 98 ° c . for 20 sec , 43 ° c . for 30 sec , and 68 ° c . for 10 min . the resulting product was digested with nhe i and kpn i , gel - purified , and ligated into the nhe i and kpn i sites in the expression plasmid , pcdna3 . 1 (+) ( invitrogen , carlsbad , calif .). dh5 e . coli were transformed with the construct and plasmid dna was purified either by double banding in ethidium bromide - cscl gradients or by anion exchange resin ( qiagen ). to form the t147n - cd40l - spd construct , the same approach was used except that the cd40l coding region was taken from the expression plasmid for t147n - cd40l [ kornbluth ]. the amino acid sequence at sequence at the junction between spd and cd40l is . . . kaalfpdg / hrrldkie . . . ( seq id no : 16 ) where the c - terminal portion begins the sequence for cd40l . to form mcd40l - spd , a similar approach was taken except that primers spd / mcd40l5 , mcd40l / spd3 , and mcd40l3 were used for amplifications involving murine cd40l sequences . the amino acid sequence at the junction between spd and murine cd40l is . . . kaalfpdg / hrrldkve . . . ( seq id no : 17 ), where the c - terminal portion begins the sequence for murine cd40l . both dna strands of each construct were sequenced to confirm that the constructs were correct . in other experiments , an entirely humanized construct , consisting of human cd40l fused to human spd , was constructed ( data not shown ). spleen cells from c3h / hej mice were stimulated with 5 μg / ml concanavalin a and 10 ng / ml il - 2 ( sigma ) for 8 hours ( 31 ). mrna was isolated using the micro fasttrack microfasttrack kit ( reagents for isolating messenger rna , invitrogen ). cdna was prepared using superscript ii reverse transcriptase ( life technologies ) and random hexamers as primers . pcr primer sequences were as follows ( where the underlined bases indicate restriction endonuclease sites for cloning into the vector ): the extracellular portion of rankl / trance was cloned by nested pcr . in the first round of pcr , 5mrankl - ext and 3mrankl - ext were used with pfu cloned polymerase ( stragene ) using the thermocycling program : 94 ° c . for 2 . 5 mm ; then 30 cycles of 94 ° c . for 10 sec , 50 ° c . for 30 sec , and 75 ° c . for 2 mm . the product was diluted 1 : 1 , 000 and 1 μl was amplified for another 30 cycles using 5mrankl - int and 3mrank - int , which contain an xho i site and a not i site respectively . the resulting product was digested with xho i , blunt - ended with t4 dna polymerase , then digested with not i and gel - purified . the cd40l - spd expression plasmid described above was digested with msc i and not i and gel purified . then the rankl / trance sequence was ligated into this vector in frame with the spd coding sequence . the amino acid sequence at the junction between spd and rankl / trance is . . . kaalfpdg / raqmdpnr . . . ( seq id no : 22 ), where the n - terminal portion is from spd and the c - terminal portion is the extracellular sequence of rankl / trance . both dna strands of each construct were sequenced to confirm that the constructs were correct . dg44 ( a line of ch0 - k1 cells deficient in dihydrofolate reductase ( dhfr )) ( 32 ) and pchip ( a plasmid containing the hamster dhfr minigene ) ( 33 ) were gifts from dr . lawrence chasin , columbia university , new york , n . y . dg44 cells were cultured in α - mem consisting of ribo - and deoxynucleoside - free α - mem ( biowhittaker , walkersville , md .) supplemented with 200 μm l - glutamine , 10 % fetal bovine serum ( fbs ) and 10 μg / ml each of adenosine , deoxyadenosine , and thymidine ( sigma ). all cell cultures described were negative in a mycoplasma rrna assay ( gen - probe , san diego ). dg44 cells in six - well plates were transfected by the method of okayama and chen (( 34 ) with 10 μg of expression plasmid and 0 . 05 μg of pchip ( 200 : 1 ratio ). after two days , the transfected dg44 were trypsinized and transferred to 100 mm plates . at this point , the media was switched to α - mem which differs from α - mem in that dialyzed fbs ( hyclone systems , logan , utah ) was used and no nucleoside supplements were added . only cells containing the dhfr minigene were able to grow in α - mem , and colonies were selected after 10 days , cloned using cloning rings , and transferred to 12 . 5 cm 2 flasks . clones were selected for expansion using an elisa to screen for the production of either raurine or human cd40l ( see below ). using the method described by kingston et al . ( 35 ), escalating doses of methotrexate were used to amplify the transfected genes over a period of 6 - 14 months until the cells grew well in 80 μm methotrexate . each expressing clone was re - cloned once or twice more in order to select the highest expressing cells . selected clones were adapted for growth in nucleoside - free ultracho media ( biowhittaker ) supplemented with 50 - 100 μg / ml ascorbic acid and 50 μm methotrexate ( sigma ). the non - adherent population was further adapted for suspension growth in roller bottles . in some experiments , the cells were adapted from α - mem to cho - s - sfm ii media ( life technologies ) supplemented with ascorbic acid and 50 μg / ml l - proline . to assay for correctly folded cd40l , wells of a maxisorb 96 - well plate ( microtitre plates for absorbing antibodies , nunc ) were coated overnight at 4 ° c . with 50 μl of carbonate - bicarbonate , ph 9 . 