The biological activity of serum IgE changes over the course of a primary response

IgE sequences in individuals living in an area of endemic parasitism show little mutational evidence of antigen selection

Patterns of somatic mutation in IgE genes from allergic individuals have been a focus of study for many years, but IgE sequences have never been reported from parasitized individuals. To study the role of antigen selection in the evolution of the anti-parasite response, we therefore generated 118 IgE sequences from donors living in Papua New Guinea (PNG), an area of endemic parasitism. For comparison, we also generated IgG1, IgG2, IgG3 and IgG4 sequences from these donors, as well as IgG1 sequences from Australian donors. IgE sequences had, on average, 23.0 mutations. PNG IgG sequences had average mutation levels that varied from 17.7 (IgG3) to 27.1 (IgG4). Mean mutation levels correlated significantly with the position of their genes in the constant region gene locus (IgG3 < IgG1 < IgG2 < IgG4). Interestingly, given the heavy, life-long antigen burden experienced by PNG villagers, average mutation levels in IgG sequences were little different to that seen in Australian IgG1 sequences (19.2). Patterns of mutation provide clear evidence of antigen selection in many IgG sequences. The percentage of IgG sequences that showed significant accumulations of replacement mutations in the complementarity determining regions ranged from 22% of IgG3 sequences to 39% of IgG2 sequences. By contrast, only 12% of IgE sequences had such evidence of antigen selection, and this was significantly less than in PNG IgG1, IgG2 and IgG4 subclass sequences (P < 0.01). The anti-parasite IgE response therefore has the reduced evidence of antigen selection that has previously been reported in studies of IgE sequences from allergic individuals.

YM-341619 suppresses the differentiation of spleen T cells into Th2 cells in vitro, eosinophilia, and airway hyperresponsiveness in rat allergic models

T helper (Th) 2 cells play a central role in the pathogenesis of allergic diseases such as allergic asthma, atopic dermatitis, and allergic rhinitis. We have found that YM-341619 hydrochloride, which suppressed IL-4-induced STAT6-dependent reporter gene expression, inhibited the differentiation of mouse spleen T cells into Th2 cells in vitro. YM-341619 suppressed the production of IL-4 and the expression of GATA-3 mRNA, a Th2 transcription factor, in T cells cultured with anti-CD3 antibody and anti-CD28 antibody in the presence of IL-4. In contrast, the production of IFN-gamma and the expression of T-bet mRNA, a Th1 transcription factor, in T cells cultured with anti-CD3 antibody in the presence of IL-12, were not effected by YM-341619. Orally administered YM-341619 (0.003-0.03 mg/kg) reduced the plasma IgE level of DNP-Ascaris-sensitized rats, but not the IgG(2a) level. YM-341619 suppressed IL-4 and IL-13 production in the splenocytes of these DNP-Ascaris-sensitized rats without augmenting IFN-gamma production. YM-341619 also dose-dependently suppressed eosinophil accumulation in the lung (0.003-3 mg/kg, p.o.) and airway hyperresponsiveness (0.3-3 mg/kg, p.o.) induced by repeated exposure to ovalbumin in ovalbumin-sensitized rats. These results suggest that YM-341619 has the ability to suppress allergen-induced Th2 responses by selectively inhibiting the differentiation of CD4(+) T cells into the Th2 subset.

Peanut epitopes for IgE and IgG4 in peanut-sensitized children in relation to severity of peanut allergy

BACKGROUND

Better understanding of the relationship between antibody response to peanut and clinical sensitivity might lead to more accurate prognostication.

OBJECTIVE

We sought to investigate peanut-specific IgE and IgG4 epitope diversity in relation to challenge-defined clinical sensitivity to peanut in a group of peanut-sensitized children.

METHODS

Clinical sensitivity was determined by means of double-blind, placebo-controlled peanut challenges in 24 sensitized children. Six atopic control subjects were included. Specific IgE and IgG4 binding to 419 overlapping 15-amino-acid peptides representing the sequence of recombinant Ara h 1, Ara h 2, and Ara h3 was analyzed by means of microarray immunoassay.

RESULTS

Peanut-sensitized patient sera bound significantly more IgE and IgG4 epitopes than control sera. This patient group reacted to the same Ara h 1, Ara h 2, and Ara h 3 epitopes as reported previously. There was a positive correlation between IgE epitope diversity (ie, number of epitopes recognized) and clinical sensitivity (r = 0.6), such that patients with the greatest epitope diversity were significantly more sensitive than those with the lowest diversity (P = .021). No specific epitopes were associated with severe reactions to peanut. IgG4 binding was observed to largely similar epitopes but was less pronounced than IgE binding and did not relate to the clinical sensitivity to peanut. IgE and IgG4 epitope-recognition patterns were largely stable over a 20-month period.

