Efficacy evaluation of Der p 1 DNA vaccine for allergic asthma in an experimental mouse model

Designing an epitope vaccine against Dermatophagoides pteronyssinus: An in silico study

The house dust mite, Dermatophagoides pteronyssinus, is a major source of the inhaled allergen Der p 1, which causes immunoglobulin E (IgE)-mediated hypersensitivity reactions manifesting in allergic diseases. To date, no drugs or vaccines effectively treat or prevent Der p 1 sensitization. We applied in silico immunoinformatics to design T-cell and B-cell epitopes that were specified and developed from the allergen Der p 1 of D. pteronyssinus. We identified the conserved epitope areas by predicting the accessibility and flexibility of B-cell epitopes, and the percentage of human leukocyte antigen representing T cells. Molecular docking using HADDOCK software indicated three optimal clusters: cluster 6 (z-score: -2.1), cluster 1 (z-score: -1.2), and cluster 3 (z-score: -0.6). The most negative Z-score was found in cluster 6, which represented three epitopes. The interaction between A chain proteins (IgE protein residues) and B chains (Der p 1 protein residues) exhibited a knowledge-based FADE and contact value >1, suggesting the best protein interactions occurred in the conserved area. Molecular dynamic simulation further predicted the stable nature of Der p 1 protein. The IQRDNGYQP region is the best candidate to be utilized as a D. pteronyssinus epitope vaccine, which could be used in the development of allergen-specific immunotherapy.

Comparing the Protection Imparted by Different Fraction Extracts of Garlic (Allium sativum L.) against Der p-Induced Allergic Airway Inflammation in Mice

Garlic (Allium sativum L.) has been used extensively as a food ingredient and medicinally, but the effect on asthmatic airway inflammation has not been studied in detail. We accordingly explored the protective effects exerted by various garlic fraction extracts against airway inflammation with Dermatophagoides pteronyssinus (Der p)-induced allergic asthma in vivo and in vitro. Garlic extraction was realized using n-hexane, dichloromethane, ethylacetate, n-butanol, and water in sequence to obtain different fraction extracts. Mice were orally administered different fractions (80 mg/kg) daily for four weeks. The histological results showed that the water fraction could ameliorate lung-based goblet cell hyperplasia, inflammatory cell infiltration, and mucus hypersecretion. The water fraction extracts decreased IgE and IgG1, and they decreased inflammatory cells as quantified in bronchoalveolar lavage fluid (BALF); however, they increased IgG2a in serum. Moreover, the water fraction extracts increased IFN-γ and IL-12 (both constituting Th1 cytokines) in BALF, but they reduced IL-13, -4, and -5 (all constituting Th2 cytokines), and also inhibited the expression of IL-1β, IL-6, and TNF-α. The water fraction also inhibited the PI3K/Akt/NF-κB signal pathways in A549 cells. These findings suggest that water fraction extracts of garlic have a clear anti-inflammatory effect on Der p-induced allergic asthma.

Dendritic cells modified with Der p1 antigen as a therapeutic potential for allergic rhinitis in a murine model via regulatory effects on IL-4, IL-10 and IL-13

OBJECTIVES

House dust mites, including Der p1, are common allergens. The current study was designed to explore the allergen-specific immune tolerance effects of Der p1-modified dendritic cells (DCs) through IL-4, IL-10 and IL-13 on an allergic rhinitis (AR) mouse model.

METHODS

A lentivirus was modified to express Derp1. Then, immature DCs from mice were infected with this modified lentivirus to generate a lenti-Derp1-GFP DCs. 24 mice were random divided into four groups (n = 6 each), AR mouse were sensitized by Derp1 allergens and treated with lenti-GFP DCs (GFP-DC/AR group), or lenti-Derp1-GFP DCs (Der p1-DC/AR group) and dexamethasone (Dex/AR group), mice in the control group were treated with PBS instead of Der p1 then also intraperitoneally injected with 5 × 10⁶ lenti-GFP DCs/mouse. AR symptoms expressed by each mouse were recorded. The proportions of CD4⁺CD25⁺Foxp3⁺ regulatory T cells among CD4⁺ T cells in the peripheral blood, and mRNA and protein expression levels of IL-4, IL-10, and IL-13 were measured.

