Priming or tolerization of the B- and Th2-dependent immune response by the oral administration of OVA-DNP is determined by the antigen dosage

B cells control maternofetal priming of allergy and tolerance in a murine model of allergic airway inflammation

BACKGROUND

Allergic asthma is a chronic lung disease resulting from inappropriate immune responses to environmental antigens. Early tolerance induction is an attractive approach for primary prevention of asthma.

OBJECTIVE

We analyzed the mechanisms of perinatal tolerance induction to allergens, with particular focus on the role of B cells in preconception and early intrauterine immune priming.

METHODS

Wild-type (WT) and B cell-deficient mice received ovalbumin (OVA) intranasally before mating. Their offspring were analyzed in a murine model of allergic airway inflammation.

RESULTS

Although antigen application before conception protected WT progeny from allergy, it aggravated allergic airway inflammation in B cell-deficient offspring. B-cell transfer restored protection, demonstrating the crucial role of B cells in perinatal tolerance induction. Effective diaplacentar allergen transfer was detectable in pregnant WT mice but not in pregnant B-cell knockout dams, and antigen concentrations in WT amniotic fluid (AF) were higher than in IgG-free AF of B cell-deficient dams. Application of OVA/IgG immune complexes during pregnancy boosted OVA uptake by fetal dendritic cells (DCs). Fetal DCs in human subjects and mice expressed strikingly higher levels of Fcγ receptors compared with DCs from adults and were highly efficient in taking up OVA/IgG immune complexes. Moreover, murine fetal DCs effectively primed antigen-specific forkhead box P3⁺ regulatory T cells after in vitro coincubation with OVA/IgG-containing AF.

CONCLUSION

Our data support a decisive role for B cells and immunoglobulins during in utero tolerance priming. These findings improve the understanding of perinatal immunity and might support the development of effective primary prevention strategies for allergy and asthma in the future.

Low-dose oral immunization with lyophilized tissue of herbicide-resistant lettuce expressing hepatitis B surface antigen for prototype plant-derived vaccine tablet formulation

Efficient immunization against hepatitis B virus (HBV) and other pathogens with plant-based oral vaccines requires appropriate plant expressors and the optimization of vaccine compositions and administration protocols. Previous immunization studies were mainly based on a combination of the injection of a small surface antigen of HBV (S-HBsAg) and the feeding with raw tissue containing the antigen, supplemented with an adjuvant, and coming from plants conferring resistance to kanamycin. The objective of this study was to develop a prototype oral vaccine formula suitable for human immunization. Herbicide-resistant lettuce was engineered, stably expressing through progeny generation micrograms of S-HBsAg per g of fresh weight and formed into virus-like particles (VLPs). Lyophilized tissue containing a relatively low, 100-ng VLP-assembled antigen dose, administered only orally to mice with a long, 60-day interval between prime and boost immunizations and without exogenous adjuvant, elicited mucosal and systemic humoral anti-HBs responses at the nominally protective level. Lyophilized tissue was converted into tablets, which preserved S-HBsAg content for at least one year of room temperature storage. The results of the study provide indications on immunization methodology using a durable, efficacious, and convenient plant-derived prototype oral vaccine against hepatitis B.

Nanogram doses of alum-adjuvanted HBs antigen induce humoral immune response in mice when orally administered

Mucosal immunity elicited by plant-based and other orally administered vaccines can serve as the first line of defense against most pathogens infecting through mucosal surfaces, but it is also considered for systemic immunity against blood-borne diseases such as hepatitis B (HB). Previous oral immunization trials based on multiple administration of high doses of HBs antigen elicited an immune response; however, a reproducible and long-lasting immunization protocol was difficult to design. The objective of this study was to evaluate the effect of dose and timing of orally delivered alum-adsorbed antigen on the magnitude of the anti-HBs humoral response. Mice were immunized orally by gavage intubation or parenterally by intramuscular injection three times, once every 2 weeks, with doses of 5, 50, or 500 ng alum-adjuvanted HBsAg. A low dose (10 ng) of HBsAg was orally administered three times in different time intervals: 2, 4, 6, and 8 weeks. The three consecutive 5-ng oral doses of the antigen induced immune response at the protective level (>or=10 mIU/ml), significantly higher than the reaction elicited by three 50 or 500 ng doses. In contrast, intramuscular delivery of these doses did not differ significantly; however, they induced a five to six times higher immune response than oral immunization. The 8-week period between each of the three oral immunizations appeared to be favorable to the anti-HBs humoral responses compared with the shorter schedules. The results presented here clearly identify the importance of low doses of antigen administered orally in extended intervals for a significantly higher anti-HBs response. This finding provides some indications concerning the strategy of orally administered vaccines, including plant-based ones.

