Patent Application: US-50172604-A

Abstract:
the invention relates to ab2 - type anti - idiotypic antibodies and fragments thereof which mimic hvi - 1 epitopes that are otherwise cryptic to the immune system and which antibodies or fragments thereof are directed against potently neutralizing anti - hiv - 1 antibodies . the invention further relates to a hybridoma cell line 3h6 expressing the anti - idiotypic antibody and to pharmaceutical compositions containing the antibody or fragment thereof . the invention also relates to hiv - 1 neutralizing ab3 - type antibodies elicited upon administration of the ab2 - type anti - idiotypic antibody or fragment thereof and to pharmaceutical compositions containing them . the invention also relates to the use of the present antibodies or fragments thereof as screening tools or as diagnostic or therapeutic agents .

Description:
it is an object of the invention to generate antigen binding components which are capable to induce neutralizing humoral immune responses against hiv - 1 . a further object of the invention is to provide novel antibodies or antibody fragments which are able to induce hiv - 1 neutralizing antibodies . the invention discloses murine antibodies and fragments thereof which are directed against an antibody of the gp41 antigen on hiv - 1 . in particular , the invention describes the generation of anti - idiotype murine ab2β directed against the human monoclonal antibody 2f5 which is known to react with a cryptic neutralizing epitope on gp41 of hiv - 1 . one of the ab2 &# 39 ; s of the present invention , i . e . the murine monoclonal ab2 designated 3h6 ( deposited under the provisions of the budapest treaty on the deposit of microorganisms at phls porton down , salisbury , uk ; ecacc acc . no . 01100279 ) blocks the binding of the human ab1 2f5 to a synthetic epitope containing at least the core epitope sequence eldkwa ( seq id no : 1 ) as well as to gp160 . 3h6 is also able to diminish the hiv - 1 neutralizing potency of 2f5 . the present invention also relates to fab - fragments derived from 3h6 antibodies , which were shown to induce neutralizing immune responses in the sera of human and non - human mammals applying a simple prime / boost regimen of immunization . thus , 3h6 fab - fragments successfully mimick an epitope that apparently lacks immunogenicity or is only poorly immunogenic on the native hiv - 1 during natural infection . an “ antibody fragment ” in the context of the present invention is an antigen - binding part of the whole antibody which retains the binding specificity of the whole antibody molecule . the term encompasses , for example , fab -, f ( ab ′) 2 -, fv - and scfv - fragments . antibody fragments can be obtained by conventional techniques well known in the art such as proteolytic digestion of antibodies , for example by papain digest , or through genetic engineering . the antibodies and antibody fragments of the present invention can also be prepared by synthetic methods known in the art , such as peptide synthesis or recombinant dna technology , once the structural nature of the antibody fragments has been analyzed by crystallization studies , sequencing methods and / or other methods well known in the art . in another embodiment , the invention relates to “ humanized ” antibodies and antibody fragments . “ humanized ” means that a non - human antibody or antibody fragment is linked with part of a human antibody . usually it means that the complimentarity determining regions ( cdr ) from the variable regions of a non - human , e . g . rodent , antibody are combined with framework regions from the variable regions of a human antibody , e . g . from a human igg . in doing so the fragment containing the antigen binding site of the non - human antibody is inserted into a suitable human antibody . methods for “ humanizing ” antibodies are state of the art . for instance , an exon encoding the variable region containing the cdr of the non - human antibody may be spliced into the framework sequence of a suitable human antibody . further , a fab - fragment of the non - human antibody may be coupled with a suitable fc - fragment of a suitable human antibody . suitable human frameworks may be found by homology searches in databases on the basis of homology to the non - human antibody . “ humanized ” antibody fragments according to the present invention may also be derived from synthetic phage libraries which use randomized combinations of synthetic human antibody variable regions , by selecting on 2f5 antibodies as