Recombinant allergens

Successive multiple ionic polymer layer coated capillaries in the separation of proteins - recombinant allergen variants as a case study

A successive multiple ionic polymer layer (SMIL) coating consisting of two pairs of poly(diallyldimethylammonium chloride) and dextran sulfate (DS) layers was applied for the separation of recombinant products of the major birch pollen allergen Betula verrucosa (Bet v 1a). The combination with volatile ammonium bicarbonate buffer at pH 6.70 offers the possibility for future MS hyphenation. The negative net charge of allergens required DS as terminal SMIL layer. The EOF was accelerated from 3.17x10(-8) m(2) V(-1) s(-1) in uncoated to 4.52x10(-8) m(2) V(-1) s(-1) in SMIL capillaries. Fresh prepared SMIL capillaries showed slight EOF acceleration due to gradual re-organization of SMIL structure until stabilization was achieved. Dry storage of SMIL capillaries prevented fluctuations in EOF and migration times and improved coating durability. However, the gradual reconstitution of entangled SMIL layers affected efficiency, but was cured by a 10 mmol/L NaOH rinsing step. Durability of SMIL capillaries in MS-applicable dimension was confirmed for > 70 runs and in total 42 h of voltage application with average intra-day precision of 0.22 and 0.79% and inter-day-precision of 0.91 and 1.17% for migration times of EOF and Bet v 1a, respectively. Final SMIL coating allowed for the separation of Bet v 1a, a hypoallergenic isoform and carbamylated variants with 150,000-685,000 plates.

Vaccination with the recombinant allergen ProDer p 1 complexed with the cationic lipid DiC14-amidine prevents allergic responses to house dust mite

The present study evaluated the prophylactic potential of ProDer p 1, the recombinant precursor form of the major mite allergen Der p 1, combined with the cationic lipid diC14-amidine in a murine model of house dust mite allergy. Naive mice vaccinated with the amidine/allergen complex developed a Th1-biased immune response characterized by the absence of specific IgE, the production of specific IgG2a, and the presence of IFN-gamma in splenocyte cultures. In contrast, ProDer p 1 adjuvanted with alum induced typical strictly Th2-biased allergic responses with strong IgG1 and IgE titers and IL-5 secretion. Removal of negatively charged sialic acids in ProDer p 1 or increasing the ionic strength reduced the binding of ProDer p 1 to the cationic liposomes and resulted in a decrease of the allergen immunogenicity, suggesting that complexation is required for triggering an optimal immune response. Finally, prophylactic vaccination with ProDer p 1-diC14-amidine reduced drastically the production of specific IgE and airway eosinophilia following subsequent immunization with Der p 1-alum and challenge with aerosolized house dust mite extracts. In conclusion, recombinant ProDer p 1 complexed with diC14-amidine could represent an efficient prophylactic vaccine against house dust mite allergy.

In vitro allergy diagnosis: should we follow the flow?

During the last 5 years, an increasing number of studies have demonstrated that flow cytometric quantification of in vitro basophil activation can be a quite performant and reliable tool to measure IgE-dependent allergen-specific responses in allergic patients. So far, most assays have used CD63 as a basophil activation marker and native allergen extracts for stimulation. However, other basophil markers and recombinant allergens have recently been introduced. The technique has been applied for the diagnosis of allergy to pollen, house dust mite, food, natural rubber latex, hymenoptera venom and drugs. In addition, the technique has proven to be useful in non-IgE-mediated reactions such as hypersensitivity to drugs as well as detection of auto-antibodies in chronic urticaria. This review will focus on some specific issues: (1) principles of flow cytometric analysis of in vitro-activated basophils, (2) general technical aspects of the technique (including passive sensitization), (3) clinical applications and (4) recommendations for further development and evaluation of the technique.

Immunologic characterization of the recombinant fire ant venom allergen Sol i 3

Individuals sensitized to fire ant stings show immunoglobulin (Ig)E antibodies against the venom protein Sol i 3. We determined the full-length complementary DNA (cDNA) sequence of this protein and expressed recombinant Sol i 3 in immunogenic form. The complete cDNA of Sol i 3 was obtained by reverse transcription polymerase chain reaction (RT-PCR) and PCR + 1 reactions using gene-specific oligonucleotides, and oligonucleotides designed from the amino acid sequence of this protein. The encoding cDNA is 705 bp in length corresponding to 235 amino acids. The first 22 amino acids are a leader sequence. The protein with an added C-terminal hexahistidine tag was expressed in insect cells using a baculovirus system. The recombinant protein was secreted into the supernatant and affinity purified with a cobalt chelating resin. The recombinant fire ant venom allergen Sol i 3 showed similar IgE binding activity to the native protein in radioallergosorbent test (RAST) and RAST inhibition assays. It was produced in both a glycosylated and an unglycosylated form. A three-dimensional reconstruction of Sol i 3 was compared with the experimentally determined structure of the related allergen Ves v 5. This model is supported by results of circular dichroism spectroscopy.