Protection against enterovirus 71 with neutralizing epitope incorporation within adenovirus type 3 hexon.

Enterovirus 71 (EV71) is responsible for hand, foot and mouth disease with high mortality among children. Various neutralizing B cell epitopes of EV71 have been identified as potential vaccine candidates. Capsid-incorporation of antigens into adenovirus (Ad) has been developed for a novel vaccine approach. We constructed Ad3-based EV71 vaccine vectors by incorporating a neutralizing epitope SP70 containing 15 amino acids derived from capsid protein VP1 of EV71 within the different surface-exposed domains of the capsid protein hexon of Ad3EGFP, a recombinant adenovirus type 3 (Ad3) expressing enhanced green fluorescence protein. Thermostability and growth kinetic assays suggested that the SP70 epitope incorporation into hypervariable region (HVR1, HVR2, or HVR7) of the hexon did not affect Ad fitness. The SP70 epitopes were thought to be exposed on all hexon-modified intact virion surfaces. Repeated administration of BALB/c mice with the modified Ads resulted in boosting of the anti-SP70 humoral immune response. Importantly, the modified Ads immunization of mother mice conferred protection in vivo to neonatal mice against the lethal EV71 challenge, and the modified Ads-immunized mice serum also conferred passive protection against the lethal challenge in newborn mice. Compared with the recombinant GST-fused SP70 protein immunization, immunization with the Ads containing SP70 in HVR1 or HVR2 elicited higher SP70-specific IgG titers, higher neutralization titers, and conferred more effective protection to neonatal mice. Thus, this study provides valuable information for hexon-modified Ad3 vector development as a promising EV71 vaccine candidate and as an epitope-delivering vehicle for other pathogens.

肠道病毒71型（EV71）是导致儿童手足口病且死亡率较高的病原体。EV71的多种中和性B细胞表位已被确定为潜在的疫苗候选物。将抗原整合入腺病毒（Ad）衣壳已被开发为一种新型疫苗方法。我们通过将包含15个氨基酸的中和性表位SP70（源自EV71衣壳蛋白VP1）整合入Ad3 - EGFP（一种表达增强型绿色荧光蛋白的3型重组腺病毒）衣壳蛋白六邻体的不同表面暴露区域，构建了基于Ad3的EV71疫苗载体。热稳定性和生长动力学分析表明，将SP70表位整合入六邻体的高变区（HVR1、HVR2或HVR7）并不影响腺病毒的适应性。SP70表位被认为在所有六邻体修饰的完整病毒粒子表面均有暴露。对BALB/c小鼠重复给予修饰后的腺病毒可增强抗SP70的体液免疫反应。重要的是，对母鼠进行修饰后的腺病毒免疫可在体内为新生小鼠提供针对致死性EV71攻击的保护，并且经修饰后的腺病毒免疫的小鼠血清也可为新生小鼠提供针对致死性攻击的被动保护。与重组谷胱甘肽S - 转移酶（GST）融合的SP70蛋白免疫相比，用在HVR1或HVR2中包含SP70的腺病毒进行免疫可引发更高的SP70特异性IgG滴度、更高的中和滴度，并为新生小鼠提供更有效的保护。因此，本研究为六邻体修饰的Ad3载体作为一种有前景的EV71疫苗候选物以及作为其他病原体的表位传递载体的开发提供了有价值的信息。