Differential control of neonatal tolerance by antigen dose versus extended exposure and adjuvant

Ig-PLP1, an immunoglobulin (Ig) chimera carrying the encephalitogenic proteolipid protein (PLP) sequence 139-151 (PLP1), induces neonatal tolerance in mice and confers resistance to experimental allergic encephalomyelitis (EAE) without the need for incomplete Freund's adjuvant (IFA). The mechanism underlying such tolerance involves organ-specific T cell regulation characterized by lymph node deviation and an unusual IFNgamma-dependent splenic anergy. This form of T cell modulation may prove useful for prevention of autoimmunity. However, since the neonatal period is susceptible to regulation, further investigations are necessary to define parameters required to establish regimens suitable for optimal protection against disease. Therefore, studies were carried out to investigate the effect that IFA, the dose of Ig-PLP1, and the number of Ig-PLP1 injections might have on Ig-PLP1-mediated neonatal tolerance and protection against disease. Herein it is reported that as little as 1 microg of Ig-PLP1 supported IFNgamma-dependent splenic anergy but lymph node deviation and protection against disease strengthened as the dose of tolerogen increased. However, when a two-injection regimen was applied, resistance to disease was observed but the mechanism manifested proliferative and cytokine unresponsiveness in both lymphoid organs. Furthermore, the use of IFA along with Ig-PLP1 yielded a suppressive mechanism similar to that of the two-injection regimen. Therefore, the dose of Ig-PLP1 displays a quantitative influence, while the number of injections of Ig-PLP1 and the presence of IFA rather drive qualitative influences on such tolerance.

Differential presentation of an altered peptide within fetal central and peripheral organs supports an avidity model for thymic T cell development and implies a peripheral readjustment for activation

Altered self peptides may drive T cell development by providing avidity of interactions low enough to potentiate positive selection but not powerful enough to trigger programmed cell death. Since the peptide repertoire in both central and peripheral organs is nearly the same, interactions of these peptides with T cells in the thymus would have to be different from those taking place in the periphery; otherwise, T cell development and maturation would result in either autoimmunity or T cell deficiency. Herein, a self and an altered self peptide were delivered to fetuses, and their presentation as well as the consequence of such presentation on T cell development were assessed. The results indicate that the self peptide was presented in both central and peripheral fetal organs and that such presentation abolished T cell responses to both peptides during adult life. However, the altered peptide, although presented in vivo as well as in vitro by splenic cells, was unable to stimulate a specific T cell clone when the presenting cells were of thymic origin and allowed offspring to be responsive to both peptides. These findings indicate that central and peripheral organs accommodate selection and peripheral survival of T cells by promoting differential altered peptide presentation.

Neonatal exposure to a self-peptide-immunoglobulin chimera circumvents the use of adjuvant and confers resistance to autoimmune disease by a novel mechanism involving interleukin 4 lymph node deviation and interferon gamma-mediated splenic anergy

