VOA常速英语2016--中和抗体有望助力艾滋病疫苗研制（在线收听）

中和抗体有望助力艾滋病疫苗研制

Researchers say powerful antibodies may hold clues to developing an effective AIDS vaccine.The antibodies were isolated from individuals already infected with HIV. Dr. Wayne Koff saysthe goal is to find a vaccine that will help the immune system fend off an HIV infection. Mostvaccines work in terms of stimulating something known as antibody, which is a proteinsubstance in the body. And they work because the antibody identifies the site on the virus.And it can attach onto the virus and kill it. Koff, chief scientific officer for IAVI, the InternationalAIDS Vaccine Initiative. He says the problem with HIV is that it's a hyper-variable virus. Thatmeans it's different all over the world. And so instead of a single strain or a couple of strains,we have millions of strains. And as a result, for a vaccine, instead of eliciting a neutralizingantibody, what one is attempting to do is to identify where the vulnerable sites on the virusthat are the same on every virus particle. And these antibodies then are known as broadlyneutralizing antibodies. So if you're exposed to a virus on one side of the globe, they wouldwork just as well as if you're exposed in some other region of the world. HIV becomes hyper-variable when it replicates. Each time, it's just a little bit different. Some scientists call thesechanges minor errors, but it's enough to confound the human immune system. The changesoccur in the outer protein of the virus, the target of neutralizing antibodies. In other words,the weak spot. The 17 antibodies that were isolated came from people infected with HIV. Wescreened about 1,800 people. About one percent of the individuals had extremely broad andpotent neutralizing antibodies against HIV. We then went back to these individuals and we tookadditional samples of blood and from those individuals we identified these broadly neutralizingantibodies. Did the people who produced these antibodies do better at fighting HIV? No, theydidn't. Most people would think if one has broadly neutralizing antibodies after HIV infectionthere should be a benefit. And that is not the case. In the case of individuals that are alreadyHIV infected, the virus is always one step in front of the immune system. But the immunesystem could react differently if it had these antibodies before infection. The real challengefor us and from a vaccine point of view is to ensure that the immune system is primed inadvance of the virus as opposed to after HIV infection. It remains to be seen if theseantibodies will have any therapeutic benefit. The next step is animal studies. The antibodieswill be given to chimpanzees to see whether they can block an HIV-like virus. Koff says initialvaccine candidates will probably be ready in three or four years. The antibody research isoutlined in an article in Nature magazine.

研究人员称，强大的抗体可能会有助于研发有效的艾滋病疫苗。因为这种抗体与艾滋病患者是相分离的。韦恩称，研究的目标是发现一种能够帮助人体免疫系统抵抗艾滋病感染的疫苗。大多数疫苗的工作原理都是激发人体内一种叫做的抗体的物质，这种物质是人体内的一种蛋白质。而抗体之所以有效是因为抗体能够识别病毒。进而附着在病毒上并将病毒杀死。韦恩是国际艾滋病疫苗行动组织（IAVI）的首席科学家。韦恩表示，不过艾滋病的复杂之处在于它是高可变病毒。也就是说，全球的艾滋病病例不尽相同。所以它不是一个或几个品系，而是成千上万个不同的品系。所以要研制艾滋病疫苗，我们要做的不是诱发中和抗体，而是要试图识别每个艾滋病分子之间的共同弱点。而这些抗体俗称为中和抗体。所以即便某个人在全球的不同的地方感染艾滋病病毒，这种疫苗一样有效。艾滋病是通过自我复制来实现高可变的。每一次变化后，都会有所不同。虽然一些科学家称这些变化只是微小的变化，但足以使人体免疫系统紊乱。这些变化会在病毒外的蛋白质上体现出来，而病毒外的蛋白质正是中和抗体找寻的目标。换句话说，病毒的蛋白质也是它的软肋。这17种分离抗体源自艾滋病患者。我们筛选了1800名患者。其中有1%的患者有很多抵抗艾滋病病毒的强力中和抗体。接下来，我们单独抽取了这1%患者的血液样品，并在其中检测出很多中和抗体。但这1%的人更能抵御艾滋病病毒吗？

答案是否定的。大多数人认为，如果某人有很多中和抗体，就能更好的抵御艾滋病。但事实并非如此。对于已经感染艾滋病的人群来说，艾滋病病毒已先于免疫系统一步。但若感染艾滋病病毒之前，免疫系统就含有中和抗体的话，免疫系统的反应就会不同。所以我们研制疫苗的关键挑战是要确保为感染病毒的患者能够在免疫系统中接入这种中和抗体。这种中和抗体的疗效还有待考察。下一步是以动物为案例进行研究。这种中和抗体会注入到黑猩猩体内以观测它们是否能抵御类似艾滋病的病毒。韦恩说，中和抗体需要大约3到4年的时间与接受对象的免疫系统相适应。这篇抗体研究的文章已发表在《Nature》上。