2016届河南省孟津县高考英语一轮复习阅读理解训练：9（含解析）_高考复习指南

2016届河南省孟津县高考英语一轮复习阅读理解训练：9（含解析）

　　As part of the study, the researchers divided breast milk into smaller fractions (部分) made up of specific proteins via a number of filters (过滤) — separating the proteins by size, electrical charge and other characteristics—and tested which of these fractions, when added to a tissue culture, prevented the cells from being infected by HIV. Eventually, they found that one particular protein was present in all the HIV-resistant fractions but in none of the others: Tenascin C.

　　Tenascin C works by blocking a key protein on HIV’s envelope that normally ties up to a receptor on a T cell’s membrane called CCR5. In doing so, Tenascin C prevents HIV from mixing with the T cell and injecting its RNA inside.

　　Still, the researchers say that other natural elements in milk might play a role in fighting HIV as well. “It’s clearly not the whole story, because we do have samples that have low amounts of this protein but still have HIV-neutralizing activity,” the study’s lead author Permar says. “So it may be acting in concert with other antiviral and antimicrobial factors in the milk.”

　　Whatever those other factors are, though, the finding vindicates (证明……的正确) recent changes to UN guidelines that recommend even HIV-positive mothers in resource-poor countries should breastfeed, if they’re taking anti-retroviral drugs to combat their own infection.

　　The next steps, Permar says, are determining which area of Tenascin C is active and whether it can effectively prevent transmission in a live animal. If it works, it could potentially be incorporated (合并) into an HIV drug with broader applications. It’s even possible that it could someday be adapted to reduce the risk of HIV transmission in adults as well as infants.