Induction of neonatal T cell tolerance to soluble antigens requires the use of incomplete Freund's adjuvant (IFA). The side effects that could be associated with IFA and the ill-defined mechanism underlying neonatal tolerance are setbacks for this otherwise attractive strategy for prevention of T cell-mediated autoimmune diseases. Presumably, IFA contributes a slow antigen release and induction of cytokines influential in T cell differentiation. Immunoglobulins (Igs) have long half-lives and could induce cytokine secretion by binding to Fc receptors on target cells. Our hypothesis was that peptide delivery by Igs may circumvent the use of IFA and induce neonatal tolerance that could confer resistance to autoimmunity. To address this issue we used the proteolipid protein (PLP) sequence 139-151 (hereafter referred to as PLP1), which is encephalitogenic and induces experimental autoimmune encephalomyelitis (EAE) in SJL/J mice. PLP1 was expressed on an Ig, and the resulting Ig-PLP1 chimera when injected in saline into newborn mice confers resistance to EAE induction later in life. Mice injected with Ig-PLP1 at birth and challenged as adults with PLP1 developed T cell proliferation in the lymph node but not in the spleen, whereas control mice injected with Ig-W, the parental Ig not including PLP1, developed T cell responses in both lymphoid organs. The lymph node T cells from Ig-PLP1 recipient mice were deviated and produced interleukin (IL)-4 instead of IL-2, whereas the spleen cells, although nonproliferative, produced IL-2 but not interferon (IFN)-gamma. Exogenous IFN-gamma, as well as IL-12, restored splenic proliferation in an antigen specific manner. IL-12-rescued T cells continued to secrete IL-2 and regained the ability to produce IFN-gamma. In vivo, administration of anti-IL-4 antibody or IL-12 restored disease severity. Therefore, adjuvant-free induced neonatal tolerance prevents autoimmunity by an organ-specific regulation of T cells that involves both immune deviation and a new form of cytokine- dependent T cell anergy.

TCR agonist and antagonist exert in vivo cross-regulation when presented on Igs

Ig-PLP1 and Ig-PLP-LR are chimeric Igs expressing proteolipid protein (PLP)-derived T cell agonist (PLP1) and antagonist (PLP-LR) peptides, respectively. Both chimeras, like free PLP1 and PLP-LR peptides, induce in vivo-specific T cell responses. However, the responses induced by Ig-PLP1 and Ig-PLP-LR were cross-reactive with both PLP1 and PLP-LR peptides, while those induced by free peptides were not. Surprisingly, despite the cross-reactivity of the responses, when Ig-PLP1 and Ig-PLP-LR were administered together into mice, a dose-dependent down-regulation of both T cell responses and a reduction of IL-2 production to background levels was observed. In contrast, when T cells induced by either Ig chimera were stimulated in vitro with mixtures of free PLP1 and PLP-LR peptides, there was no down-regulation of proliferation or decrease in IL-2 production. These data indicate that Ig-PLP1 and Ig-PLP-LR exert adverse reactions on one another at the level of naive T cells, resulting in an opposite antagonism. However, naive T cells experiencing either chimera develop into cross-reactive cells, acquire resistance to TCR triggering by closely related but different peptides, and support responsiveness.

Presentation of a T cell receptor antagonist peptide by immunoglobulins ablates activation of T cells by a synthetic peptide or proteins requiring endocytic processing

T cell receptor (TCR) antagonism is being considered for inactivation of aggressive T cells and reversal of T cell-mediated autoimmune diseases. TCR antagonist peptides silence aggressive T cells and reverse experimental allergic encephalomyelitis induced with free peptides. However, it is not clear whether free antagonist peptides could reverse natural disease where the antigen is presumably available for endocytic processing and peptides gain access to newly synthesized class II MHC molecules. Using an efficient endocytic presentation system, we demonstrate that a proteolipid protein (PLP) TCR antagonist peptide (PLP-LR) presented on an Ig molecule (Ig-PLP-LR) abrogates the activation of T cells stimulated with free encephalitogenic PLP peptide (PLP1), native PLP, or an Ig containing PLP1 peptide (Ig-PLP1). Free PLP-LR abolishes T cell activation when the stimulator is free PLP1 peptide, but has no measurable effect when the stimulator is the native PLP or Ig-PLP1. In vivo, Ig-PLP1 induces a T cell response to PLP1 peptide. However, when coadministered with Ig-PLP-LR, the response to PLP1 peptide is markedly reduced whereas the response to PLP-LR is normal. Free PLP-LR coadministered with Ig-PLP1 has no effect on the T cell response to PLP1. These findings indicate that endocytic presentation of an antagonist peptide by Ig outcompete both external and endocytic agonist peptides whereas free antagonist hinders external but not endocytic agonist peptide. Direct contact with antagonist ligand and/or trans-regulation by PLP-LR-specific T cells may be the operative mechanism for Ig-PLP-LR-mediated downregulation of PLP1-specific T cells in vivo. Efficient endocytic presentation of antagonist peptides, which is the fundamental event for either mechanism, may be critical for reversal of spontaneous T cell-mediated autoimmune diseases where incessant endocytic antigen processing could be responsible for T cell aggressivity.

