美媒：H7N9病毒正在適應(yīng)人類或致全球大疫情
2013-04-15 參考消息
http://health.sohu.com/20130415/n372750144.shtml
美國媒體稱，對導(dǎo)致多名中國人死亡的禽流感病毒所做的基因分析描繪出一種不斷進(jìn)化以適應(yīng)人類細(xì)胞的病毒,，這引發(fā)了人們對它可能會引發(fā)新的全球性流感疫情的擔(dān)憂,。
美國每日科學(xué)網(wǎng)站4月12日指出，這項合作研究是由以日本國立感染癥研究所流感病毒研究中心的田代真人,、威斯康星大學(xué)麥迪遜分校和東京大學(xué)的河岡義裕領(lǐng)導(dǎo)的小組完成的,，該研究刊登在《歐洲監(jiān)控》周刊的最新一期上。這一小組研究了從該病原體的四名受害人身上分離出的H7N9病毒以及從禽類和上海一市場附近的環(huán)境中分離出的樣本的基因序列,。
禽流感領(lǐng)域的著名專家河岡義裕說：“從人身上,，而不是從禽類和環(huán)境中分離出來的病毒發(fā)生的蛋白質(zhì)變異讓病毒能夠在人類細(xì)胞中高效生長，也讓它們能在與人類上唿吸道吻合的溫度下生長,，這一溫度低于我們在禽類身上發(fā)現(xiàn)的溫度,。”
報道稱,，這些從中國研究者存入某國際數(shù)據(jù)庫的基因序列中獲得的發(fā)現(xiàn)提供了有關(guān)一種令人不安的新型禽流感的首批分子層面的線索,，中國疾病預(yù)防控制中心3月31日上報了首例人感染這種禽流感的病例。河岡義裕說,，盡管預(yù)測它可能會引發(fā)大疫為時過早,，但有明確跡象顯示這種病毒正在適應(yīng)哺乳動物，尤其是人類宿主,。
報道指出,，流感病毒要高效地復(fù)制和傳播靠的是附著和強占其宿主的活細(xì)胞的能力。盡管禽流感鮮少感染人類,，但有時可以適應(yīng)人類,，對人類健康構(gòu)成嚴(yán)重威脅。河岡義裕和他的同事在《歐洲監(jiān)控》的報告中斷言：“這些病毒擁有哺乳動物流感病毒的若干典型特征,，這些特征多半有助于它們獲得感染人類的能力,，且會引起人們對它們可能會引發(fā)大疫情的擔(dān)憂。”
據(jù)悉,，河岡義裕是威斯康星大學(xué)麥迪遜分校獸醫(yī)學(xué)院的教員,，同時在東京大學(xué)任職，他解釋說,，研究中大部分病毒——不管是來自人類還是禽類——表面的蛋白質(zhì)血凝素都表現(xiàn)出變異現(xiàn)象,。河岡義裕說，這些變異讓它們能輕易感染人類細(xì)胞,。
Could New Flu Spark Global Flu Pandemic?
New Bird Flu Strain Seen Adapting to Mammals, Humans
ScienceDaily, Apr. 12, 2013
http://www./releases/2013/04/130412192402.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+sciencedaily+(ScienceDaily:+Latest+Science+News)
Apr. 12, 2013 — A genetic analysis of the avian flu virus responsible for at least nine human deaths in China portrays a virus evolving to adapt to human cells, raising concern about its potential to spark a new global flu pandemic.
The collaborative study, conducted by a group led by Masato Tashiro of the Influenza Virus Research Center, National Institute of Infectious Diseases, and Yoshihiro Kawaoka of the University of Wisconsin-Madison and the University of Tokyo, appears in the current edition (April 11, 2013) of the journal Eurosurveillance. The group examined the genetic sequences of H7N9 isolates from four of the pathogen's human victims as well as samples derived from birds and the environs of a Shanghai market.
"The human isolates, but not the avian and environmental ones, have a protein mutation that allows for efficient growth in human cells and that also allows them to grow at a temperature that corresponds to the upper respiratory tract of humans, which is lower than you find in birds," says Kawaoka, a leading expert on avian influenza.
The findings, drawn from genetic sequences deposited by Chinese researchers into an international database, provide some of the first molecular clues about a worrisome new strain of bird flu, the first human cases of which were reported on March 31 by the Chinese Center for Disease Control and Prevention. So far, the new virus has sickened at least 33 people, killing nine. Although it is too early to predict its potential to cause a pandemic, signs that the virus is adapting to mammalian and, in particular, human hosts are unmistakable, says Kawaoka.
Access to the genetic information in the viruses, he adds, is necessary for understanding how the virus is evolving and for developing a candidate vaccine to prevent infection.
Influenza virus depends on its ability to attach to and commandeer the living cells of its host to replicate and spread efficiently. Avian influenza rarely infects humans, but can sometimes adapt to people, posing a significant risk to human health.
"These viruses possess several characteristic features of mammalian influenza viruses, which likely contribute to their ability to infect humans and raise concerns regarding their pandemic potential," Kawaoka and his colleagues conclude in the Eurosurveillance report.
Kawaoka, a faculty member in the UW-Madison School of Veterinary Medicine who also holds a faculty appointment at the University of Tokyo, explains that the majority of the viruses in the study -- from both humans and birds -- display mutations in the surface protein hemagglutinin, which the pathogen uses to bind to host cells. Those mutations, according to Kawaoka, allowed them to easily infect human cells.
In addition, the isolates from patients contained another mutation that allows the virus to efficiently replicate inside human cells. The same mutation, Kawaoka notes, lets the avian virus thrive in the cooler temperatures of the human upper respiratory system. It is in the cells of the nose and throat that flu typically gains a hold in a mammalian or human host.
Kawaoka and his colleagues also assessed the response of the new strain to drugs used to treat influenza, discovering that one class of commonly used antiviral drugs, ion channel inhibitors which effectively bottle up the virus in the cell, would not be effective; the new strain could be treated with another clinically relevant antiviral drug, oseltamivir.
In addition to Kawaoka and Tashiro, co-authors of the Eurosurveillance report include Tsutomu Kageyama, Seiichiro Fujisaki, Emi Takashita, Hong Xu, Shinya Yamada, Yuko Uchida, Gabriele Neumann and Takehiko Saito. The work was supported by Grants-in-Aid for Pandemic Influenza Research and Grant-in-Aid for Specially Promoted Research from the Ministry of Health, Labour and Welfare, Japan; by the NIAID Center for Research on Influenza Pathogenesis (CRIP, HHSN266200700010C); by a Grant-in-Aid for Specially Promoted Research, by the Japan Initiative for Global Research Network on Infectious Diseases from the Ministry of Education, Culture, Sports, Science, and Technology, Japan; and by ERATO, Japan.