antigen . humanized antibodies are referred to hereinafter by using the prefix “ hu ”, e . g . the term “ hu3h6 ” refers to a humanized 3h6 antibody . in a still further embodiment the invention relates to chimeric antibodies . “ chimeric ” antibodies are antibodies in which the whole of the variable regions of a non - human , in particular rodent , antibody are expressed along with human constant regions of antibodies . this may provide antibodies with human effector functions . “ chimeric ” antibodies may be created on the molecular level by fusing non - human exons encoding variable regions containing the antigen binding site with human exons encoding antibody constant regions . chimeric mouse / human antibodies are identified hereinafter by the prefix “ mo / hu ”, e . g . the term “ mo / hu3h6 ” refers to a chimeric mouse / human 2h6 antibody . where the term “ 3h6 ” is used without identifying prefix the term shall relate to the murine ab2 antibody 3h6 , e . g . as produced by cell line 3h6 ( ecacc acc . no . 01100279 ), unless another meaning is derivable from the respective context . such other meaning would include using the term 3h6 as a generic term encompassing each one or all of the group elements : murine , chimeric and humanized 3h6 antibodies . in yet another embodiment the present invention relates to an antibody - cytokine construct , wherein the vh and vl chains of a chimeric mo / hu3h6 antibody ( fig6 ) are fused with human fc and ckappa chains , resulting in a recombinant expression protein having an igg isotype . a chimeric igg molecule is able to pass the placenta , wherefore it is expected that the aforementioned construct may sucessfully interfere with and inhibit or prevent a mother - to - child transmission of hiv - 1 . anti - idiotypic antibody 3h6 fab - fragments as well as the mo / hu3h6 fc - gamma antibodies induce humoral immune responses and trigger the immune system to induce neutralising antibodies . in a further embodiment the present invention relates to an antibody or antibody fragment that is associated , e . g . fused or coupled , with an immunoactive molecule that improves the immunogenic nature of the antibodies induced by the antibody or antibody fragment upon administration to a mammalian individual . for instance , the antibody fragment may be coupled to a structure , for instance a cytokine such as , e . g ., il - 4 , which enhances the immunoreactivity of said mammal and preferably causes an increased b - cell response , which is of particular importance in the treatment of hiv . the present invention also relates to entire ab2 antibodies , particularly to antibody 3h6 including murine 3h6 , chimeric mo / hu3h6 and hu3h6 , wherein the antibody is associated ( e . g . coupled , fused or linked ) with any such immunoresponse stimulating molecule , as well as to mixtures comprising at least one antibody and / or anti - hiv - effective fragment thereof in combination with at least one cytokine - associated , particularly il - 4 associated , antibody and / or anti - hiv - effective fragment thereof . the term “ anti - hiv - effective fragment ” as used herein relates to antibody fragments that are reactive with hiv - 1 neutralizing antibody 2f5 ( ecacc accession no . 90091704 ) and which inhibit or prevent the hiv - 1 neutralization activity of antibody 2f5 and / or the binding of antibody 2f5 to gp41 of hiv - 1 , and which are preferably effective in eliciting , upon proper administration to a mammal , 2f5 type anti - hiv - 1 antibodies . therapeutic use of interleukines in the treatment of cancer and viral infections is applied since years . additionally , some cytokines like il - 2 are diminished in early phases of infection . especially in hiv - 1 therapies considerable indications and independent studies point out that il - 15 may be of great benefit . similarly to il - 2 , il - 15 is responsible for the proliferation of activated t - and nk - cells , assists the distribution of ifn - γ and stimulates the generation of immune - globulines in b - cells . il - 15 mrna is detected in different tissues and is regulated tightly . il - 15 induces proliferation of cd8 + memory cells , while il - 2 inhibits the proliferation of cd8 + memory cells . therefore , il - 15 was chosen as a possible candidate in the concept of developing an improved hiv vaccine according to the present invention , and particularly at least for the reasons that it a ) supports the generation of neutralising antibodies in a patient &# 39 ; s b lymphocytes , and b ) also stimulates the