Engineering of doubly antigenized immunoglobulins expressing T and B viral epitopes

BACKGROUND

Concomitant with the advent of molecular biology techniques and the ability of immunoglobulins (Ig) to recognize proteins, carbohydrates, lipopeptides and nucleic acids, vaccinologists have taken advantage to develop a variety of prophylactic and therapeutic vaccine prototypes. Presentation of epitopes to the immune system by Ig molecules as a carrier platform offers several advantages: (i) long exposure of the antigen to antigen processing cells (APCs) by virtue of their long half life, (ii) lack of the immune response to self Ig, focusing the immune response to protective epitopes rather than irrelevant epitopes, (iii) it takes advantage of the properties of Fc fragment of various isotypes like crossing the placenta (IgG) or homing in epithelia (IgA), and (iv) targeting various antigens by virtue of their binding specificity.

OBJECTIVES

This study was aimed to genetically and enzymatically engineer immunoglobulins (Igs) able to express and to deliver concomitantly immunodominant T and B viral epitopes.

STUDY DESIGN

Using a genetic engineering approach we replaced the complementary determining region 3 (CDR3) and complementary determining region 2 (CDR2) of an anti-arsonate 91A3 mAb with the immunodominant HA110-120 T cell epitope and HA150-159 B cell epitope of hemagglutinin (HA) of influenza A/PR8 virus, respectively. The second doubly antigenized Ig (Ig-HA-Gal-B) was constructed on an Ig in which CDR3 was replaced with HA110-120 T cell epitope while the HA150-159 B cell epitope was enzymatically assembled through an imidic bond on the galactose (Gal) residues of the carbohydrate moiety.

RESULTS AND CONCLUSIONS

Both genetically and genetically/enzymatically doubly antigenized Ig constructs (dAIg) were properly folded and they were able to activate peptide-specific T cells and to elicit anti-viral antibody response in mice. This demonstrates that the CDR loops as well as carbohydrate moieties of immunoglobulins represent permissive sites for grafting foreign epitopes without altering the structural integrity of immunoglobulins and the immunogenicity of the viral peptides.

Purification of antigenized immunoglobulins derivatized with monomethoxypolyethylene glycol

Genetically engineered immunoglobulins (Igs) carrying viral B or T cell peptides in the CDR3 loop, function as efficient delivery system of the defined viral epitopes. Two of these antigenized Igs (AIgs) were derivatized with 2-O-monomethoxypolyethylene glycol-4,6-dichloro-s-triazine (mPEG). Herein, we describe a two-step strategy to purify mPEG-derivatized AIgs (AIgs-mPEG). Unreacted mPEG polymers were removed by size-exclusion chromatography using ammonium hydrogencarbonate as a buffer system. Mildly PEGylated AIgs were isolated from free and highly derivatized AIgs by anion-exchange chromatography. Electrophoretic analysis indicated that the AIgs-mPEG preparation contained less than 4 x 10(-4) M unreacted mPEG. This strategy may be applied to other mPEG-derivatized monoclonal antibodies.