RESULTS

DCs infected with lenti-Derp1-GFP stimulated the maturation of DCs. Compared with the GFP-DC/AR group, mice in the Der p1-DC/AR group showed an ameliorated allergic response, a significant decrease in the levels of serum IgE, IgG1, and histamine, and a decrease in the expression of IL-4 and IL-13 mRNA and protein in the nasal mucosa. The expression of IL-10 increased in the Der p1-DC/AR group to a level similar to that observed in the Dex/AR group.

CONCLUSIONS

These results indicate that Der p1-modified DCs have therapeutic potential for AR via downregulation of IL-4 and IL-13, and upregulation of IL-10.

Derp1-modified dendritic cells attenuate allergic inflammation by regulating the development of T helper type1(Th1)/Th2 cells and regulatory T cells in a murine model of allergic rhinitis

The CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) are known to regulate Th2-induced allergic rhinitis (AR). In this study, we evaluated the efficacy of Derp1-modified dendritic cells (DCs) in AR immunotherapy. Derp1 was synthesized and transfected into DCs to generate Derp1-modified DCs. Phenotypes of Derp1-modified DCs were analyzed with flow cytometry using antibodies against DC markers CD11c, CD11b, CD59, CD103 and Toll-like receptor 1(TLR1). Four groups of subject mice were formed; the controls were treated with immature DCs, while the AR mice models were sensitized with Derp1(AR) and treated with DCs(DC-AR) or Derp1-modified DCs (Derp1DC-AR). The frequency of sneezing and scratching, eosinophil cell count, and Th1/Th2 ratio in the spleen were measured for all groups. The percentage of CD4⁺CD25⁺Foxp3⁺ Tregs in peripheral blood mononuclear cells was measured using flow cytometry; serum IgE, IgG1, and histamine were measured using enzyme-linked immunosorbent assay; expression levels of transcription factors T-bet, GATA3, Foxp3+ and IL-10 were analyzed using reverse transcription-polymerase chain reaction, and Western blot used in analyzed expression of Foxp3+ and IL-10 in nasal mucosa. Treatment with Derp1-modified DCs ameliorated the allergic response. The Derp1DC-AR group had significantly lower eosinophil cell count and the IgE, IgG1, and histamine levels than the AR and DC-AR groups, and higher mRNA levels of Th1 transcription factors T-bet, IL-10 and Foxp3 in nasal mucosa than DC-AR mice, but Th2 transcription factors GATA3 mRNA expression level has the opposite results. Furthermore, the Th1/Th2 ratio and percentage of CD4⁺CD25⁺Foxp3⁺ Tregs was significantly lower in the AR group (p<0.05), but higher in the Derp1DC-AR group than in the control group (p<0.01). Thus, the Derp1-modified DCs increased the percentage of CD4⁺CD25⁺Foxp3⁺Tregs and influenced the balance of Th1/Th2, showing an immunotherapeutic effect against AR.

Protective effect of forsythiaside A on OVA-induced asthma in mice

Forsythiaside A (FSA), an active constituent isolated from the Chinese medicinal herb Forsythia suspensa, has been known to have anti-inflammatory effect. However, the effect of FSA on allergic airway inflammation remains unclear. The aim of this study was to investigate the effect of FSA on OVA-induced asthma in mice. Mice model of asthma was induced by OVA. OVA-induced airway hyperresponsiveness (AHR) and inflammatory cells in BALF were detected. The production of IgE, IL-4, IL-5, IFN-γ, and IL-13 were detected by ELISA. The effects of FSA on Nrf2 and NF-κB signaling pathways were detected by western blot analysis. The results showed that treatment of FSA significantly attenuated OVA-induced lung histopathological changes. FSA inhibited OVA-induced AHR and inflammatory cells in BALF. OVA-induced IgE, IL-4, IL-5, and IL-13 production were also inhibited by FSA. Western blot analysis showed that treatment of FSA inhibited OVA-induced NF-κB activation. Treatment of FSA dose-dependently up-regulated the expression of Nrf2 and HO-1. In addition, we found that FSA up-regulated the expression of Nrf2 and HO-1 both in A549 cells and MS-H cells. Taken together, FSA suppressed inflammatory responses in OVA-induced asthma through activating Nrf2/HO-1 signaling pathway. FSA may be a promising potential preventive agent for asthma treatment.