cellular immunity by increasing the number of cd8 + memory cells of said patient . moreover , while infusion of il - 2 to aids patients showed severe side effects at higher doses , il - 15 is far less harmful and is even detected in new - born babies . accordingly , in a further embodiment the present invention relates to an anti - idiotypic ab2 antibody or antibody fragment reactive with antibody 2f5 , preferably to ab2 3h6 or a fragment thereof , that is associated , e . g . fused or coupled , with il - 15 as an immunoactive molecule . in a preferred embodiment , the invention relates to a fusion protein consisting of the chimeric mo / hu3h6 or humanized antibody hu3h6 and human il - 15 , i . e . to a recombinant protein which is a fusion protein consisting of mo / hu3h6 or hu3h6 and a human il - 15 tail at the c - terminus of the antibody heavy chain ( fig6 ). the fusion proteins induce neutralising , 2f5 like antibodies in a mammalian recipient while at the same time proliferation of cd8 + memory cells is stimulated through the action of the il - 15 tail . moreover , apart from the aforementioned activity of the cytokine - associated ab2 antibodies of the present invention to induce memory t cell activity , a combination of an ab2 antibody or anti - hiv - effective fragment thereof and a cytokine - associated ab2 antibody or anti - hiv - effective fragment thereof allows to develop optimal therapeutic effects by adjusting the ratio of the components to each other , typically in an anti - hiv - 1 vaccine . in a preferred embodiment , the invention relates to a mixture or composition , typically an hiv - 1 vaccine , comprising at least one antibody or effective fragment thereof selected from the group consisting of 3h6 , fragment of 3h6 , mo / hu3h6 , fragment of mo / hu3h6 , hu3h6 , and fragment of hu3h6 in combination with at least one cytokine - associated , preferably il - 4 or il - 15 associated antibody or effective fragment thereof , the antibody or fragment being selected from the same group consisting of 3h6 , fragment of 3h6 , mo / hu3h6 , fragment of mo / hu3h6 , hu3h6 , and fragment of hu3h6 . the proper ratio can be determined using in vitro models for each recipient prior to administration . usally this determination will comprise decreasing the ab2 - associated il - 15 concentration to a minimal level and to supplement the hu3h6 antibody up to a concentration that ensures at least some , preferably the best possible induction of the humoral immune response . sera of 3h6 induced immune responses show both specific binding inhibition patterns of 2f5 on the antigen as well as significant in vitro neutralization potency . furthermore , the anti - 2f5 - ab2β 3h6 , while reacting strongly with the homologous ab1 , does not recognize isotype matched control antibodies demonstrating high specificity for the idiotype with no cross - reactivity to irrelevant ig &# 39 ; s . thus , the anti - idiotypic antibody 3h6 may be used , either directly as a vaccine to induce protective and neutralizing immune responses , or as a tool contributing to the design of an hiv - 1 vaccine that also successfully induces protective and neutralizing b - cell responses . ab2s can be suitable for vaccination of hiv - 1 infected newborns , whose immune system might be tolerant to stimulation with other antigens [ 37 , 38 ]. at the first glance ab2 3h6 represents a vaccine antigen capable to induce neutralizing immune responses . immunization with ab2 3h6 shall avoid the induction of antibody - dependent enhancement of infection responses ( ade ) observed in polyclonal sera of hiv - 1 positive individuals [ 39 - 42 ]. the ab1 2f5 was passively administered in gram - quantities to human volunteers . no signs of ade have been observed in these human volunteers despite the fact that complement activation was detected [ 29 ]. as ab2 3h6 induces 2f5 - like specificities in the sera of immunized animals it can be expected that ade - phenomena observed with polyclonal sera of hiv - positive individuals [ 43 ] can be avoided upon vaccination with ab2 3h6 . for the use as a pharmaceutical the antibodies and antibody fragments of the present invention may be part of a composition together with a pharmaceutically acceptable carrier . thus , in a further embodiment the present invention relates to pharmaceutical compositions , particularly vaccines , which comprise the ab2 antibodies or antibody fragments of the present invention together with a suitable , optionally immunogenic , carrier and / or adjuvant . in yet another