40 buffer containing 0 . 5 μg / ml 24 - 31 anti - human cd40l mab ( ancell ) or mr1 anti - murine mab ( bioexpress , lebanon , n . h .). wells were blocked with 3 % bovine serum albumin ( bsa ) in pbs . 100 μl samples were added to the wells either neat or diluted in a dilution buffer consisting of 1 % bsa , 0 . 9 % nacl , 50 mm tris ph 7 . 40 , and 0 . 1 % peroxide - free tween 20 ( sigma ). after shaking for 2 h at 600 rpm , a plate washer was used to wash the plate four times with 0 . 9 % nacl , 50 mm tris ph 7 . 40 , and 0 . 1 % peroxide - free tween 20 . then , 100 μl of diluent buffer containing 1 μg / ml biotinylated 24 - 31 anti - human cd40l mab ( ancell ) or mr1 anti - murine cd40l mab ( pharmingen , san diego , calif .) was added to each well and again shaken for 2 h . following another four washes , 100 μl of diluent buffer containing 1 μg / ml of streptavidin - alkaline phosphatase ( jackson ) was added to each well and the plate was shaken for 1 hour . lastly , after another four washes , color was developed for 10 - 20 min using 100 μl / well of bluephos ( kierkegaard & amp ; perry ), stop solution was added , and the wells were read at 650 μm in a plate reader . conditioned ultracho media was filtered using a 0 . 2μ pes filter unit ( nalgene ) and stored at 4 ° c . for up to 3 months . a preliminary size fractionation was performed by ultrafiltration through a 100 kda - cutoff 76 mm membrane ( ym - 100 , millipore ) in a 400 ml stirred cell at 10 lbs / sq . inch pressure of argon . media was concentrated to about 10 ml , diluted to 100 ml with buffer , and again concentrated to 10 ml for a total of 3 cycles of ultrafiltration and buffer exchange . buffer was 50 mm bicine ( calbiochem ), adjusted to ph 9 . 0 with naoh ( about 32 mm na ), and 1 mm edta to prevent the activity of any metalloproteinase . using fplc equipment ( amersham - pharmacia ), the concentrate was filtered through a 0 . 45μ filter , placed into a 10 ml superloop , applied to a 10 × 30 mm column ( hr10 / 30 , amersham - pharmacia ) packed with fractogel so 3 650m ( em biosciences ), and eluted at 0 . 5 ml / min at 4 ° c . with a linear gradient of 0 - 500 mm nacl in buffer . as described by the manufacturer , the resolution of proteins on fractogel so 3 is enhanced by using a long , thin column geometry . fractions were collected and screened for human or murine cd40l by elisa . positive fractions were pooled , concentrated by ultrafiltration ( centriprep - 30 , millipore ), filtered through a 0 . 45μ filter , and applied to a superose 6 column ( amersham - pharmacia ) in phosphate - buffered saline . c3h / hej mice were euthanized by co 2 inhalation under a protocol approved by the animal subjects committee of the san diego va healthcare system . splenocytes were isolated by centrifugation over lympholyte - m ( accurate chemical & amp ; scientific corp ., westbury , n . y .) and b cells were isolated by negative selection using anti - cd43 immunomagnetic beads ( miltenyi biotec inc ., auburn , calif .). the resting b cells were suspended in dulbecco &# 39 ; s mem with 10 % fbs at a concentration of 1 × 10 6 / ml , and 100 μl was added to the wells of 96 - well flat - bottomed plates . 100 μl of dilutions of murine cd40l - spd in media or media alone were added to the wells , which were incubated in 8 . 5 % co 2 at 37 ° c . for 48 hours . then , 0 . 5 μci / well of 3 h - thymidine was added to each well , and the cells were collected 4 h later onto glass fiber filters using an automated cell harvester . a scintillation counter was used to determine the incorporated radioactivity . venous blood from consenting subjects was used as a source of human b cells under a protocol approved by the ucsd institutional review board . blood was collected into syringes containing 5 u / ml heparin and peripheral blood mononuclear cells ( pbmc ) were isolated by centrifugation over ficoll - hypaque . the cells were suspended at 2 × 10 5 / ml in rpmi 1640 containing 200 μm l - glutamine , 10 % fbs , 0 . 