Aminoguanidine administered during the induction of oral tolerance alters the systemic response of the tolerised rats

Herewith we investigated the role of nitric oxide synthase (NOS)-II in the establishment of oral tolerance induced by low antigen dose. To accomplish this, we used a rat model of oral tolerance induced by intragastric administration of low doses of ovalbumin (OVA). NOS-II was inhibited in vivo during the onset of tolerance by intraperitoneal (i.p.) treatment with aminoguanidine (AMG), a selective NOS-II inhibitor. Four experimental groups were generated: (TOL), tolerised rats, receiving OVA but no AMG; (TAG), rats tolerised with OVA and simultaneously receiving AMG i.p.; (CAG), controls treated with AMG but no oral antigen; and (CONT), controls receiving neither OVA nor AMG treatment. The state of oral tolerance was evaluated in all groups by analysing several immune parameters upon subcutaneous administration of OVA in Freund's complete adjuvant. First, we were able to determine that NOS-II inhibition altered the TH1/TH2 balance in tolerised rats, driving the TH2 anti-OVA response in TOL rats towards TH1 in TAG animals, which showed enhanced delayed hypersensitivity responses. Second, splenocyte cultures from TAG rats showed lower levels of IL-10 production compared to TOL samples as determined by ELISA analysis. Last, we detected the presence of a functional distinct Tr1 regulatory T cell population in spleen samples recovered from TAG animals. Contrary to what happened with TOL Tr1 cells, the levels of Tr1 cells in TAG samples were modified by in vitro stimulation with OVA. All together, these data indicate a preponderant role for NOS-II in the process of oral tolerance induced by low antigen dose.

Should Younger Siblings of Peanut-Allergic Children Be Assessed by an Allergist before Being Fed Peanut?

The objective of this study was to determine the risk of peanut allergy in siblings of peanut-allergic children. In 2005-2006, 560 households of children born in 1995 in the province of Manitoba, Canada, were surveyed. The index children (8-to 10-year-olds) were assessed by a pediatric allergist and had skin-prick testing and/or capRAST for peanut allergy. Surveys were completed by parents for siblings to determine the presence of peanut allergy. Of 560 surveys, 514 (92%) were completed. Twenty-nine (5.6%) index children were peanut allergic. Fifteen of 900 (1.7%) siblings had peanut allergy. Four of 47 (8.5%) were siblings of peanut-allergic children and 11 of 853 (1.3%) were siblings of non-peanut-allergic children. The risk of peanut allergy was markedly increased in siblings of a peanut-allergic child (odds ratio 6.72, 95% confidence interval 2.04-22.12). Siblings of peanut-allergic children are much more likely to be allergic to peanut. An allergy assessment by a qualified allergist should be routinely recommended before feeding peanut to these children.

The risk of developing food allergy in premature or low-birth-weight children

BACKGROUND

Premature or low-birth-weight children have increased gut permeability compared with term or normal-birth-weight children.

OBJECTIVE

To determine whether premature or low-birth-weight children have an increased risk of developing food allergy compared with term or normal-birth-weight children.

