Research shows an evolution of HIV in the body. "We're getting a very good feel that the virus that transmits to an individual is different a bit from the virus that ultimately evolves after months and years of replication." 

Dr. Fauci describes the virus initially transmitted as being "very restricted in its diversity, which interestingly, may make it even easier to block than we would have thought. Now having said that, _________________________________, but the nature of the virus is something that is very important." Fauci will discuss the "brief window of opportunity and vulnerability" at this month's 18th International AIDS Conference in Vienna. 

"_________________________________, it establishes what we call a reservoir that is almost impossible, with the tools that we have now, to eradicate." 

Studying those early infections, Fauci says, _________________________________and the development of a vaccine. He says test results of a new microbicide will be released at the AIDS conference. Past microbicides have failed to block HIV, but this candidate releases antiretroviral drugs.

答案：

(1)we haven't been successful in blocking anything right now
(2)Once the virus establishes itself and truly begins to replicate
(3)could lead to insights for a better prevention and treatment of HIV/AIDS