Administration of Ag85B showed therapeutic effects to Th2-type cytokine-mediated acute phase atopic dermatitis by inducing regulatory T cells

Allergen specific immunotherapy with plasmid DNA encoding OVA-immunodominant T cell epitope fused to Tregitope in a murine model of allergy

BACKGROUND

Peptide-based immunotherapy (PIT) was introduced as an attractive approach in allergen-specific immunotherapy (AIT). However, PIT clinical trials have shown variable results, and immune response to peptides is not precisely predictable. On the other hand, induction of antigen-specific tolerance may be augmented when allergens are combined with the regulatory T cell epitope (Tregitope). This study aimed to evaluate the therapeutic administration of a plasmid DNA encoding Tregitope and ovalbumin (OVA) immunodominant epitope in the murine model of allergy.

METHODS

Following the induction of allergic rhinitis by ovalbumin, vaccinated group received three doses of recombinant plasmid containing Signal peptide-Tregitope-OVA T cell epitope. After the final OVA challenge, clinical symptoms, histopathological changes, OVA-specific IgE level, and cytokine secretion pattern of spleen cells were examined.

RESULTS

Our data are showing that AIT with the recombinant DNA vaccine significantly suppressed airway inflammation; reduced eosinophilic infiltration in the nasal mucosa; decreased expression level of IL-4 and IL-17 in spleen cells, while IFN-γ, IL-10, and TGF-β expression were increased. Moreover, OVA-specific IgE levels were also decreased.

CONCLUSION

These results suggest that Tregitope-immunodominant T cell epitope fusion can act as a safe and effective approach in DNA-based allergen-specific immunotherapy.

Long-term protective immunity induced by an adjuvant-containing live-attenuated AIDS virus

The use of an adjuvant in vaccination is thought to be effective for enhancing immune responses to various pathogens. We genetically constructed a live attenuated simian human immunodeficiency virus (SHIV) to express the adjuvant molecule Ag85B (SHIV-Ag85B). SHIV-Ag85B could not be detected 4 weeks after injection in cynomolgus macaques, and strong SHIV-specific T cell responses were induced in these macaques. When the macaques in which SHIV-Ag85B had become undetectable were challenged with pathogenic SHIV89.6P at 37 weeks after SHIV-Ag85B had become undetectable, SHIV89.6P was not detected after the challenge. Eradication of SHIV89.6P was confirmed by adoptive transfer experiments and CD8-depletion studies. The SHIV-Ag85B-inoculated macaques showed enhancement of Gag-specific monofunctional and polyfunctional CD8⁺ T cells in the acute phase of the pathogenic SHIV challenge. The results suggest that SHIV-Ag85B elicited strong sterile immune responses against pathogenic SHIV and that it may lead to the development of a vaccine for AIDS virus infection.

Allergy Vaccines Using a Mycobacterium-Secreted Antigen, Ag85B, and an IL-4 Antagonist

In recent decades, the prevalence of allergic diseases, including bronchial asthma, airway hypersensitivity, hay fever, and atopic dermatitis, has been increasing in the industrialized world, and effective treatments probably require manipulating the inflammatory response to pathogenic allergens. T helper (Th) 2 cells are thought to play a crucial role in the initiation, progression, and persistence of allergic responses in association with production of interleukin (IL)-4, IL-5, and IL-13. Therefore, a strategy of a shift from Th2- to Th1-type immune response may be valuable in the prophylaxis and management of allergic diseases. It is also necessary to develop prophylactic and therapeutic treatment that induces homeostatic functions in the multifaceted allergic environment, because various factors including innate and adaptive immunity, mucosal immune response, and functional and structural maintenance of local tissue might be involved in the pathogenesis of allergic disorders. We review herein recent findings related to the curative effect for mouse models of asthma and atopic dermatitis using DNA-, virus-, and protein-based vaccines of a Mycobacterium secretion antigen, Ag85B, and a plasmid encoding cDNA of antagonistic IL-4 mutant.