METHODS

The 1995 Manitoba Birth Cohort was studied using the Manitoba Health Services Insurance Plan (MHSIP) database. This database is a population-based, health care administrative and prescription database. It has records of every child born and subsequent utilization of the provincial health care system. The diagnosis of food allergy (ICD-9-CM code of 693 in hospital/medical claims or a prescription of injectable epinephrine excluding a sole diagnosis of venom allergy) was obtained up until the year 2002. The relative risks of food allergy in premature or low-birth-weight children compared with term or normal-birth-weight children were determined.

RESULTS

A total of 13,980 children were born in 1995 and continue to live in the province of Manitoba. Of these, 592 children (4.23%) were found to have food allergy and epinephrine was prescribed in 316 (2.26%) children. No gestational age or birth weight group had a statistically significant increased risk for food allergy.

CONCLUSION

Prematurity and low birth weight are not associated with a change in risk for development of food allergy in childhood.

CLINICAL IMPLICATIONS

Immaturity of the gastrointestinal tract or immune response does not seem to change the risk for development of food allergies. We ask whether early exposure to food antigens may protect premature children by increasing immune tolerance to those antigens.

Systemic and mucosal immunity induced by oral somatic transgene vaccination against glycoprotein B of pseudorabies virus using live attenuatedSalmonella typhimurium

Glycoprotein B mediates the absorption and penetration of the pseudorabies virus in the form of an immunodominant Ag, and represents a major target for the development of new vaccines. This study evaluated the efficiency of live attenuated Salmonella typhimurium SL7207 for the oral delivery of DNA vaccine encoding the pseudorabies virus glycoprotein B (pCI-PrVgB) in vivo, leading to the generation of both systemic and mucosal immunity against the pseudorabies virus Ag. An oral transgene vaccination of pCI-PrVgB using a Salmonella carrier produced a broad spectrum of immunity at both the systemic and mucosal sites, whereas the intramuscular administration of a naked DNA vaccine elicited no mucosal immunoglobulin (Ig)A response. Interestingly, the Salmonella-mediated oral transgene vaccination of the pseudorabies virus glycoprotein B biased the immune responses to the Th2-type, as determined by the IgG2a/IgG1 ratio and the cytokine production profile. However, oral vaccination mediated by Salmonella harbouring pCI-PrVgB showed inferior protection to systemic immunization against virulent pseudorabies virus infection. The expression of transgene delivered by Salmonella bacteria in antigen-presenting cells of both the systemic and mucosal-associated lymphoid tissues was further demonstrated. These results highlight the potential use of live attenuated S. typhimurium for an oral transgene pseudorabies virus glycoprotein B vaccination to induce broad immune responses.

The potential role of allergen-specific sublingual immunotherapy in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease associated with increasing prevalence, morbidity, and cost in developed Western countries. Frequently associated with respiratory allergy during adulthood, atopic dermatitis often represents the first phenotypic appearance of atopy in early childhood when the allergic 'march' starts and progressively moves toward food allergy, asthma, and rhinitis. At present, a consistent body of evidence supports the view that atopic dermatitis may represent the skin compartmentalization of a systemic allergic inflammation. Lymphocytes infiltrating early lesional skin express a T helper (Th) 2 pattern of cytokine secretion (increased levels of interleukin [IL]-4 and/or IL-13 and decreased levels of interferon-gamma) as well as the typical Th2-type chemokine receptor CCR4, specific to the thymus and activation-regulated chemokines. Keratinocytes from patients with atopic dermatitis produce thymic stromal lymphopoietin, a novel cytokine that supports the early lymphocyte development in mouse models, and activates dendritic cells involved in the pathogenesis of allergic diseases in humans. Increased levels of circulating hemopoietic precursor cells have been reported in atopic dermatitis, as in allergic asthma and rhinitis. Furthermore, the recognition of CD34+ hemopoietic precursor cells, and evidence for cellular differentiation/maturational events occurring within atopic dermatitis skin lesion infiltrates, are consistent with the recent reinterpretation of the Th2/Th1 paradigm, where Th2 cells appear to belong to the early stages and Th1 to the ultimate stages of a linear, rather than divergent, pattern of lymphoid differentiation. This more detailed understanding of the immunologic derangements contributing to the atopic dermatitis pathogenesis has led to growing interest in allergen-specific immunotherapy for the disease. Due to the complexity intrinsic to atopic dermatitis and the lack of consensus-based guidelines for standardized outcome measure, only eight studies are available in the literature for a qualitative evaluation of this treatment approach. Two of these studies were double blind and placebo controlled, and six were cohort studies. Immunotherapy was found to be effective in one controlled study and five observational reports. Uncertain results were provided by one low-powered, controlled study, and negative outcomes were raised by a unique study performed with oral immunotherapy, which is not an effective route of mucosal allergen administration. Thus, more efficacy studies are required before immunotherapy could be recommended for the routine treatment of atopic dermatitis. Allergen-specific sublingual immunotherapy, given its excellent safety profile and ability to interfere with the systemic aspects of allergic inflammation, appears a good potential candidate for the pathogenetic treatment of the disease.