832 μm cyclosporin a ( sigma ), and 25 ng / ml human il - 4 ( r & amp ; d systems ) and incubated in 5 % co 2 at 37 ° c . as described by schultze et al . ( 36 ). at intervals , the cells were stained with cychrome - conjugated anti - cd19 and pe - conjugated anti - cd80 ( b7 - 1 ) monoclonal antibodies ( pharmingen ) and analyzed by flow cytometry . as previously described [ kornbluth ], monocytes were isolated from pbmc by adherence to fibronectin - coated plates , plated into 48 - well plates , and then cultured in rpmi1640 containing 2 μm l - glutamine and 10 % autologous serum for 7 - 10 days . monolayers of the matured cells ( about 2 × 10 5 / well ), termed monocyte - derived macrophages or mdm , were then washed in media and cultured in 1 ml / well rpmi 1640 containing 2 μm l - glutamine and 10 % heat - inactivated fbs . alternatively , dendritic cells ( dc ) were formed from monocytes by adding gm - csf and il - 4 to the culture media , and the resulting dc were used 6 days later . preparations of cd40l - spd were added to the wells as indicated . as a positive control , 100 ng / ml bacterial lipopolysaccharide ( lps ) from e . coli 0111 : b4 ( calbiochem ) was added . supernatants were collected 24 h later and analyzed for cytokine content using elisa ( r & amp ; d systems ). to express cd40l and other tnfsf members as stable , multimeric proteins , the coding region of the extracellular , c - terminal portion of cd40l was joined in - frame to the collectin , surfactant protein d ( spd ). the n - terminus of spd contains two cysteines which form the disulfide bonds necessary for the 4 - armed cruciate structure of the overall molecule [ brown - augsburger , 1996 ]. c - terminal to these cysteines in spd is a long triple - helical collagenous “ stalk ” which ends in the “ neck ” region that promotes the trimerization of each arm of the structure . immediately after this neck region , the coding sequence for the extracellular portion of cd40l was added , in place of the carbohydrate recognition domain ( crd ) of spd . the collectins were chosen as the framework for the multimeric construct because of their multi - subunit structure and the trimeric nature of their stalk regions . appropriateness of replacing the crd of a collectin with the extracellular region of a tnfsf member is further supported by structural studies of the two protein families . an analysis of the crd crystal structure of another collectin , acrp30 , indicated that it was structurally superimposable upon the crystal structures of the extracellular regions of cd40l , tnf , and fas [ shapiro , 1998 ]. the successful expression of the collectin - tnfsf fusion protein , cd40l - spd , indicates that other tnfsf members ( table i ) could be conjoined to spd in a similar manner and that other collectins besides spd ( table ii ) could be used as a protein framework instead of spd . because these molecules are formed entirely from naturally occurring proteins , the production of an immune response ( e . g ., antibodies ) to these fusion proteins is minimized . by deleting portions of the stalk region of the tnfsf proteins , additional constructs can be made which may be even less immunogenic . the coding regions for the extracellular portion of human cd40l , human t147n - cd40l , an inactive mutant of cd40l , or murine cd40l were joined to the neck region of murine spd , replacing the spd crd ( fig1 ). a cmv - driven expression plasmid for the construct was co - transfected with a dhfr minigene into dnfr - deficient cho cells . following selection in nucleoside - free media , expressing cho clones were amplified by culture in ascending doses of methotrexate . the resulting clones produced about 1 - 10 μg / ml of the fusion protein over a 3 day period in media containing fbs . clones were adapted for growth as suspension cells in two types of serum - free media . murine cho - spd produced in ultracho ( serum free powdered medium , biowhittaker ) was largely retained ( about 60 % as determined by elisa ) by a 1 , 000 kda cutoff ultrafiltration membrane ( pall corp ., port washington , n . y . ), consistent with a large multimeric complex formed by the stacking of the spd portion of the molecule . however , in cho - s - sfm ii ( serum free , low protein medium . life technologies ), nearly all elisa - detectable murine cho - spd passed through a 100 kda cutoff ultrafiltration membrane ( millipore ), suggesting that the protein was either folding incorrectly in this media or was being degraded by proteolysis . consequently , the purification method was optimized for the spent ultracho media . purification procedures were developed for murine cd40l - spd , but the same methods could be applied to human cd40l - spd with minor modifications . murine cd40l - spd has a predicted m . w . of 49 kda per chain , or about 600 kda per 12 - chain , cruciate molecule , the amino acid sequence predicts a pi of 9 . 10 . accordingly , conditioned media was concentrated by ultrafiltration through a 100 kda cutoff filter , which also fractionates the sample on a size basis . after diafiltration into 50 mm bicine , ph 9 . 