House dust mite DNA vaccine candidate development of full length and poly-th1 epitopes

Abstract

Allergy is an immune dysregulation against allergens that lead to T-helper type 2 (Th2) immune response and specific IgE production. House dust mite is the most common cause of airway allergic diseases of which 60-70% of patients have detectable anti-house dust mite IgE antibodies. Der p 1 (Dermatophagoides pteronyssinus) protein is one of the major HDM allergens that can sensitize the immune system in an allergic prone person for whom develops an allergic disease. Thus developing a safe and effective HDM vaccine to induce Th1 responses to down regulate Th2 responses is warranted. This study was to developed and optimize a house dust mite (HDM) Der p1 DNA vaccine to generate specific Th1-type responses as a prototype vaccine to be further evaluated its role as a HDM immunotherapy To develop an efficient DNA vaccine, humanized synthetic gene encoding mature Der p 1 allergen was cloned into pHIS plasmid vector containing a CpG motif. The CpG motif, toll-like receptor 9 (TLR9) ligand, served as an adjuvant to activate powerful specific Th1 responses. The protein expression of the construct was tested in pGFP-mHuDer p 1 transfected HEK cells and showed a detection of the chimeric GFP-Der p 1 protein. Intradermally immunizations of pHIS-mHuDer p 1 or control plasmids with and without liposome were performed in Balb/c mice. The immunogenicity was examined by ELISA assays. The results showed mice vaccinated with pHIS-mHuDer p 1 mounted Der p1 specific Th1 immune responses, as evidenced by the detection of specific IgG2a antibody, while it was not detected in control group. Of interest, mice immunized with lipoplexes (liposome-pHIS-mHuDer p 1 DNA) were more efficient to generate faster and higher Der p 1 specific IgG2a responses. An HDM allergic mouse model had also been developed, ProDer p 1 with alum was injected intraperitoneally into mice and had shown a specific Th2 response with IgG1 and IgE antibodies against Der p 1 protein. In conclusions, a humanized Der p1 DNA vaccine has been developed preclinically. Replacing dust mite codons to mammalian codon usage had increased protein expression and its immunogenicity significantly. Immunogenicity studies in mice, when the recombinant humanized Der p 1 DNA injection intradermally showed specific Th1 immune response. Moreover, the lipoplexes formulation was significantly increased the efficacy of the DNA vaccine. This candidate vaccine is therefore warranted for further development as a therapeutic vaccine for house dust mite allergy.