Codelivery of DNA coding for the soluble form of CD86 results in the down-regulation of the immune response to DNA vaccines

The costimulatory pathway that includes CD80, CD86, CD28, and CTLA-4 plays a key role in regulating T cell activation and tolerance and is a promising therapeutic target. We have studied the possibility of down-regulating the immune response to DNA vaccine by codelivery of a plasmid coding for the extracellular domains of CD86 (pDelta86). We found that DeltaCD86 was able to inhibit the engagement of FcCTLA-4 but not of FcCD28 to CD80 and CD86 expressed on COS cells. Coadministration of plasmid pDelta86 encoding for the extracellular domains of CD86 along with a plasmid encoding for the glycoprotein D (pgD) of herpes simplex virus-2 (a membrane-bound protein) by the im route in mice resulted in a strong inhibition of the cell-mediated immune response in the spleen and in draining lymph nodes. In addition, when pDelta86 was coadministered together with a plasmid encoding for the ovalbumin (pOVA) (a soluble protein), a strong inhibition of the cell-mediated immune response was observed in draining lymph nodes and only a partial inhibition was found in the spleen. Furthermore, only a partial down-regulation of the humoral immune response was observed. The mechanism involved could be a preferential engagement of DeltaCD86 to CTLA-4 leading to the transmission of a negative signal to T lymphocytes.

Oral transgene vaccination mediated by attenuated Salmonellae is an effective method to prevent Herpes simplex virus-2 induced disease in mice

An attenuated strain of Salmonella typhimurium has been used as a carrier for oral genetic immunization. The eukaryotic expression vector pCMV containing the gene of the glycoprotein D (gD) of the herpes simplex virus 2 was used to transform Salmonellae. The oral immunization with the transformed salmonellae elicited a strong cellular immune response in both, the mucosal and systemic compartments (spleen, ileal lymph nodes and Peyer patches). The immune response mainly consisted in a dramatic activation of IFN-gamma-secreting cells. Twenty hours following the challenge with five lethal doses of virus, mRNA for IFN-gamma was observed in vaginal tissues from mice immunized with salmonella harboring the plasmid pgD but not in tissues from mice immunized by the intramuscular route with pgD. After an intravaginal challenge all immunized mice survived without developing symptoms. Furthermore, the immunization with Salmonella resulted in a more effective control of viral shedding than intramuscular immunization. We have unequivocally demonstrated by the introduction of an intron in the green fluorescent protein that the expression of the plasmid was due to the transcription of the protein by an eukaryotic nuclear process and not as a result of expression of the protein by the bacteria. Macrophages and dendritic cells were found expressing the protein in systemic and mucosal compartments of the immune system.

