Seasonal human influenza virus continues to cause morbidity and mortality annually, and highly pathogenic avian influenza (HPAI) viruses along with other emerging influenza viruses continue to pose pandemic threats. Vaccination is considered the most effective measure for controlling influenza; however, current strategies rely on a precise vaccine match with currently circulating virus strains for efficacy, requiring constant surveillance and regular development of matched vaccines. Current vaccines focus on eliciting specific antibody responses against the hemagglutinin (HA) surface glycoprotein; however, the diversity of HAs across species and antigenic drift of circulating strains enable the evasion of virus-inhibiting antibody responses, resulting in vaccine failure. The neuraminidase (NA) surface glycoprotein, while diverse, has a conserved enzymatic site and presents an appealing target for priming broadly effective antibody responses. Here we show that vaccination with parainfluenza virus 5 (PIV5), a promising live viral vector expressing NA from avian (H5N1) or pandemic (H1N1) influenza virus, elicited NA-specific antibody and T cell responses, which conferred protection against homologous and heterologous influenza virus challenges. Vaccination with PIV5-N1 NA provided cross-protection against challenge with a heterosubtypic (H3N2) virus. Experiments using antibody transfer indicate that antibodies to NA have an important role in protection. These findings indicate that PIV5 expressing NA may be effective as a broadly protective vaccine against seasonal influenza and emerging pandemic threats.

IMPORTANCE Seasonal influenza viruses cause considerable morbidity and mortality annually, while emerging viruses pose potential pandemic threats. Currently licensed influenza virus vaccines rely on the antigenic match of hemagglutinin (HA) for vaccine strain selection, and most vaccines rely on HA inhibition titers to determine efficacy, despite the growing awareness of the contribution of neuraminidase (NA) to influenza virus vaccine efficacy. Although NA is immunologically subdominant to HA, and clinical studies have shown variable NA responses to vaccination, in this study, we show that vaccination with a parainfluenza virus 5 recombinant vaccine candidate expressing NA (PIV5-NA) from a pandemic influenza (pdmH1N1) virus or highly pathogenic avian influenza (H5N1) virus elicits robust, cross-reactive protection from influenza virus infection in two animal models. New vaccination strategies incorporating NA, including PIV5-NA, could improve seasonal influenza virus vaccine efficacy and provide protection against emerging influenza viruses.

季节性人类流感病毒每年继续导致发病和死亡，高致病性禽流感（HPAI）病毒与其他新兴流感病毒一起继续构成大流行的威胁。接种疫苗被认为是控制流感最有效的措施；然而，当前的策略依赖精确的疫苗与当前流行的病毒株的匹配才能发挥功效，因此需要不断地监视和定期开发匹配的疫苗。当前的疫苗专注于引起针对血凝素（HA）表面糖蛋白的特异性抗体反应。然而，HAs跨物种的多样性和循环株的抗原漂移使得能够逃避病毒抑制抗体的反应，从而导致疫苗失败。神经氨酸酶（NA）表面糖蛋白虽然多种多样，具有保守的酶促位点，并提出了引诱广泛的有效抗体反应的诱人靶标。在这里我们显示副流感病毒5（PIV5）的疫苗接种是一种有前途的表达禽流感（H5N1）或大流行性流感（H1N1）流感病毒的NA的活病毒载体，引起NA特异性抗体和T细胞反应，从而提供了针对同源和异源的保护流感病毒挑战。PIV5-N1 NA疫苗接种提供了针对异型（H3N2）病毒攻击的交叉保护。使用抗体转移的实验表明，针对NA的抗体在保护中具有重要作用。这些发现表明，表达NA的PIV5可以有效地作为针对季节性流感和新出现的大流行性威胁的保护性疫苗。一种表达禽流感（H5N1）或大流行性流感（H1N1）流感病毒NA的有前途的活病毒载体，引发了NA特异性抗体和T细胞反应，从而提供了针对同源和异源流感病毒攻击的保护作用。PIV5-N1 NA疫苗接种提供了针对异型（H3N2）病毒攻击的交叉保护。使用抗体转移的实验表明，针对NA的抗体在保护中具有重要作用。这些发现表明，表达NA的PIV5可以有效地作为针对季节性流感和新出现的大流行性威胁的保护性疫苗。一种表达禽流感（H5N1）或大流行性流感（H1N1）流感病毒NA的有前途的活病毒载体，引发了NA特异性抗体和T细胞反应，从而提供了针对同源和异源流感病毒攻击的保护作用。PIV5-N1 NA疫苗接种提供了针对异型（H3N2）病毒攻击的交叉保护。使用抗体转移的实验表明，针对NA的抗体在保护中具有重要作用。这些发现表明，表达NA的PIV5可以有效地作为针对季节性流感和新出现的大流行性威胁的保护性疫苗。PIV5-N1 NA疫苗接种提供了针对异型（H3N2）病毒攻击的交叉保护。使用抗体转移的实验表明，针对NA的抗体在保护中具有重要作用。这些发现表明，表达NA的PIV5可以有效地作为针对季节性流感和新出现的大流行性威胁的保护性疫苗。PIV5-N1 NA疫苗接种提供了针对异型（H3N2）病毒攻击的交叉保护。使用抗体转移的实验表明，针对NA的抗体在保护中具有重要作用。这些发现表明，表达NA的PIV5可以有效地作为针对季节性流感和新出现的大流行性威胁的保护性疫苗。

重要性季节性流感病毒每年引起相当大的发病率和死亡率，而新兴病毒则构成潜在的大流行威胁。当前认可的流感病毒疫苗依靠血凝素（HA）的抗原匹配来选择疫苗菌株，尽管人们越来越意识到神经氨酸酶（NA）对流感病毒疫苗功效的贡献，但大多数疫苗还是依靠HA抑制效价来确定功效。尽管NA在免疫学上优于HA，并且临床研究表明对疫苗接种的NA反应存在差异，但在这项研究中，我们显示了用大流行性流感（pdmH1N1）病毒表达NA（PIV5-NA）的副流感病毒5重组候选疫苗接种或高致病性禽流感（H5N1）病毒引起强烈感染，在两种动物模型中对流感病毒感染具有交叉反应性保护。纳入NA的新疫苗接种策略（包括PIV5-NA）可以提高季节性流感病毒疫苗的功效，并提供针对新兴流感病毒的保护。