The effectiveness of different rat IgG subclasses as IgE-blocking antibodies in the rat basophil leukaemia cell model

In vivo Induction of Functional Inhibitory IgG Antibodies by a Hypoallergenic Bet v 1 Variant

Allergic sensitization to the major allergen Bet v 1 represents the dominating factor inducing a vast variety of allergic symptoms in birch pollen allergic patients worldwide, including the pollen food allergy syndrome. In order to overcome the huge socio-economic burden associated with allergic diseases, allergen-specific immunotherapy (AIT) as a curative strategy to manage the disease was introduced. Still, many hurdles related to this treatment exist making AIT not the patients’ first choice. To improve the current situation, the development of hypoallergen-based drug products has raised attention in the last decade. Herein, we investigated the efficacy of the novel AIT candidate BM4, a hypoallergenic variant of Bet v 1, to induce treatment-relevant cross-reactive Bet v 1-specific IgG antibodies in two different mammals, Wistar rats and New Zealand White rabbits. We further analyzed the cross-reactivity of BM4-induced Wistar rat antibodies with the birch pollen-associated food allergens Mal d 1 and Cor a 1, and the functional capability of the induced antibodies to act as IgE-blocking IgG antibodies. Enzyme-linked immunosorbent assay (ELISA) was used to determine the titers of rat IgG1, IgG2a, IgG2b, and IgE, as well as rabbit IgG and IgE antibodies. To address the functional relevance of the induced IgG antibodies, the capacity of rat sera to suppress binding of human IgE to Bet v 1 was investigated by using an inhibition ELISA and an IgE-facilitated allergen-binding inhibition assay. We found that the treatment with BM4 induced elevated Bet v 1-specific IgG antibody titers in both mammalian species. In Wistar rats, high BM4-specific IgG1, IgG2a, and IgG2b titers (10⁴ to 10⁶) were induced, which cross-reacted with wild-type Bet v 1, and the homologous allergens Mal d 1 and Cor a 1. Rat allergen-specific IgG antibodies sustained upon treatment discontinuation. Sera of rats immunized with BM4 were able to significantly suppress binding of human IgE to the wild-type allergens and CD23-mediated human IgE-facilitated Bet v 1 binding on B cells. By contrast, treatment-induced IgE antibody levels were low or undetectable. In summary, BM4 induced a robust IgG immune response that efficiently blocked human IgE-binding to wild-type allergens, underscoring its potential therapeutic value in AIT.

E. coli Nissle 1917 is a safe mucosal delivery vector for a birch-grass pollen chimera to prevent allergic poly-sensitization

Allergic poly-sensitization affects a large number of allergic patients and poses a great challenge for their treatment. In this study we evaluated the effects of the probiotic Escherichia coli Nissle 1917 (EcN) expressing a birch and grass pollen allergen chimera 'Bet v 1, Phl p 1 and Phl p 5' (EcN-Chim) on allergy prevention after oral or intranasal application in poly-sensitized mice. In contrast to oral application, intranasal pretreatment with EcN-Chim prior to poly-sensitization led to a significant reduction of lung inflammation (eosinophils, IL-5, and IL-13 in bronchoalveolar lavage) along with suppressed levels of allergen-specific serum IgE. The suppression was associated with increased levels of allergen-specific IgA in lungs and serum IgG2a along with increased Foxp3, TGF-β, and IL-10 mRNA in bronchial lymph nodes. In vitro EcN induced high levels of IL-10 and IL-6 in both lung and intestinal epithelial cells. Importantly, using in vivo imaging techniques we demonstrated that intranasally applied EcN do not permanently colonize nose, lung, and gut and this strain might therefore be a safe delivery vector against allergy in humans. In conclusion, our data show that intranasal application of recombinant EcN expressing a multiallergen chimera presents a novel and promising treatment strategy for prevention of allergic poly-sensitization.

IgG subclass co-expression brings harmony to the quartet model of murine IgG function

A model of murine IgG function is presented in which the co-expression of the IgG subclasses is a central feature, class switching occurs before the commencement of somatic hypermutation, and there is little switching between subclasses. It is named the quartet model to emphasize the harmony that comes from the simultaneous presence of the four subclasses. In this model, IgG3 and IgG2b antibodies are particularly important early in the response, when T-cell help may be limiting. IgG3 initiates inflammation through complement fixation, whereas IgG2b provides early FcγR-mediated effector functions. As T-cell help strengthens, IgG2a antibodies increase the power of the response, whereas IgG1 production helps limit the inflammatory drive and limits immunopathology. The model highlights the fact that murine IgG subclasses function quite differently to human IgG subclasses. This allows them to serve the special immunological needs of a species that is vulnerable because of its small size.