Effects of mycobacteria major secretion protein, Ag85B, on allergic inflammation in the lung

Many epidemiological studies have suggested that the recent increase in prevalence and severity of allergic diseases such as asthma is inversely correlated with Mycobacterium bovis bacillus Calmette Guerin (BCG) vaccination. However, the underlying mechanisms by which mycobacterial components suppress allergic diseases are not yet fully understood. Here we showed the inhibitory mechanisms for development of allergic airway inflammation by using highly purified recombinant Ag85B (rAg85B), which is one of the major protein antigens secreted from M. tuberculosis. Ag85B is thought to be a single immunogenic protein that can elicit a strong Th1-type immune response in hosts infected with mycobacteria, including individuals vaccinated with BCG. Administration of rAg85B showed a strong inhibitory effect on the development of allergic airway inflammation with induction of Th1-response and IL-17and IL-22 production. Both cytokines induced by rAg85B were involved in the induction of Th17-related cytokine-production innate immune cells in the lung. Administration of neutralizing antibodies to IL-17 or IL-22 in rAg85B-treated mice revealed that IL-17 induced the infiltration of neutrophils in BAL fluid and that allergen-induced bronchial eosinophilia was inhibited by IL-22. Furthermore, enhancement of the expression of genes associated with tissue homeostasis and wound healing was observed in bronchial tissues after rAg85B administration in a Th17-related cytokine dependent manner. The results of this study provide evidence for the potential usefulness of rAg85B as a novel approach for anti-allergic effect and tissue repair other than the role as a conventional TB vaccine.

Intranasally administered antigen 85B gene vaccine in non-replicating human Parainfluenza type 2 virus vector ameliorates mouse atopic dermatitis

Atopic dermatitis (AD) is a refractory and recurrent inflammatory skin disease. Various factors including heredity, environmental agent, innate and acquired immunity, and skin barrier function participate in the pathogenesis of AD. T -helper (Th) 2-dominant immunological milieu has been suggested in the acute phase of AD. Antigen 85B (Ag85B) is a 30-kDa secretory protein well conserved in Mycobacterium species. Ag85B has strong Th1-type cytokine inducing activity, and is expected to ameliorate Th2 condition in allergic disease. To perform Ag85B function in vivo, effective and less invasive vaccination method is required. Recently, we have established a novel functional virus vector; recombinant human parainfluenza type 2 virus vector (rhPIV2): highly expressive, replication-deficient, and very low-pathogenic vector. In this study, we investigated the efficacy of rhPIV2 engineered to express Ag85B (rhPIV2/Ag85B) in a mouse AD model induced by repeated oxazolone (OX) challenge. Ear swelling, dermal cell infiltrations and serum IgE level were significantly suppressed in the rhPIV2/Ag85B treated mouse group accompanied with elevated IFN-γ and IL-10 mRNA expressions, and suppressed IL-4, TNF-α and MIP-2 mRNA expressions. The treated mice showed no clinical symptom of croup or systemic adverse reactions. The respiratory tract epithelium captured rhPIV2 effectively without remarkable cytotoxic effects. These results suggested that rhPIV2/Ag85B might be a potent therapeutic tool to control allergic disorders.

Heat-killed bacillus Calmette-Guérin and Mycobacterium kansasii antigen 85B combined vaccination ameliorates dermatitis in a mouse model of atopic dermatitis by inducing regulatory T cells

BACKGROUND

Atopic dermatitis (AD) is a recurrent inflammatory skin disease characterized by dominant T-helper (Th) 2 cytokine response. Bacillus Calmette-Guérin (BCG) has been used for preventing tuberculosis, and is regarded as a strong Th1 cytokine inducer. Antigen (Ag) 85B is a secretory protein present in Mycobacterium species that induces Th1 cytokine production.

OBJECTIVES

We investigated the effects of combined vaccination of heat-killed BCG (hkBCG) and Mycobacterium kansasii Ag85B in an AD mouse model.

METHODS

For the AD model, keratin 14 promoter-derived caspase-1 overexpressing mice (KCASP1Tg) were used. The mice received a combination therapy of hkBCG at age 3 weeks and Ag85B twice weekly for 11 weeks from the 4th week; Ag85B monotherapy from the 4th week; hkBCG monotherapy at the 3rd week; or control saline. Areas of skin lesions, cytokine mRNA expression and serum interleukin (IL)-18 and immunoglobulin (Ig) E levels were analysed. Inducible Foxp3+  regulatory T cells (iTreg), IL-10-producing T cells (Tr1), and interferon (IFN)-γ/IL-4/IL-17-producing T cells were evaluated in the spleen.

RESULTS

Saline-treated mice and hkBCG monotherapy mice spontaneously developed severe dermatitis. However, combined therapy with hkBCG and Ag85B significantly suppressed the development of skin lesions and mast cell infiltrations. Elevations of the serum IgE and IL-18 levels were significantly suppressed with combined therapy. Mice treated with hkBCG and Ag85B had a normal number of iTreg in the spleen, and decreased number of both IL-4- and IL-17-producing CD4+ T cells. The effect of Ag85B monotherapy was limited.

CONCLUSIONS

Combined vaccination with hkBCG and Ag85B decreases AD skin lesions by inducing regulatory T cells, suggesting that this vaccination is a potent and novel therapeutic strategy for AD.

