Genetically engineered vaccines

The Role of Lipids in Development of Allergic Responses

Most allergic diseases are caused by activation of Th2 type immune responses resulting in the production of specific IgE against proteins found in normally harmless substances such as pollen, mites, epithelia or food. Allergenic substances are composed, in addition to proteins, of other compounds such as carbohydrates and lipids. Those lipids are able to promote the development of Th2-type responses associated with allergy. There are lipids found in pollen, milk or insect venom that are specifically recognized by CD1 restricted unconventional T lymphocytes, which can promote allergic reactions. Furthermore, a large number of allergens are proteins containing hydrophobic parts that specifically bind lipids that are capable to favor allergenic immune responses. Also, lipids associated to substances like pollen, dander, epithelia or the bacteria can act on cells of the innate system, including dendritic cells, which in turn lead to the differentiation of Th2-type clones. Finally, lipids may also influence the ability of allergens to be exposed to the immune system within the oral, respiratory or intestinal mucosa where allergic response occurs with great frequency.

Immunotherapy with a recombinant hybrid molecule alleviates allergic responses more efficiently than an allergenic cocktail or pollen extract in a model of chenopodium album allergy

BACKGROUND

The aim of this study is to assess the therapeutic potential of a recombinant hybrid molecule (rHM) alongside an allergenic cocktail from recombinant wild-type allergens as well as pollen extract on Chenopodium album allergy, using a BALB/c mouse model.

METHODS

The BALB/c mice had already been sensitized to C. album via intraperitoneal injections of alum-adsorbed allergenic cocktail and immunotherapy procedure was followed by subcutaneous injections of the rHM, allergenic cocktail and pollen extract at weekly intervals. Humoral immune responses were determined via measurement of specific antibodies in serum. Splenocytes of immunized mice were stimulated in vitro and then proliferation responses, cytokine secretion and mRNA expression of genes involved in immunotherapy were examined by ELISA and real-time PCR.

RESULTS

Sensitized mice were identified with high specific IgE against allergenic cocktail when compared with healthy mice. Immunotherapy with the rHM induced the highest ratio of the IgG2a/IgG1 levels compared to allergenic cocktail or C. album pollen extract. The rHM was able to induce proliferative responses as well as the allergenic cocktail in cultured splenocytes. Immunotherapy with the rHM significantly improved secretion of IFN-γ and IL-10, while secretion of IL-13 rapidly diminished. Interestingly, mRNA expression of GATA3 was strongly decreased in rHM-treated mice whereas mRNA expression of T-bet and Foxp3 was significantly increased.

CONCLUSION

Our results prove that immunotherapy with the rHM effectively controlled allergic responses by shifting from a Th2-like immune response to a Th1-dominated immune response.

Enhancement of protective immune responses induced by Toxoplasma gondii dense granule antigen 7 (GRA7) against toxoplasmosis in mice using a prime-boost vaccination strategy

Effective vaccines against Toxoplasma gondii may contribute to preventing and controlling the spread of toxoplasmosis, which is important for improving outcomes of infections in humans and livestock animals. The dense granule antigen 7 (GRA7) of T. gondii might be an immunodominant antigen for a vaccine candidate. In the present study, a further exploration of its vaccine effect, a heterologous prime-boost vaccination strategy with a recombinant eukaryotic plasmid pEGFP-GRA7 and a recombinant protein GRA7 expressed from a prokaryotic plasmid pET30-GRA7, was performed in BALB/c mice. The data reveal that a DNA prime-protein boost vaccination induces both humoral and cellular immune responses against T. gondii associated with high levels of total IgG, IgG2a isotype and gamma interferon (IFN-γ). Challenge experiments further show that the DNA prime-protein boost vaccination significantly increases survival rate (60%), compared with controls in which all died within 8 days of challenge. Therefore, the DNA prime-protein boost vaccination based on GRA7 might be a promising regimen for further development of an effective vaccine against T. gondii.

Antibody repertoire complexity and effector cell biology determined by assays for IgE-mediated basophil and T-cell activation

Effector cell activation and T-cell activation, the latter mediated by facilitated antigen presentation, are immunological mechanisms that play crucial roles in the manifestation and maintenance of allergic disease. In addition to their relevance for the pathogenesis of allergy in-vivo, in-vitro assays based on these immunological mechanisms have been established and used for diagnostics, for monitoring the progression of disease and for the effect of specific immunotherapy as well as for basic research purposes. Here we review different parameters that affect effector cell activation and facilitated antigen uptake and presentation, including assay designs, readout parameters and critical experimental conditions. Central to the two immunological mechanisms is complex formation between allergen-specific IgE, allergen, and cell surface-anchored immunoglobulin receptor; the high affinity IgE-receptor FcεRI on basophils and mast cells, and the low affinity IgE-receptor FcεRII (CD23) on B-cells. Accordingly, the effect of IgE repertoire complexity and allergen diversity on effector cell and facilitated antigen presentation is discussed in detail.

Expression and characterization of natural-like recombinant Der p 2 for sublingual immunotherapy

BACKGROUND

Recombinant allergens with a native conformation represent an alternative to natural extracts for immunotherapy and diagnostic purposes.

METHODS

We produced the Der p 2 mite allergen in Pichia pastoris and Escherichia coli. After purification by cation exchange chromatography, recombinant molecules were compared to their natural counterpart based upon structural (disulfide bonds, secondary structure, thermal stability) and immunological properties (antibody reactivity, basophil and T cell activation, tolerance induction in a murine sublingual immunotherapy model).

