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en Construction of a Recombinant Allergen-Producing Probiotic Bacterial Strain: Introduction of a New Line for a Live Oral Vaccine Against Chenopodium album Pollen Allergy ایمنی شناسی Immunology Background: During the last two decades, significant advances have been made in the fields of lactococcal genetics and protein expression. Lactococcus lactis (L. lactis) is an effective vector for protein expression and can be used as an antigen delivery system. Hence, L. lactis is an ideal candidate for mucosal immunotherapy. Profilin (Che a 2), the major allergen in Chenopodium album, is one of the most important causes of allergic diseases in desert and semi-desert areas, especially in Iran, Saudi Arabia, and Kuwait that was cloned and expressed in L. lactis for the first time. Methods: To construct L. lactis that expressed Che a 2, a DNA sequence was cloned and used to transform bacteria. Expression of Che a 2 was analyzed via monitoring of related RNA and protein. Hydrophobicity, adherence to HT-29 cells, antibiotic resistance, resistance to gastrointestinal contents, pH, and bile salt in recombinant and native L. lactis were evaluated. Results: Immunoblot analyses demonstrated that recombinant Che a 2 is expressed as a 32 kDa dimeric protein immunological studies showed it can bind human IgE. Both native and recombinant bacteria were sensitive to low pH and simulated gastric conditions. Bacterial survival was reduced 80-100% after 2 h of exposure to pH 1.5-2. Both native and recombinant bacteria were able to grow in 0.3 and 2% bile salts. After incubation of recombinant L. lactis in simulated gastric and intestinal juices for one and two hours, respectively, cell survival was reduced by 100%. Adhesion capability in both strains was minimal and there were no significant differences in any of our tests between native and recombinant bacteria. Conclusion: Successfully recombinant L. lactis with capability of expression Che a 2 was produced and revealed it is sensitive to gastrointestinal contents. Chenopodium pollen allergen, Oral vaccines, Probiotic bacteria, Recombinant L. lactis 16 27 http://rbmb.net/browse.php?a_code=A-10-1-16&slc_lang=en&sid=1 Leila Roozbeh Nasiraie 10031947532846005950 10031947532846005950 No Department of Food Science and Technology, Ferdowsi University of Mashhad, Mashhad, Iran Farideh Tabatabaie 10031947532846005951 10031947532846005951 No Department of Food Science and Technology, Ferdowsi University of Mashhad, Mashhad, Iran Mojtaba Sankian 10031947532846005952 10031947532846005952 No Immunobiochemistry Lab, Immunology Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Fakhri Shahidi 10031947532846005953 10031947532846005953 No Department of Food Science and Technology, Ferdowsi University of Mashhad, Mashhad, Iran Abdolreza Varasteh varastehA@mums.ac.ir 10031947532846005954 10031947532846005954 Yes Immunobiochemistry Lab, Allergy Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran