Expression of a human monoclonal anti-(rhesus D) Fab fragment in Escherichia coli with the use of bacteriophage lambda vectors

Incomplete Antibodies May Reduce ABO Cross-Match Incompatibility: A Pilot Study

OBJECTIVE

Any erythrocyte transfusion among humans having type A or B blood groups is impossible due to antibodies causing fatal transfusion complications. A cross-match test is performed to prevent immune transfusion complications before transfusion. Our hypothesis is that the fragment antibody (Fab) part of the antibody (incomplete antibody) may be used to prevent an immune stimulus related to the complete antibody. Therefore, we designed a pilot study to evaluate the effectiveness of these incomplete antibodies using cross-match tests.

MATERIALS AND METHODS

Pepsin enzyme and staphylococcal protein A columns were used to cut anti-A and anti-B monoclonal antibodies and purify their Fab (2) fragments, respectively. An Rh-positive erythrocyte suspension with purified anti-A Fab (2) solution and B Rh-positive erythrocyte suspension with purified anti-B Fab (2) solution were combined correspondingly. Cross-match tests were performed by tube and gel centrifugation methods. The agglutination levels due to the anti-A and anti-B Fab (2) antibodies and their effects on the agglutination normally observed with complete antibodies were then measured.

RESULTS

No agglutination for the purified incomplete anti-A Fab (2) with A Rh+ erythrocyte and anti-B Fab (2) with B Rh+ erythrocyte combinations was observed in the tube cross-match tests. These agglutination levels were 1+ in two wells in the gel centrifugation cross-match tests. Fab (2)-treated erythrocytes were also resistant to the agglutination that normally occurs with complete antibodies.

CONCLUSION

We determined that the Fab (2) fragments of antibodies may not only be used to obtain a mild or negative reaction when compared to complete antibodies, but they might also be used for decreasing ABO incompatibility. Incomplete antibodies might be a therapeutic option in autoimmune hemolytic anemia and they may also be used in solid organ or hematopoietic stem cell transplantation. Therefore, we have planned an in vivo study to prove these in vitro findings.

In vitro functional test of two subclasses of an anti-RhD antibody produced by transient expression in COS cells

For over 35 years hemolytic disease of the fetus and newborn (HDFN) due to RhD has been effectively prevented by anti-RhD antibodies obtained from alloimmunized women or deliberately immunized men. However, due to the reduced number of immunized women and for ethical reasons it is foreseen that other sources of anti-RhD will be needed. One such source is recombinant human antibodies. Here we describe the construction of plasmids encoding two subclasses (IgG1 and IgG3) of an anti-RhD antibody, their transient expression in COS cells, and subsequent functional characterization of the antibodies with regard to specificity and ability to mediate a respiratory burst. The recombinant anti-RhD antibodies were specific for the RhD antigen and were able to mediate a respiratory burst. Thus these antibodies might be of use as future rhesus prophylaxis.

Inhibition of hepatitis C virus nonstructural protein, helicase activity, and viral replication by a recombinant human antibody clone

Hepatitis C virus (HCV) nonstructural protein 3 (NS3), with its protease, helicase, and NTPase enzymatic activities, plays a crucial role in viral replication, and therefore represents an ideal target for the development of anti-viral agents. We have developed a recombinant human antibody (Fab) that reacts with the helicase domain of HCV NS3. The affinity-purified Fab antibody completely inhibited the helicase activity of HCV NS3 at equimolar concentration. To evaluate the effect of the Fab on HCV replication, the clone encoding the Fab gene was put into an expression vector, which converts Fab into a complete IgG1 antibody. Using a DNA-based transfection model, we demonstrated that intracellular expression of this antibody resulted in significant reduction of HCV-negative strand RNA synthesis. Intracellular expression of this antibody into either a stable cell line replicating subgenomic RNA, or a transient full-length HCV replication model, reduced both HCV RNA and viral protein expression. These results support the use of recombinant antibody fragments to inhibit NS3 enzyme as a novel, feasible, and effective approach for inhibiting HCV replication.

V(D)J germline gene repertoire analysis of monoclonal D antibodies and the implications for D epitope specificity

BACKGROUND

The D antigen is a highly immunogenic human RBC antigen. Alloimmunization against the D antigen produces high-affinity antibodies that cause hemolytic transfusion reactions and HDN.

STUDY DESIGN AND METHODS

Cloning and subsequent sequence analysis of 11 new samples of monoclonal anti-D was performed in an attempt to identify V(D)J germline gene usage. Sequences were compared and analyzed with 37 previously published samples of anti-D for identification of V(H) and V(L) pairings, canonical structures, and conformation of restricted germline gene usage.