00 ( also containing 1 mm edta added to inhibit metalloproteinases ), the sample was applied to a variety of cationic exchange resins . using source 30s ( amersham - pharmacia ), most of the elisa - detectable protein did not bind and was recovered in the flow - through . however , as reported by morris et al . { morris }, fractogel so 3 650m retained the protein . the retention by this tentacular resin and not by source 30s suggests binding to positively charged residues that are not on the protein surface . using a linear nacl gradient , elisa - detectable protein elutes at between 0 . 15 - 0 . 30 m nacl under these conditions ( fig2 ). in selected experiments , the protein was further purified using a superose 6 sizing column . most of the elisa - detectable protein eluted in the excluded volume , indicating an apparent m . w . of greater than 1 , 000 kda ( fig3 ). schultze et al . described a system using cd40l - expressing cells plus il - 4 and cyclosporin a ( to inhibit t cell growth ) as a means to grow very large numbers of b cells from a small sample of blood . because cd40l activates these b cells to express high levels of b7 molecules ( cd80 and cd86 ), the proliferating b cells were effective in presenting peptide antigens and rival non - dividing dendritic cells as antigen - presenting cells ( apcs ) ( 36 ). to determine if the cd40l - spd fusion protein could replace cd40l - expressing cells in this system , pbmc were cultured with cd40l - spd in addition to il - 4 and cyclosporin a . under these conditions the cells grew to saturation density every three days . after three weeks , the cultures were almost entirely cd19 + b cells which express high levels of cd80 ( fig4 ). this indicates that cd40l - spd can be used in ex vivo systems where a soluble yet effective form of cd40l is needed to stimulate cells for immunotherapeutic applications . resting murine b cells are particularly difficult to stimulate with most soluble forms of cd40l . even with murine cd40l - cd8 fusion proteins , it is necessary to crosslink the protein with antibodies against cd8 in order to achieve maximal proliferation in culture [ klauss , 1999 ]. accordingly , resting murine b cells were negatively selected with immunomagnetic beads . as shown in fig5 , murine cd40l - spd was as effective as anti - igm antibody in driving b cells to proliferate . this indicates that cd40l - spd can mimic the multivalent interactions that occur when a responding cell comes in contact with cd40l - bearing activating cells . cd40l is a powerful stimulant for macrophages ( reviewed in ( 28 )) and dendritic cells ( 40 ). accordingly , preparations of cd40l - spd were added to monocyte - derived macrophages and the production of mip - 1β was used as a measure of stimulation . as shown in fig6 , both human and murine cd40l - spd were able to stimulate macrophages , whereas the t147n - cd40l - spd mutant was inactive as expected . these examples define a new method of producing multimeric ( i . e ., many trimers ) of cd40l as a fusion protein with spd . also prepared and expressed were similar fusion proteins between raurine rankl / trance ( tnfsf 11 ) or murine cd27l / cd70 ( tnfsf7 ) joined to murine spd ( data not shown ). this suggests that virtually all tnfsf members could be successfully produced as fusion proteins with spd . furthermore , it is also likely that other collectins besides spd could be used in these fusions , given the strong structural homologies between the crds of the collectins and the extracellular domains of tnfsf members [ shapiro ] which can be substituted for these crds . given the 17 known tnfsf members and 9 known collecting , at least 153 fusion protein combinations are possible . spd was selected for initially because it is a soluble homopolymer . other collecting , such as surfactant protein a , have strong binding affinities to lipids and specific cell receptors . although removal of the crd abrogates much of this binding , it may be partially mediated by the neck region sequence , which the fusion proteins retain . accordingly , it would be expected that collectins other than spd might confer different cell - binding and pharmacokinetic behaviors upon a fusion protein . for example , macrophages are known to take up and degrade whole spd [ dong , 1998 ]. if a fusion protein other than spd were used , the disposition of the fusion protein in vivo might be altered . additionally , metalloproteinases are known to degrade the collectin , c1q , so that a fusion with c1q may alter the degradation of the fusion protein . for example , because cd40l activates macrophages and other cells to produce metalloproteinases , which could potentially degrade the collagenous portion of spd and other collecting . cleavage of the collagenous stalk would then be expected to release single - trimers of cd40l , which could diffuse away from the original parent molecule , much like a slow - release formulation of