Derivatization with monomethoxypolyethylene glycol of Igs expressing viral epitopes obviates adjuvant requirements

Ig molecules expressing within the CDR3 loop viral B or T cell epitopes were derivatized with mPEG 5,000. Pegylated Ig were used to investigate the in vitro and in vivo effect of pegylation on the immunogenicity of viral epitopes expressed in chimeric Ig. Two chimeras were used in this study: Ig-HA carrying a CD4 epitope corresponding to amino acid residues 110-120 of the hemagglutinin (HA) of PR8 influenza A virus and Ig-V3C, a murine-human chimera carrying a consensus B cell epitope from the V3 loop of HIV-1 gp120 protein. Pegylated Ig-HA (Ig-HA-mPEG) with 6 to 8% substituted lysine residues showed in vivo resistance to enzymatic degradation and persisted significantly in blood circulation and lymphoid organs. Moreover, Ig-HA-mPEG was able to activate in vitro HA110-120-specific hybridoma T cells and to prime T cell proliferative response in vivo without requirement for adjuvant. Also, mildly pegylated Ig-V3C (Ig-V3C-mPEG) administered into BALB/c mice in the absence of adjuvant induced specific Ab response to V3C peptide with insignificant response to xenogeneic human Ig determinants.

Derivatization with monomethoxypolyethylene glycol of Igs expressing viral epitopes obviates adjuvant requirements

Ig molecules expressing within the CDR3 loop viral B or T cell epitopes were derivatized with mPEG 5,000. Pegylated Ig were used to investigate the in vitro and in vivo effect of pegylation on the immunogenicity of viral epitopes expressed in chimeric Ig. Two chimeras were used in this study: Ig-HA carrying a CD4 epitope corresponding to amino acid residues 110-120 of the hemagglutinin (HA) of PR8 influenza A virus and Ig-V3C, a murine-human chimera carrying a consensus B cell epitope from the V3 loop of HIV-1 gp120 protein. Pegylated Ig-HA (Ig-HA-mPEG) with 6 to 8% substituted lysine residues showed in vivo resistance to enzymatic degradation and persisted significantly in blood circulation and lymphoid organs. Moreover, Ig-HA-mPEG was able to activate in vitro HA110-120-specific hybridoma T cells and to prime T cell proliferative response in vivo without requirement for adjuvant. Also, mildly pegylated Ig-V3C (Ig-V3C-mPEG) administered into BALB/c mice in the absence of adjuvant induced specific Ab response to V3C peptide with insignificant response to xenogeneic human Ig determinants.

Induction of antibodies to the human immunodeficiency virus type 1 by immunization of baboons with immunoglobulin molecules carrying the principal neutralizing determinant of the envelope protein

The hypervariable region 3 (V3) within the disulfide-bridged loop of the envelope protein of the human immunodeficiency virus type 1 (HIV-1) contains an amino acid sequence that was defined as a principal neutralizing determinant (PND). A 19-amino acid residue consensus sequence (designated V3C) predicted from the PND sequences of 245 isolates as well as a sequence from the PND of the WMJ2 HIV-1 isolate (designated V3M) were expressed on the variable region of murine-human immunoglobulin (Ig) chimeras that were designated Ig-V3C and Ig-V3M, respectively. The HIV-1 sequences on the Ig chimeras preserved their antigenicity and interacted with antibodies specific for peptides encompassing the V3C and V3M sequences. In baboons, Ig-V3C and Ig-V3M induced antibodies that bound V3C and V3M peptides as well as the glycoprotein gp120 envelope protein of HIV-1 MN isolate. In addition, the baboons' antisera were able to prevent infection of CD4 SupT1 susceptible T cells by HIV-1 MN. Finally, Ig-V3M chimeras were able to stimulate in vitro production of antibodies specific for the HIV-1 envelope-derived peptides by lymphocytes from HIV-1-infected human subjects.