embodiment the present invention relates to ab3 antibodies ( anti - anti - idiotypic antibodies ) elicted by the present ab2 antibodies or antibody fragments of the 3h6 type , as well as to pharmaceutical compositions , including vaccines , which comprise ab3 antibodies or antibody fragments directed against ab2 3h6 and preferably directed against the binding epitope of ab2 3h6 . in a most preferred embodiment , these ab3 ntibodies or antibody fragments are of a nature such that they neutralize hiv - 1 . pharmaceutical compositions containing such an ab3 antibody or fragment thereof are useful for passive immunization against hiv - 1 . the antibodies or antibody fragments of the present invention may be administered in dosages of about 0 . 5 to about 10 μg / kg body weight , and preferably boosted in one or more , usually periodic , intervals . the pharmaceutical compositions of the present invention containing either ab2 3h6 antibodies or fragments thereof , or anti - 3h6 ab3 antibodies or fragments whereof may be administered prophylactically to prevent an individual from getting hiv - 1 infected , as well as therapeutically to inhibit or stop progression of disease in an hiv - 1 infected individual . female balb / c mice , 8 - 10 weeks old , were obtained from charles river ( sulzfeld , germany ). immunoglobulin subclass standards and isotype - specific anti - mouse antisera were purchased from sigma ( st . louis , mass .). monoclonal anti - hiv - 1 antibody 2f5 was purified and used as antigen binding fragment ( fab ′) for immunization . antibodies were digested with mercuripapain ( sigma ) and the digest purified with protein - a - sepharose 4 ff - column . 50 μg of the 2f5 fab ′ were injected intraperetoneal once in complete freund &# 39 ; s adjuvant ( cfa ) and after three and six weeks again with incomplete freund &# 39 ; s adjuvant ( ifa ). four days before spleen - ectomization the animals were boosted for the last time . spleenocytes were prepared on day 46 after the first immunization . the serum titer of mice was used as criteria for the development of immunocompetent spleenocytes . only mice with an anti - 2f5 titer of at least 1 : 100 , 000 were used for fusion . according to standard protocols the spleen cells were fused with x63 - ag - 8 . 653 cells and plated in 96 - well plates . hat - selection was started the day after fusion and supernatants of growing wells were first tested for mouse igg production using a mouse mab as standard protein . polyclonal goat anti - mouse - γ - chain antibody ( sigma ) was diluted 1 : 500 in coating buffer ( 0 . 1n na 2 co 3 / nahco 3 ph 9 . 6 ) and 100 μl per well were precoated onto microtiter plates ( elisa grade i ; nunc , denmark ). after each incubation step the plates were washed three times with pbs containing 0 . 1 % tween 20 adjusted to ph 7 . 2 . the standard mouse mab was serially diluted , starting with 200 ng / ml ( dilution buffer contained 1 % bsa in washing buffer ). 50 μl per well of standard or serially diluted sample were allowed to bind to the precoated well for 1 h , and after washing the plates , we used 50 μl of 1 : 5 , 000 diluted goat anti - mouse igg + igm poly hrp80 ( rdi inc .) as second antibody . after 1 h incubation time , the plates were stained with opd and read at 492 nm ( reference wavelength 620 nm ). for the screening of antibodies against the 2f5 idiotype , the supernatants of 2170 hat - resistant hybridoma were tested for igg production . 65 positive clones were found . approx . 10 % of supernatants of the igg positive clones were also reacting with antibody 2f5 . for initial screening of idiotype binding antibodies , 96 - well microtiter plates were coated overnight at 4 ° c . with 2f5 - igg1 , 2f5 - igg3 or 2g12 , another gp120 recognizing human anti - hiv - 1 antibody [ 31 ]. samples were diluted 2 8 in dilution buffer starting with 200 ng / ml . the ab2s were visualized as described for the mouse igg elisa . the antibodies 3h6 , 4f6 , and 6f8 could be stabilized and were tested for their binding capacity in elisa with different precoatings . the anti - idiotypic antibody 1g1 , directed against a different neutralizing anti - hiv - 1 antibody , namely 2g12 ( ecacc acc . no . 93091517 ; for details see wo 96 / 33219 ), served as control . table 1 shows the relative binding properties of ab2s with different idiotypes . 