A little red-eyed frog could hold the key to ending the scourge¹ of AIDS.

Scientists have found that a chemical in the skin of the Australian red-eyed tree frog can block infection by HIV - the virus that causes AIDS - by destroying the viral particles.

They hope further research could lead to an "after-exposure" lotion² to protect against HIV and AIDS.

The chemical is part of the frog's defences. Special glands³ on their skin produce and store packets of the compound, which is released when they are injured or alarmed and acts to protect them from infection by killing⁴ fungi⁵, bacteria and viruses.

The ability to target HIV was discovered when researchers at Vanderbilt University in Nashville, Tennessee, decided⁶ to investigate whether the chemical was effective against viruses that infect humans.

In tests using human immune system cells, the chemical killed HIV particles but left the immune cells unharmed. It is thought to work by damaging the membrane⁷ of each viral particle, either by punching holes which cause it to fall apart, or through a "detergent⁸ effect" which breaks apart fatty molecules⁹ in the membrane.

Research leader Dr Scott Van-Compernolle said: "There are lots of substances which destroy viruses but the trick is finding one that doesn't also destroy the membrane of our cells. That is why these frog peptides are unique."

Further tests showed the chemical could stop the virus being passed between cells, thus blocking infection. The scientists infected cells with HIV, treated them with the frog chemical and then exposed them to healthy cells. The virus appeared to have vanished.

They hope it will be possible to develop a cream to target infected cells. Dr Van-Compernolle said: "It seems it would work really well in just the way the frogs use it - as a cream. We envisage¹⁰ something prophylactic¹¹ so if you were exposed to HIV through unprotected sex, you could use this cream or a suppository to give you a fairly high dose of the proteins in the region where you thought the virus might be."

It could still be effective if used hours after exposure. "We showed you can successfully treat the infected cells up to eight hours after they were exposed to the virus," said Dr VanCompernolle. "The virus has already got in those cells but this is still able to block the infection." The scientists have now won a grant from the American Foundation for AIDS Research to continue the work. Its director of research, Dr Rowena Johnston, said no creams exist which could be applied¹² to the body after exposure to HIV.

But she added: "The first generation of these products is now not far from being developed. They could be applied prior to sex or perhaps taken in the same way as the contraceptive pill. Alternatively, if the woman is HIV positive, she could protect her partner from infection. It would be a fantastic tool for HIV prevention. We are so far from having an AIDS vaccine¹³, we are not going to wait around for 15 years and do nothing in the meantime."

But destruction of the rainforest in north Queensland, Australia, means there are declining numbers of red-eyed tree frogs, which have bright green backs, yellow sides, a cream belly¹⁴ and orange inside legs.

Dr Van-Compernolle said: "These frogs have evolved over millions of years to produce these peptides. They have already tested them for us, to fight their own viruses and bacteria. Around the world there are huge and rapid declines in the numbers of amphibian¹⁵ species. When we don't take care of the ecosystems¹⁶ we have on the planet we risk losing something like this."

　　参考译文：

　　小小的红眼树蛙可能是人们摆脱艾滋病困扰的关键所在。美国研究人员日前研究发现，澳大利亚红眼树蛙的皮肤中含有一种化学物质，这种化学物质可以通过破坏HIV病毒来阻断艾滋病的传播。

　　据美国《休斯顿时报》10月9日报道，这种化学物质是红眼树蛙防卫武器中的一部分。红眼树蛙皮肤上的特殊腺体能够产生并存储这种物质。当它们受伤或是受惊吓时，这种物质就会被释放出来，并且通过杀死细菌和病毒来防止感染，保护其自身的安全。

　　美国田纳西州范德比尔特大学的研究人员使用人体免疫细胞进行了相关试验后发现，这种化学物质能够杀死HIV病毒微粒，但同时又不会破坏人体免疫细胞。研究人员认为，这种化学物质是通过破坏每个病毒微粒的细胞膜来起作用的。它可能是通过在细胞膜上打孔或者是经由一种“清洁作用”使病毒微粒的细胞膜受到破坏的。

　　对此，此项研究的负责人斯科特博士表示，很多物质都能摧毁病毒细胞，但我们希望的是找到一种既能杀死有害病毒又不会对人体免疫细胞造成危害的物质。这就是为什么我们会说这些青蛙皮肤中的缩氨酸是独一无二的。

　　而更多的研究显示，这种物质能阻止艾滋病病毒在细胞间的传递，从而阻止传染的发生。科学家使用青蛙皮肤中的缩氨酸来治疗一些受到HIV感染的细胞，然后又让这些细胞接触健康的细胞。研究结果显示，细胞上的HIV病毒都逐渐消失不见。

　　报道说，人们希望更进一步的研究能有助于科学家制造出一种可用于抑制HIV病毒和艾滋病的 “接触后”药物洗剂。

　　现在，科学家们也正在设想利用这种特殊的化学物质制造出一种预防药物。如果某些人因为无防护措施的两性关系而接触到了HIV病毒，就可以在病毒可能存在的地方使用这种药物洗剂。即使是在接触之后的数小时使用，这种洗剂也可以发挥功效。目前，该项目的科学家们已经获得了美国艾滋病研究基金会的批准，得以继续进行更为深入的研究。

　　该研究同时也面临着一个问题，即澳大利亚昆士兰北部的雨林地区破坏严重，这就意味着红眼树蛙的数量正在逐渐减少。因此，红眼树蛙可能会成为最应该受到保护的物种之一。

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