RESULTS

The V(H) and V(L) pairings used by the new D MoAbs resulted in seven canonical combinations, three of which had not been described previously. Preferential usage of gene segments from the VH3 and VH4 families and of D3, D6, JH6, and DPK9 germline gene segments was also determined. Three samples of anti-D from different donors were found to use similar V(H) and V(kappa) germline genes, despite the fact that two of the antibodies recognized epD6/7 and the third recognized epD1. From the cumulative analysis of the anti-D IgG, 24 V(H) and V(L) gene pairings were identified, resulting in only 10 canonical structures.

CONCLUSIONS

Despite the potential for diversity, only a minority of V(H) and V(L) germline genes are used by anti-D. Consequently, V(H) and V(L) pairings and the resulting canonical structures are similarly restricted.

HLA (A*0201) Mimicry by Anti-Idiotypic Monoclonal Antibodies

Soluble MHC Ags and anti-Id (anti-anti-MHC) Abs have both been shown to inhibit MHC alloantigen-specific B cell responses in vivo. We hypothesized that some anti-idiotypic Abs function as divalent molecular mimics of soluble HLA alloantigen. To test this idea, we studied two well-defined anti-idiotypic mAbs, T10-505 and T10-938, elicited in syngeneic BALB/c mice by immunization with CRll-351, an HLA-A2,24,28-specific mAb. Each anti-Id induced “Ab-3” Abs in rabbits that cross-reacted with HLA-A2 but not with HLA-B Ags. Furthermore, each anti-Id could bind to and block Ag recognition by Ha5C2.A2, a human homologue of mAb CRll-351. Both anti-Id mAb displayed weak reactivity with the human mAb SN66E3, which recognized an overlapping but distinct determinant of HLA-A2 Ags; neither reacted with human mAb MBW1, which recognized a nonoverlapping HLA-A2 determinant. Amino acid sequence comparison of mAb CRll-351 heavy and light chain variable region complementarity-determining regions (CDRs) with those of mAb Ha5C2.A2 and SN66E3 revealed short regions of homology with both human mAb; a large insert in the light chain CDR1 of mAb SN66E3 distinguished it from both CRll-351 and Ha5C2.A2. The amino acid sequences of mAb T10-505 and T10-938, which differed markedly from each other, revealed no homology to the α2 domain sequence of HLA-A*0201 that contains the CRll-351 mAb-defined epitope. We conclude that structurally different anti-Id Abs can mimic a polymorphic conformational epitope of an HLA Ag. In the case of T10-505 and T10-938 mimicry was not based on exact replication of the epitope by the hypervariable loops of the anti-Id mAb.

Obtaining a functional recombinant anti-rhesus (D) antibody using the baculovirus-insect cell expression system

The cloning and production of a human anti-rhesus (Rh) D monoclonal antibody (mAb) using the baculovirus-insect cell expression system is described. This monoclonal recombinant antibody R.D7C2 derived from a human parental IgM lambda immunoglobulin was obtained after immortalization of lymphocytes by Epstein-Barr virus (EBV). The human heavy (VH) and light (VL) variable regions were cloned from the parental cell line and genetically fused to the human constant IgG1 heavy (H) and light (L) chain genes (gamma 1 and lambda, respectively). A recombinant baculovirus was constructed that directs the co-expression of genes encoding both genetically fused heavy and light chains under the control of two late and strong baculovirus promoters. After infecting the Spodoptera frugiperda (Sf9) insect cell line with this baculovector, a complete IgG1 mAb was secreted in the culture medium indicating that each immunoglobulin chain was correctly processed and assembled with a functional glycosylation into a tetrameric form. In vitro analysis showed that the functional properties of R.D7C2 using agglutination tests were efficient for the specific recognition of Rh-D-positive red blood cells (RBC). In addition, R.D7C2 showed effector functions of the gamma 1 heavy chain resulting in the lysis of Rh+ papain RBC by an antibody-directed cellular cytotoxicity mechanism. These results demonstrate that R.D7C2 can be produced in the baculovirus-insect cell expression system as a source for potential therapeutic application in the treatment of the haemolytic disease of the newborn.

Human monoclonal Fab fragments specific for viral antigens from combinatorial IgA libraries

BACKGROUND

IgA constitutes the first line of immune defense, interacting with a variety of environmental antigens. Following infection with respiratory syncytial virus (RSV) individuals frequently exhibit elevated serum IgA titers specific for the virus. Previously combinatorial IgG libraries have successfully been used to clone such human antibody responses.

OBJECTIVES

Here we evaluate the possibility of constructing combinatorial IgA libraries on the surface of filamentous phage to retrieve human viral-specific IgA Fab fragments.