4f6 and 6f8 reacted with all antibodies and seemed to recognize an epitope at the constant region . the antibody 1g1 specifically binds to 2g12 , while 3h6 recognizes both isotypes of 2f5 and it was negative for 2g12 . competitive binding assays were performed as previously described [ 32 ]. different concentrations of ab2 ( 50 , 500 ng / ml ) were preincubated with 1 : 2 dilutions of 2f5 starting with 100 ng / ml . after 1 hour the antibodies were allowed to react with the antigen on the plate . the solid phase was coated with the synthetic 2f5 epitope gggleldkwasl ( seq . id no . 13 ) at a concentration of 2 μg / ml and the final binding of 2f5 was detected as described [ 33 ]. the elisa competition assay was designated to describe the remaining binding capacity of 2f5 to the eldkwa - epitope after preincubation with ab2 . ab2 3h6 inhibits or prevents the binding of 2f5 to the epitope depending on the concentrations applied . fig1 describes the decline of 2f5 binding to the gggleldkwasl ( seq . id no . 13 ) precoated plate with increasing concentrations of 3h6 . even 50 ng / ml 3h6 could reduce the binding properties of 31 ng / ml 2f5 by more than one third ( 37 % reduction of the od ) and 500 ng / ml resulted in 83 % reduction of od while the ab2 6f8 did not diminish the binding of 2f5 to the epitope . since the binding affinity of 2f5 to the gst -( glutathion s - transferase ) eldkwa fusion - protein is 1 . 7 × 10 7 m − 1 [ 33 ] the inhibition pattern of ab2 3h6 was acceptable for further studies . similar results were obtained when replacing gggleldkwasl with other synthetic peptides containing the eldkwa epitope or slightly modified , particularly functionally equivalent , variants thereof including functionally equivalent homologues or functionally equivalent variants occurring due to the degeneracy of the genetic code and / or due to variability of the hiv - 1 viruses , the variants preferably being selected from the group consisting of eldnwa ( seq id no . 2 ), elnkwa ( seq id no . 3 ), leldkwa ( seq id no . 4 ), leldnwa ( seq id no . 5 ), lelnkwa ( seq id no . 6 ), eldkwas ( seq id no . 7 ), eldnwas ( seq id no . 8 ), elnkwas ( seq id no . 9 ), leldkwas ( seq id no . 10 ), leldnwas ( seq id no . 11 ), lelnkwas ( seq id no . 12 ). interaction of 2f5 with the different ab2s was further investigated in a neutralization assay as described previously [ 26 ]. the assay was performed with hiv - 1 strain nl4 - 3 infected aa - 2 cells ( niaid , bethesda , md .) as indicator cells using p24 antigen as virus replication marker . serial dilutions of ab2 antibodies ( starting concentration of 250 μg / ml ) were mixed with constant amounts of 2f5 or 2g12 as negative control ( 10 μg / ml of each neutralizing antibody ) and pre - incubation with virus before addition of aa - 2 cells and further incubated for 5 days . virus replication was measured in a p24 - elisa at the time point of termination of the assay [ 34 ]. the ratios of p24 antigen production in ab - containing cultures ( vn ) to p24 antigen production in control cultures ( vo ), taking into account the input p24 , were calculated and ab concentrations ( μg / ml ) causing x % neutralization were plotted . each test included a virus titration to determine the actual tissue culture infectious dose 50 ( tcid 50 ) and the viral titer was determined by linear regression analysis . tests were considered to be valid in case of viral titers between 10 2 - 10 3 tcid 50 . fig2 shows the in vitro neutralization of hiv - 1 nl4 - 3 after preincubation of ab2 3h6 with 2f5 and 2g12 . 2f5 and 2g12 alone neutralize 90 % of the virus at a concentration of 3 μg / ml and 99 % of the virus at 12 μg / ml and 11 μg / ml , respectively ( data not shown ). the 2f5 and 2g12 concentration was kept constant at 10 μg / ml . 50 μl of 2f5 or 2g12 were incubated with serial dilution of the ab2s , 3h6 , 4f6 , 6f8 and only 3h6 was able to deplete neutralization of 2f5 ( 4f6 and 6f8 are not plotted ). fig1 b describes the percent neutralization representing the remaining neutralizing capacity of 10 μg / ml 2f5 and 2g12 with increasing amounts of 3h6 . 3 . 9 μg / ml of 3h6 extinguish the 2f5 neutralization properties and 1 . 9 μg / ml are able to reduce neutralizing capacity of 2f5 for 5 %. this means that 3h6 and 2f5 react in nearly equimolar ratio , since the molecular weight of the two corresponding antibodies may vary due to oligomerization or cleavage . 3h6 is not able to reduce neutralization of 2g12 at concentration as high as 250 μg / ml . ab2 3h6 was able to reduce 2f5 neutralization for 95 % at 3 . 9 μg / ml . sequence of the variable regions of the heavy and light chains of antibody 3h6 : a ) amino acid sequence of the heavy chain variable region ( vh ) of anti - idiotypic antibody 3h6 ( seq id no . 