Independent genetic control of B- and T-cell tolerance in strains of mouse selected for extreme phenotypes of oral tolerance

Two strains of mice were genetically selected for susceptibility (TS-Ab/HetS strain) or resistance (TR-Ab/HetS strain) to oral tolerance of the humoral response by using ovalbumin (OVA). The progressive interstrain divergence produced by bi-directional selective breeding during 15 generations demonstrated the polygenic nature of oral tolerance. This paper shows the humoral and delayed-type hypersensitivity (DTH) responses, after intragastric administration of OVA and subsequent immunization with that immunogen in complete Freund adjuvant (CFA). Only the TS-Ab/HetS mice were tolerant for immunoglobulin (Ig)G production with its tolerance degree being the same as that obtained when Al ((OH)(3)) was employed. The DTH reactivity was not correlated to the antibody responsiveness, because both the TS-Ab/HetS and TR-Ab/HetS strains had their DTH reactions suppressed. The cyclophosphamide (Cy) pretreatment prevented DTH suppression on TR-Ab/HetS but do not in TS-Ab/HetS mice. Interstrain difference was also observed for the splenic index in the Cy-treated groups, although the number of splenocytes was the same. Flux cytometry cell analysis showed the recovery of CD3(+) cell numbers in both strains, but only the TR-Ab/HetS mice had their CD4/CD8 pattern restored. These results suggest: firstly, the independent control of DTH and humoral tolerance responsiveness; secondly no support for the clonal anergy concept; and thirdly the matrix proteins neo-synthesis after Cy treatment may facilitate the tolerance abrogation.

Enhanced immunological tolerance against allograft rejection by oral administration of allogeneic antigen linked to cholera toxin B subunit

A single oral intragastric administration of cholera toxin B subunit (CTB) conjugated to allogeneic thymocytes (ATC, 4 x 10(7) cells) under conditions allowing the CTB to bind the complex to GM1 ganglioside receptors was shown to be efficacious in inducing peripheral T cell tolerance associated with significant suppression of both primary and secondary accelerated rejection of heart allografts when tested in mice. Allogeneic in vivo delayed-type hypersensitivity (DTH), in vitro cytotoxicity responses, and mixed lymphocyte reactions (MLR) by T cells from mesenteric lymph nodes (MLN), popliteal lymph nodes (PLN), and spleen were significantly reduced in mice treated with the CTB-ATC conjugate, as were also the numbers of cells in these organs producing IL-2, IFN-gamma, or IL-4. In contrast, a marked increase in the production of IL-4 in Peyer's patches (PP) and of TGF-beta(1) in PLN was observed. The suppressive potential of T cells from PP and/or MLN after oral treatment with CTB-ATC was further evident by intraperitoneal transfer of such cells from CTB-ATC-treated animals to primed recipients, which led to marked suppression of both allogen-specific DTH and MLR responses. A critical role for PP in inducing peripheral tolerance after oral CTB-ATC treatment was indicated by the absence of tolerance induction in animals whose PP had been destroyed before treatment with CTB-ATC. The results indicate that the protection against allograft rejection by oral treatment with CTB-ATC is mediated by T cells and associated with a strong induction of IL-4 production at mucosal sites and TGF-beta(1) at the effector sites.

Oral Administration of Myelin Basic Protein Is Superior to Myelin in Suppressing Established Relapsing Experimental Autoimmune Encephalomyelitis

Oral administration of a myelin component, myelin basic protein (MBP), induces immunological unresponsiveness to CNS Ags and ameliorates murine relapsing experimental autoimmune encephalomyelitis (REAE). However, a recent clinical trial in which multiple sclerosis patients were treated with repeated doses of oral myelin was unsuccessful in reducing disease exacerbations. Therefore, we directly compared the tolerizing capacity of myelin vs MBP during REAE in B10.PL mice. Oral administration of high doses of myelin, either before disease induction or during REAE, did not provide protection from disease or decrease in vitro T cell responses. In contrast, repeated oral administration of high doses of MBP suppressed established disease and MBP-specific T cell proliferation and cytokine responses. The frequency of IL-2-, IFN-γ-, and IL-5-secreting MBP-specific T cells declined with MBP feeding, implicating anergy and/or deletion as the mechanism(s) of oral tolerance after high Ag doses. We have previously shown that the dosage and timing of Ag administration are critical parameters in oral tolerance induction. Studies presented here demonstrate that Ag homogeneity is also important, i.e., homogeneous Ag (MBP) is more effective at inducing oral tolerance than heterogeneous Ag (myelin).