STUDY DESIGN

Bone marrow from an HIV-1 seropositive donor was used as RNA source to construct combinatorial IgA kappa and lambda libraries of approximately 10(7) clones.

RESULTS

By affinity selection using an immobilized recombinant RSV FG protein, two unique IgA Fab fragments producing clones (AD5 and AD23) reactive with the selecting antigen were isolated. One of the Fab fragments was found to be specific for RSV F glycoprotein and bind with high apparent affinity (2 x 10(8) M-1). The other binds with lower affinity and exhibits cross-reactivity with other antigens.

CONCLUSION

The strategy described, involving construction of combinatorial IgA libraries on the surface of filamentous phage, should be generally applicable to the investigation of both mucosal and systemic human IgA immune responses, and may become an important tool for evaluation of mucosal vaccine regimes.

Two-phase approach for the expression of high-affinity human anti-human immunodeficiency virus immunoglobulin Fab domains in Escherichia coli

We describe here a two-phase approach for the development of high-affinity human anti-HIV immunoglobulin Fab domains in a bacterial expression system. The first phase of this technique involves the generation of human hybridoma cell lines producing high-affinity antibodies (MAbs). Anti-HIV-1 human MAbs from peripheral blood lymphocytes (PBLs) were prepared from an HIV-1-seropositive patient and from an HIV-1-seronegative volunteer immunized with HIV-1 rgp160. One MAb (T15G1), derived from the blood of the seropositive donor, was specific for HIV-1 gp41, recognized gp41 on the surface of HIV-1-infected cells and bound this antigen with an apparent dissociation constant of 4 x 10(-10) M. A second MAb (M7B5), developed from the immunized volunteer, was specific for HIV-1 gp120 with a dissociation constant on the order of 8 x 10(-10) M, but was unable to recognize cell surface antigen. In the second phase of this technique the Fab domains of these two MAbs were molecularly cloned into a bacterial expression vector. mRNA was isolated from the M7B5 and T15G1 hybridoma cell lines and used as a template for the production of cDNA. The cDNA was amplified using the polymerase chain reaction (PCR) technique, and then fused, in frame, into a bacterial expression vector. The recombinant Fabs (rFabM7B5 and rFabT15G1) were expressed as dicistronic messages in bacteria using the IPTG-inducible lactose promoter (LacZ). DNA sequencing was used to define the gamma chain isotypes and the VH and VL chain gene usage. The binding specificities of rFabM7B5 and rFabT15G1 were indistinguishable from their respective intact MAbs.(ABSTRACT TRUNCATED AT 250 WORDS)

New approaches for the development and application of monoclonal antibodies for the diagnosis and therapy of human cancer

Monoclonal antibodies (MAbs) represent potentially important reagents for both the diagnosis and therapy of human cancer. Innovative approaches are resulting in the improved production of MAbs and an enhanced ability to use these molecules therapeutically. Application of genetic engineering to MAb development is also resulting in the production of MAbs displaying enhanced target specificity. Of particular value for cancer therapy will be catalytic, bispecific, anti-idiotypic and human MAbs. By using agents that can augment the expression of tumor-associated antigens on cancer cells, a further increase in the utility of MAbs in cancer therapy will be forthcoming.

Bacterially expressed Fabs of monoclonal antibodies neutralizing tumour necrosis factor alpha in vitro retain full binding and biological activity

Antibody fragments specific for the human tumour necrosis factor alpha (TNF alpha) have been cloned from lambda combinatorial expression libraries using total RNA obtained from three different hybridoma cell lines of therapeutic interest. The previously described bacteriophage lambda vectors, lambda HC2 and lambda LC1, were modified to create unique antibody cloning sites in the combinatorial construct and a novel tag peptide was inserted at the C-terminal end of the expressed Fd chain. Sequence analysis of the cloned Fabs indicated that two of them were derived from a single B cell. Expression in E. coli showed that the amount of recovered Fab in the bacterial culture medium was related to the sequences of the variable coding regions. Hybrid Fabs created by chain exchange of similar antibodies were as active as the originally paired Fabs in binding assays. The relative affinities and the capacities of the bacterially expressed Fabs to neutralize TNF alpha cytotoxicity in vitro were identical to those of the parental antibodies. The results demonstrate that, using an in vitro approach, it is possible to generate from existing hybridoma cell lines high affinity Fabs which retain antigen specificity. The cloning sites incorporated into the C-terminal parts of these Fabs will now permit their further modification to include additional functional characteristics not possible with the original hybridoma antibodies.