Efficient loading of identical viral peptide onto class II molecules by antigenized immunoglobulin and influenza virus

Several prior reports have identified peptides that are naturally associated with major histocompatibility complex (MHC) class II molecules on presenting cells. We have examined the delivery of a peptide from exogenous sources to MHC class II molecules. The peptide derives from the influenza virus hemagglutinin (HA) and activates a CD4+ T cell hybridoma. In functional assays of antigen presentation, this epitope is delivered effectively to T cells either in the context of influenza virus or chimeric immunoglobulin (Ig) molecules (Ig-HA) in which the peptide has replaced the CDR3 loop of the heavy chain. We find that the identical 11-mer peptide can be isolated from mouse MHC class II antigens whether the exogenous source of peptide is free HA peptide, the Ig-HA chimera, or ultraviolet-inactivated PR8 influenza virus. The Ig-HA chimera proves to be the most efficient vehicle for charging class II molecules via the exogenous route. Given the fact that self Igs represent natural long-lived carriers, we suggest that antigenized Igs have considerable potential for peptide delivery to MHC molecules in situ.

Chimeric influenza virus induces neutralizing antibodies and cytotoxic T cells against human immunodeficiency virus type 1

Expression vectors based on DNA or plus-stranded RNA viruses are being developed as vaccine carriers directed against various pathogens. Less is known about the use of negative-stranded RNA viruses, whose genomes have been refractory to direct genetic manipulation. Using a recently described reverse genetics method, we investigated whether influenza virus is able to present antigenic structures from other infectious agents. We engineered a chimeric influenza virus which expresses a 12-amino-acid peptide derived from the V3 loop of gp120 of human immunodeficiency virus type 1 (HIV-1) MN. This peptide was inserted into the loop of antigenic site B of the influenza A/WSN/33 virus hemagglutinin (HA). The resulting chimeric virus was recognized by specific anti-V3 peptide antibodies and a human anti-gp120 monoclonal antibody in both hemagglutination inhibition and neutralization assays. Mice immunized with the chimeric influenza virus produced anti-HIV antibodies which were able to bind to synthetic V3 peptide, to precipitate gp120, and to neutralize MN virus in human T-cell culture system. In addition, the chimeric virus was also capable of inducing cytotoxic T cells which specifically recognize the HIV sequence. These results suggest that influenza virus can be used as an expression vector for inducing both B- and T-cell-mediated immunity against other infectious agents.

Contrasting efficacy of presentation by major histocompatibility complex class I and class II products when peptides are administered within a common protein carrier, self immunoglobulin

Major histocompatibility complex (MHC) class I and II products are specialized to present antigens via different intracellular processing routes. Peptides originating from proteins in the cytoplasm can gain access to class I peptide-binding grooves, most likely in the rough endoplasmic reticulum. Peptides from proteins in acidic endocytic vacuoles gain access to class II. It has been proposed that MHC class I products also can capture peptides from "exogenous" or noninfectious sources, and this assumption underlies the use of intact proteins as vaccines for CD8+ cytotoxic T lymphocytes. Here we describe quantitative information comparing the efficacy of peptide presentation from exogenous proteins by administering a class I- and II-restricted peptide within the same context, the CDR3 loop of the VH domain of a self immunoglobulin. Antigen-presenting cells (APC), including primary dendritic cells, efficiently present an influenza hemagglutinin peptide from the immunoglobulin (Ig) carrier (50% maximal response at 10 nM Ig-HA) to an MHC class II-restricted T cell. In contrast, these same APC are unable to present an influenza nucleoprotein (NP) peptide from the same context (1 microM Ig-NP) to an MHC class I-restricted T cell. Ig-NP DNA transfectants do present the nucleoprotein viral peptide on class I. Thus, peptides within the complementarity-determining region loops of Ig carriers can be presented on class I or II MHC products, but the endocytic compartment, when offered MHC class I- and II-restricted peptides within the same carrier protein context, favors presentation by class II by at least 1000-fold.

