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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

　　VRC01 and VRC02 occur naturally and are produced by what are called RSC3 memory-specific B cells, an extremely rare component of the immune system. Using flow cytometry, the NIH team could isolate only 29 of those cells from among the 25 million cells that they screened. Furthermore, the proteins produced by those B cells often are immature and it appears that the proteins must undergo a series of combinations before they become functional VRC01 or VRC02.

　　X-ray crystallography allowed the researchers "to identify the [antibody's] binding site down to the atomic level structure…. It is a particularly invariant part of the CD4 binding site, which is exposed," Mascola says. He calls that knowledge "a blueprint from which to design new vaccines. It allows us to try to design a protein that mimics and presents that specific site to the immune system" to stimulate B cells "to crank out the antibody."

　　Mascola acknowledges the complex nature of the VRC01 and VRC02 antibodies and their low naturally occurring numbers may prove to be an obstacle to developing a vaccine. It is too early to understand all of the issues surrounding the stimulation of antibody production and the concentration necessary to afford protection from infection.

　　The VRC research team has designed vaccine antigens that already are in preclinical study in small animals. If those prove successful, the work may advance into a monkey model, although it is not completely clear how monkeys can control the simian version of HIV and not progress to advanced disease. The identification of VRC01 and VRC02 may also help to advance a better understanding of the disease in monkeys.

　　Mascola says these discoveries also may lead to development of a "therapeutic vaccine" or immune-based therapy that helps train the immune system of an HIV-infected person to better control the virus without the use of drugs.

　　It may be possible to mass-produce these antibodies for passive administration as an adjunct or substitute for current small molecule drugs used to treat HIV. And if production costs can be reduced sufficiently there may be a role for them in topical microbicides as a preventative for HIV exposure.

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