中級 533 タグ追加 保存
動画の字幕をクリックしてすぐ単語の意味を調べられます!
単語帳読み込み中…
字幕の修正報告
From the time that HIV was first discovered to be the virus that causes AIDS, back in
1983, scientists have been working on developing a vaccine. Here we are, more than 30 years
later – so why don’t we have a vaccine yet? Oh, and by the way, what is a vaccine
and how does it work to prevent an infectious disease?
Unlike anti-viral medicines used to treat infections, vaccines work by training a person’s
immune system before exposure to a virus, so that the immune system can fight off the
virus and prevent that person from becoming infected.
HIV presents some unique challenges to developing a vaccine. First, HIV attacks the very immune
cells that are sent by the body to kill it off, and inserts its genes inside these cells.
After that happens, the only way to get rid of HIV is to kill off the infected cells.
That leads to the second challenge, which is that HIV infected cells can hide out and
remain “dormant” or asleep, making it difficult or impossible for other killer immune
cells to find it. Thirdly, every time HIV reproduces, it makes a lot of genetic mistakes.
And unlike many living things (including humans) that have certain systems in place to correct
these mistakes, HIV is a “sloppy” virus that doesn’t fix itself. So, HIV changes
over time, and it has been difficult to find a vaccine that will protect against all of
these changes.
So, how do we propose to build a vaccine? First, you should know that there is never
any live or killed HIV in a vaccine, which is a strategy used by some other vaccines
against less dangerous viruses. Also, no one participating in a vaccine study is ever exposed
to HIV as part of the study!
Now that we have that out of the way, the goal of an ideal HIV vaccine is to activate
both antibodies and T cells, so that the immune system is ready to fight off HIV. Antibodies
are proteins that attach to HIV before HIV can infect a cell, thereby preventing infection.
An example of how this works is the polio vaccine. After you get a polio vaccine, you
develop antibodies against polio that are ready to attack if you ever come in contact
with the polio virus. We’d like to develop an HIV vaccine that develops antibodies that
would attack the many strains of HIV that exist. Another strategy is to train T cells
to recognize and fight off HIV so that, when HIV enters, the T cells could kill the virus.
All HIV vaccines are made with synthetic, manufactured imitations of parts of HIV, a
strategy that can never cause infection, but can train the immune system to fight off HIV.
The most successful HIV vaccine strategy so far is a combination of 2 HIV vaccines tested
in Thailand that prevented 31% of new infections. This vaccine isn’t licensed, but scientists
are using information from this study to make more powerful and long-lasting vaccines that
can be used for populations around the world.
One thing to know is that the most common way to diagnose actual HIV infection is to
test for HIV antibodies. A person who becomes HIV infected generates antibodies against
HIV, but because they are only developed weeks after infection, they can’t prevent infection.
These antibodies can keep HIV in check for a while, but eventually HIV comes out of hiding
and causes AIDS, unless a person is treated with antiretrovirals (HIV medicines). Measuring
HIV antibodies is a relatively cheap and easy way to test whether someone has been HIV infected,
but the test doesn’t usually turn positive until several weeks or several months after
infection, because that’s the length of time it takes to develop antibodies without
a vaccine. Some people who get a vaccine will also be antibody positive, because they have
“vaccine-induced” antibodies, also known as VISP. Other tests can be done to tell the
difference between “vaccine-induced seropositivity (VISP) and actual infection. These other tests
are available at all research sites that conduct HIV vaccine trials and HIV vaccine trial volunteers
can continue to get HIV testing for free at these sites, even after the study has ended.
Over 35 million people worldwide are currently living with HIV/AIDS. Fortunately, we’re
part of the way toward developing a safe and highly effective HIV vaccine. And with a committed
and diverse partnership of community members, scientists, educators and policymakers, we
could ultimately defeat our century’s biggest epidemic.
コツ:単語をクリックしてすぐ意味を調べられます!

読み込み中…

Vaccines 101: What will it take to develop an HIV vaccine?

533 タグ追加 保存
You-kai Wang 2015 年 11 月 4 日 に公開
お勧め動画

コメント

読み込み中…
  1. 1. クリック一つで単語を検索

    右側のスプリクトの単語をクリックするだけで即座に意味が検索できます。

  2. 2. リピート機能

    クリックするだけで同じフレーズを何回もリピート可能!

  3. 3. ショートカット

    キーボードショートカットを使うことによって勉強の効率を上げることが出来ます。

  4. 4. 字幕の表示/非表示

    日・英のボタンをクリックすることで自由に字幕のオンオフを切り替えられます。

  5. 5. 動画をブログ等でシェア

    コードを貼り付けてVoiceTubeの動画再生プレーヤーをブログ等でシェアすることが出来ます!

  6. 6. 全画面再生

    左側の矢印をクリックすることで全画面で再生できるようになります。

  1. クイズ付き動画

    リスニングクイズに挑戦!

  1. クリックしてメモを表示

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