13 ): b ) amino acid sequence of the light chain variable region ( vl ) of anti - idiotypic antibody 3h6 ( seq id no . 14 ): after purification of ab2 ( 3h6 ) by affinity chromatography it was digested with mercuripapain ( sigma ) and the digest purified with protein - a - sepharose 4 ff - column . three balb / c mice were injected with 5 μg of the 3h6fab ′ intraperetoneally and after three weeks again , both times with freund &# 39 ; s incomplete adjuvant . another week later the mice were sacrificed and blood and ascites samples were collected . the samples were analyzed by elisa for igg titer as described above . three balb / c mice were immunized with 5 μg / ml 3h6fab ′ fragment fia solution . unfortunately , after the second immunization the animals developed ascites and had to be sacrificed without finishing the immunization scheme . serum and ascites were shown to have total igg titers up to 2 mg / ml . the results of igg titers , binding capacity and competition assay are summarized in table 2 . the binding to gggleldkwasl ( seq . id no . 13 ) and gp160 in an elisa was illustrated in fig2 by plotting the cut - off dilution of the polyclonal serum and ascites . end point titers ( cut - off ) were calculated as the reciprocal of the highest dilution that resulted in an od at least two times greater than the od obtained with corresponding preimmune igg . serum and ascites samples of the 3h6 immunized mice were assayed for binding to the synthetic epitope gggleldkwasl ( seq . id no . 13 ) ( 1 μg / ml in coating buffer ) and recombinant gp160 ( 1 μg / ml in coating buffer ). the mouse antibodies were detected as described above . in another specificity test the serial dilutions of ab3 samples were coincubated with a constant amount of 2f5 on a gp160 precoated plate . the 2f5 binding capacity at increasing dilutions of ab3 , starting with 1 : 10 , was examined . the 2f5 antibody was utilized at 25 ng / ml and a serial dilution of ab3 samples starting with 1 : 10 was used as competitor . ab3 sera that most potently competed with 2f5 binding on the antigen also exhibited in vitro neutralization potency . fig3 illustrates the reduction of 2f5 binding to the precoated gp160 in terms of competition with the ab3 samples . the neutralizing activity of ab3 sera and ascites was assessed by inhibition of syncitium formation of hiv - 1 strain rf nt . serial dilutions of serum , ascites or control antibody ( 2f5 ) were pre - incubated with virus ( 10 2 - 10 3 tcid 50 / ml ) for 1 h at 37 ° c . before addition of aa - 2 cells . starting dilutions of serum and ascites were 1 : 5 in culture medium . cells were incubated for 5 days before assessment of syncitium formation . experiments were performed with 4 replicates per dilution step . the presence of at least one syncitium per well was considered as indication for hiv - 1 infection . the 50 % inhibiting concentration ( ic 50 ) was calculated according to the method of reed and muench [ 35 ]. experiments included a virus titration of the inoculum to confirm the infectious titer . the neutralizing properties of serum and ascites were tested with hiv - 1 laboratory strain rf nt . samples were diluted initially 1 : 5 , sterilized by 0 . 2μ filtration and used at a starting concentration of 1 : 10 in the aa - 2 syncytia inhibition assay in quadruplicates . the virus - titer ( tcid 50 / ml ) was determinated to be 10 2 . 75 . the ascites samples and serum 1 did not show any antiviral effect . sera 2 and 3 reached an ic50 at dilutions 1 : 14 . 1 and 1 : 11 . 9 respectively . serum 1 didn &# 39 ; t show neutralization as well as the ascites samples . 3h6 vl and vh coding sequences are isolated from the murine mab ab2 / 3h6 via rt - pcr from the cultivated hybridoma cell line ( see example 1 ). thereafter human cκ and igg fc domains are fused to the variable fragments of 3h6 by soe - pcr ( splicing by overlapping extension ) and subsequently cloned into the eucaryotic expression vector pires . this cloning step results in a bicistronic expression cassette with cmv - promoter — chimeric 3h6 heavy chain - internal ribosomal entry site ( ires )— chimeric 3h6 light chain — sv40 polya . the final plasmid is called p3h6 mhhc / lc . human il - 15 cdna is amplified by pcr and fused to the antibody heavy chain domain by soe - pcr resulting in a fusion protein mo / hu3h6 / il - 15 as shown in fig6 . this mo / hu3h6 / il - 15 heavy chain replaces the 3h6 chimeric heavy chain in the expression plasmid p3h6 mhhc / lc resulting