RESULTS

The Der p 2.0101 isoform was confirmed to be prevalent in Dermatophagoides pteronyssinus extracts. It was then produced as a secreted molecule in P. pastoris or refolded from E. coli inclusion bodies. The yeast-expressed rDer p 2 molecule exhibits a natural-like disulfide bridge distribution and secondary structure, whereas the E. coli-derived rDer p 2 presents some heterogeneity in cysteine bonds and a lower stability following thermal stress. The two recombinant as well as natural Der p 2 molecules exhibit comparable IgE recognition and activate basophil and CD4+ T cells. Sublingual immunotherapy of nDer p 2- sensitized mice using either one of the rDer p 2 molecules efficiently decreases airway hyperresponsiveness as well as Th2 responses.

CONCLUSIONS

Natural and recombinant Der p 2 molecules produced in P. pastoris and E. coli exhibit comparable immunological properties despite distinct structural features. Natural-like cysteine pairing is a critical parameter to identify stable, well-folded and homogenous proteins appropriate for immunotherapy and diagnostic purposes.

House dust mite allergens in asthma and allergy

IgE antibodies in house dust mite (HDM) allergy follow a predictable pattern. Half are directed against two dominant allergens and the remainder largely against four midpotency allergens. This hierarchical pattern is not changed by the titre of the IgE response or severity of disease. The structures of these allergens are known and they can be produced as authentic recombinant allergens. There is also evidence that the allergenicity is augmented by the biological activity of the key allergens, validating them as targets for vaccination. Collectively, these developments should facilitate the development of new diagnostics, improve immunotherapy and allow vaccination with defined reagents. Highly purified recombinant polypeptides representing the important mite allergens are now available so that informative and reproducible experiments can be performed with mite allergens in place of poorly defined and variable extracts.

Disruption of allergenic activity of the major grass pollen allergen Phl p 2 by reassembly as a mosaic protein

The recognition of conformational epitopes on respiratory allergens by IgE Abs is a key event in allergic inflammation. We report a molecular strategy for the conversion of allergens into vaccines with reduced allergenic activity, which is based on the reassembly of non-IgE-reactive fragments in the form of mosaic proteins. This evolution process is exemplified for timothy grass pollen-derived Phl p 2, a major allergen for more than 200 million allergic patients. In a first step, the allergen was disrupted into peptide fragments lacking IgE reactivity. cDNAs coding for these peptides were reassembled in altered order and expressed as a recombinant mosaic molecule. The mosaic molecule had lost the three-dimensional structure, the IgE reactivity, and allergenic activity of the wild-type allergen, but it induced high levels of allergen-specific IgG Abs upon immunization. These IgG Abs crossreacted with group 2 allergens from other grass species and inhibited allergic patients' IgE binding to the wild-type allergen. The mosaic strategy is a general strategy for the reduction of allergenic activity of protein allergens and can be used to convert harmful allergens into safe vaccines.

Genetic Engineering of the Major Timothy Grass Pollen Allergen, Phl p 6, to Reduce Allergenic Activity and Preserve Immunogenicity

On the basis of IgE epitope mapping data, we have produced three allergen fragments comprising aa 1-33, 1-57, and 31-110 of the major timothy grass pollen allergen Phl p 6 aa 1-110 by expression in Escherichia coli and chemical synthesis. Circular dichroism analysis showed that the purified fragments lack the typical alpha-helical fold of the complete allergen. Superposition of the sequences of the fragments onto the three-dimensional allergen structure indicated that the removal of only one of the four helices had led to the destabilization of the alpha helical structure of Phl p 6. The lack of structural fold was accompanied by a strong reduction of IgE reactivity and allergenic activity of the three fragments as determined by basophil histamine release in allergic patients. Each of the three Phl p 6 fragments adsorbed to CFA induced Phl p 6-specific IgG Abs in rabbits. However, immunization of mice with fragments adsorbed to an adjuvant allowed for human use (AluGel-S) showed that only the Phl p 6 aa 31-110 induced Phl p 6-specific IgG Abs. Anti-Phl p 6 IgG Abs induced by vaccination with Phl p 6 aa 31-110 inhibited patients' IgE reactivity to the wild-type allergen as well as Phl p 6-induced basophil degranulation. Our results are of importance for the design of hypoallergenic allergy vaccines. They show that it has to be demonstrated that the hypoallergenic derivative induces a robust IgG response in a formulation that can be used in allergic patients.

Overview of new vaccines and technologies

Molecular technology has given us a greater insight into the aetiology of disease, the functioning of the immune system and the mode of action of veterinary pathogens. The knowledge gained has been used to develop new vaccines with specific, reactive antigens which elicit protective immune mediated responses (humoral and/or cell mediated) in the host. These vaccines should not burden the immune system by initiating responses against non-essential antigens. However, the efficacy of these vaccines is only as good as the delivery technology or route used to present them to the immune system. Some vaccines, traditionally given by the parenteral route, are now given by the natural route; either orally or intranasally. Two major advantages, often interrelated, are the rapid onset of immunity and stimulation of the local, mucosal immunity. These new technologies are now making an impact on current vaccine development. The balance has to be found between what is technologically feasible and what will provide at least as good a protective immunity as current, conventional vaccines. As new and emerging diseases appear globally, new opportunities arise for molecular and conventional technologies to be applied to both the development and delivery of novel vaccines, as well as the improvement of vaccines in current use.