Scientists from Antigen Express, a wholly owned subsidiary of Generex Biotechnology (GNBT), and France's Stallergenes (GENP.PA) have co-authored a peer review article titled "Researchers Distinct Characteristics of Seasonal Bet v 1 vs. Perennial Der p 1/Der p 2 Allergen-Specific CD4+ T Cell Responses". The article will appear in a future edition of "Clinical & Experimental Allergy" and is available online ahead of print as of November 24th. Stallergenes is a biopharmaceutical company dedicated to immunotherapy treatments for the prevention and treatment of allergy-related respiratory diseases, such as allergic rhinoconjunctivitis, rhinitis and asthma.
Stallergenes has been researching the potential of using Ii-Key peptide tetramers as an assay to monitor T cell responses to allergens as part of a collaboration with Antigen Express that was signed in 2005. Since Antigen Express' proprietary Ii-Key peptide hybrids are potent at stimulating CD4+ T cells, in theory they would be useful in detecting the presence of allergen-specific autoimmune T cells in the blood. The CD4+ T cell responses to the Ii-Key assay will evidently help Stallergenes identify which patients would benefit from the specific immunotherapies which they are developing.
The new research article compares the CD4+ T cell responses against seasonal (Bet v 1) and perennial (Der p 1, Der p 2) allergens. Bet v 1 refers to birch pollen allergen while Der p 1, Der p 2 are considered to be the major allergens derived from house dust mites. The researchers inform that "major histocompatibility complex class II peptide tetramers were engineered to monitor allergen-specific T cell responses". A little cheating from Wikipedia tells us that "histocompatibility is the property of having the same, or mostly the same, alleles of a set of genes called the major histocompatibility complex. These genes are expressed in most tissues as antigens, to which the immune system makes antibodies".
The new report from Antigen Express and Stallergenes states that "tetramer+ cells were detected in 19 patients allergic to house dust mites (HDM), seven allergic to birch pollen, 13 allergic to both and nine non-allergics". The report concludes that "different memory CD4+ T cell responses are elicited in the context of chronic vs. seasonal stimulation with the allergen(s). The heterogeneity in the patterns of CD4+ T cell responses observed in patients allergic to HDMs should be taken into account for specific immunotherapy".
A previous peer review published in 2008 by Antigen Express and Stallergenes, titled "Single Cell Assessment of Allergen-Specific T Cell Responses with MHC Class II Peptide Tetramers", revealed that the complex class II peptide tetramers, such as those mentioned in in the new report, were peptides that are "chemically conjugated with the Ii-Key peptide from the MHC invariant chain to facilitate peptide exchange and binding to MHC class II molecules". In the report, the researchers described that the CD4+ T helper cells that are activated to respond to specific allergens can be identified with high sensitivity ex vivo using Ii-Key hybrids. The researchers of the article remarked that Ii-Key peptide tetramers "will also be extremely useful to monitor the efficacy of various immunotherapeutic strategies in humans, using an immunological readout, possibly helping to identify surrogate biological markers of clinical efficacy" and that "Ii-Key conjugate peptides is the most efficient procedure to expand Bet v 1(141-155)-specific CD4+ T cells, allowing to detect such cells in both allergic and healthy individuals".
In April, Stallergenes announced the positive results of a phase III clinical trial conducted in the US for its sublingual grass pollen immunotherapy tablet, Oralair. The Phase III study is the first conducted in the US, after successfully completing four Phase III clinical trials conducted in Europe. Oralair has already been approved by German regulators, and Stallergenes has retained Torreya Partners in hopes of helping them secure a partner for the US market by mid-2011. Stallergenes is currently planning their NDA filing to be submitted to the FDA.
Stallergenes is aware that they also need help in evaluating which patients would most benefit from their allergen immunotherapy tablets, and in their scientific research reports we find evidence that this help may come from an Antigen Express designed assay. Antigen Express' ability to turn their Ii-Key peptide tetramer assay research into a revenue generating asset may not be such a far fetched dream. While that dream remains to be seen, this positive research report concerning Antigen Express' proprietary Ii-Key technology is certainly a step in the right direction.