Food Animal Health Research Program, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH, United States.
Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, IN, United States.
Front Immunol. 2018 May 2;9:934. doi: 10.3389/fimmu.2018.00934. eCollection 2018.
Annually, swine influenza A virus (SwIAV) causes severe economic loss to swine industry. Currently used inactivated SwIAV vaccines administered by intramuscular injection provide homologous protection, but limited heterologous protection against constantly evolving field viruses, attributable to the induction of inadequate levels of mucosal IgA and cellular immune responses in the respiratory tract. A novel vaccine delivery platform using mucoadhesive chitosan nanoparticles (CNPs) administered through intranasal (IN) route has the potential to elicit strong mucosal and systemic immune responses in pigs. In this study, we evaluated the immune responses and cross-protective efficacy of IN chitosan encapsulated inactivated SwIAV vaccine in pigs. Killed SwIAV H1N2 (δ-lineage) antigens (KAg) were encapsulated in chitosan polymer-based nanoparticles (CNPs-KAg). The candidate vaccine was administered twice IN as mist to nursery pigs. Vaccinates and controls were then challenged with a zoonotic and virulent heterologous SwIAV H1N1 (γ-lineage). Pigs vaccinated with CNPs-KAg exhibited an enhanced IgG serum antibody and mucosal secretory IgA antibody responses in nasal swabs, bronchoalveolar lavage (BAL) fluids, and lung lysates that were reactive against homologous (H1N2), heterologous (H1N1), and heterosubtypic (H3N2) influenza A virus strains. Prior to challenge, an increased frequency of cytotoxic T lymphocytes, antigen-specific lymphocyte proliferation, and recall IFN-γ secretion by restimulated peripheral blood mononuclear cells in CNPs-KAg compared to control KAg vaccinates were observed. In CNPs-KAg vaccinated pigs challenged with heterologous virus reduced severity of macroscopic and microscopic influenza-associated pulmonary lesions were observed. Importantly, the infectious SwIAV titers in nasal swabs [days post-challenge (DPC) 4] and BAL fluid (DPC 6) were significantly ( < 0.05) reduced in CNPs-KAg vaccinates but not in KAg vaccinates when compared to the unvaccinated challenge controls. As well, an increased frequency of T helper memory cells and increased levels of recall IFNγ secretion by tracheobronchial lymph nodes cells were observed. In summary, chitosan SwIAV nanovaccine delivered by IN route elicited strong cross-reactive mucosal IgA and cellular immune responses in the respiratory tract that resulted in a reduced nasal viral shedding and lung virus titers in pigs. Thus, chitosan-based influenza nanovaccine may be an ideal candidate vaccine for use in pigs, and pig is a useful animal model for preclinical testing of particulate IN human influenza vaccines.
每年，猪流感 A 病毒（SwIAV）都会给养猪业造成严重的经济损失。目前通过肌肉注射使用的灭活 SwIAV 疫苗提供同源保护，但对不断进化的田间病毒提供的异源保护有限，这归因于呼吸道中诱导的黏膜 IgA 和细胞免疫应答水平不足。一种使用粘膜粘附性壳聚糖纳米粒子（CNPs）通过鼻腔（IN）途径给药的新型疫苗输送平台有可能在猪中引发强烈的粘膜和全身免疫应答。在这项研究中，我们评估了 IN 壳聚糖包封的灭活 SwIAV 疫苗在猪中的免疫应答和交叉保护效力。用壳聚糖聚合物为基础的纳米粒子（CNPs-KAg）包封了杀死的 SwIAV H1N2（δ谱系）抗原（KAg）。候选疫苗两次以雾剂形式通过 IN 途径施用于仔猪。然后，给接种疫苗和对照组猪用一种人畜共患的、具有毒力的异源 SwIAV H1N1（γ谱系）进行攻毒。用 CNPs-KAg 接种的猪在鼻腔拭子、支气管肺泡灌洗液（BAL）和肺裂解物中表现出增强的 IgG 血清抗体和粘膜分泌型 IgA 抗体反应，这些反应针对同源（H1N2）、异源（H1N1）和异亚型（H3N2）流感 A 病毒株。在攻毒之前，与对照组 KAg 疫苗相比，在 CNPs-KAg 疫苗接种的猪的外周血单核细胞中观察到细胞毒性 T 淋巴细胞、抗原特异性淋巴细胞增殖和再刺激时 IFN-γ分泌的频率增加。在 CNPs-KAg 接种的猪中，与异源病毒攻毒相比，鼻拭子[攻毒后第 4 天（DPC）]和 BAL 液（DPC 6）中的传染性 SwIAV 滴度显著（<0.05）降低，但在未接种疫苗的对照组中未降低。此外，还观察到气管支气管淋巴结细胞中 T 辅助记忆细胞的频率增加和 IFNγ的水平增加。总之，通过 IN 途径递送的壳聚糖 SwIAV 纳米疫苗在呼吸道中引发了强烈的交叉反应性粘膜 IgA 和细胞免疫应答，导致猪的鼻病毒脱落减少和肺部病毒滴度降低。因此，壳聚糖基流感纳米疫苗可能是一种理想的候选疫苗，可用于猪，并且猪是用于测试 IN 人类流感疫苗的临床前颗粒的有用动物模型。