Sappanone A Attenuates Allergic Airway Inflammation in Ovalbumin-Induced Asthma

BACKGROUND

Sappanone A (SA) is isolated from the heartwood of Caesalpinia sappan and exerts a wide range of pharmacological activities. In the present study, we investigated the protective effects of SA on allergic asthma in a murine model of ovalbumin (OVA)-induced asthma.

METHODS

BALB/c mice were sensitized and challenged. Then, the mice were intraperitoneally injected with SA (12.5, 25 and 50 mg/kg) 1 h before OVA challenge; 24 h after the last challenge, the mice were sacrificed, and data were collected by different experimental methods.

RESULTS

The results showed that SA dose-dependently reduced inflammatory cell counts, levels of cytokines IL-4, IL-5 and IL-13, and OVA-specific IgE in bronchoalveolar lavage fluid. The level of IFN-γ decreased by OVA was upregulated by the treatment with SA. Furthermore, SA was found to attenuate the airway inflammation and mucus hypersecretion induced by the OVA challenge. In addition, SA dose-dependently upregulated the expression of Nrf2 and HO-1. SA inhibited OVA-induced asthma by activating the Nrf2 signaling pathway.

CONCLUSIONS

These data suggest that SA may have a potential use as a therapeutic agent for asthma.

Abietic acid attenuates allergic airway inflammation in a mouse allergic asthma model

Abietic acid (AA), one of the terpenoids isolated from Pimenta racemosa var. grissea, has been reported to have anti-inflammatory and immunomodulatory effects. However, the anti-allergic effects of AA remain unclear. The aim of this study was to investigate the anti-allergic effects of AA in an ovalbumin (OVA)-induced asthma murine model. The model of mouse asthma was established by induction of OVA. AA (10, 20, 40mg/kg) was administered by oral gavage 1h after the OVA treatment on days 21 to 23. At 24h after the last challenge, bronchoalveolar lavage fluid (BALF) and lung tissues were collected to assess pathological changes, cytokines production, and NF-κB expression. The results showed that AA attenuated lung histopathologic changes, inflammatory cells infiltration, and bronchial hyper-responsiveness. AA also inhibited OVA-induced the nitric oxide (NO), IL-4, IL-5, IL-13, and OVA-specific IgE production, as well as NF-κB activation. In conclusion, the current study demonstrated that AA exhibited protective effects against OVA-induced allergic asthma in mice and the possible mechanism was involved in inhibiting NF-κB activation.

For t 2 DNA vaccine prevents Forcipomyia taiwana (biting midge) allergy in a mouse model

BACKGROUND

Forcipomyia taiwana (biting midge) is the most prevalent allergenic biting insect in Taiwan, and 60% of the exposed subjects develop allergic reactions. Subjects with insect allergy frequently limit their outdoor activities to avoid the annoyingly intense itchy allergic reactions, leading to significant worsening of their quality of life. Allergen-specific immunotherapy is the only known therapy that provides long-term host immune tolerance to the allergen, but is time-consuming and cumbersome. This study tested whether the For t 2 DNA vaccine can prevent allergic symptoms in For t 2-sensitized mice.

MATERIALS AND METHODS

Two consecutive shots of For t 2 DNA vaccine were given to mice with a 7-day interval before sensitization with recombinant For t 2 proteins, using the two-step sensitization protocol reported previously.

RESULTS

The For t 2 DNA vaccine at 50 μg prevented the production of For t 2-specific IgE (P < 0.05), as well as midge allergen-challenge-induced scratch bouts, midge allergen-induced IL-13 and IL-4 production from splenocytes, and inflammatory cell infiltrations in the lesions 48 h after intradermal challenge.

