Wang Shixia, Taaffe Jessica, Parker Christopher, Solórzano Alicia, Cao Hong, García-Sastre Adolfo, Lu Shan
Department of Medicine, University of Massachusetts Medical School, 364 Plantation Street, Lazare Research Building, Worcester, MA 01605-2397, USA.
J Virol. 2006 Dec;80(23):11628-37. doi: 10.1128/JVI.01065-06. Epub 2006 Sep 20.
Effective antibody responses provide crucial immunity against influenza virus infection. The hemagglutinin (HA) protein is the major target of protective antibody responses induced by viral infection and by vaccination with both inactivated and live-attenuated flu vaccines, but knowledge about the optimal designs of protective HA antigens from different flu serotypes is still limited. In this study, we have significantly improved the immunogenicity of HA-expressing DNA vaccines by using codon-optimized HA sequences for either an H1 serotype (A/NewCal/20/99) or an H3 serotype (A/Panama/2007/99) human influenza A virus and then used these constructs as model antigens to identify the optimal HA antigen designs to elicit high-level protective antibody responses. Two forms of HA antigen, a wild-type, full-length HA and a secreted form with transmembrane (TM) domain-truncated HA, were produced. Both forms of HA DNA vaccines, from either H1 or H3 serotypes, were able to elicit high levels of HA-specific immunoglobulin G responses in immunized rabbits as measured by enzyme-linked immunosorbent assay. Interestingly, the abilities of H1 HA and H3 HA antigens to elicit hemagglutination inhibition (HI) and neutralizing antibody (NAb) responses differ. For the H1 HA antigens, the full-length HA induced significantly higher HI and NAb responses than did the TM-truncated HA. For the H3 HA antigen, both the full-length HA and TM-truncated HA induced high levels of HI and NAb responses. These data indicate that H1 and H3 antigens have different expression requirements for the induction of an optimal protective antibody response and that the structure integrity of HA antigens is critical for eliciting type-specific protective antibody responses. Our findings will have an important impact on future subunit-based flu vaccine development.
有效的抗体反应为抵抗流感病毒感染提供关键的免疫力。血凝素（HA）蛋白是病毒感染以及使用灭活和减毒活流感疫苗接种所诱导的保护性抗体反应的主要靶点，但对于来自不同流感血清型的保护性HA抗原的最佳设计的了解仍然有限。在本研究中，我们通过使用针对H1血清型（A/NewCal/20/99）或H3血清型（A/Panama/2007/99）人类甲型流感病毒的密码子优化的HA序列，显著提高了表达HA的DNA疫苗的免疫原性，然后使用这些构建体作为模型抗原，以确定引发高水平保护性抗体反应的最佳HA抗原设计。制备了两种形式的HA抗原，一种野生型全长HA和一种跨膜（TM）结构域截短的分泌型HA。通过酶联免疫吸附测定法测量，来自H1或H3血清型的两种形式的HA DNA疫苗均能够在免疫的兔子中引发高水平的HA特异性免疫球蛋白G反应。有趣的是，H1 HA和H3 HA抗原引发血凝抑制（HI）和中和抗体（NAb）反应的能力有所不同。对于H1 HA抗原，全长HA诱导的HI和NAb反应明显高于TM截短的HA。对于H3 HA抗原，全长HA和TM截短的HA均诱导高水平的HI和NAb反应。这些数据表明，H1和H3抗原在诱导最佳保护性抗体反应方面具有不同的表达要求，并且HA抗原的结构完整性对于引发型特异性保护性抗体反应至关重要。我们的发现将对未来基于亚单位的流感疫苗开发产生重要影响。
