Section of Pediatric Tropical Medicine, Departments of Pediatrics and Molecular Virology and Microbiology, and National School of Tropical Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
Parasite Immunol. 2012 Aug-Sep;34(8-9):404-11. doi: 10.1111/j.1365-3024.2012.01371.x.
Na-ASP-2 is a major protein secreted by infective third-stage larvae (L3) of the human hookworm Necator americanus upon host entry. It was chosen as a lead vaccine candidate for its ability to elicit protective immune responses. However, clinical development of this antigen as a recombinant vaccine was halted because it caused allergic reactions among some of human volunteers previously infected with N. americanus. To prevent IgE-mediated allergic reactions induced by Na-ASP-2 but keep its immunogenicity as a vaccine antigen, we designed and tested a genetically engineered fusion protein, Fcγ/Na-ASP-2, composed of full-length Na-ASP-2 and truncated human IgG Fcγ1 that targets the negative signalling receptor FcγRIIb expressed on pro-allergic cells. The chimeric recombinant Fcγ/Na-ASP-2 protein was expressed in Pichia pastoris and shared the similar antigenicity as native Na-ASP-2. Compared to Na-ASP-2, the chimeric fusion protein efficiently reduced the release of histamine in human basophils sensitized with anti-Na-ASP-2 IgE obtained from individuals living in a hookworm-endemic area. In dogs infected with canine hookworm, Fcγ/Na-ASP-2 resulted in significantly reduced immediate-type skin reactivity when injected intradermally compared with Na-ASP-2. Hamsters vaccinated with Fcγ/Na-ASP-2 formulated with Alhydrogel(®) produced specific IgG that recognized Na-ASP-2 and elicited similar protection level against N. americanus L3 challenge as native Na-ASP-2.
Na-ASP-2 是人体钩虫（Necator americanus）感染性第三期幼虫（L3）进入宿主时分泌的主要蛋白质。它因其能够引发保护性免疫反应而被选为主要疫苗候选物。然而，由于该抗原在先前感染过 N. americanus 的人类志愿者中引起过敏反应，其作为重组疫苗的临床开发已被停止。为了防止 Na-ASP-2 引起的 IgE 介导的过敏反应，同时保持其作为疫苗抗原的免疫原性，我们设计并测试了一种基因工程融合蛋白，Fcγ/Na-ASP-2，它由全长 Na-ASP-2 和靶向表达于致敏细胞上的负信号受体 FcγRIIb 的截断人 IgG Fcγ1 组成。该嵌合重组 Fcγ/Na-ASP-2 蛋白在毕赤酵母中表达，并具有与天然 Na-ASP-2 相似的抗原性。与 Na-ASP-2 相比，该嵌合融合蛋白可有效减少从钩虫流行地区获得的抗 Na-ASP-2 IgE 致敏的人嗜碱性粒细胞中组胺的释放。在感染犬钩虫的狗中，与 Na-ASP-2 相比，Fcγ/Na-ASP-2 皮内注射时会导致即刻型皮肤反应明显减少。用 Alhydrogel（®）配制的 Fcγ/Na-ASP-2 疫苗接种的仓鼠产生了特异性 IgG，可识别 Na-ASP-2，并引发与天然 Na-ASP-2 相似的对 N. americanus L3 挑战的保护水平。