a drug . also , the membrane - proximal portion of cd40l has been retained in cd40l - spd . this sequence also contains protease - susceptible amino acid sequences , which can be eliminated by mutagenesis to retard the cleavage of cd40l from the fusion protein . mutations in such proteinase cleavage site ( s ) would delay such cleavage and favor the local persistence of the cd40l stimulus . cd40l - spd is a large macromolecule (& gt ; 1 , 000 kda ), and the other tnfsf - collectin fusion proteins would be expected to be similarly large . for native spd , the aggregates that spontaneously form measure 100 nm in diameter . when injected into tissue , this large a complex would be expected to remain at the injection site for a prolonged period . localization of the tnfsf - containing protein would also be expected to reduce any systemic toxicity caused by the release of free single - trimers into the circulation . for example , soluble cd40l in blood has been linked to disease activity in lupus , and this smaller molecule may even cross the glomerulus to cause damage to renal tubules [ kato and kipps , j . clin . invest . november 1999 ]. on the other hand , because cd40l induces the production of chemokines which attract immune cells [ kornbluth ], t cells , monocytes , and dendritic cells would be expected migrate to the site where cd40l - spd was injected . this might be advantageous if cd40l - spd were used as a vaccine adjuvant . in mice , soluble cd40l ( scd40lt ) stimulates igg1 production but not cytotoxic t lymphocytes ( ctls ) [ wong , 1999 ]. interestingly , the same protein that is expressed from an injected plasmid stimulates both a strong antibody and ctl response [ gurunathan , 1998 ]. in the latter case , the plasmid would be expected to deliver a localized supply of cd40l , whereas the scd40lt protein is free to diffuse away . support for the localized use of cd40l in an adjuvant formulation is provided by a study using a plasmid expressing full - length membrane cd40l , which was very effective in stimulating both humoral and ctl immune responses [ mendoza , 1997 ]. similarly , injection of adenovirus expressing membrane cd40l has potent antitumor activity in mice [ kikuchi , 1999 ]. similar considerations would likely apply to other fusion proteins between the tnfsf and collectins . finally , for immunostimulatory proteins , it is particularly important that the protein not be antigenic if repeated injections are needed . for example , vaccination with tnf - μ modified by the addition of short peptide sequences was able to induce the production of disease - modifying anti - tnf - μ autoantibodies [ dalum , 1999 ]. because cd40l - spd and other tnfsf - collectin fusion proteins are formed from endogenous protein sequences ( with the possible exception of the peptide sequence at the junction ), the production of antibodies might not limit the effectiveness of repeated injections . in conclusion , fusions between tnfsf members and collectins offer a novel means of generating large protein complexes which can provide localized stimulation at an injection site . because of the multimeric nature of the collectin backbone , such fusion proteins may mimic the multivalent ligand surface presented by the membrane forms of tnfsf members to tnfrsf - bearing responding cells . moreover , by limiting systemic toxicity while maintaining localized efficacy , such fusion proteins may have a role as vaccine adjuvants against infectious agents and tumors . *( as of nov . 1 , 1999 ) known members of ligands in the tnf superfamily , taken from the human gene nomenclature committee at http :// 222 . gene . ucl . ac . uk / users / hester / tnftop . htm all collectins are formed as multimers of trimeric subunits , each containing a collagenous domain . the c - terminus of each collectin contains a crd which binds carbohydrates and other ligands . because of the tight similarities between the known crd structures and the extracellular domains of tnfsf members , it is likely that the crd of any collectin could be replaced with the extracellular domain of any tnfsf member in a structurally compatible manner . while the present invention has now been described in terms of certain preferred embodiments , and exemplified with respect thereto , one skilled in the art will readily appreciate that various modifications , changes , omissions and substitutions may be made without departing from the spirit thereof . it is intended , therefore , that the present invention be limited solely by the scope of the following claims . banchereau , j ., and r . m . steinman . 1998 . dendritic cells and the control of immunity . nature 392 : 245 - 252 . bazzoni , f ., and b . beutler . 1996 . the tumor necrosis factor ligand and receptor families . new england journal of medicine 334 : 1717 - 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