The role of casein-specific IgA and TGF-β in children with food protein-induced enterocolitis syndrome to milk

BACKGROUND

Food protein-induced enterocolitis syndrome (FPIES) is a gastrointestinal hypersensitivity disorder with a poorly understood pathophysiology and no biomarkers to aid in diagnosis.

OBJECTIVE

To investigate humoral and cellular responses to casein in children with milk-FPIES, including the role of casein-specific (cs) IgA and T-cell mediated TGF-β responses.

PATIENTS AND METHODS

Thirty-one children previously diagnosed with milk-FPIES were challenged with milk. Twelve age-matched children with FPIES to other foods and 6 milk-tolerant children without a history of FPIES were used as controls. Casein-specific IgE, IgG, IgG4, and IgA were measured in serum and TGF-β levels in supernatants of casein-stimulated PBMCs.

RESULT

Twenty-six children with milk-FPIES reacted (active milk-FPIES) and five tolerated milk (milk-FPIES resolved) during food challenge. All of them had significantly lower levels of csIgG, csIgG4, and csIgA than control children (p-value<0.001). There were no TGF-β responses in supernatants of active milk-FPIES children.

CONCLUSION

Children with milk-FPIES have low levels of csIgG, csIgG4, and csIgA. In particular, children with active FPIES to cow's milk have deficient T-cell mediated TGF-β responses to casein, rendering TGF-β a promising biomarker in identifying children who are likely to experience FPIES reactions to this allergen. Prospective studies are needed to validate these findings, elucidate their role in FPIES pathophysiology, and establish the diagnostic utility of TGF-β in milk-induced FPIES.

Egg-white-specific IgA and IgA2 antibodies in egg-allergic children: is there a role in tolerance induction?

BACKGROUND

Decreased serum food-specific IgA antibodies have been associated with allergic disease in cross-sectional, case-control studies. The purpose of this study was to prospectively compare egg-white-(EW)-specific IgA and IgA2 levels between egg-allergic children and children tolerating egg.

METHODS

Seventeen egg-allergic children were followed prospectively. Total IgA, EW-specific IgA, and EW-specific IgA2 levels were measured in their sera with a sensitive ELISA. As negative controls were used children with no previous history of egg allergy. Egg-allergic children with or without concomitant milk allergy were evaluated as additional controls with measurement of casein-specific IgA.

RESULTS

After 2.5 ± 0.9 yrs, nine out of the 17 allergic children became tolerant and eight remained allergic to baked egg. Baseline EW-specific IgA2 levels were significantly lower in the egg-allergic subjects (median 23.9 ng/ml) compared with the negative control subjects (99.4 ng/ml) and increased significantly by 28% over the study time period in eight out of the nine allergic children that became tolerant to baked egg. There was no significant change over time in EW-specific IgA in any of the study groups. Non-milk-allergic subjects with concomitant egg allergy had almost threefold higher casein-specific IgA levels than the milk- and egg-allergic subjects (p = 0.025).

CONCLUSIONS

These results suggest a potential role for allergen-specific IgA2 antibodies in the induction of food tolerance. Furthermore, they support the hypothesis that immature or impaired production of allergen-specific IgA2 may be associated with the pathophysiology of food allergy, a defect that seems to be selective for the culprit allergen.

In vitro modelling of rat mucosal mast cell function in Trichinella spiralis infection

Intestinal infection with the parasitic nematode, Trichinella spiralis, provides a robust context for the study of mucosal mast cell function. In rats, mucosal mast cells are exposed to parasites during the earliest stage of infection, affording an opportunity for mast cells to contribute to an innate response to infection. During secondary infection, degranulation of rat mucosal mast cells coincides with expulsion of challenge larvae from the intestine. The goal of this study was to evaluate the rat bone marrow-derived mast cells (BMMC) and the rat basophilic leukaemia cell line (RBL-2H3) as models for mucosal mast cells, using parasite glycoproteins and antibody reagents that have been tested extensively in rats in vivo. We found that BMMC displayed a more robust mucosal phenotype. Although T. spiralis glycoproteins bound to mast cell surfaces in the absence of antibodies, they did not stimulate degranulation, nor did they inhibit degranulation triggered by immune complexes. Parasite glycoproteins complexed with specific monoclonal IgGs provoked release of rat mast cell protease II (RMCPII) and β-hexosaminidase from both cell types in a manner that replicated results observed previously in passively immunized rats. Our results document that RBL-2H3 cells and BMMC model rat mucosal mast cells in the contexts of innate and adaptive responses to T. spiralis.

