College of Life and Environmental Sciences, Minzu University of China, Beijing, People's Republic of China.
PLoS Negl Trop Dis. 2012;6(9):e1842. doi: 10.1371/journal.pntd.0001842. Epub 2012 Sep 27.
Studies have shown that a bacterial fibronectin attachment protein (FAP) is able to stimulate strong systemic and mucosal antibody responses when it is used alone or co-administrated with other antigens (Ags). Thus, it has been suggested to be a promising adjuvant candidate for the development of efficient vaccines. However, the co-administered Ags and FAP were cloned, expressed and purified individually to date. In a recent study, we first evaluated the adjuvanticity of a fibronectin-binding peptide (FBP, 24 amino acids) of Mycobacterium avium FAP fused with Echinococcus multilocularis tetraspanin 3 (Em-TSP3) by detecting systemic and local antibody responses in intranasally (i.n.) immunized BALB/c mice.
METHODOLOGY/PRINCIPAL FINDINGS: Em-TSP3 and FBP fragments were linked with a GSGGSG linker and expressed as a single fusion protein (Em-TSP3-FBP) using the pBAD/Thio-TOPO expression vector. BALB/c mice were immunized i.n. with recombinant Em-TSP3-FBP (rEm-TSP3-FBP) and rEm-TSP3+CpG and the systemic and local antibody responses were detected by ELISA. The results showed that both rEm-TSP3-FBP and rEm-TSP3+CpG evoked strong serum IgG (p<0.001) and IgG1 responses (p<0.001), whereas only the latter induced a high level IgG2α production (p<0.001), compared to that of rEm-TSP3 alone without any adjuvant. There were no significant differences in IgG and IgG1 production between the groups. Low level of serum IgA and IgM were detected in both groups. The tendency of Th1 and Th2 cell immune responses were assessed via detecting the IgG1/IgG2α ratio after the second and third immunizations. The results indicated that i.n. immunization with rEm-TSP3-FBP resulted in an increased IgG1/IgG2α ratio (a Th2 tendency), while rEm-TSP3+CpG caused a rapid Th1 response that later shifted to a Th2 response. Immunization with rEm-TSP3-FBP provoked significantly stronger IgA antibody responses in intestine (p<0.05), lung (p<0.001) and spleen (p<0.001) compared to those by rEm-TSP3+CpG. Significantly high level IgA antibodies were detected in nasal cavity (p<0.05) and liver (p<0.05) samples from both groups when compared to rEm-TSP3 alone without any adjuvant, with no significant difference between them.
I.n. administration of rEm-TSP3-FBP can induce strong systemic and mucosal antibody responses in immunized BALB/c mice, suggesting that fusion of Em-TSP3 with FBP is a novel, prospective strategy for developing safe and efficient human mucosal vaccines against alveolar echinococcosis (AE).
研究表明，当单独使用或与其他抗原（Ag）共同给药时，一种细菌纤维连接蛋白附着蛋白（FAP）能够刺激强烈的全身和粘膜抗体反应。因此，它被认为是开发有效疫苗的有前途的佐剂候选物。然而，迄今为止，共同给药的 Ag 和 FAP 是单独克隆、表达和纯化的。在最近的一项研究中，我们首次通过检测鼻腔内（i.n.）免疫的 BALB/c 小鼠的全身和局部抗体反应，评估了分枝杆菌 FAP 的纤维连接蛋白结合肽（FBP，24 个氨基酸）与细粒棘球绦虫四跨膜蛋白 3（Em-TSP3）融合的佐剂活性。
方法/主要发现：Em-TSP3 和 FBP 片段用 GSGGSG 接头连接，并使用 pBAD/Thio-TOPO 表达载体表达为单个融合蛋白（Em-TSP3-FBP）。BALB/c 小鼠经鼻腔内（i.n.）免疫重组 Em-TSP3-FBP（rEm-TSP3-FBP）和 rEm-TSP3+CpG，并通过 ELISA 检测全身和局部抗体反应。结果表明，rEm-TSP3-FBP 和 rEm-TSP3+CpG 均能诱导强烈的血清 IgG（p<0.001）和 IgG1 反应（p<0.001），而仅后者诱导高水平 IgG2α 产生（p<0.001），而 rEm-TSP3 本身没有任何佐剂。两组之间 IgG 和 IgG1 的产生没有显著差异。两组血清 IgA 和 IgM 水平均较低。在第二次和第三次免疫后通过检测 IgG1/IgG2α 比值评估 Th1 和 Th2 细胞免疫反应的趋势。结果表明，rEm-TSP3-FBP 的鼻腔内免疫导致 IgG1/IgG2α 比值升高（Th2 趋势），而 rEm-TSP3+CpG 引起快速的 Th1 反应，随后转向 Th2 反应。与 rEm-TSP3+CpG 相比，rEm-TSP3-FBP 免疫在肠道（p<0.05）、肺部（p<0.001）和脾脏（p<0.001）中引起更强的 IgA 抗体反应。与 rEm-TSP3 单独使用相比，两组鼻腔（p<0.05）和肝脏（p<0.05）样本中均检测到显著高水平的 IgA 抗体，两组之间无显著差异。
鼻腔内给予 rEm-TSP3-FBP 可诱导免疫 BALB/c 小鼠产生强烈的全身和粘膜抗体反应，表明 Em-TSP3 与 FBP 的融合是开发针对细粒棘球蚴病（AE）的安全有效的人类粘膜疫苗的一种新的、有前途的策略。
