肌肉注射豬流行性下痢類病毒顆粒疫苗合併豬趨化因子CCL25/28以誘發豬隻系統性及黏膜免疫保護力

Abstract

研發安全、經濟及有效刺激黏膜免疫反應疫苗為對抗腸道病毒性疾病重要目標。在本論文中，應用新穎的多效型桿狀病毒載體系統（Polycistronic baculovirus expression vector）成功建構出由豬流行性下痢病毒（Porcine epidemic diarrhea virus; PEDV）棘狀蛋白（Spike protein; S）、膜蛋白（Membrane protein; M）及封套蛋白（Envelope protein; E）組成之類病毒顆粒（Virus-like particle），並於離乳豬評估豬流行性下痢類病毒顆粒疫苗在有或無添加黏膜趨化因子佐劑CCL25 和CCL28（CCL25/28）之免疫原性及保護性。結果證實，經肌肉注射類病毒顆粒疫苗無論是否合併趨化因子佐劑可激發出對抗豬流行性下痢棘狀蛋白的系統性IgG和細胞免疫; 當豬隻免疫豬流行性下痢類病毒顆粒合併有CCL25/28，可更加增加對抗豬流行性下痢棘狀蛋白的系統性IgG、黏膜IgA 及細胞免疫等免疫調節反應，當豬隻經豬流行性下痢病毒攻毒後，相較控制組，兩組經類病毒顆粒免疫的組別皆呈現輕微的臨床表徵及較低的糞便排毒量，除此之外，添加CCL25/28之類病毒顆粒可使豬隻有更明顯的對抗豬流行性下痢病毒之免疫保護效果。本結果顯示類病毒顆粒添加CCL25/28 為具有潛力的豬流行性下痢疫苗，且此策略可延伸應用於其他腸道病毒疫苗之發展。

Generation of a safe, economical, and effective vaccine capable of inducing mucosal immunity is critical for the development of vaccines against enteric viral diseases. In the current study, virus-like particles (VLPs) containing the spike (S), membrane (M), and envelop (E) structural proteins of porcine epidemic diarrhea virus (PEDV) expressed by the novel polycistronic baculovirus expression vector were generated. The immunogenicity and protective efficacy of the PEDV VLPs formulated with or without mucosal adjuvants of CCL25 and CCL28 (CCL25/28) were evaluated in postweaning pigs. While pigs intramuscularly immunized with VLPs alone were capable of eliciting systemic anti-PEDV S-specific IgG and cellular immunity, co-administration of PEDV VLPs with CCL25/28 could further modulate the immune responses by enhancing systemic anti-PEDV S-specific IgG and mucosal IgA and cellular immunity. After challenging with PEDV, both VLPs-immunized groups showed milder clinical signs with reduced fecal viral shedding as compared with those in the control group. Furthermore, pigs immunized with VLPs adjuvanted with CCL25/28 showed superior immune protection against PEDV. Our results suggest that VLPs formulated with CCL25/28 may be a potential PEDV vaccine candidate and the same strategy may serve as a platform for other enteric viral vaccine development.