Mancera Gracia José Carlos, Pearce Douglas S, Masic Aleksandar, Balasch Monica
Zoetis Belgium S.A., Zaventem, Belgium.
Zoetis Inc., Veterinary Medicine Research and Development, Kalamazoo, MI, United States.
Front Vet Sci. 2020 Sep 22;7:647. doi: 10.3389/fvets.2020.00647. eCollection 2020.
Influenza A viruses cause acute respiratory infections in swine that result in significant economic losses for global pig production. Currently, three different subtypes of influenza A viruses of swine (IAV-S) co-circulate worldwide: H1N1, H3N2, and H1N2. However, the origin, genetic background and antigenic properties of those IAV-S vary considerably from region to region. Pigs could also have a role in the adaptation of avian influenza A viruses to humans and other mammalian hosts, either as intermediate hosts in which avian influenza viruses may adapt to humans, or as a "mixing vessel" in which influenza viruses from various origins may reassort, generating novel progeny viruses capable of replicating and spreading among humans. These potential roles highlight the importance of controlling influenza A viruses in pigs. Vaccination is currently the main tool to control IAV-S. Vaccines containing whole inactivated virus (WIV) with adjuvant have been traditionally used to generate highly specific antibodies against hemagglutinin (HA), the main antigenic protein. WIV vaccines are safe and protect against antigenically identical or very similar strains in the absence of maternally derived antibodies (MDAs). Yet, their efficacy is reduced against heterologous strains, or in presence of MDAs. Moreover, vaccine-associated enhanced respiratory disease (VAERD) has been described in pigs vaccinated with WIV vaccines and challenged with heterologous strains in the US. This, together with the increasingly complex epidemiology of SIVs, illustrates the need to explore new vaccination technologies and strategies. Currently, there are two different non-inactivated vaccines commercialized for swine in the US: an RNA vector vaccine expressing the HA of a H3N2 cluster IV, and a bivalent modified live vaccine (MLV) containing H1N2 γ-clade and H3N2 cluster IV. In addition, recombinant-protein vaccines, DNA vector vaccines and alternative attenuation technologies are being explored, but none of these new technologies has yet reached the market. The aim of this article is to provide a thorough review of the current epidemiological scenario of IAV-S, the challenges faced in the control of IAV-S infection and the tools being explored to overcome those challenges.
甲型流感病毒可引起猪的急性呼吸道感染，给全球生猪生产造成重大经济损失。目前，三种不同亚型的猪甲型流感病毒（IAV-S）在全球共同流行：H1N1、H3N2和H1N2。然而，这些IAV-S的起源、遗传背景和抗原特性在不同地区差异很大。猪在甲型流感病毒适应人类和其他哺乳动物宿主的过程中也可能发挥作用，既可能作为甲型流感病毒适应人类的中间宿主，也可能作为一个“混合容器”，来自不同来源的流感病毒在其中可能发生重配，产生能够在人类中复制和传播的新型子代病毒。这些潜在作用凸显了控制猪体内甲型流感病毒的重要性。疫苗接种是目前控制IAV-S的主要手段。传统上，含佐剂的全灭活病毒（WIV）疫苗一直用于产生针对主要抗原蛋白血凝素（HA）的高度特异性抗体。WIV疫苗安全，在不存在母源抗体（MDA）的情况下可预防抗原性相同或非常相似的毒株。然而，它们对异源毒株的效力会降低，或者在存在MDA的情况下效力也会降低。此外，在美国，接种WIV疫苗并受到异源毒株攻击的猪中出现了疫苗相关的呼吸道疾病加重（VAERD）情况。这一点，再加上猪流感病毒日益复杂的流行病学情况，说明有必要探索新的疫苗接种技术和策略。目前，在美国有两种不同的非灭活猪用疫苗商业化：一种是表达H3N2第IV簇HA的RNA载体疫苗，另一种是含有H1N2γ分支和H3N2第IV簇的二价改良活疫苗（MLV）。此外，重组蛋白疫苗DNA载体疫苗和替代减毒技术也在探索中，但这些新技术都尚未上市。本文旨在全面综述IAV-S的当前流行病学情况、控制IAV-S感染面临的挑战以及为克服这些挑战而探索的手段。
