Science：改造HIV病毒，促进AIDS疫苗研发

生物谷

HIV gets a makeover: A few adjustments to the AIDS virus could alter the course of research
HIV病毒

       AIDS研究发展缓慢的部分原因在于研发的疫苗如同“圆洞中的香椿”找不到合适的动物模型检测疗效。HIV-1病毒不能在猴细胞中进行复制，因此研究人员一直利用一种叫做短尾猴免疫缺陷病毒（macaque  version  of  simian  immunodeficiency  virus，SIVmac）感染动物，以期获得用于检测候选治疗途径或者候选疫苗疗效的动物模型，但最终得到的能够有效抵御SIV的疫苗在人类临床实验中效果并不显著。最近，洛克菲勒和Aaron  Diamond  艾滋病研究中心的研究人员利用遗传工程学和压力筛选（forced  adaptation，生物通编者译）的联合疗法，研制出一种新型AIDS病毒，此病毒能够在人细胞和猴细胞中快速复制，有望改善疫苗研究。

        Science杂志10月6日一篇文章中，Retrovirology  实验室负责人Paul  Bieniasz副教授对其与同事通过采用SIV病毒成分对HIV病毒的一小段结构进行改造而绕过灵长类细胞天然免疫性机制进行了详细描述。（灵长类细胞的免疫机制能够阻止HIV病毒在猴细胞中进行复制）。Bieniasz说：“整个过程看上去并不复杂，但是它花费了我们两年的时间。”

        Bieniasz与论文第一作者Theodora  Hatziioannou合作，绕过了实验中遇到的两大难题：首当其冲的是在猴细胞中一种叫做TRIM5的蛋白，此蛋白识别HIV-1衣壳，但是不识别SIV的衣壳。首先将编码HIV-1衣壳的基因更换为编码SIVmac病毒衣壳的基因，然后经过几轮压力筛选，Hatziioannou得到可以入侵猴细胞并逃逸TRIM5识别的HIV-1突变体。

        第二道难关在于：宿主产生的APOBEC蛋白能够引发入侵的病毒发生突变而将病毒杀死，但是HIV-1能够利用一种叫做Vif的蛋白破坏APOBEC而抵御宿主的攻击。猴APOBEC蛋白不受人类HIV-1病毒Vif蛋白影响。因此Hatziioannou为人类HIV-1病毒更换编码SIV  Vif  的基因，经过又一次压力筛选后得到繁殖力旺盛的病毒株。

        研究人员定名最后得到的病毒株为simian  tropic  HIV  (stHIV)，作为HIV-1的一种突变型，虽然只与原代病毒有10％的差异，但是能够有效感染灵长类细胞，可用于检测候选治疗方案的疗效。Bieniasz说：“假如我们能够在动物实验中使病毒发挥在培养组织中相似的功能，就有可能改变目前ADIS疫苗和治疗途径的研究方法。”

Tweaking HIV. A newly engineered version of the AIDS virus, dubbed stHIV, replicates robustly in rhesus monkey cells.

The slow pace of AIDS research can be pinned, in no small part, on something akin to the square-peg-round-hole conundrum. The HIV-1 virus won’t replicate in monkey cells, so researchers use a monkey virus — known as SIVmac, or the macaque version of simian immunodeficiency virus — to test potential therapies and vaccines in animals. But therapies and vaccines that are effective on SIV don’t necessarily translate into human success.

Now, using a combination of genetic engineering and forced adaptation, researchers at Rockefeller and the Aaron Diamond AIDS Research Center have created a version of the AIDS virus that replicates vigorously in both human and monkey cells — an advance that has the potential to revolutionize vaccine research.

In a paper published in the last issue of Science, Paul Bieniasz, associate professor and head of the Laboratory of Retrovirology, describes how he and his colleagues maneuvered around the intrinsic immunity of primate cells by replacing just a few parts of the human virus — the ones responsible for blocking replication in monkey cells — with components from SIV. “Overall, the virus is a mixture of engineering and forced evolution,” Bieniasz says. “It sounds simple, in theory, but it took us two years to do.”

Bieniasz and Theodora Hatziioannou, a research scientist in the lab and the paper’s first author, had to overcome two major obstacles: the first was a protein called TRIM5 that, in monkeys, recognizes the outer shell or “capsid” of HIV-1 but not that of SIV. By swapping out the capsid region of the HIV-1 genome for that of the monkey virus, and then selectively growing the viruses that replicated most robustly, over several generations Hatziioannou created an HIV-1 mutant that could evade the monkey cells’ TRIM5 recognition.
Another bit of engineering was required to get around the second obstacle: APOBEC proteins produced by a host normally cause invading viruses to mutate so much that they can’t survive, but HIV-1 uses a protein called Vif to destroy APOBEC and prevent the attack. Monkey APOBEC proteins, however, aren’t susceptible to the human virus’s Vif. So Hatziioannou did another swap — the SIV Vif gene for the HIV one — and then another round of forced adaptation to create viruses that would multiply with vigor.

The researchers dubbed their end result simian tropic HIV (stHIV): a form of HIV-1 that only differs from the original by about 10 percent, but can effectively infect primate cells and be used to test potential therapies. “If we can make this virus work in animals the way it works in tissue culture, it will likely change the way that AIDS vaccine and therapeutics research is done,” Bieniasz says.