スペイン風邪の原因究明とH5N1型鳥インフルエンザとの関連についての２つの記事

以下の２つの記事はいずれも、スペイン風邪の原因とH5N1型鳥インフルエンザについての報告
1918年のスペイン風邪ビールスをつかった猿の実験で８日後に呼吸器障害をおこした。感染の初期にビールスはホストの免疫システムに何かをして、ビールスの急速な増加をもたらすことが明らかとなった。
スペイン風邪ビールスはH5N1型鳥インフルエンザと類似の動きをすること。免疫システムの抗ビールス機能を停止させ、さらに免疫システムそのものが肺を攻撃し、その結果、肺は液体と犠牲者victimの海に溺れることになるという。
この研究成果は、感染の初期における治療に新たな道を開く上で大きな貢献をなしたと言える。
http://www.medicalnewstoday.com/healthnews.php?newsid=61063&nfid=rssfeeds
Spanish Flu Gives Clues To Deadliness Of Avian Flu
Main Category: Bird Flu / Avian Flu News
Article Date: 18 Jan 2007 - 0:00 PST

By infecting monkeys with Spanish flu, an international team of scientists think they may have discovered clues as to why the H5N1 Avian flu virus is so deadly to humans.

The scientists report their findings in the current issue of Nature.

The illness progressed rapidly and within 8 days of exposure the monkeys had such acute respiratory distress that they had to be euthanized.

The 1918 virus was reconstructed from genes recovered from tissue samples that had been preserved from the 1918 pandemic.

The scientists also noticed that the monkeys' normal antiviral response did not protect against the infection. It appeared that the virus itself had switched off the antiviral part of the monkeys' immune system and this lack of protection contributed to the rapid and deadly progress of the disease.

In effect, the monkeys' altered immune system mounted an attack on the respiratory system, filling the lungs with fluid.

A tentative conclusion of the study is that the higher lethality of the 1918 flu virus could be down to its ability to disable the immune system's antiviral response. This is how one virologist member of the study team, Yoshihiro Kawaoka from the University of Wisconsin-Madison, put it: "Somehow, early in infection, this virus does something to the host that allows it to grow really well. But we don't know what that is."

People infected with H5N1 avian flu virus have shown a similar immune system response and rapid progression of the infection.

It could be that the two strains share an ability to switch off the antiviral part of the immune system. If that is so, then this study has made a significant contribution to understanding the progress of the disease in humans too, and opens the door to developing treatments that can be administered in the early stages of the illness, perhaps to re-enable the weakened parts of the altered immune system.

http://www.medicalnewstoday.com/medicalnews.php?newsid=61079&nfid=rssfeeds
Study Uncovers A Lethal Secret Of 1918 Influenza Virus
Main Category: Flu / SARS News
Article Date: 20 Jan 2007 - 19:00 PST

In a study of non-human primates infected with the influenza virus that killed 50 million people in 1918, an international team of scientists has found a critical clue to how the virus killed so quickly and efficiently.

Writing this week (Jan. 18, 2007) in the journal Nature, a team led by University of Wisconsin-Madison virologist Yoshihiro Kawaoka reveals how the 1918 virus - modern history's most savage influenza strain - unleashes an immune response that destroys the lungs in a matter of days, leading to death.

The finding is important because it provides insight into how the virus that swept the world in the closing days of World War I was so efficiently deadly, claiming many of its victims people in the prime of life. The work suggests that it may be possible in future outbreaks of highly pathogenic flu to stem the tide of death through early intervention.

The study "proves the 1918 virus was indeed different from all of the other flu viruses we know of," says Kawaoka, a professor in the UW-Madison School of Veterinary Medicine and at the University of Tokyo.

By infecting monkeys with the virus, the team was able to show that the 1918 virus prompted a deadly respiratory infection that echoed historical accounts of how the disease claimed its victims.

Importantly, the new work shows that infection with the virus prompted an immune response that seems to derail the body's typical reaction to viral infection and instead unleashes an attack by the immune system on the lungs. As immune cells attack the respiratory system, the lungs fill with fluid and victims, in essence, drown. The mechanisms that contribute to the lethality of the virus were uncovered by University of Washington researchers using functional genomics, a technique in which researchers analyze the gene functions and interactions. Learning more about the virulence mechanisms of the 1918 flu virus may help researchers understand how to keep the virus from causing such a severe immune response.

"This study in macaques, combined with our earlier research showing the host response in mice infected with the 1918 flu, suggests that the host immune response is out of control in animals infected with the virus," said Michael G. Katze, professor of microbiology at the University of Washington in Seattle, who led the functional genomics portion of the new study and led the previous mouse-based study. "Our analysis revealed potential mechanisms of virulence, which we hope will help us develop novel antiviral strategies to both outwit the virus and moderate the host immune response."

The same excessive immune reaction is characteristic of the deadly complications of H5N1 avian influenza, the strain of bird flu present in Asia and which has claimed nearly 150 human lives but has not yet shown a capacity to spread easily among people.

"What we see with the 1918 virus in infected monkeys is also what we see with H5N1 viruses," Kawaoka says, suggesting that the ability to modulate immune response may be a shared feature of the most virulent influenza viruses.

Upon infection, the virus grew rapidly in the infected animals, suggesting the agent somehow sets the stage for virulent infection: "Somehow, early in infection, this virus does something to the host that allows it to grow really well," says Kawaoka. "But we don't know what that is."