National Veterinary Institute, Technical University of Denmark, Kemitorvet Building 204, DK-2800 Kongens Lyngby, Denmark.
Department of Veterinary and Animal Sciences, University of Copenhagen, Grønnegårdsvej 2, DK-1870 Frederiksberg C, Denmark.
Viruses. 2020 Feb 23;12(2):248. doi: 10.3390/v12020248.
The degree of antigenic drift in swine influenza A viruses (swIAV) has historically been regarded as minimal compared to that of human influenza A virus strains. However, as surveillance activities on swIAV have increased, more isolates have been characterized, revealing a high level of genetic and antigenic differences even within the same swIAV lineage. The objective of this study was to investigate the level of genetic drift in one enzootically infected swine herd over one year. Nasal swabs were collected monthly from sows ( = 4) and piglets ( = 40) in the farrowing unit, and from weaners ( = 20) in the nursery. Virus from 1-4 animals were sequenced per month. Analyses of the sequences revealed that the hemagglutinin (HA) gene was the main target for genetic drift with a substitution rate of 7.6 × 10 substitutions/site/year and evidence of positive selection. The majority of the mutations occurred in the globular head of the HA protein and in antigenic sites. The phylogenetic tree of the HA sequences displayed a pectinate typology, where only a single lineage persists and forms the ancestor for subsequent lineages. This was most likely caused by repeated selection of a single immune-escape variant, which subsequently became the founder of the next wave of infections.
与人类甲型流感病毒株相比，猪流感 A 病毒（swIAV）的抗原漂移程度历来被认为较小。然而，随着对 swIAV 的监测活动增加，更多的分离株被表征，即使在同一 swIAV 谱系内也揭示出高度的遗传和抗原差异。本研究的目的是调查在一年时间内一个地方性感染猪群中的遗传漂移程度。每月从产房的母猪（=4）和仔猪（=40）以及保育舍的断奶猪（=20）中采集鼻拭子。每月对 1-4 只动物的病毒进行测序。序列分析显示，血凝素（HA）基因是遗传漂移的主要目标，其取代率为 7.6×10 取代/位点/年，存在正选择的证据。大多数突变发生在 HA 蛋白的球形头部和抗原位点。HA 序列的系统发育树显示出一种梳状拓扑结构，其中只有一个谱系持续存在，并成为后续谱系的祖先。这很可能是由于对单一免疫逃逸变体的反复选择，随后该变体成为下一波感染的创始人。
