Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
J Virol. 2013 Dec;87(24):13480-9. doi: 10.1128/JVI.02434-13. Epub 2013 Oct 2.
Influenza H3N2 A viruses continue to circulate in swine and occasionally infect humans, resulting in outbreaks of variant influenza H3N2 [A(H3N2)v] virus. It has been previously demonstrated in ferrets that A(H3N2)v viruses transmit as efficiently as seasonal influenza viruses, raising concern over the pandemic potential of these viruses. However, A(H3N2)v viruses have not acquired the ability to transmit efficiently among humans, which may be due in part to existing cross-reactive immunity to A(H3N2)v viruses. Although current seasonal H3N2 and A(H3N2)v viruses are antigenically distinct from one another, historical H3N2 viruses have some antigenic similarity to A(H3N2)v viruses and previous exposure to these viruses may provide a measure of immune protection sufficient to dampen A(H3N2)v virus transmission. Here, we evaluated whether prior seasonal H3N2 influenza virus vaccination or infection affects virus replication and transmission of A(H3N2)v virus in the ferret animal model. We found that the seasonal trivalent inactivated influenza virus vaccine (TIV) or a monovalent vaccine prepared from an antigenically related 1992 seasonal influenza H3N2 (A/Beijing/32/1992) virus failed to substantially reduce A(H3N2)v (A/Indiana/08/2011) virus shedding and subsequent transmission to naive hosts. Conversely, ferrets primed by seasonal H3N2 virus infection displayed reduced A(H3N2)v virus shedding following challenge, which blunted transmission to naive ferrets. A higher level of specific IgG and IgA antibody titers detected among infected versus vaccinated ferrets was associated with the degree of protection offered by seasonal H3N2 virus infection. The data demonstrate in ferrets that the efficiency of A(H3N2)v transmission is disrupted by preexisting immunity induced by seasonal H3N2 virus infection.
H3N2 甲型流感病毒继续在猪群中传播，偶尔会感染人类，导致变异 H3N2 [A(H3N2)v] 流感病毒的爆发。此前已在雪貂中证实，A(H3N2)v 病毒的传播效率与季节性流感病毒相当，这引发了对这些病毒大流行潜力的担忧。然而，A(H3N2)v 病毒尚未获得在人群中高效传播的能力，这可能部分归因于对 A(H3N2)v 病毒存在交叉反应性免疫。虽然目前的季节性 H3N2 和 A(H3N2)v 病毒彼此之间具有不同的抗原性，但历史上的 H3N2 病毒与 A(H3N2)v 病毒具有一定的抗原相似性，以前接触过这些病毒可能会提供一定程度的免疫保护，足以抑制 A(H3N2)v 病毒的传播。在这里，我们评估了季节性 H3N2 流感病毒疫苗接种或感染是否会影响雪貂动物模型中 A(H3N2)v 病毒的复制和传播。我们发现，季节性三价灭活流感疫苗（TIV）或一种由抗原相关的 1992 年季节性 H3N2（A/Beijing/32/1992）病毒制备的单价疫苗并不能显著减少 A(H3N2)v（A/Indiana/08/2011）病毒脱落和随后向易感宿主的传播。相反，经季节性 H3N2 病毒感染引发的雪貂表现出在受到挑战后 A(H3N2)v 病毒脱落减少，这削弱了向易感雪貂的传播。与接种疫苗的雪貂相比，感染雪貂中检测到的特异性 IgG 和 IgA 抗体滴度更高与季节性 H3N2 病毒感染提供的保护程度相关。这些数据表明，在雪貂中，由季节性 H3N2 病毒感染引起的固有免疫会破坏 A(H3N2)v 传播的效率。