The effect of adjuvants on the immune response induced by a DBL4ɛ-ID4 VAR2CSA based Plasmodium falciparum vaccine against placental malaria

A vaccine protecting women against placental malaria could be based on the sub-domains of the VAR2CSA antigen, since antibodies against the DBL4ɛ-ID4 subunit of the VAR2CSA protein can inhibit parasite binding to the placental ligand chondroitin sulphate A (CSA). Here we tested the ability of DBL4ɛ-ID4 to induce binding-inhibitory antibodies when formulated with adjuvants approved for human use. We have characterized the immune response of DBL4ɛ-ID4 in combination with Freund's complete and incomplete adjuvant and with three adjuvants currently being used in clinical trials: Montanide(®) ISA 720, Alhydrogel(®) and CAF01. Antibodies induced against DBL4ɛ-ID4 in combination with these adjuvants inhibited parasite binding to CSA from 82% to 99%. Although, different epitope recognition patterns were obtained for the different formulations, all adjuvant combinations induced strong Th1 and Th2 type responses, resulting in IgG with similar binding strength, with to the DBL4ɛ-ID4 antigen. These results demonstrate that the DBL4ɛ-ID4 antigen is highly immunogenic and that binding inhibitory antibodies are induced when formulated with any of the tested adjuvants.

Expulsion of secondary Trichinella spiralis infection in rats occurs independently of mucosal mast cell release of mast cell protease II

Our aim was to elucidate the contribution of mucosal mast cells to the effector phase of a secondary immune response to Trichinella spiralis. During secondary infection, rats expel 90-99% of T. spiralis first-stage larvae from the intestine in a matter of hours. This phenomenon appears to be unique to rats and has been called rapid expulsion. Primary intestinal infection by T. spiralis induces mastocytosis, and mast cell degranulation occurs when challenged rats exhibit rapid expulsion. These observations have engendered the view that mast cells mediate rapid expulsion. In this study, we report that immunization of adult Albino Oxford rats by an infection limited to the muscle phase did not induce intestinal mastocytosis, yet such rats exhibited rapid expulsion when challenged orally. Although mastocytosis was absent, the protease unique to mucosal mast cells, rat mast cell protease II (RMCPII), was detected in sera at the time of expulsion. We further evaluated mast cell activity in neonatal rats that display rapid expulsion. Pups born to infected dams displayed rapid expulsion, and RMCPII was detected in their sera. By feeding pups parasite-specific mAbs or polyclonal Abs before challenge infection, it was possible to dissociate mast cell degranulation from parasite expulsion. These results indicate that rapid expulsion can occur in the absence of either intestinal mastocytosis or RMCPII release. Furthermore, release of RMCPII is not sufficient to cause expulsion. The data argue against a role for mast cells in the mechanism underlying the effector phase of protective immunity against T. spiralis in rats.

Active and passive immunizations with Bordetella colonization factor A protect mice against respiratory challenge with Bordetella bronchiseptica

Bordetella colonization factor A (BcfA) is an outer membrane immunogenic protein, which is critical for efficient colonization of the murine respiratory tract. These properties of BcfA prompted us to examine its utility in inducing a protective immune response against Bordetella bronchiseptica in a mouse model of intranasal infection. Mice vaccinated with BcfA demonstrated reduced pathology in the lungs and harbored lower bacterial burdens in the respiratory tract. Immunization with BcfA led to the generation of BcfA-specific antibodies in both the sera and lungs, and passive immunization led to the reduction of B. bronchiseptica in the tracheas and lungs. These results suggest that protection after immunization with BcfA is mediated in part by antibodies against BcfA. To further investigate the mechanism of BcfA-induced immune clearance, we examined the role of neutrophils and macrophages. Our results demonstrate that neutrophils are critical for anti-BcfA antibody-mediated clearance and that opsonization with anti-BcfA serum enhances phagocytosis of B. bronchiseptica by murine macrophages. We show that immunization with BcfA results in the production of gamma interferon and subclasses of immunoglobulin G antibodies that are consistent with the induction of a Th1-type immune response. In combination, our findings suggest that the mechanism of BcfA-mediated immunity involves humoral and cellular responses. Expression of BcfA is conserved among multiple clinical isolates of B. bronchiseptica. Our results demonstrate the striking protective efficacy of BcfA-mediated immunization, thereby highlighting its utility as a potential vaccine candidate. These results also provide a model for the development of cell-free vaccines against B. bronchiseptica.