Priming of cytotoxic T lymphocytes at various stages of ontogeny with transfectoma cells expressing a chimeric Ig heavy chain gene bearing an influenza virus nucleoprotein peptide

The amino acid residues 147-161 of the nucleoprotein (NP) of influenza virus represent a T cell epitope recognized by cytotoxic T cells (CTLs) in association with Kd class I molecules. When SP2/0 myeloma B cells are transfected with a chimeric heavy chain gene bearing this particular NP(147-161) peptide, they are lysed by CTLs specific for the NP(147-161) peptide. Cells that are transfected with this heavy chain chimera and the parental light chain secreted a soluble Ig-NP chimera and were also lysed by the CTLs. Herein, we present evidence that transfectoma cells are able to induce in vitro proliferation of NP specific CTL, whereas immobilized Ig-NP chimeras do not. Furthermore, the transfectoma cells expressing the chimeric heavy chain prime NP specific CTLs in adult as well as in newborn mice, while SP2/0 cells coated with NP(147-161) synthetic peptide do not. These data indicate that the NP peptide needs to be cleaved from the Ig context in order to be presented to T cells and that only endogenously generated NP peptide is immunogenic.

In vivo priming effect during various stages of ontogeny of an influenza A virus nucleoprotein peptide

In vivo priming of cytotoxic T lymphocytes (CTL) by an influenza virus nucleoprotein (NP) peptide was studied at various stages of development. Adult mice immunized twice with the NP peptide in complete Freund's adjuvant and incomplete Freund's adjuvant, respectively, produce significant CTL responses. Neonates immunized at birth with large amounts of NP peptide and boosted twice with the peptide during adulthood, also mount a weak but significant CTL response. By contrast, offspring from mothers immunized with the NP peptide at days 15, 17, and 19 of pregnancy showed unresponsiveness to the peptide subsequent to a similar regimen of peptide immunization at the age of 1 month. The data indicate that the contact of T cell precursors with antigen during fetal life induces CTL tolerance, whereas, after birth the precursors are not susceptible to tolerogenic signals.

A sensitive method to detect defined peptide among those eluted from murine MHC class II molecules

We developed a sensitive competitive inhibition radioimmunoassay able to trace pmoles of a defined peptide eluted from major histocompatibility complex (MHC) class II molecules that were subsequently fractionated by RP-HPLC. In this assay we used a model synthetic peptide corresponding to amino acid residues 110-120 from the hemagglutinin (HA) of PR8 influenza virus, and affinity purified rabbit antibodies specific for this peptide. The HA110-120 peptide binds to I-Ed class II molecules on the surface of APCs and is recognized by specific CD4+ T helper cells. 2PK3 B lymphoma cells (H-2d) were pulsed with HA110-120 peptide or PR8 virus, lysed, the MHC class II molecules extracted, and bound peptides eluted. After separation by RP-HPLC, the fractions were tested for inhibition of the binding of rabbit anti-HA110-120 antibodies to peptide coated microtiter plates. A significant inhibitory activity was observed with one peak when the cells were pulsed with HA110-120 peptide and two peaks when pulsed with PR8 virus. The inhibitory activity was correlated with the presence of HA110-120 peptide as demonstrated by peptide sequencing. The assay is reproducible and sensitive to 1 pmol of antigenic peptide. This assay can be useful to identify microbial peptides with defined structure and antigenicity among the multiple peptides bound to class II molecules.

Presentation of a viral T cell epitope expressed in the CDR3 region of a self immunoglobulin molecule

Synthetic peptides corresponding to microbial epitopes stimulate T cell immunity but their immunogenicity is poor and their half-lives are short. A viral epitope inserted into the complementarity-determining region 3 (CDR3) loop of the heavy chain of a self immunoglobulin (Ig) molecule was generated from the Ig context and was presented by I-Ed class II molecules to virus-specific, CD4+ T cells. Chimeric Ig-peptide was presented 100 to 1000 times more efficiently than free synthetic peptide and was able to prime virus-specific T cells in vivo. These features suggest that antigenized Ig can provide an improved and safe vaccine for the presentation of microbial and other peptides.

