中国研究者チームによる「SCIENECE」論文
| Highly Pathogenic H5N1 Influenza Virus Infection in Migratory Birds 渡り鳥における高病原性H5N1インフルエンザウイルスの感染 25 May 2005; accepted 29 June 2005 Published online 06 July 2005; 10.1126/science.1115273 Jinhua Liu,1* Haixia Xiao,2,6* Fumin Lei,3* Qingyu Zhu,4 Kun Qin,1 Xiaowei Zhang,5 Xinglin Zhang,1 Deming Zhao,1 Guihua Wang,2,6 Youjun Feng,2,6 Juncai Ma,2 Wenjun Liu,2 Jian Wang,5 George F. Gao2† 1College of Veterinary Medicine, China Agricultural University, Beijing 100094, China. 2Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China. 3Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China. 4Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing 100071, China. 5Beijing Genomics Institute, Chinese Academy of Sciences, 101300, China. 6Graduate School, Chinese Academy of Sciences, Beijing, China. *These authors contributed equally to this work. †To whom correspondence should be addressed. E-mail: gaof@im.ac.cn 邦訳 H5N1鳥インフルエンザウイルスは、近年、人も含めて多くの種で病原性を獲得してきている。 今回、我々は２００５年５月から６月に中国青海湖で１０００羽以上の渡り鳥に発生した流行について報告する。 膵臓壊死や神経学的異常症状が中心的症状であった。 ４種類のH5N1株が分離され遺伝子配列が調べられたが、遺伝子の再集合が認められ、それは以前香港でハヤブサから分離され、高病原性として知られている株と関連していた。分離ウイルスの実験動物への接種実験で典型的高病原性鳥フル感染症状と病理所見を認めた。 鳥インフルエンザウイルスは少なくとも３種類、すなわちH5,H7,H9株は最近家禽農場で警戒すべきウイルスとして浮上してきているが、同じく世界の公衆衛生学上でも大きな関心が持たれている。 最初に鳥から人へ感染した事例は１９９７年の香港で発生したが、２００３年以来、高病原性のH5N1株はアジア１０カ国で鳥での流行を起こしてきて、人においても５３人の命を奪った。 最近まで希な事例を除いて渡り鳥（水棲鳥）は、鳥インフルエンザには感染発病しないと考えられていたが、我々はここに中国青海湖で渡り鳥の間で発生した高病原性H5N1ウイルス感染の流行について報告する。 ２００５年５月４日、青海省の鳥島で数羽の鳥の死亡が確認された。６月下旬まで１０００羽以上の鳥が死亡した。この湖は冬期間東南アジア（チベットやインド）で過ごす渡り鳥の重要な繁殖地の一つとなっている。ガンやカモメなど数種類の野鳥が感染した。二つの主要な症状が認められた。異常な神経的症状（振戦と項部緊張；オピストトーヌス）、および下痢である。 組織所見では膵臓壊死が認められ、これは以前にアヒルやガチョウで報告されていた所見と一致した。脳組織所見ではグリア細胞の増殖、血管周辺への細胞浸潤（perivascular cuffing）、および血管内鬱血を認めた。血清学的検査ではガンとカモメ、各１羽から高濃度のH5N1ウイルスに対する抗体を検出した。 内臓や脳、咽頭ぬぐい液、総排泄腔からウイルス数株を分離した。 異なった４種の鳥から分離されたウイルスは遺伝子が同じか、ほとんど類似していた。「 GenBank」に登録されている遺伝子配列と一致するものは無かったから、今回分離されたウイルスの遺伝子は再集合しているものであることが示唆された。 ８個の遺伝子配列のうち５個が(M, PA, PB1, PB2 and NS)、香港で２００４年ハヤブサから分離された遺伝子配列と近似していた。 今回我々は分離された４種類のウイルス株についていくつかの特徴を認めた：第一として、ＨＡ基の開裂部（cleavage site）の基本的アミノ酸配列がPQGERRRKKR/Gであること、第二として、 PB2 遺伝子における高病原性決定部の存在（最初に１９９７年の香港の例で認められた）、そして第三として、同じく高病原性として特徴づけられている、ＮＡ基での２０個のアミノ酸の欠如、である。 分離ウイルスの毒性を調べるためにマウスと鶏にウイルスが接種された。接種された８羽全ての鶏が２０時間以内に死亡した。そして８匹のマウスのうち７匹が７２時間以内に死亡して、残りの１匹は９６時間で死亡した。 以前、中国でアヒルから分離されたウイルス株の毒性は、マウスや鶏で調べた限り低かった。それ故我々は（今回の結果から）、（H5N1）ウイルスが東南アジアでの越冬期間に遺伝子の再集合を起こして変異していると推定した。 原文 H5N1 avian influenza virus (AIV) has emerged as a pathogenic entity for a variety of species, including humans, in recent years. Here we report an outbreak among migratory birds on Lake Qinghaihu, China, in May and June 2005, in which more than a thousand birds were affected. Pancreatic necrosis and abnormal neurological symptoms were the major clinical features. Sequencing of complete genomes of four H5N1 AIV strains isolated revealed to be reassortants related to a peregrine falcon isolate from Hong Kong and showed known “highly pathogenic” characteristics. Experimental animal infections reproduced typical highly pathogenic AIV-infection symptoms and pathology. Avian influenza virus (AIV) involving at least three subtypes, H5, H7 and H9, has emerged as an important pathogen in the poultry industry and is of major current global public health concern (1). The first case report of chicken to human transmission was in Hong Kong in 1997 (2); since 2003, H5N1, a highly pathogenic AIV, has emerged in 10 Asian countries, including Thailand, Vietnam and China (Fig. 1), and claimed at least 53 human lives. Until recently, migratory waterfowl seemed to be exempt from widespread infection, although sporadic cases were recorded (3). Here, we describe an outbreak of highly pathogenic H5N1 infection among waterfowl in Lake Qinghaihu, Gangcha County, Qinghai Province, western China (Fig. 1). On May 4th, 2005, a few birds were found dead on “Bird Island” and by the end of June more than a thousand birds were affected. This lake is one of the most important breeding locations for migratory birds that overwinter in Southeast Asia, Tibet and India (Fig. 1). Several species were infected, including the bar-headed goose (Anser