Removal of amphipathic epitopes from genetically engineered antibodies: production of modified immunoglobulins with reduced immunogenicity

Several approaches have been developed to reduce the human immune response to nonhuman antibodies. However, chimeric antibodies and humanized antibodies often have decreased binding affinity. We described a new approach for reducing the immunogenicity of chimeric antibodies while maintaining the affinity. This approach seeks to prevent the recognition of murine immunogenic peptides from the antibody variable region by human lymphocytes. Putative immunogenic epitopes in the variable region are identified and subjected to site directed mutagenesis to make them human and/or to break the amphipathic motifs. The R3 antibody, which blocks the epidermal growth factor (EGF) receptor, was used as a model system to test this approach. Four segments containing possible amphipathic epitopes were found in the heavy variable domain using the program AMPHI. Six amino acids within two of these segments were substituted by the corresponding residues from a homologous human sequence. No mutations were made in the murine light variable domain. Experiments in monkeys suggested that the "detope" R3 antibody was less immunogenic than its chimeric analogue. A search for possible amphipathic epitopes in the Kabat database revealed the presence of conserved patterns in the different families of variable region sequences, suggesting that the proposed method may be of general applicability.     

Allergen-specific regulation of allergic rhinitis in mice by intranasal exposure to IgG1 monoclonal antibody Fab fragments against pathogenic allergen

Fab fragments (Fabs) have the ability to bind to specific antigens but lack the Fc portion for binding to receptors on immune and inflammatory cells that play a critical role in allergic diseases. In the present study, we investigated whether Fabs of an allergen-specific IgG1 monoclonal antibody (mAb) inhibited allergic rhinitis in mice. BALB/c mice sensitized by intraperitoneal injections of ovalbumin (OVA) plus alum on days 0 and 14 were intranasally challenged with OVA on days 28–30, and 35. Fabs prepared by the digestion of an anti-OVA IgG1 mAb (O1–10) with papain were also intranasally administered 15 min before each OVA challenge. The results showed that treatment with O1–10 Fabs significantly suppressed the sneezing frequency, associated with decrease of OVA-specific IgE in the serum and infiltration by mast cells in the nasal mucosa seen following the fourth antigenic challenge; additionally, the level of mouse mast cell protease-1, a marker of mast cell activation, in serum was decreased. Furthermore, infiltration of eosinophils and goblet cell hyperplasia in the nasal mucosa at the fourth challenge were inhibited by treatment with O1–10 Fabs. In conclusion, these results suggest that intranasal exposure to Fabs of a pathogenic antigen-specific IgG1 mAb may be effective in regulating allergic rhinitis through allergen capture by Fabs in the nasal mucosa before the interaction of the intact antibody and allergen.     

Suppression of reaginic antibodies with modified allergens. II. Abrogation of reaginic antibodies with allergens conjugated to polyethylene glycol

The two immunogenic preparations, ovalbumin (OA) and the nondialysable constituents of the aqueous extract of ragweed pollen (RAG), were conjugated with polyethylene glycols of molecular weights of 6,000 and 20,000 (PEG6 and PEG20) with the aid of cyanuric chloride. The i.v. administration of OA-PEG6 or OA-PEG20 into normal mice or into mice sensitized to a state of immediate hypersensitivity to dinitrophenylated OA (DNP3-OA) resulted, respectively, in the suppression of the primary or secondary IgE responses to DNP and OA. Similarly, the administration of RAG-PEG6 abrogated the primary as well as the ongoing anti-RAG reaginic responses in mice sensitized to RAG. The unresponsiveness of spleen cells from animals which had received a tolerogenic dose of OA-PEG6 was also maintained after transfer into X-irradiated (550 rad) mice. The suppressive effects of the tolerogenic PEG conjugates of OA and RAG were shown to be immunologically specific. It is, therefore, suggested that PEG-modified allergens may prove useful for the abrogation of the IgE response to a variety of allergens responsible for conditions of common hypersensitivity in man.     

