课程咨询

托福考试网 托福资料下载 托福资讯 0元讲座 水平测试

托福考试练习
新东方在线 > TOEFL > 托福阅读 > 正文
托福培训

扫码免费领资料

内含托福全科备考资料

更有免费水平测试及备考规划

托福培训

扫码关注掌握一手留学资讯

回复XDF免费水平测试

录播精讲 直播课HOT

托福阅读材料之艾滋病毒超级抗体

2015-01-14 17:20:57来源：网络

　　Researchers have identified several antibodies that can neutralize the virus. Most of them bind weakly to small, often deep, pockets on the virus. In most instances, once infection becomes established rapidly mutating HIV evolves resistance to those narrowly focused antibodies, often by adding glycans or sugars to its outer envelope, which shields or blocks antibody access to the binding site.

　　What is needed is an antibody that binds strongly to a surface site on the virus, and which cannot be easily blocked. It is also important that the binding site is greatly conserved across the many strains of HIV.

　　Researchers at NIH Vaccine Research Center (VRC) decided to look at neutralizing antibodies in the blood of persons who are able to better control HIV infection. Elite controllers were not part of the mix because they seem to control HIV through their adaptive immunological system T cell mechanisms.

　　Using sophisticated reverse-engineering techniques, the researchers identified three proteins that are broadly neutralizing, which they labeled VRC01, VRC02 and VRC03. They also isolated the B cells that produced them.

　　The first two antibodies have very similar chemical structures and bind to HIV's gp120 trimer spike on its surface. The virus uses the trimer to link up with a CD4 receptor, which is the first of many steps taken to enter and infect a host cell. The antibody and gp120 spike bind in a way that is, in part, similar to the way that the spike and CD4 receptor bind.

　　As a result, VRC01 and VRC02 binding is particularly long and strong compared with the bonds formed by other antibodies. Further, the binding site on the gp120 spike is well exposed and not likely to become blocked by the addition of sugars to the viral envelope.

　　The two antibodies neutralized 91 percent of the 190 different HIV isolates that the team tested. Those isolates represent all of the various clades or strains of HIV present worldwide, says John Mascola, one of the VRC research team leaders. Also, the antibodies were able to neutralize all of the limited number of HIV variants that are transmitted sexually—a key point, because 80 percent of all new infections result from sexual activity.


本文关键字: 托福阅读材料

上一页 1 2 3 下一页

托福辅导

关注新东方在线托福

托福机经·Official题目练习

考前重点突破·听说读写海量资料

更多资料

关注新东方在线托福，
回复【XDF】获取大礼包

托福辅导
  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加】，回复对应关键字领取学习资料。
更多>>
更多内容

免费获取托福备考大礼包

微信扫描下方二维码 立即领取

托福辅导
更多>>
更多公益讲座>>
更多>>
更多资料
托福TPO 托福听力练习 托福口语练习 托福阅读练习 托福写作练习
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10