The nucleoprotein (NP) of type A influenza virus (IAV) is highly conserved across all virus strains, making it an attractive candidate antigen for universal vaccines. While various studies have explored NP-induced mucosal immunity, here we interrogated the mechanistic differences between intramuscular (IM) and intranasal (IN) delivery of a recombinant adenovirus carrying NP fused with a bifunctional CD40 ligand. Despite being less effective than IM delivery in inducing systemic cellular immune responses and antibody-dependent cellular cytotoxicity (ADCC), IN immunization elicited superior antigen-specific recall humoral and cellular response in the nasal associated lymphoid tissue (NALT) of the upper respiratory tract, the initial site of immune recognition and elimination of inhaled pathogens. IN vaccination also induced significantly stronger pulmonary T cell responses in the lower respiratory tract than IM vaccination, in particular the CD8 T cells. Moreover, blocking lymphocyte circulation abrogated IM but not IN immunization induced protection, illustrating the critical role of local memory immune response upon viral infection. Notably, the CD40-targeted nasal delivery not only improved the magnitude but also the breadth of protection, including against lethal challenge with a newly isolated highly pathogenic avian H5N1 strain. These findings are informative for the design of universal mucosal vaccines, where the predominant mode of protection is independent of neutralizing antibodies.

中文翻译：

---

剖析流感病毒核蛋白诱导的针对不同病毒株的粘膜免疫的免疫机制。


A 型流感病毒 （IAV） 的核蛋白 （NP） 在所有病毒株中都高度保守，使其成为通用疫苗的有吸引力的候选抗原。虽然各种研究已经探讨了 NP 诱导的粘膜免疫，但在这里我们询问了携带 NP 与双功能 CD40 配体融合的重组腺病毒的肌内 （IM） 和鼻内 （IN） 递送之间的机制差异。尽管在诱导全身细胞免疫反应和抗体依赖性细胞毒性 （ADCC） 方面不如 IM 递送有效，但 IN 免疫在上呼吸道鼻相关淋巴组织 （NALT） 中引起了卓越的抗原特异性回忆体液和细胞反应，这是免疫识别和消除吸入病原体的初始部位。与 IM 疫苗接种相比，IN 疫苗接种还诱导了下呼吸道的肺 T 细胞反应明显更强，尤其是 CD8 T 细胞。此外，阻断淋巴细胞循环消除了 IM 而不是 IN 免疫诱导的保护，说明了病毒感染后局部记忆免疫反应的关键作用。值得注意的是，靶向 CD40 的鼻腔输送不仅提高了保护的强度，而且提高了保护的广度，包括抵御新分离的高致病性禽 H5N1 毒株的致命攻击。这些发现为通用粘膜疫苗的设计提供了信息，其中主要的保护模式独立于中和抗体。