Gene gun immunization with clinically relevant allergens aggravates allergen induced pathology and is contraindicated for allergen immunotherapy

Gene gun immunization has been associated with the induction of a heterologous type of immune response characterized by a T(H)1-like immune reaction on the cellular level, i.e. generation of IFN-gamma secreting CD8(+) T-cells, yet a T(H)2 biased serology as indicated by high IgG1:IgG2a ratios and induction of IgE. Nevertheless, gene gun immunization using the model molecule beta-galactosidase has been argued to prevent IgE induction and to promote T(H)1 cells with respect to allergy DNA immunization. In our current study, we evaluated the potential of gene gun immunization to prevent type I allergic reactions comparing beta-galactosidase with two clinically relevant allergens, and further investigated the effect of gene gun immunization on relevant lung parameters. BALB/c mice were immunized with plasmids encoding the birch pollen allergen Bet v 1, the grass pollen allergen Phl p 5, or the model molecule beta-galactosidase, either by gene gun or intradermal injection followed by sensitization and intranasal provocation with the respective allergen. IgG1 and IgG2a antibody titers were determined by ELISA. IgE levels were evaluated in a rat basophil release assay. The severity of eosinophilia was determined in bronchoalveolar lavages, and the overall infiltrate was analyzed by histology on lung paraffin sections. Gene gun immunization induced a T(H)2-biased immune reaction, which did not prevent from production of IgE after subsequent sensitization. This T(H)2 effect was influenced by the nature of the antigen, with a more pronounced T(H)2-bias for the allergens Bet v 1 and Phl p 5 compared to beta-galactosidase. Gene gun immunization with all three antigens promoted eosinophil influx into the lung and did not alleviate lung pathology after intranasal provocation. In contrast to needle injection of plasmid DNA, which triggers a clearly T(H)1-biased and allergy-preventing immune response, gene gun application fails to induce anti-allergic reactions with all tested antigens and is therefore contraindicated for allergen-specific immunotherapy.     

T-cell activation by transgenic rice seeds expressing the genetically modified Japanese cedar pollen allergens

Transgenic rice seeds that contain genetically modified Cry j 1 and Cry j 2, the two major allergens of Cryptomeria japonica (Japanese cedar; JC), have been developed as immunotherapeutic candidates for JC pollinosis. Because the transgenic rice (TG-rice) seeds express allergens containing whole amino acid sequences of Cry j 1 and Cry j 2 in the endosperm tissue (edible part of rice grain), they can potentially target all Cry j 1- and Cry j 2-specific T-cells. However, it was unknown whether antigenicity of Cry j 1 and Cry j 2 could be completely preserved in TG-rice seeds. We verified the antigenicity of TG-rice seeds to T-cells through the analysis of the proliferative responses of T-cells in Cry j 1- or Cry j 2-immunized mice or T-cell lines to TG-rice seed extract. First, four mouse strains were immunized with Cry j 1 or Cry j 2. T-cells in the immunized mice proliferated on treatment with TG-rice seed extract, but not non-transgenic wild-type rice (WT-rice) seed extract. Furthermore, T-cell lines were established from the spleen cells of the immunized mice. Each T-cell line resulted in a proliferative response to TG-rice seed extract, but not to WT-rice seed extract, suggesting that TG-rice seeds certainly express T-cell epitopes corresponding to T-cell lines. Considering the modified amino acid sequences of Cry j 1 and Cry j 2 in TG-rice seeds, the expression of specific T-cell epitopes suggested that TG-rice seeds express all possible T-cell epitope repertoires of Cry j 1 and Cry j 2.     

Costs associated with persistent allergic rhinitis are reduced by levocetirizine

BACKGROUND: Allergic rhinitis was recently classified by the ARIA guidelines as persistent or intermittent. Levocetirizine was shown to improve symptoms and health-related quality of life of patients with persistent allergic rhinitis in the XPERT study, a 6-month randomized double blind placebo-controlled trial. OBJECTIVE: To assess the total costs of persistent allergic rhinitis, and the effect of long-term treatment with levocetirizine on these costs from several perspectives (societal, social security system, and employers). METHODS: Direct medical cost parameters (medications, physician visits and hospitalizations) and time lost parameters (workdays and Usual Daily Activities (UDA) lost) related to persistent allergic rhinitis and its comorbidities (asthma, sinusitis, otitis and upper respiratory infection) were measured. A cost analysis was performed using 2002 French costing data. RESULTS: From a societal perspective, the total cost of persistent allergic rhinitis without long-term treatment was estimated at 355.06/patient/month. From a social security perspective, levocetirizine treatment yielded an additional cost of 2.78/patient/month, compared to no-treatment. However, levocetirizine reduced the total cost of persistent allergic rhinitis and its comorbidities by 152.93/patient/month from a societal perspective and by 64.70/patient/month from an employer perspective. Most gains resulted from a decrease in the lost workdays and UDA in the levocetirizine group. CONCLUSION: The cost of persistent allergic rhinitis is substantial. Treatment with levocetirizine reduces the cost of persistent allergic rhinitis and its comorbidities to the society by 152.93/patient/month while improving symptoms and health-related quality of life.     