CONCLUSIONS

This study is the first to demonstrate that DNA vaccine encoding midge allergen is effective in preventing allergic skin inflammation induced by biting midge. Immunotherapy using For t 2 DNA vaccine can protect mice from being sensitized by midge allergen and may be a promising treatment for biting midge allergy in the future.

PLGA-Der p1 Vaccine Inhibited Tumor Growth in a Murine Model of Lung Cancer

BACKGROUND AND AIMS

We undertook this study to investigate the influence of PLGA-Dermatophagoides protein 1 (Der p1) vaccine on the growth of Lewis lung cancer (LLC) cells in C57/BL/6 mice.

METHODS

After subcutaneous transplantation of LLC, cells were injected into the axilla of C57/BL/6 mice. Five mice received intraperitoneal (i.p.) injection of PLGA-Der p1 vaccine, and another five mice received i.p. injection of PBS or PLGA as control. Body weight of C57/BL/6 mice and tumor growth were measured. Morphological change of tumor was observed under optical microscope. The expression of Ki67 and CD34 protein was detected by immunohistochemistry analysis. The concentration of IL-4 and IFN-γ in the splenocyte culture medium was detected by ELISA.

RESULTS

The growth of transplanted tumor was inhibited markedly by PLGA-Der p1 vaccine. The protein level of Ki67 and CD34 was significantly lower in PLGA-Der p1 vaccine group than in the control group (p < 0.05). The level of IFN-γ of the splenocyte culture medium was significantly higher in PLGA-Der p1 vaccine group than that in the control group (p < 0.05). However, the level of IL-4 in the splenocyte culture medium was obviously lower in PLGA-Der p1 vaccine group than that in the control group (p < 0.05).

CONCLUSION

PLGA-Der p1 vaccine has a significant inhibitory effect on the growth of LLC cells in C57/BL/6 mice by inducing the production of a Th1 cytokine profile.

Intranasal immunization with DNA vaccine coexpressing Der p 1 and ubiquitin in an allergic rhinitis mouse model

BACKGROUND

The worldwide prevalence of allergic rhinitis (AR) is increasing, whereas treatments for AR remain limited in effect. Therefore, a new type of effective drug is eagerly in demand.

OBJECTIVE

To create a hypoallergenic vaccine by forced ubiquitination.

METHODS

In the present study, we constructed a DNA vaccine coexpressing Der p 1 allergen and murine ubiquitin, which used chitosan as a carrier. Through the vitro and vivo experiments, we evaluated its protective efficacy against AR.

RESULTS

The results indicated that the DNA vaccine pVAX1-Ub-Derp1/CS had been successfully constructed. This nanoparticle could not only transfect 293T cells in vitro but also transform cells in vivo. The inflammation of nasal mucosa in an AR murine model via immunization with pVAX1-Ub-Derp1/CS was less severe than those without treatments. Furthermore, it found that mice immunized with pVAX1-Ub-Derp1/CS generated a high level of specific IgG but a low level of specific IgE (P < .01). The significantly increased levels of interferon-γ and the significantly decreased levels of interleukins 4, 10, and 17 indicated that a TH1-type response was elicited by immunization with pVAX1-Ub-Derp1/CS (P < .01). This effect was especially stronger through intranasal immunization.

CONCLUSION

Nasal mucosal immunization and ubiquitination are efficacious strategies to enhance the efficiency and safety of DNA vaccine. The nanoparticle pVAX1-Ub-Derp1/CS is expected to be a new kind of effective vaccine for AR.

