Institute for Glycomics, Griffith University, Gold Coast Campus, Gold Coast, Queensland, Australia.
PLoS One. 2013 Sep 6;8(9):e72003. doi: 10.1371/journal.pone.0072003. eCollection 2013.
NhhA (Neisseria hia homologue) is an outer membrane protein from Neisseria meningitidis, the causative agent of meningococcal disease. The protein is surface exposed and its expression in a wide range of meningococcal strains suggests it is a promising vaccine candidate. In addition, immunization of mice with outer membrane vesicles of strains that overexpress NhhA in conjunction with one of TbpA, Omp85 or NspA results in synergistic bactericidal responses. We previously showed that the NhhA sequence is highly conserved between strains, with the majority of the differences localized to four distinct variable regions located in the amino-terminal region of the mature protein. In this study, N. meningitidis strains were constructed that over-express wild-type NhhA. Strains expressing truncated versions of NhhA, with deletions from the amino-terminal region that removed the most variable regions, were also made. These expression strains were also modified so that immunodominant, phase- and antigenically-variable outer membrane proteins were not expressed, truncated lipooligosaccharide (LOS) expression was genetically fixed (no phase variability), and capsular polysaccharide expression abolished. Outer membrane vesicles derived from these strains were used to immunize mice. As previously observed, a synergistic effect involving another antigen, TbpA, was required to demonstrate bactericidal activity. The highest bactericidal response against a heterologous strain was obtained with a truncated variant of NhhA. These results indicate that removal of (a) variable region(s) does not reduce bactericidal responses against NhhA, and that bactericidal targets exist in regions other than the variable N-teminus. This provides the basis for future examination of responses against truncated NhhA in protecting against heterologous NhhA strains, and further evaluation of truncated NhhA as a candidate for inclusion in a vaccine against all serogroups of N. meningitidis.
NhhA（脑膜炎奈瑟菌同源物）是脑膜炎奈瑟菌的外膜蛋白，是脑膜炎球菌病的病原体。该蛋白表面暴露，在多种脑膜炎奈瑟菌菌株中表达，表明它是一种有前途的疫苗候选物。此外，用过度表达 NhhA 的菌株的外膜囊泡免疫小鼠，同时结合 TbpA、Omp85 或 NspA 中的一种，会导致协同杀菌反应。我们之前表明，NhhA 序列在菌株之间高度保守，大多数差异定位于成熟蛋白氨基末端区域的四个不同可变区。在这项研究中，构建了过度表达野生型 NhhA 的脑膜炎奈瑟菌菌株。还构建了表达 NhhA 截断版本的菌株，这些截断版本从氨基末端区域缺失了最可变的区域。这些表达菌株还经过修饰，使免疫显性、相和抗原可变的外膜蛋白不表达，截断的脂寡糖（LOS）表达被遗传固定（无相位变异），并使荚膜多糖表达被破坏。从这些菌株衍生的外膜囊泡被用于免疫小鼠。如前所述，需要另一种抗原 TbpA 的协同作用才能证明杀菌活性。针对异源菌株获得的最高杀菌反应是用 NhhA 的截断变体获得的。这些结果表明，去除（一个）可变区不会降低针对 NhhA 的杀菌反应，并且杀菌靶标存在于可变 N 末端以外的区域。这为未来研究针对截短 NhhA 的反应在预防异源 NhhA 菌株中的作用以及进一步评估截短 NhhA 作为预防所有脑膜炎奈瑟菌血清群疫苗候选物提供了基础。