CONCLUSION

Clinical sensitivity, as determined by means of double-blind, placebo-controlled peanut challenge, is positively related to a more polyclonal IgE response, which remains stable over time.

IgG and IgE avidity characteristics of peanut allergic individuals

The role of antibody avidity in allergy is poorly understood and there is no existing literature describing antibody avidity in food allergy. The main aim of this study was to investigate IgE and IgG avidity to a total peanut protein extract (TPPE) and purified Ara h 2 in a group of well-characterized peanut allergic individuals. Forty peanut allergic patients underwent a double-blind placebo-controlled low-dose peanut challenge, during which the severity of the patients' peanut allergy was scored. Serum peanut-specific IgE (psIgE) and IgG (psIgG) concentrations were measured for 37 individuals and the avidities of the same antibodies to a TPPE and purified Ara h 2 were determined using a thiocyanate ELISA method. Both IgE and IgG avidity to Ara h 2 showed weak positive correlations with challenge score [r = 0.459 (p = 0.012) and r = 0.486 (p = 0.003), respectively]. IgE avidity to TPPE showed a weak positive correlation with skin prick test results (SPT), r = 0.467 (p = 0.004) and there was an inverse relationship between the ratio of total IgE:psIgE and challenge score r = -0.561 (p < 0.001). No significant relationship was found between the ratios of IgE avidity:IgG avidity and challenge score or SPT. This is the first description of IgE and IgG avidity in peanut allergy, and it appears that the avidities of IgE and IgG antibodies to purified Ara h 2 are weakly related to the severity of peanut allergy (as measured by a challenge score).

Immune reactions and allergy in experimental anisakiasis

The third-stage larvae (L3) of the parasitic nematode, Anisakis simplex, have been implicated in the induction of hyperimmune allergic reactions in orally infected humans. In this work, we have conducted a review of an investigation into immune reactions occurring in animals experimentally infected with A. simplex L3. The patterns of serum antibody productions in the experimental animals against excretory-secretory products (ESP) of A. simplex L3 contributed to our current knowledge regarding specific humoral immune reactions in humans. In our review, we were able to determine that L3 infection of experimental animals may constitute a good model system for further exploration of immune mechanisms and allergy in anisakiasis of humans.

Factors responsible for differences between asymptomatic subjects and patients presenting an IgE sensitization to allergens. A GA2LEN project

The synthesis of allergen-specific IgE is required for the development of allergic diseases including allergic rhinitis and allergic asthma (patients), but many individuals with allergen-specific IgE do not develop symptoms (asymptomatic subjects). Differences may exist between asymptomatic subjects and patients. Whether the presence of allergen-specific IgE translates into clinical allergy most likely depends on a complex interplay of multiple factors. These include a family history of atopy, the levels of total serum IgE and, allergen-specific IgE or IgG, epitope-specificity of IgE and their degree of polyclonality (mono- vs polysensitized), as yet unidentified serum factors, the balance of T regulatory cells (Treg) and Th1/Th2 cells, the polymorphisms of the high affinity receptor for IgE (FcepsilonRI) and other factors regulating the activation of FcepsilonRI-bearing cells. Asymptomatic subjects may be more often monosensitized than patients who may be more often polysensitized. There are many unanswered important questions that need to be addressed in order to better understand how IgE sensitization translates into clinical allergy. The assessment of differences between the asymptomatic and symptomatic groups of subjects represent one of the scientific programs of Global Allergy and Asthma European Network funded by the European Union and the hypotheses underlying these differences are presented in this paper.

The time course of biological and immunochemical allergy states induced by anisakis simplex larvae in rats

Oral infection by Anisakis simplex third stage larvae (L3) frequently gives rise to an allergic response. To comprehend the allergic and immune responses induced by L3, we investigated the kinetics of specific antibody isotype expression and the time course of biological and immunochemical allergy states using sera prepared from rats orally infected with L3 twice, with an interval of 9 weeks between infections. Biological and immunochemical allergy states were analysed by RBL-2H3 exocytosis and by indirect ELISA for IgE, respectively. The peak IgM at reinfection (RI) was comparable or similar to that at primary infection (PI) both in levels analysed by indirect ELISA and in antigen recognition analysed by Western blot. IgG1 and IgG2a levels were higher and showed accelerated kinetics after RI vs. after PI. However, the level of IgG2b was substantially lower than that of IgG2a. Peak immunochemical and biological allergy states for RI were higher and were reached faster than those for PI. The peak biological allergy state was observed at 1 week postreinfection and this occurred sooner than that for the peak immunochemical allergy state found at 2 weeks postreinfection. Our analysis of the relationship between specific IgE avidity and biological allergy state did not show any meaningful correlation. These results suggest that the allergic response induced by L3 oral infection is predominantly caused by reinfection and that this is accompanied by an elevated IgM level, which further suggests that the biological allergy state might not be related to specific IgE avidity.