Changes of cytokine mRNA expression and IgG responses in rats infected with Capillaria hepatica

The mRNA expression of several cytokines was evaluated in splenocytes and mesenteric lymph node (MLN) cells of rats infected with Capillaria hepatica by reverse-transcription (RT)-PCR until week 12 after infection. IgG1 and IgG2a, which are associated with Th1 and Th2 response, respectively, were also assessed by ELISA. The results indicated that the majority of cytokines, including the Th1 (IL-2 and IFN-gamma) and Th2 cytokines (IL-4, IL-5 and IL- 10) were expressed at maximal levels during the early stage of infection (after week 1-2), and the ELISA data also evidenced a similar pattern of changes in IgG1 and IgG2a. Th1 and Th2 cytokines responded in a similar fashion in this rat model. The expression of cytokines in splenocytes was significantly higher than that in MLN cells, thereby indicating that cytokine production is controlled more by spleen than by MLN. In addition, the observation that IFN-gamma expression increased unexpectedly at the time of maximal egg production (6 weeks after infection) indicated that IFN- gamma is a cytokine reacting against egg production. However, increased IL-5 expression occurring in tandem with worm activity indicated that the activity of C. hepatica might be controlled by IL-5 expression.

Immunization with Trichinella spiralis Korean isolate larval excretory-secretory antigen induces protection and lymphocyte subset changes in rats

Protection and immune responses were studied in rats immunized with Trichinella spiralis muscle stage larval excretory-secretory antigen (ES Ag) without adjuvant. Protection was assessed by the degree of adult worm burden and the yield of muscle (diaphragmatic) larvae after challenge infection with live larvae. Lymphocyte subsets were identified by flow cytometry in the spleen and peripheral blood. Cytokine production and specific IgG, IgG1 and IgG2a antibody responses were measured. Immunization with ES Ag produced highly significant protection against adult stages (98.4%) and muscle larvae (82.9%). Th2 type cytokines (IL-10, IL-4) were predominant. Anti-muscle stage larval ES Ag antibody was significantly elevated in the order IgG2a > IgG1 > IgG on the 2nd day after final immunization and on the 7th day after challenge infection. Expression of CD4+ and the CD4+/CD8+ ratio from spleen and blood were significantly increased compared to the control. These results demonstrate that immunization with T. spiralis antigen can elicit robust immune response, resulting in complete protection against infective larvae, and this protection can be achieved without the use of any adjuvant.

Influence of carrier protein conjugation site and terminal modification of a GnRH-I peptide sequence in the development of a highly specific anti-fertility vaccine. Part I

PROBLEM

We previously immunoneutralized gonadotrophin releasing hormone (GnRH), using an analogue of GnRH (des-1 GnRH-I), conjugated to tetanus toxoid via a carbodiimide reaction. The castration effect on the reproductive system was not consistent in all the treated animals. Therefore, we examined the possibility that conjugation to the carrier protein via the N- or C-terminal could have an effect on efficacy.

METHOD OF STUDY

GnRH analogue sequences were synthesized consisting of an additional cysteine at either terminal and specific conjugation was carried out using a bifunctional linker agent.

RESULTS

Conjugation of the monomer through the N-terminal proved to be a highly effective means of causing immunocastration in terms of decreased gonadotrophin and testosterone concentrations and testicular size, whereas conjugation through the C-terminal proved to be ineffective. This was reflected in the ability of the antibodies to bind native GnRH, but not the levels of the anti-GnRH antibodies.

CONCLUSION

Immunoneutralization efficacy was attributed to the importance of preserving the GnRH C-terminal.

