雞熱休克70之DNA異種疫苗可抑制犬腫瘤生長

Abstract

接種異種動物之去氧核醣核酸 (xenogeneic DNA) 被認為是一種有效治療腫瘤的方式，此種疫苗可使免疫系統針對表現於腫瘤之自我抗原，產生特異性抗體及毒殺型T細胞，克服腫瘤免疫耐受性。熱休克蛋白70 (HSP70) 表現於許多腫瘤，且被認為與腫瘤生長有密切的關係。本研究乃接種雞 (chicken HSP70, chHSP70) DNA疫苗至具傳染性花柳性腫瘤犬隻，作為異種動物DNA以引發對抗自我抗原的免疫反應。實驗共分三組：第一組 (G1) 於接種腫瘤前施打此DNA疫苗，用以評估預防效果。第二組 (G2) 於接種腫瘤後施打疫苗，用以評估此 DNA疫苗之治療效果。第三組 (G3)的免疫計劃與第一組相同，僅於第三劑給予方式由肌肉電衝改為經皮注射。另有4隻未經治療的腫瘤接種犬 (No treatment, NT) 做為控制組。除此之外，每組疫苗組皆另有一隻腫瘤接種犬隻注射空白載體做為質體控制組。結果顯示，本疫苗於G1有明顯抑制腫瘤生長的效果 (第9周)，其腫瘤也比第G2 (第18周)、G3 (第12周)和NT組 (第14周) 較早消退。在腫瘤消退期，G1之CD4+腫瘤浸潤淋巴球也顯著的高於G2及NT (56.77% vs. 23.56% and 22.73% )。週邊血液單核細胞對腫瘤細胞的毒殺能力在三組疫苗組中皆顯著性上升。ELISpot試驗顯示，於腫瘤消退期，G1之犬 HSP70 特異性IFN-

Immunization with xenogeneic DNA is a promising cancer treatment, as it generates autoantibodies and cytotoxic T cells to break the tumor tolerance against self-antigens. Heat shock protein 70 (HSP70) is overexpressed in many kinds of tumors and is believed to be heavily involved in tumor progression. This study employed a xenogeneic chicken HSP70 (chHSP70) DNA vaccine in a canine transmissible venereal tumor (CTVT) model in beagles to break the tumor tolerance by inducing immune responses towards canine HSP70 self-antigens. In this study, three vaccination groups were created: the first (G1) was designed to evaluate the prophylactic efficiency of the chHSP70 DNA vaccine by delivering the vaccine prior to tumor inoculation; the second (G2) was designed to evaluate the therapeutic efficacy in developed tumors by vaccinating the dogs after tumor inoculation; and the third (G3) consisted of the same vaccination schedule as that of G1, with the exception that the intramuscular injection/electroporation method used to administer the third vaccination in G1 was replaced with a transdermal injection. Four CTVT-bearing dogs that received no treatment (NT) served as controls, and one dog in each vaccination group immunized with empty vector served as a vector control. Tumor growth was notably inhibited only in the G1 dogs, in which the vaccination program triggered tumor regression much sooner (beginning in week 9) than in the G2 (week 18), G3 (week 12) and NT (week 14) dogs. The CD4+ subpopulation of tumor-infiltrating lymphocytes was significantly increased during tumor regression in the G1 dogs as compared with the G2 and NT dogs (56.77% vs. 23.56% and 22.73%, respectively) and was similar to that of G3. The tumor-specific cytotoxicity of peripheral blood mononuclear cells (PBMCs) in all dogs in the three vaccination groups was dramatically enhanced, and ELISpot assay indicated that canine HSP70-specific IFN-