Immunochemical and Biological Analysis of Allergenicity with Excretory-Secretory Products of Anisakis simplex Third Stage Larva

BACKGROUND

Anisakis simplex third stage larvae (L3) are parasites that frequently give rise to allergic responses. The larvae molt into fourth stage larvae (L4), and at each stage they produce L3-excretory-secretory products (L3-ESP) and L4-ESP, respectively, which are different in their main protein constituents. Although the allergenicity of L4-ESP has been investigated by several research groups, research on the allergenicity of L3-ESP has not been carried out by any researcher. In this investigation, the allergenicity and antigenicity of L3-ESP were investigated in comparison with L4-ESP, using rat sera.

METHODS

Rat sera were produced by L3 oral infection two times with a 9-week interval. Larvae ESP prepared by culture were concentrated and fractioned using lyophilizer and a centrifugal filter device, respectively. Immunochemical analysis was performed using both indirect ELISA and immunoblot. Biological allergenicity was analyzed by RBL-2H3 exocytosis.

RESULTS

With the indirect ELISA, the optical density (OD) value of the nonfractioned (NF)-L3ESP was only one third of that of the NF-L4ESP in both specific IgM and IgG. On measuring specific IgE, the OD of NF-L3ESP was less than one tenth of that of NF-L4ESP. In addition, neither antigen nor allergen was shown in NF-L3ESP, but it was shown in NF-L4ESP with immunoblot. However, the biological allergenicity of NF-L3ESP was comparable to that of NF-L4ESP. To demonstrate the presence of any allergen, L3-ESP was fractioned and found to carry twelve visualized allergen bands from 10 to 186 kDa by immunoblot.

CONCLUSIONS

These results indicate that L3-ESP may include the important allergens necessary to induce the allergy by L3 oral infection, as compared to L4-ESP.

Brown Norway rat ovalbumin-specific immunoglobulin E antibodies increase the human basophil expression of CD63 marker

Anaphylactic shock is an immunoglobulin E (IgE)-dependent hypersensitivity. Biological tests like leucocyte histamine release (LHR) and human basophil activation (HBA), frequently used in human allergy, reflect both the amount of IgE fixed on cells and the cellular reactivity. To assess whether serum-specific IgE from Brown Norway (BN) rats prepared for ovalbumin (OVA)-induced anaphylactic shocks can activate human basophils which has a potential interest in experimental allergy: such a test could rapidly assert an IgE sensitization in laboratory animals genetically T-helper 2 (Th2)-predisposed. Rats (n = 39) were immunized three times (day 0, day 5 and day 21) with OVA injected subcutaneously. One week after the third immunization, a shock was induced with an intravenous (i.v.) bolus of OVA. Sensitization was assessed by passive cutaneous anaphylaxis (PCA) test and dosages of serum IgE antibodies anti-OVA by enzyme-linked immunosorbent assay. Blood basophils were counted before and during the shock. Before the shock induction (at day 21), an LHR test was performed on rat blood, and human basophils were sensitized with rat sera. HBA was demonstrated by the increase in the percentage of cells expressing CD63 antigen membrane, measured by flow cytometry. Twenty-one days after the first subcutaneous (s.c.) immunization, the rat serum induced a significant HBA. HBA was observed neither with the same serum previously heated nor with the serum from nonimmunized rats (NIRs). OVA-specific IgEs were significantly increased in immunized rat (IR) serum. The PCA test was negative when the serum was previously heated (56 degrees C). We never observed any circulating basophils, and LHR test was negative. After OVA i.v. administration, all IRs died rapidly. HBA testing strongly suggests a mediation by specific IgE in the increase of CD63 in BN rats. Thus, HBA test seems useful in assessing whether an experimental allergy was induced in animals genetically predisposed to an immune response, Th2-mediated, like BN rat. We also conclude that rat basophil activation does not participate in the histamine release during anaphylactic shock in sensitized BN rats.