A recombinant human Fab expressed in Escherichia coli neutralizes rabies virus

A recombinant human anti-rabies monoclonal antibody (MAb-57) Fab was prepared by cloning the heavy (Fd)- and light-chain domains into the same bacterial expression vector. To construct the recombinant Fab, mRNA was extracted from MAb-57-producing hybridoma cells, reverse transcribed, and then amplified by polymerase chain reaction (PCR) by using oligonucleotides specific for immunoglobulin heavy- and light-chain DNA sequences. PCR-amplified Fd-chain cDNA was fused, in frame, between a bacterial leader peptide (PelB) at the amino terminus and a 10-amino-acid peptide tag at the carboxy terminus. The PCR-amplified lambda-chain cDNA was also fused to the PelB leader peptide. The immunoglobulin Fab was then expressed as a dicistronic message in bacteria by using the isopropyl-beta-D-thiogalactopyranoside-inducible lactose promotor (lacZ). DNA sequencing was used to define the gamma-chain isotype (immunoglobulin G1) and VH (VHI) chain and VL (V lambda II) chain gene usage. The recombinant Fab (rFab57) specifically bound the rabies virus coat glycoprotein, while the Fd and lambda chains, when expressed individually, did not. The binding specificity of rFab57 was indistinguishable from that of the intact MAb in direct enzyme-linked immunosorbent assays; however, the dissociation constant of rFab57 for rabies virus protein G was approximately 1 log10 U lower than that of complete MAb-57 in competition enzyme-linked immunosorbent assays. A fluorescent-focus inhibition assay showed that bacterially expressed rFab was capable of neutralizing rabies virus strain CVS-11. We conclude that a human Fab expressed in bacteria maintains its specificity and biologic activity.

Antibody expression in bacteriophage systems: The future of monoclonal antibodies?

Bacteriophage systems have been utilized to express and isolate antibodies. This promising technology has been evolving rapidly and has the potential to revolutionize the way in which monoclonal antibodies are generated. This review focuses on the many recent advances that have been made in obtaining monoclonal antibodies from bacteriophage systems.

Effects of IL-4, IL-5, and IL-6 on growth and immunoglobulin production of Epstein-Barr virus-infected human B cells

In the present study we investigated whether interleukin-4 (IL-4), IL-5, and IL-6 could enhance the efficiency of Epstein-Barr virus (EBV) transformation for the generation of specific human monoclonal antibody (HuMAb)-producing B-cell lines directed against erythrocyte Rhesus(D) antigen. In newly EBV-infected B cells, IL-4 and IL-6 caused a comparable enhancement of proliferation and of total IgG and IgA production. IL-6 showed a much stronger effect than IL-4 on IgM production, whereas IL-4 was unique in inducing IgE production. No stimulatory effects of IL-5 on either growth or Ig production were observed. Although addition of IL-6 resulted during the early phase after EBV infection in high numbers of Ag-specific antibody-producing wells, this did not result in an increased number of stable HuMAb-secreting cell lines. When the effects of cytokines were tested on established polyclonal EBV B cells, in a high cell density culture system, only IL-6 was able to enhance Ig secretion, while no effect could be demonstrated on proliferation. These studies substantiate that IL-6 is an important regulator of proliferation and Ig production, and that it acts at distinct stages after EBV infection, but does not increase the final overall recovery of Ag-specific EBV B-cell lines.

Human combinatorial antibody libraries to hepatitis B surface antigen

Human antibody Fab fragments that bind to hepatitis B surface antigen (HBsAg) were generated by using a recombinant phage surface-display expression system. Characterization of HBsAg-specific Fab fragments isolated from two vaccinated individuals reveals diversity in specificity of antigen binding and in the sequences of the complementarity-determining region. The sequence results show examples of human light-chain promiscuity that result in fine specificity changes and a strong relationship to a human germ-line gene. This application illustrates further that this technique is a powerful tool to isolate distinct human antibodies against immunogenic viral targets.

Immunization of hu-PBL-SCID mice and the rescue of human monoclonal Fab fragments through combinatorial libraries

Antibodies are usually prepared from recently boosted animals and reflect ongoing immune responses. In humans, this is restrictive as ethical constraints generally prevent antigen-boosting. Therefore the rich memory compartment of human antibody responses remains largely untapped. Severe combined immune deficiency (SCID) mice populated with human cells allow the stimulation of human antibody memory without the usual constraints. Here we show how peripheral blood lymphocytes can be stimulated by antigen to produce large secondary responses after transfer to SCID mice. Specific monoclonal human Fab fragments can then be isolated from the mice by repertoire cloning even when the human donor's last contact with antigen was more than 17 years ago.