Engineered immunoglobulin molecules as vehicles for T cell epitopes

The variable regions (V) of immunoglobulins (Ig) bear antigenic determinants that can stimulate both humoral and cellular immune responses subsequent to hetero, allo or iso-immunization. The expression of these determinants by Igs usually correlates with the presence of specific amino acid residues within the CDR loops of the V regions. Since the CDR loops varies in length, we reasoned that they would represent permissive sites to insert foreign peptides and create antigenized Igs expressing selected determinants. Taking advantage of these properties and the fact that Igs are self and long-lived molecules, we expressed a CTL and a helper epitope of influenza virus nucleoprotein and hemagglutinin respectively, within the heavy chain CDR3 loop of an anti-arsonate antibody. We found that foreign peptides comprised of 11 to 15 amino acid residues can be expressed within the V region of the heavy chain without alteration of pairing with the light chain. More striking, the cellular processing machinery is able to generate the peptides from the Ig context which were then recognized by specific T cells. Furthermore, the engineered Igs are able to induce T cell responses specific for the inserted peptide and for influenza virus. The use of engineered Ig molecules as vehicles for T and B cell peptides might represent a valuable strategy to generate safe, long lived reagents able to stimulate strong specific immune responses. This would then overcome the short half life of synthetic peptides based vaccines and the side effects seen in case of recombinant viral proteins or inactivated viruses based vaccines.

Further studies on the adjuvanticity of stearyl tyrosine and ester analogues

A new family of immunoadjuvants, long-chain stearyl esters of amino acids and peptides, are described and examined with bacterial and viral vaccines. The parent compound, stearyl tyrosine, displayed significant adjuvant activity with these vaccines. Stearyl glycyl glycine displayed superior activity with viral vaccines. A number of analogues of stearyl tyrosine were adjuvant-active. Further, these adjuvants were able to elicit a neutralizing antibody response. Stearyl tyrosine and stearyl ester analogues represent promising adjuvants for human vaccines.

A single amino acid mutation in CDR3 of the 3-14-9 L chain abolished expression of the IDA 10-defined idiotope and antigen binding

The ABPC 48 myeloma protein and the 3-14-9 mAb derive their V region genes from the same VH and V kappa gene families. They also share a cross-reactive idiotope defined by the anti-Id mAb IDA 10. Whereas ABPC 48 is specific for bacterial levan, 3-14-9 showed a significant Ag-binding activity to aminophenyl-beta-N-acetylglucosaminide (AZO). In order to define the molecular basis of idiotope expression and Ag-binding activity, we have cloned the genes encoding the 3-14-9 H and L chain V region genes, generated antibodies that carry mutations within the L chain genes, by site-directed mutagenesis, and investigated the effects of those mutations with respect to IDA 10 idiotope expression and binding to AZO. Our findings show that, whereas expression of the IDA 10-defined idiotope requires association of both the H and L chains, a single change (glycine to phenylalanine) at position 91 in the third complementarity-determining region of the L chain abolished both idiotope expression and Ag-binding activity. In addition, a L chain change of alanine to threonine at position 25 allowed idiotope expression to some extent but significantly reduced binding activity to AZO. These data suggest that a single amino acid change can play a crucial role in the functional activity and structural integrity of antibodies.

A single amino acid mutation in CDR3 of the 3-14-9 L chain abolished expression of the IDA 10-defined idiotope and antigen binding

The ABPC 48 myeloma protein and the 3-14-9 mAb derive their V region genes from the same VH and V kappa gene families. They also share a cross-reactive idiotope defined by the anti-Id mAb IDA 10. Whereas ABPC 48 is specific for bacterial levan, 3-14-9 showed a significant Ag-binding activity to aminophenyl-beta-N-acetylglucosaminide (AZO). In order to define the molecular basis of idiotope expression and Ag-binding activity, we have cloned the genes encoding the 3-14-9 H and L chain V region genes, generated antibodies that carry mutations within the L chain genes, by site-directed mutagenesis, and investigated the effects of those mutations with respect to IDA 10 idiotope expression and binding to AZO. Our findings show that, whereas expression of the IDA 10-defined idiotope requires association of both the H and L chains, a single change (glycine to phenylalanine) at position 91 in the third complementarity-determining region of the L chain abolished both idiotope expression and Ag-binding activity. In addition, a L chain change of alanine to threonine at position 25 allowed idiotope expression to some extent but significantly reduced binding activity to AZO. These data suggest that a single amino acid change can play a crucial role in the functional activity and structural integrity of antibodies.