Proteolytic antigens interfere with endosome/lysosome fusion in epithelial cells

The airway epithelial barrier function is important in maintaining the homeostasis in the body. A number of airway disorders are associated with the epithelial barrier dysfunction. The present study aims to elucidate a possible mechanism by which the proteolytic allergens compromise the epithelial barrier function. The airway epithelial cell line, RPMI 2650 cells (Rp cells) and kidney epithelial cell line, MDCK cells, were cultured to be monolayers and used as an in vitro epithelial barrier model. House dust mite antigen, Der P1 (Der) was used as an antigen that has the proteolytic property. The epithelial barrier permeability and transepithelial resistance (TER) were used as the indicators of epithelial barrier function. Both epithelial cell lines could endocytose Der in the culture. Some of the Der was transported across the epithelial barrier to the basal chambers of the Transwells without affecting the TER. The endocytic Der could suppress the expression of ubiquitin E3 lases A20 and further interfered with the fusion of endosome/lysosome in the epithelial cells. Mite antigen, Der, can interfere with the fusion of endosome/lysosome in epithelial cells to induce the epithelial barrier dysfunction.

Safety and immunogenicity of a DNA vaccine encoding human calcium-activated chloride channel 1 (hCLCA1) in asthmatic mice

BACKGROUND

Calcium-activated chloride channels (CLCAs) have been found to be preferentially expressed on the secretory epithelium. They may play a pivotal role in mucous overproduction by bronchial goblet cells in asthma. It has been reported that the inhibition of CLCAs with niflumic acid could relieve the symptoms of asthma. However, niflumic acid has serious adverse effects. DNA vaccination is considered to be a promising strategy to treat allergic diseases such as asthma and dust mite allergy.

METHODS

We constructed a vaccine encoding human CLCA1 (hCLCA1) and evaluated its effects on promoting antibodies against hCLCA1 and the related preventive function in a mouse model of asthma.

RESULTS

Our results reveal that the induced hCLCA1 antibodies can be detected in the first 2 weeks after immunization with hCLCA1 plasmids (hCLCA1-p) by intramuscular injection and augmented gradually in the following several weeks. The autoantibodies against hCLCA1 induced by the DNA vaccine bound to three segments of the mouse CLCA3 (mCLCA3) protein, including the amino terminal (PepN), the carboxyl terminal (PepC) and the middle of the protein (PepM). In our study, mice immunized with hCLCA1-p developed fewer pathological changes compared with other control groups, including a remarkable reduction in the air pressure-time index of the trachea, the number of eosinophils and mast cells in the bronchoalveolar lavage fluid and the mRNA level of MUC5AC in goblet cells.

CONCLUSION

Taken together, our results suggest that a DNA vaccine encoding the CLCA protein may have potential as a useful pharmacotherapy for asthma in the future.

In planta expression of a mature Der p 1 allergen isolated from an Italian strain of Dermatophagoides pteronyssinus

European (Dermatophagoides pteronyssinus) and American (Dermatophagoides farinae) house dust mite species are considered the most common causes of asthma and allergic symptoms worldwide. Der p 1 protein, one of the main allergens of D. pteronyssinus, is found in high concentration in mites faecal pellets, which can became easily airborne and, when inhaled, can cause perennial rhinitis and bronchial asthma. Here we report the isolation of the Der p 1 gene from an Italian strain of D. pteronyssinus and the PVX-mediated expression of its mature form (I-rDer p 1) in Nicotiana benthamiana plants. Human sera from characterized allergic patients were used for IgE binding inhibition assays to test the immunological reactivity of I-rDer p 1 produced in N. benthamiana plants. The binding properties of in planta produced I-rDer p 1 versus the IgE of patients sera were comparable to those obtained on Der p 1 preparation immobilized on a microarray. In this paper we provide a proof of concept for the production of an immunologically active form of Der p 1 using a plant viral vector. These results pave the way for the development of diagnostic allergy tests based on in planta produced allergens.

Induction of immune tolerance in asthmatic mice by vaccination with DNA encoding an allergen-cytotoxic T lymphocyte-associated antigen 4 combination