in the second expression plasmid p3h6 mhhc - il - 15 / lc . two recombinant cho - cell - lines are generated by cotransfection : one cell line expressing the mouse / human chimeric antibody mo / hu3h6 and the second cell - line expressing the same antibody with human il - 15 at the c - terminus of the 3h6 heavy chain ( mo / hu3h6 / il - 15 ). the target plasmids described above are cotransfected together with the plasmid pdhfr coding for the mouse dihydrofolate - reductase ( dhfr ) by lipofectin ®. subsequent selection of transfected cells is performed using geneticin sulfate ( g418 ). methotrexate ( mtx ) is used as amplification marker . after expansion of the subclones , screening for the best producing clone is done with an elisa and flow cytometry with a commercial anti - human il - 15 mab and the mab 2f5 . the selection process is repeated before the subclone with the highest secretion rate of the desired protein is expanded . thereafter , quantification and comparison of the amounts of secreted and intracellularly retained protein of the mo / hu3h6 or mo / hu3h6 / il - 15 fusion protein is carried out . protein purification is done by affinity chromatography , optionally followed by ion - exchange chromatography . the isolated and purifed fusion protein mo / hu3h6 / il - 15 is subjected to analytical determination of the biochemical properties including determination of : affinity to the il - 2 / il - 15 - r using the biacore or isothermal microcalorimetry ; molecule size using gel filtration columns and native gel electrophoresis ; in vitro stability of the immunocytokine by incubation in human serum ; competition assay of the mo / hu3h6 / il - 15 fusion protein with the mo / hu3h6 antibody molecule to compare their binding capacity ; in vitro neutralisation experiments to describe the inhibiting properties of the mo / hu3h6 and the mo / hu3h6 / il - 15 fusion proteins diffusion through biological membranes , binding to the corresponding receptors , e . g . il - 2 / il - 15 - r on selected tissues using immuno - histological assays . the construction and expression of the mo / hu3h6 / il - 4 fusion protein is done analogously . the results from in vitro experiments confirm both the hiv - 1 neutralisation activity as well as the b cell response stimulating activity of the above disclosed fusion protein constructs of the present invention ( data not shown herein ). 1 . herlyn , d ., et al ., anti - idiotype cancer vaccines : pre - clinical and clinical studies . in vivo , 1991 . 5 ( 6 ): p . 615 - 23 . 2 . jerne , n . k ., j . roland , and p . a . cazenave , recurrent idiotopes and internal images . embo journal , 1982 . 1 ( 2 ): p . 243 - 7 . 3 . nisonoff , a ., idiotypes : concepts and applications . journal of immunology , 1991 . 147 ( 8 ): p . 2429 - 38 . 4 . ertl , h . c . and c . a . bona , criteria to define anti - idiotypic antibodies carrying the internal image of an antigen . vaccine , 1988 . 6 ( 2 ): p . 80 - 4 . 5 . bruck , c ., et al ., nucleic acid sequence of an internal image - bearing monoclonal anti - idiotype and its comparison to the sequence of the external antigen . proceedings of the national academy of sciences of the united states of america , 1986 . 83 ( 17 ): p . 6578 - 82 . 6 . kennedy , r . c . and r . attanasio , concepts of idiotype - based vaccines for hepatitis b virus and human immunodeficiency virus . canadian journal of microbiology , 1990 . 36 ( 11 ): p . 811 - 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6 . 12 . sikorska , h . m ., therapeutic applications of antiidiotypic antibodies . journal of biological response modifiers , 1988 . 7 ( 4 ): p . 327 - 58 . 13 . attanasio , r . and r . c . kennedy , idiotypic cascades associated with the cd 4 - hiv gp 120 interaction : principles for idiotype - based vaccines . international reviews of immunology , 1990 . 7 ( 1 ): p . 109 - 19 . 14 . kang , c . y ., et al ., development of hiv / aids vaccine using chimeric gag - env virus - like particles . biological chemistry , 1999 . 380 ( 3 ): p . 353 - 64 . 15 . del guercio , p ., aids and immune dysfunction . alternative etiologic mechanisms . contributions to microbiology and immunology , 1989 . 11 : p . 289 - 304 . 16 . sutor , g . c ., et al ., neutralization of hiv - 1 by anti - idiotypes to monoclonal anti - cd4 . potential for idiotype immunization against hiv . journal of immunology , 1992 . 149 ( 4 ): p . 1452 - 61 . 17 . shearer , m . h ., et al ., idiotype cascades associated with the cd 4 - 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