Altenburg Arwen F, van de Sandt Carolien E, van Trierum Stella E, De Gruyter Heidi L M, van Run Peter R W A, Fouchier Ron A M, Roose Kenny, Saelens Xavier, Volz Asisa, Sutter Gerd, de Vries Rory D, Rimmelzwaan Guus F
Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
Medical Biotechnology Center, VIB, Ghent, Belgium.
J Virol. 2016 Oct 28;90(22):10209-10219. doi: 10.1128/JVI.01633-16. Print 2016 Nov 15.
Due to antigenic drift of influenza viruses, seasonal influenza vaccines need to be updated annually. These vaccines are based on predictions of strains likely to circulate in the next season. However, vaccine efficacy is greatly reduced in the case of a mismatch between circulating and vaccine strains. Furthermore, novel antigenically distinct influenza viruses are introduced into the human population from animal reservoirs occasionally and may cause pandemic outbreaks. To dampen the impact of seasonal and pandemic influenza, vaccines that induce broadly protective and long-lasting immunity are preferred. Because influenza virus-specific CD8 T cells are directed mainly against relatively conserved internal proteins, like nucleoprotein (NP), they are highly cross-reactive and afford protection against infection with antigenically distinct influenza virus strains, so-called heterosubtypic immunity. Here, we used modified vaccinia virus Ankara (MVA) as a vaccine vector for the induction of influenza virus NP-specific CD8 T cells. To optimize the induction of CD8 T cell responses, we made several modifications to NP, aiming at retaining the protein in the cytosol or targeting it to the proteasome. We hypothesized that these strategies would increase antigen processing and presentation and thus improve the induction of CD8 T cell responses. We showed that NP with increased degradation rates improved CD8 T cell activation in vitro if the amount of antigen was limited or if CD8 T cells were of low functional avidity. However, after immunization of C57BL/6 mice, no differences were detected between modified NP and wild-type NP (NPwt), since NPwt already induced optimal CD8 T cell responses.
Due to the continuous antigenic drift of seasonal influenza viruses and the threat of a novel pandemic, there is a great need for the development of novel influenza vaccines that offer broadly protective immunity against multiple subtypes. CD8 T cells can provide immunity against multiple subtypes of influenza viruses by the recognition of relatively conserved internal antigens. In this study, we aimed at optimizing the CD8 T cell response to influenza A virus by making modifications to influenza A virus nucleoprotein (NP) expressed from the modified vaccinia virus Ankara (MVA) vaccine vector. These modifications resulted in increased antigen degradation, thereby producing elevated levels of peptides that can be presented on major histocompatibility complex (MHC) class I molecules to CD8 T cells. Although we were unable to increase the NP-specific immune response in the mouse strain used, this approach may have benefits for vaccine development using less-immunogenic proteins.
由于流感病毒的抗原漂移，季节性流感疫苗需要每年更新。这些疫苗是基于对下一季可能流行毒株的预测。然而，如果流行毒株与疫苗毒株不匹配，疫苗效力会大幅降低。此外，新的抗原性不同的流感病毒偶尔会从动物宿主传播到人类群体中，并可能引发大流行。为减轻季节性流感和大流行性流感的影响，诱导广泛保护性和持久免疫力的疫苗是首选。由于流感病毒特异性CD8 T细胞主要针对相对保守的内部蛋白，如核蛋白（NP），它们具有高度交叉反应性，并能提供针对抗原性不同的流感病毒株感染的保护，即所谓的异亚型免疫。在此，我们使用改良安卡拉痘苗病毒（MVA）作为疫苗载体来诱导流感病毒NP特异性CD8 T细胞。为优化CD8 T细胞反应的诱导，我们对NP进行了多项修饰，旨在将该蛋白保留在细胞质中或靶向蛋白酶体。我们假设这些策略会增加抗原加工和呈递，从而改善CD8 T细胞反应的诱导。我们发现，如果抗原量有限或CD8 T细胞的功能亲和力较低，降解率增加的NP能在体外改善CD8 T细胞的激活。然而，在对C57BL/6小鼠进行免疫后，未检测到修饰后的NP与野生型NP（NPwt）之间存在差异，因为NPwt已经能诱导最佳的CD8 T细胞反应。
由于季节性流感病毒的持续抗原漂移以及新的大流行威胁，迫切需要开发能提供针对多种亚型广泛保护性免疫的新型流感疫苗。CD8 T细胞可通过识别相对保守的内部抗原提供针对多种流感病毒亚型的免疫。在本研究中，我们旨在通过对改良安卡拉痘苗病毒（MVA）疫苗载体表达的甲型流感病毒核蛋白（NP）进行修饰，优化对甲型流感病毒的CD8 T细胞反应。这些修饰导致抗原降解增加，从而产生更高水平的肽，这些肽可在主要组织相容性复合体（MHC）I类分子上呈递给CD8 T细胞。尽管我们未能在所使用的小鼠品系中增加NP特异性免疫反应，但这种方法可能对使用免疫原性较低的蛋白进行疫苗开发有益。