An approach to the understanding of the nasal early-phase reaction induced by nasal allergen challenge

Quantitative determinations of the inflammatory mediators in nasal secretions were performed and correlated with the objective nasal symptoms within 1 h after nasal allergen challenge (NAC). Twenty-six patients with seasonal allergic rhinitis were enrolled outside the pollen season. All measurements were performed before (as a baseline control) and at 1, 5, 10, 30, and 60 min after NAC. This study aimed to clarify the pathogenic mechanism of the early-phase reaction (EPR) by monitoring the evolution of early-phase mediators in nasal secretions and the presence of nasal symptoms during this period. The results showed that, after NAC, the maximal mediator concentration was already reached after 1 min for histamine (124 ng/g), 5 min for tryptase (56 μU/g), and 5-10 min for leukotriene C₄ (40 ng/g). Itching and sneezing started as early as 20-30 s, and they were predominant symptoms within 5 min. Rhinorrhea and nasal obstruction started a few minutes after NAC and lasted until more than 1 h after NAC. There was no significant correlation between any single mediator and nasal symptoms during the sampling period. In conclusion, this study demonstrated that during the EPR the presence of nasal symptoms involves a complex mechanism, reflecting the interaction between the mediators released by inflammatory cells, and the receptors on different target organs. When evaluating symptoms during the EPR, one must consider not only the severity of these symptoms but also the time period within which these symptoms occur. For the symptoms of nasal obstruction and rhinorrhea, the early-phase reaction often lasted more than 1 h.     

IgA rheumatoid factor and IgG dietary protein antibodies are associated in rheumatoid arthritis

This study sought to determine whether patients with rheumatoid arthritis (RA) were immunologically sensitised to dietary protein (DP). Using an enzyme linked immunosorbent assay (ELISA), antibodies to milk and wheat proteins were measured in 93 unselected out-patients with classical or definite RA. Of these 93, 53 had raised levels of IgG antibodies to one or both dietary proteins (DP). In the DP antibody positive group, 48 patients (90%) also had raised levels of IgA rheumatoid factor (measured by ELISA) while only 7 (17%) of the 40 DP antibody negative patients had detectable IgA RF; P less than 0.02. There was no association between IgM rheumatoid factor and dietary protein antibodies. These results demonstrate that in RA, raised levels of IgA RF are associated with an increased IgG response to antigens which enter the body through the gastrointestinal tract. A breakdown in gastrointestinal tolerance to dietary antigens may play a role in the immunopathogenesis of RA in these patients who might therefore benefit from dietary manipulation.     

IgG subclass distribution of anti-HBs antibodies following vaccination with cDNA HBsAg.

Serum samples were obtained during follow-up of nine young adults vaccinated over 1 year with cDNA hepatitis B antigen. The absolute amounts of anti-HBs IgG subclass antibodies present in the sera were determined by comparing the optical densities (OD) obtained using an antigen-specific ELISA with those obtained by serial dilutions of known amounts of human IgG1-4. The calibration curves for each IgG subclass were corrected for the corresponding coating efficiency. Our data suggest that HBs antibody responses of vaccinated subjects occur in all IgG subclasses but IgG1 and IgG2 are the major subclasses involved.     

Inhibition of CD23‐dependent facilitated allergen binding to B cells following vaccination with genetically modified hypoallergenic Bet v 1 molecules