Allergen-specific immunotherapy is a potential treatment for allergic diseases. We constructed an allergen-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)-encoding DNA vaccine, administered it directly to antigen-presenting cells (APCs), and investigated its ability and mechanisms to ameliorate allergic airway inflammation in an asthmatic mouse model. An allergen-CTLA-4 DNA plasmid (OVA-CTLA-4-pcDNA₃.₁) encoding an ovalbumin (OVA) and the mouse CTLA-4 extracellular domain was constructed and transfected into COS-7 cells to obtain the fusion protein OVA-CTLA-4, which was able to bind the B7 ligand on dendritic cells (DCs), and induced CD25⁺ Foxp3⁺ regulatory T (Treg) cells by the coculture of naive CD4⁺ T cells with DCs in vitro. In an animal study, BALB/c mice were sensitized and challenged with OVA to establish the asthmatic model. Vaccination with a high dose of OVA-CTLA-4-pcDNA₃.₁ significantly decreased interleukin-4 (IL-4) and IL-5 levels and eosinophil counts and prevented OVA-induced reduction of the gamma interferon level in the bronchoalveolar lavage fluid. In addition, these mice suffered less severe airway inflammation and had lower levels of OVA-specific IgE and IgG1 titers in serum. Also, high-dose OVA-CTLA-4-pcDNA₃.₁ vaccination inhibited the development of airway hyperreactivity and prevented OVA-induced reduction of the percentages of Foxp3⁺ Treg cells in the spleen. Our results indicate that a high dose of allergen-CTLA-4-encoding DNA vaccine was more effective in preventing an allergen-induced Th2-skewed immune response through the induction of Treg cells and may be a new alternative therapy for asthma.

Plasma protein profiles in early asthmatic responses to inhalation allergen challenge

Although mediators, such as lipids, cytokines, and chemokines, are related to the appearance of an IPR, there has been no reliable indicator to predict conditions for the appearance of an IPR. In this study, we adopted a proteomic approach to investigate the pathogenesis at the level of the plasma proteins and to develop plasma markers to predict the appearance of an IPR following an inhalation challenge with Dermatophagoides pteronyssinus (D.p.). Sixteen mild asthmatics were recruited. Plasma was obtained before challenge and when a decline in forced expiratory volume in 1 s (FEV(1)) values greater than 20% from the phosphate-buffered saline value was achieved during D.p. allergen challenge (positive responders), or at 60 min after the highest concentration of D.p. allergen was inhaled (negative responders). After comparing normalized volumes of the spots in the two groups, differentially expressed spots were identified using intra-gel digestion and mass spectrometric analysis. Before D.p. antigen challenge, four spots of gamma fibrinogen and its isoforms were significantly decreased and two spots of complement C3 fragments were significantly increased in the positive responders compared to the negative responders. After D.p. antigen challenge, complement C3 fragment was persistently higher, while gamma fibrinogen was lower in the positive responders than in the negative responders. A validation study using Western blotting showed that gamma fibrinogen expression in the IPR-positive asthmatics was significantly decreased compared to the average of the IPR-negative asthmatic control group. These results indicate that alterations in the complement cascade and fibrinogen may predispose patients to the appearance of an immediate response to D.p. allergen challenge and may provide plasma markers to predict the appearance of an IPR.

From population structure to genetically-engineered vectors: New ways to control vector-borne diseases?

Epidemiological studies on vectors and the pathogens they can carry (such as Borrelia burgdorferi) are showing some correlations between infection rates and biodiversity highlighting the "dilution" effects on potential vectors. Meanwhile other studies comparing sympatric small rodent species demonstrated that rodent species transmitting more pathogens are parasitized by more ectoparasite species. Studies on population structure and size have also proven a difference on the intensity of the parasitic infection. Furthermore, preliminary results in genetic improvement in mosquitoes (genetic markers, sexing, and genetic sterilization) will also increase performance as it has already been shown in field applications in developing countries. Recent results have greatly improved the fitness of genetically-modified insects compared to wild type populations with new approaches such as the post-integration elimination of transposon sequences, stabilising any insertion in genetically-modified insects. Encouraging results using the Sterile Insect Technique highlighted some metabolism manipulation to avoid the viability of offspring from released parent insect in the wild. Recent studies on vector symbionts would also bring a new angle in vector control capabilities, while complete DNA sequencing of some arthropods could point out ways to block the deadly impact on animal and human populations. These new potential approaches will improve the levels of control or even in some cases would eradicate vector species and consequently the vector-borne diseases they can transmit. In this paper we review some of the population biology theories, biological control methods, and the genetic techniques that have been published in the last years that are recommended to control for vector-borne diseases.