Cells expressing an H chain Ig gene carrying a viral T cell epitope are lysed by specific cytolytic T cells

The epitope corresponding to amino acid residues 147-161 of the nucleoprotein (NP) of influenza A virus is recognized by CTL in association with H-2Kd class I Ag. Herein, we engineered an Ig molecule carrying this CTL epitope by replacing the diversity gene segment of the H chain V region of an anti-arsonate antibody with an oligonucleotide that encodes the CTL epitope. The chimeric H chain gene was expressed either alone or together with the parental L chain in the nonsecreting BALB/c myeloma B cell line, SP2/0. The Ig produced by cells transfected with both the chimeric H chain and parental L chains genes expressed the NP epitope but lost the original arsonate binding activity. In addition, SP2/0 cells expressing the chimeric H chain either alone or together with the parental L chain were lysed by class I restricted NP-epitope specific CTL. By contrast, SP2/0 cells pulsed with soluble chimeric Ig molecules were not lysed by the specific CTL. These observations indicate that: 1) this particular CTL epitope can be expressed on Ig molecules without altering the H and L chain pairing; 2) this CTL epitope can be generated from this chimeric Ig in which it is surrounded by flanking regions distinct from those of the viral NP; and 3) the generation of this CTL epitope from the Ig molecule requires the endogenous pathway as do viral proteins.

Cells expressing an H chain Ig gene carrying a viral T cell epitope are lysed by specific cytolytic T cells

The epitope corresponding to amino acid residues 147-161 of the nucleoprotein (NP) of influenza A virus is recognized by CTL in association with H-2Kd class I Ag. Herein, we engineered an Ig molecule carrying this CTL epitope by replacing the diversity gene segment of the H chain V region of an anti-arsonate antibody with an oligonucleotide that encodes the CTL epitope. The chimeric H chain gene was expressed either alone or together with the parental L chain in the nonsecreting BALB/c myeloma B cell line, SP2/0. The Ig produced by cells transfected with both the chimeric H chain and parental L chains genes expressed the NP epitope but lost the original arsonate binding activity. In addition, SP2/0 cells expressing the chimeric H chain either alone or together with the parental L chain were lysed by class I restricted NP-epitope specific CTL. By contrast, SP2/0 cells pulsed with soluble chimeric Ig molecules were not lysed by the specific CTL. These observations indicate that: 1) this particular CTL epitope can be expressed on Ig molecules without altering the H and L chain pairing; 2) this CTL epitope can be generated from this chimeric Ig in which it is surrounded by flanking regions distinct from those of the viral NP; and 3) the generation of this CTL epitope from the Ig molecule requires the endogenous pathway as do viral proteins.

Adjuvanticity of stearyl tyrosine on the antibody response to peptide 503-535 from HIV gp160

In this present report we compare the humoral immune response induced by immunization with an HIV-1 gp160 peptide corresponding to amino acid sequence 503-535 complexed with different adjuvants. Specifically, the antipeptide, anti-HIV-1 gp160 and neutralizing antibody responses were measured in groups of mice and baboons that received peptide 503-535 conjugated to a carrier protein in either saline, alum, or stearyl tyrosine. The highest antibody responses were induced when mice and baboons were immunized with peptide adsorbed on stearyl tyrosine. These data indicate that stearyl tyrosine represents a potent candidate as a nontoxic adjuvant not only for subunit viral vaccines, but also for HIV peptides.