Background Vaccination with hypoallergenic recombinant Bet v 1 derivatives (Bet v 1 fragments and Bet v 1 trimer) is associated with the induction of IgG antibodies specific to natural Bet v 1. Objective To investigate whether IgG antibodies induced following vaccination with genetically modified hypoallergenic Bet v 1 derivatives are able to inhibit IgE‐facilitated binding of allergen‐IgE complexes to B cells. Methods Sera from 46 patients obtained before and after subcutaneous vaccination with Bet v 1 trimer (n=14), Bet v 1 fragments (n=11) or placebo (n=21) were incubated with recombinant (r) Bet v 1 and an indicator serum (IS) from a birch pollen‐allergic patient with high CD23 binding capacity. Bet v 1 immune complexes were added to a CD23‐expressing B cell line and co‐operative binding of Bet v1‐IgE complexes to CD23 was measured with a polyclonal anti‐IgE FITC antibody using a bio‐functional cellular flow cytometric assay. Results When sera from patients vaccinated with rBet v 1 derivatives were incubated with Bet v 1 and the IS, a reduction of IgE binding to CD23 was observed. This effect was not seen when sera from placebo‐treated patients were used. The decrease in CD23/IgE binding was statistically significant in the trimer group [pre‐ vs. post‐specific immunotherapy (SIT): P=0.02; trimer vs. placebo: P<0.04] but not in the Bet v 1 fragments‐treated group. Trimer‐treated patients had higher levels of Bet v 1‐specific IgG than fragment‐treated patients. The degree of inhibitory activity of IgE‐facilitated allergen binding correlated with Bet v 1‐specific IgG levels following SIT (R=0.492; P=0.012). Conclusion Vaccination with both recombinant Bet v 1 derivatives induces Bet v 1‐specific IgG antibodies, which are able to inhibit the co‐operative binding of allergen‐IgE complexes to CD23, and may thereby reduce allergen‐specific T cell responses. Cite this as: I. Pree, M. H. Shamji, I. Kimber, R. Valenta, S. R. Durham and V. Niederberger, Clinical & Experimental Allergy, 2010 (40) 1346–1352.     

High IgG4 antibody level is associated with failure of immunotherapy with inhalant allergens

We have analysed all available data on the relationship between IgG4 Ab level and clinical effect of immunotherapy (IT) with inhalant allergens. The data from three of the seven independent studies could, without reservations, be analysed by a joint statistical analysis. We found that late high IgG4 Ab level, measured at the end of IT, was strongly associated with treatment failure ( P = 6.54 ± 10⁵; n = 67). The ratio of risks for treatment success in the group with late low IgG4 Ab level was 1.82, whereas the ratio of risks for treatment failure in the group with late high IgG4 Ab level was 11.4. The data from a fourth, presumably comparable, study further supported the existence of an association between high IgG4 Ab level and treatment failure. In contrast, two other studies found that high mean IgG4 Ab level was associated with good clinical response. Possible reasons for this apparent discrepancy are discussed. We also found that early high IgG4 Ab level, measured within 3 months after initiation of IT, was strongly associated with treatment failure after 1–2 years of IT ( P = 1.05 ± 10⁻⁴; n = 30). The sensitivity and specificity of early high IgG4 Ab level as indicator for treatment failure was 100% and 83%, respectively. At the prevalences found in the present study, the predictive value of early high IgG4 Ab level for treatment failure was 0.6, whereas the predictive value of early low IgG4 Ab level for treatment success was 1.00.     

Tolerance to experimental contact sensitivity induced by T cell vaccination

It was shown previously that experimental autoimmune diseases could be prevented or treated specifically by administering suitably attenuated autoimmune T lymphocytes to animals, a process termed T cell vaccination (Cohen, I. R., Sci. American 1988. 256: 52). We now report that T cell vaccination is an effective way of inducing tolerance to contact sensitivity to simple chemical haptens. Vaccines were prepared from populations of lymph node cells from specifically sensitized mice by activating the T cells with the T cell mitogen concanavalin A and then treating the T cell blasts with glutaraldehyde. The vaccinated mice showed decreased delayed sensitivity responses to the specific sensitizing antigen and developed significant delayed sensitivity responses to the T cells of the same specificity as those used for vaccination. Thus, T cell vaccination against contact sensitivity reactions appears to function similarly to T cell vaccination against autoimmune disease.     

Major allergens in soybean and clinical significance of IgG4 antibodies investigated by IgE- and IgG4-immunoblotting with sera from soybean-sensitive patients

Background Soybean occasionally causes food allergy but its major allergens have not been sufficiently confirmed. The relationship between food allergy and food-specific IgG4 has also not been defined. Objective We investigated the allergenicity of soybean proteins and the clinical significance of soybean-specific IgG4. Methods We detected IgE- and IgG4-binding proteins in soybean by immunoblotting with sera from 30 soybean-sensitive patients (including seven patients with positive soybean challenge tests). The extract from soybeans was fractionated into tbe whey fraction and the globulin fraction. Results Ten and eight proteins were detected as IgE- and IgG4-binding proteins, respectively, with a significant difference between tbe patient and control groups. Among the IgE-binding proteins, the proteins with molecular weights of 20000 and 58000 in the whey traction, and 26000 and 31000 in the globulin Traction, had a particularly high IgE detection rate and high specificity. Two patients with positive challenge tests showed a quite different pattern in which only a protein with a molecular weight of 78000 in the globulin fraction was detectable with serum IgE in both patients. The majority of lgG4-binding proteins were not consistent witb tbe IgE-binding proteins. The strong reactivity of lgG4 was observed in all five infants among seven patients with positive challenge tests, and three of them had a very weak IgE reactivity. Conclusions There were various antigenic proteins in soybean. Five proteins with molecular weights of 20000 and 58000 in the whey fraction, and 26000. 31000 and 78000 in the globulin fraction, were considered major allergens in the IgE-mediated reaction. Results of IgE- and IgG4-immunoblotting suggested that soybean-specific IgG4 may act anaphy lactically in patients witb soybean allergy.     