Probing antigen-antibody binding processes by impedance measurements on ion-sensitive field-effect transistor devices and complementary surface plasmon resonance analyses: development of cholera toxin sensors

Impedance measurements on ISFET devices are employed to develop new immunosensors. The analysis of the transconductance curves recorded at variable frequencies, upon the formation of antigen-antibody complexes on the ISFET devices, allows determination of the biomaterial film thicknesses. Complementary surface plasmon resonance measurements of analogous biosensor systems, using Au-coated glass slides as support, reveal similar film thicknesses of the biomaterials and comparable detection limits. A dinitrophenyl antigen layer is immobilized on the ISFET gate as a sensing interface for the anti-dinitrophenyl antibody (anti-DNP-Ab). The anti-DNP-Ab is analyzed with a sensitivity that corresponds to 0.1 microg mL(-1). The assembly of the biotinylated anti-anti-DNP-Ab and avidin layers on the base anti-DNP-Ab layer is characterized by impedance measurements. The development of an ISFET-based sensor for the cholera toxin is described. The anti-cholera toxin antibody is immobilized on the ISFET device. The association of the cholera toxin (CT) to the antibody is monitored by the impedance measurements. The detection limit for analyzing CT is 1.0 x 10(-11) M.

IgG-dependent activation of human mast cells following up-regulation of FcgammaRI by IFN-gamma

It has been reported that FcgammaRI is up-regulated on human mast cells (huMC) by IFN-gamma and aggregation of this receptor using mouse F(ab')(2) specific for receptor-bound, mouse anti-CD64 F(ab')(2) results in activation. To determine whether huMC can similarly be stimulated by aggregation of FcgammaRI-bound human IgG, IFN-gamma-treated, CD34(+)-derived, cultured huMC were sensitized with human immunoglobulins and activation was evaluated following addition of antibodies specific for each IgG isotype. Degranulation was also examined following simultaneous IgG- and IgE-dependent aggregation of FcgammaRI and Fc(epsilon)RI. Activation of IFN-gamma-treated huMC sensitized with 100 ng/ml IgG(1) resulted in 40% beta-hexosaminidase (beta-hex) release; minimal degranulation was observed using IgG(2), IgG(3) or IgG(4). IgG(1)-dependent activation led to PGD(2) and LTC(4) generation as well as elevated cytokine production, most notably TNF-alpha. Preincubation of cells with F(ab')(2) from CD64-specific clones 10.1 and 32.2 reduced IgG(1)-mediated beta-hex release by 46% and 74%, respectively. While IgG-dependent cell stimulation induced half-maximal degranulation by 11 min, IgE-dependent activation resulted in half maximal responses within 1 min. Simultaneous activation of huMC via FcgammaRI and Fc(epsilon)RI led to additive degranulation using suboptimal concentrations of IgG(1) and IgE. Activation of huMC thus may occur via monomeric IgG and FcgammaRI thereby providing a novel paradigm for huMC recruitment into inflammation.

Immunoneutralisation of GnRH-I, without cross-reactivity to GnRH-II, in the development of a highly specific anti-fertility vaccine for clinical and veterinary use

In recent years, several forms of gonadotrophin releasing hormone (GnRH) molecules have been isolated from primate brain. These molecules are very similar in sequence and this raises the question of whether previously developed neutralisation vaccines based on GnRH (now termed GnRH-I) would remove other forms of GnRH (namely GnRH-II) as well. As the function of these other molecules has not yet been clearly defined, potential health risks could exist by their ablation. In view of the high sequence homology between the molecules, this paper describes the production of highly specific polyclonal antibodies against GnRH-I and GnRH-II, with negligible cross-reactivity. The ultimate aim of this is to develop an anti-fertility vaccine which does not present any inappropriate side-effects, caused by neutralisation of a GnRH molecule which may or may not be directly involved in reproduction. Several formulations were investigated, based on analogues of the following molecules, conjugated to tetanus toxoid: 1. GnRH-I pGlu-His-Trp-Ser-Try-Gly-Leu-Arg-Pro-Gly-NH2 and 2. GnRH-II pGlu-His-Trp-Ser-His-Gly-Trp-Tyr-Pro-Gly-NH2. The specificity of the antibodies produced was examined, together with effects on fertility and any inappropriate side-effects. Immunostaining of hypothalamic sections was carried out, using the generated antisera, to determine the regional distribution of GnRH-I and GnRH-II neurones, as well as to further evaluate the specificity of the antibodies.