indicus), great black-headed gull (Larus ichthyaetus) and brownheaded gull (Larus brunnicephalus). Two key symptoms were noticed: abnormal neurological signs (tremor and opisthotonus) and diarrhea. Among the gross lesions, pancreatic necrosis was obvious and was confirmed by tissue section where extensive areas of lytic necrosis were seen, consistent with pathology observed in domestic geese and ducks infected with H5N1 AIV (3). Brain sections revealed glial cell infiltration, perivascular cuffing, and congestion in the blood vessels. Serological tests (4) from one bar-headed goose and one brown-headed gull confirmed the presence of high-titer antibody against H5N1 AIV. Several H5N1 viruses were isolated from the viscera, brain and the swabs of the oropharynx and cloaca of sick and dead birds. Four of the isolates from different bird species were completely sequenced (4) and appeared to be closely related. None of the GenBank sequence data for known H5N1 AIV genomes completely matched our sequences, implying the viruses are reassortants. Five of the eight genomic segments (M, PA, PB1, PB2 and NS) were closely related to a Hong Kong 2004 isolate (A/peregrine falcon/HK/D0028/04) (3). We observed several characteristics in our four isolates: first, the sequence, PQGERRRKKR/G, denoting multiple basic amino acids at the cleavage site of the haemagglutinin (HA); second, a virulence island in the PB2 gene, E627K, first seen in Hong Kong in 1997 (5); and third, a deletion of 20 amino acids in NA (amino acid position 49-69), also associated with high virulence. To test virulence, mice and chickens were infected with the BhGoose/QH/1/05 (4) isolate. All eight infected chickens died within 20 hours and seven of eight infected mice died within 72 hours, and the last died 96 hours post-infection. Earlier isolates taken from ducks in China were less virulent in mice and chickens (6). Hence we speculate that viruses might be emerging from reassortants originating in birds overwintering in Southeast Asia (7). The occurrence of highly pathogenic H5N1 AIV infection in migrant waterfowl indicates that this virus has the potential to be a global threat: Lake Qinghaihu is a breeding center for migrant birds that congregate from Southeast Asia, Siberia, Australia and New Zealand. References and Notes 1. R. J. Webby, R. G. Webster, Science 302, 1519 (2003). 2. K. Subbarao et al., Science 279, 393 (1998). 3. K. S. Li et al., Nature 430, 209 (2004). 4. Materials and methods are available as supporting material on Science Online. 5. M. Hatta et al., Science 293, 1840 (2001). 6. H. Chen et al., Proc. Natl. Acad. Sci. USA 101, 10452 (2004). 7. T. H. Cheng et al., Fauna Sinica. Aves, Vol. 2. Anseriformes, Science Press, Beijing, pp 1 (1979). 8. Supported by grants from the Ministry of Science and Technology, PR China (grant nos. 2004BA519A29, 2004BA519A11, 2004BA519A10 and 2004BA519A50; National Basic Research Program [973] of China 2005CB523000), from the Chinese Academy of Sciences (The President Fund and the CAS-Information-Special grant no. INF105-SDB-3-A2) and from the National Natural Sciences Foundation of China (NSFC, grant nos. 30471282 and 30228025). Sequence data derived from this study were deposited in GenBank with accession no. DQ100542-DQ100573. Supporting Online Material www.sciencemag.org/cgi/content/full/1115273/DC1 Materials and Methods Figs. S1 and S2 References and Notes 25 May 2005; accepted 29 June 2005 Published online 06 July 2005; 10.1126/science.1115273 Include this information when citing this paper. Fig. 1. (A) The reported H5N1 AIV prevalence sites during the 2004 outbreak in China are highlighted in yellow (www.china.com.cn/chinese/zhuanti/qlg/483177.htm). The migratory routes of the bar-headed goose (Anser indicus) to Lake Qinghaihu are indicated by arrows. (B) Sick bar-headed goose (Anser indicus) showing typical opisthotonus before dying. (C) Bar-headed goose pancreas with pin-point necrotic lesions. (D) Microscopic lesions of bar-headed goose brain showing congestion in the blood vessels (white arrows) and glial cell infiltration (black arrow). Haematoxylin and eosin ×25 (bar, 50 ? m). |