Bui Vuong Nghia, Ogawa Haruko, Trinh Dai Quang, Nguyen Tham Hong Thi, Pham Nga Thi, Truong Duc Anh, Bui Anh Ngoc, Runstadler Jonathan, Imai Kunitoshi, Nguyen Khong Viet
Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, 2-11 Inada, Hokkaido, Obihiro, 080-8555, Japan.
Virus Genes. 2014 Oct;49(2):278-85. doi: 10.1007/s11262-014-1089-1. Epub 2014 Jun 1.
This study reports the genetic characterization of a highly pathogenic avian influenza virus subtype H5N1 isolated from a moribund domestic duck in central Vietnam during 2012. In the moribund duck's flock, within 6 days after vaccination with a commercial H5N1 vaccine (Re-5) to 59-day-old birds, 120 out of 2,000 ducks died. Genetic analysis revealed a substantial number of mutations in the HA gene of the isolate in comparison with the vaccine strains, Re-1 and Re-5. Similar mutations were also found in selected Vietnamese H5N1 strains isolated since 2009. Mutations in the HA gene involved positions at antigenic sites associated with antibody binding and also neutralizing epitopes, with some of the mutations resulting in the modification of N-linked glycosylation of the HA. Those mutations may be related to the escape of virus from antibody binding and the infection of poultry, interpretations which may be confirmed through a reverse genetics approach. The virus also carried an amino acid substitution in the M2, which conferred a reduced susceptibility to amantadine, but no neuraminidase inhibitor resistance markers were found in the viral NA gene. Additional information including vaccination history in the farm and the surrounding area is needed to fully understand the background of this outbreak. Such understanding and expanded monitoring of the H5N1 influenza viruses circulating in Vietnam is an urgent need to provide updated information to improve effective vaccine strain selection and vaccination protocols, aiding disease control, and biosecurity to prevent H5N1 infection in both poultry and humans.
本研究报告了2012年从越南中部一只濒死家鸭中分离出的高致病性禽流感病毒H5N1亚型的基因特征。在该濒死鸭群中，对59日龄的鸭接种市售H5N1疫苗（Re-5）后6天内，2000只鸭中有120只死亡。基因分析显示，与疫苗株Re-1和Re-5相比，分离株的血凝素（HA）基因发生了大量突变。自2009年以来在越南分离的部分H5N1毒株中也发现了类似突变。HA基因的突变涉及与抗体结合相关的抗原位点以及中和表位的位置，其中一些突变导致HA的N-连接糖基化发生改变。这些突变可能与病毒逃避抗体结合以及家禽感染有关，这一解释可通过反向遗传学方法得到证实。该病毒的M2蛋白也存在一个氨基酸替换，使其对金刚烷胺的敏感性降低，但在病毒的神经氨酸酶（NA）基因中未发现对神经氨酸酶抑制剂的耐药标记。需要包括该养殖场及周边地区疫苗接种史在内的更多信息，以全面了解此次疫情的背景。对越南境内传播的H5N1流感病毒进行此类了解并扩大监测，对于提供最新信息以改进有效的疫苗株选择和疫苗接种方案、协助疾病控制以及生物安全措施以预防H5N1在家禽和人类中的感染而言，是一项迫切需求。