Secretion of thymidine kinase to increase the effectivity of suicide gene therapy results in the loss of enzymatic activity

Low efficiency of gene transfer is one of the major limitations of gene therapy. A solution to this problem may be transmission; by modification of the transgene, the gene product can be secreted and internalized by the surrounding cells. Cancer gene therapy using the herpes simplex thymidine kinase (HSV-TK) suicide gene is a promising treatment, and TK has been used in clinical trials with some success. However, this kind of therapy has limited efficacy due to the low level of gene transfer reached. A modified TK protein, capable of migrating from the producing cell to neighboring cells, would result in a greater proportion of cells affected by the treatment. As a first step towards transmission, we constructed a secretory form of HSV-TK by including the Igkappa leader peptide in the gene. An endoplasmatic reticulum export signal was added to the construct to further improve its secretion. Secretion and protein production in cancer cells, the enzymatic activity of the modified proteins and the ability of the modified TK to sensitize cancer cells to ganciclovir were tested. Addition of the Igkappa leader resulted in high levels of secretion of HSV-TK, with up to 70% of the total amount of protein secreted. Inclusion of an ER export signal did not further improve secretion. The enzyme activity of the secreted TK however, was decreased when compared to native TK. This study is the first to report on secretion of TK, and provides a first step in a novel strategy to improve the efficiency of cancer gene therapy. The loss of function in secreted TK however, may present a major hurdle in the development of a transmitted form of TK.

DNA vaccines and allergic diseases

1. Allergic diseases are characterized by inappropriate immune responses to common environmental antigens. The prevalence of these diseases has been increasing worldwide for reasons that are not exactly clear. 2. Current treatment is largely symptomatic. Because the initial observation that simple plasmid DNA injections resulted in in vivo protein expression and induction of adaptive immune responses to the encoded antigen, the potential of modifying the allergic immune responses by DNA vaccination so as to treat and prevent these diseases has been explored extensively. 3. In the present paper we review preclinical studies using animal models of allergic diseases, with an emphasis on DNA vaccine design, for house dust mite allergens-related allergic asthma.

[Genetic immunization: new ways for protective and therapeutic vaccines against allergic diseases]

Gene vaccines have proven to be a powerful tool to induce anti-allergic immune responses. Their underlying functional principle is based on the recruitment of allergen-specific Th1 cells and the establishment of a Th1 cytokine milieu, which protects against the development of a Th2-biased response and balances an already ongoing Th2-type response. Genetic immunization also offers novel approaches to the major problems associated with protein immunization, such as crosslinking of preexisting IgE on mast cells/basophils or induction of de novo synthesis of IgE by the protein immunization itself. In addition to the description of the principles of gene vaccination, this review gives a short overview of recently developed anti-allergic gene vaccines with an optimized efficacy and safety profile.

Is genetic vaccination against allergy possible?

Genetic immunization has proven a powerful method to induce antiallergic immune responses. The underlying functional principle has been described to be based on the recruitment of allergen-specific Th1 cells, CD8+ cells and the establishment of a Th1 cytokine milieu, which prevent the development of a Th2-biased response in a protective setup and can balance an ongoing Th2-type response in a therapeutic situation. Genetic immunization with plasmid DNA offers innovative solutions to the major problems associated with protein immunization, such as crosslinking of pre-existing immunoglobulin E on mast cells/basophils or induction of de novo synthesis of immunoglobulin E by the protein immunization itself. It easily enables the routine production of hypoallergenic vaccines, which do not translate native allergens, thus avoiding potential anaphylactic side effects. DNA vaccines can also be applied as mixtures of single vaccines, making them interesting candidates for treatment based on component-resolved diagnosis, followed by an individualized therapy with the relevant allergens. In addition to the description of up-to-date allergen gene vaccine approaches, this review gives an overview of animal studies dealing with the following topics: danger signals as the inherent adjuvant properties, methods to optimize the vaccine immunogenicity, modulation of the immune response, nonparenteral applications and low-dose vaccination strategies.