Therapeutic effects of mycobacterial secretory proteins against established asthma in BALB/c mice

Purpose

Live/killed mycobacteria and culture supernatants can suppress asthmatic reactions. This study investigated whether mycobacterial secretory proteins have therapeutic effects on asthma.

Methods

Mycobacterium bovis bacille Calmette-Guérin (BCG; 2×10⁵ CFUs) and mycobacterial secretory proteins (Ag85 complex, 38-kDa protein or MPB70; 4 or 20 µg) were administered intraperitoneally to female BALB/c mice with established airway hyperresponsiveness. One week after treatment, the mice underwent a methacholine challenge test, and then inflammatory cell numbers in bronchoalveolar lavage fluid (BAL) and around bronchi (<500 µm), and cytokine levels in splenocyte supernatants, were assessed.

Results

BCG and all of the tested secretory proteins significantly improved airway sensitivity compared to baseline values (P<0.05). The secretory protein Ag85 complex significantly suppressed airway reactivity also (P<0.05), while 38-kDa protein significantly suppressed reactivity and maximal narrowing (P<0.05). The number of eosinophils in BAL and around bronchi, and the goblet cell proportion, were also significantly reduced in mice in both the BCG and secretory protein groups compared to the asthma control group. IFN-γ/IL-5 ratios were significantly higher in mice treated with BCG, 4 µg MPB70 or 4 µg 38-kDa protein than in asthma control mice (P<0.05), and were negatively associated with airway hyperresponsiveness, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05). IL-17A was positively correlated with IL-5 (r=0.379, P<0.001), maximal airway narrowing, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05).

Conclusions

Secretory proteins from BCG and M. tuberculosis and live BCG were effective against established asthma, their effects being accompanied by increased IFN-γ/IL-5 ratios. Thus, allergic asthma could be effectively treated with mycobacterial secretory proteins.

Ag85B DNA vaccine suppresses airway inflammation in a murine model of asthma

Background

In allergic asthma, Th2 lymphocytes are believed to play important roles in orchestrating airway eosinophilia and inflammation. Resetting the Th1/Th2 imbalance may have a therapeutic role in asthma. The mycobacterium tuberculosis 30-kilodalton major secretory protein (antigen 85B, Ag85B) can protect animals from M. tuberculosis infection by inducing a Th1-dominant response.

Methods

In this study, the Ag85B gene was cloned into pMG plasmids to yield the pMG-Ag85B plasmid. The expression of Ag85B gene in murine bronchial epithelia cells was detected by Western blotting and immunohistochemical staining after intranasal immunization with reconstructed pMG-Ag85B plasmids. The protective effect of pMG-Ag85B plasmids immunization in airway inflammation was evaluated by histological examination and bronchoalveolar lavage (BAL). IL-4 and IFN-γ levels in the BAL and supernatant from splenocyte culture were determined using ELISA kits.

Results

The Ag85B gene was successfully expressed in murine bronchial epithelia cells by intranasal immunization with reconstructed pMG-Ag85B plasmids. Using a murine model of asthma induced by ovalbumin (OVA), pMG-Ag85B immunization significantly inhibited cellular infiltration across the airway epithelium with a 37% decrease in the total number of cells (9.6 ± 2.6 × 10⁵/ml vs. 15.2 ± 3.0 × 10⁵/ml, p < 0.05) and a 74% decrease in the number of eosinophils (1.4 ± 0.2 × 10⁵/ml vs. 5.4 ± 1.1 × 10⁵/ml, p < 0.01) compared with the OVA-sensitized control group. There was no difference in the number of neutrophils in BAL fluid between the pMG-Ag85B group, the OVA-sensitized control group and the empty pMG group. IL-4 production was significantly decreased in the BAL fluid (32.0 ± 7.6 pg/ml vs. 130.8 ± 32.6 pg/ml, p < 0.01) and in the splenocyte supernatant (5.1 ± 1.6 pg/ml vs. 10.1 ± 2.3 pg/ml, p < 0.05) in the pMG-Ag85B group compared with the OVA-sensitized control group, while IFN-γ production was increased in the BAL fluid (137.9 ± 25.6 pg/ml vs. 68.4 ± 15.3 pg/ml, p < 0.05) and in the splenocyte supernatant (20.1 ± 5.4 pg/ml vs. 11.3 ± 3.2 pg/ml, p < 0.05).

Conclusion

In a murine model of asthma induced by OVA, intranasal immunization with pMG-Ag85B significantly reduced allergic airway inflammation with less eosinophil infiltration. This protective effect was associated with decreased IL-4 and increased IFN-γ production in the BAL fluid and in the supernatant of cultured splenocytes.