VOA标准英语2015--古巴发现一种侵袭性艾滋病毒（在线收听）

Aggressive HIV Found in Cuba 古巴发现一种侵袭性艾滋病毒

An aggressive form of HIV has been discovered in Cuba. It develops into full-blown AIDS within just three years. Researchers said the progression happens so fast that treatment with antiretroviral drugs may come too late.

Professor Anne-Mieke Vandamme said Cuban health officials first alerted her about the aggressive form of AIDS. They asked for help in finding out what was happening.

“We have a collaborative project with Cuba and the Cuban clinicians had noticed that they recently had more and more patients who were progressing much faster to AIDS than they were used to [seeing]. In this case, most of these patients had AIDS even at diagnosis already,” she said.

Vandamme is a full medical professor at the University of Leuvan in Belgium. She and her team studied more than 70 patients and divided them into various groups. One group was made up of those who developed AIDS quickly.

“So this group of patients that progressed very fast, they were all recently infected. And we know that because they had been HIV negative tested one or a maximum two years before,” she said.

She said that on average, without treatment, HIV infection takes 5 to 10 years to become full-blown AIDS. That’s determined by the scarcity of CD-4 immune cells and the number of opportunistic infections a patient has.

Usually, she said, a fast progression of HIV to AIDS is more a result of the patient’s weak immune system rather than the particular subtype of HIV involved. What’s happening in Cuba is different.

“Here we had a variant of HIV that we found only in the group that was progressing fast. Not in the other two groups. We focused in on this variant [and] tried to find out what was different. And we saw it was a recombinant of three different subtypes,” she said.

This new form of HIV is a combination of sub-types A, D and G. It’s been named CRF19.

Vandamme said, “Another thing was that they had much more virus in their blood than the other patients. So, what we call the viral load was higher in these patients. “

The patients with the aggressive form of HIV also had higher levels of a molecule called RANTES. It’s released as part of the immune response and raises the alarm about infection.

Researchers have determined why this form of HIV progresses to AIDS so quickly. Vandamme said for infection to take place, HIV has to attach itself to a cell at – what she calls – anchor points. In medical terms they’re called co-receptors.

Vandamme said, “There are two types of co-receptors that HIV can use: CCR5 or CXCR4. And in the normal progression of the HIV to AIDS it often happens that the virus switches co-receptor. It almost always starts with using CCR5 and then it switches to CXCR4 after many years. And once it switches the progression to AIDS goes very fast.”

But instead of taking many years to switch co-receptors, the new form of HIV in Cuba does it less than three years.

Vandamme says the inclusion of HIV subtype D in the new variant may be key. It contains an enzyme that enables HIV to reproduce in greater numbers – and it takes proteins from other subtypes and uses them in new virus particles.

The good news is that the aggressive form of HIV responds to most antiretroviral drugs. The bad news is people may not realize they have full-blown AIDS until it’s too late for therapy to do any good.

Vandamme said the variant has been seen before in Africa, but there were very few such patients and it does not appear to be spreading there. However, it is in wide circulation now in Cuba and now can be easily studied. So, there may be an African link, but further study is needed.

She said it’s vital for people having unprotected sex with multiple partners to be tested for HIV early and often.