Induction of IgG antibodies against the GD2 carbohydrate tumor antigen by vaccination with peptide mimotopes

The disialoganglioside GD2, a carbohydrate antigen, is expressed on all tumors of neuroectodermal origin, including melanoma, neuroblastoma, sarcoma and small cell lung cancer. Due to its specific expression on tumor surfaces, GD2 is an attractive target for immunotherapies. The mouse/human chimeric anti-GD2 mAb ch14.18 is already applied in melanoma and neuroblastoma trials as a passive immunotherapy. To establish an active immunotherapy alternative, we aimed to replace the poorly immunogenic ganglioside with immunogenic peptides. Previously, we used the ch14.18 antibody to select GD2 peptide mimics from a phage display library. In the present study, two mimics of the ch14.18 epitope were coupled to keyhole limpet hemocyanin and used for immunizing BALB/c mice. Induction of a specific humoral immune response towards the original antigen GD2, both purified and expressed on neuroblastoma and melanoma cells, could be demonstrated in ELISA, Western blot, and immunofluorohistochemistry. As the elicited antibodies were of the IgG isotype, the mimotope conjugates were capable of recruiting T cell help and inducing memory phenomena. In conclusion, we show that an epitope of the carbohydrate antigen GD2 can successfully be translated into immunogenic peptide mimotopes. Our immunization experiments indicate that GD2 mimotopes are suitable for active immunotherapy of GD2-expressing tumors.     

Suppression of reaginic antibodies with modified allergens. I. Reduction in allergenicity of protein allergens by conjugation to polyethylene glycol.

The conjugates of ovalbumin (OA) and of the nondialysable constitutents of the aqueous extract of ragweed pollen (RAG) with polyethylene glycols of molecular weights of 6,000 or 20,000 (PEG6 or PEG20) were shown to be nonantigenic, nonallergenic and nonimmunogenic. Thus, the i.v. administration of OA-PEG and RAG-PEG conjugates into mice did not elicit antibodies to OA and RAG, respectively, and these conjugates were shown to suppress in an immunologically specific manner the capacity of these animals to mount primary as well as secondary IgE responses to sensitizing doses of dinitrophenylated OA or of RAG. Moreover, the Peg-modified antigens did not combine either in vitro or in vivo with IgE antibodies directed against the natural antigens. Hence, OA-PEG and RAG-PEG conjugates were incapable of triggering allergic reactions in animals possessing IgE antibodies to the unmodified antigens. These PEG-modified antigens were also shown to be tolerogenic.     

Quantitative assessments of IgG and IgE antibodies to inhalant allergens in patients with atopic dermatitis

Using antigen-binding radioimmunoassays, we have measured class specific antibodies against two major inhalant allergens, antigen P₁ from D. Pteronyssinus and Rye I from grass pollen, in sera from 69 patients with atopic dermatitis. The results show that many of the patients have IgE ab to these allergens in keeping with their skin tests. In all cases, the IgE ab was paralleled by IgG ab to the same allergen. In many sera, IgE ab to these inhalant allergens made a significant contribution to the total serum IgE. With two other allergens to which these patients had not been exposed, specific IgE ab was detected in only one serum, whereas the 42 sera tested did not contain IgE ab to diphtheria toxin. Eleven of the adult patients with atopic dermatitis had no history of asthma and had strongly positive skin tests. This group of patients had levels of total IgE and specific ab to antigen P₁ that were very similar to those found in a comparable group of patients who had both atopic dermatitis and asthma. Our recent finding that allergens applied to the skin can induce delayed eczematous lesions provides a mechanism by which allergens could contribute to skin lesions. Our present results support the view that specific sensitivity to common allergens should be taken into account in considering the causes of these patients' skin lesions.