扑灭猪流感的关键疫苗技术？

　　

生物通报道，猪流感事件不断升级，墨西哥，美国，乃至全球人的目光都盯在猪流感身上。时至今日，美国感染猪流感的人数已经增至40人，一个位于美国马里兰的生物技术公司声称他们有帮助快速开发猪流感疫苗的技术。

 

这家公司就是Novavax公司，在过去的几年里，Novavax公司已经成功的制备禽流感H5N1乃至其他几种流感的疫苗，他们的研发人员开发了一种病毒样颗粒（Virus-like particles，VLP）疫苗技术，将病毒膜蛋白挂在脂质基质上模拟病毒。就在3月份，Novavax公司和美国疾控中心（CDC）的人合作的研究成果刚发布，他们声称以1918西班牙流感病毒为研究对象的病毒样颗粒疫苗能有效的为小鼠提供免疫保护。

 

目前，流行在北美的猪流感被疑为H1N1，这一疫情引发了美国和世界卫生组织的高度关注，美国进入紧急卫生状态。

 

来自梅奥诊所疫苗研究中心的一名免疫学家Gregory Poland称，Novavax公司的病毒样颗粒疫苗技术确实是一项开发疫苗的新颖技术，但是未曾检测，不能定论。目前该公司的这一疫苗还没有得到FDA的批准，市面上唯一获得批准的病毒样颗粒疫苗是人乳头状瘤病毒疫苗。

 

Novavax公司的副总裁Thomas Johnston表示，以Novavax公司现在的实力，用病毒样颗粒疫苗技术制备猪流感疫苗只需10-12周的时间，包括从基因测序到正式的产品出炉。这种病毒样颗粒疫苗技术的优势在于，只要获得病毒基因序列就能马上设计出疫苗。Thomas表示，Novavax公司和其他生物技术公司，制药公司一样在上周就拿到了猪流感（H1N1）毒株的基因序列数据。我们现在已经开始着手设计猪流感疫苗。

 

Novavax公司疫苗发展部副总Gale Smith说，我们先克隆病毒关键基因，接着用昆虫细胞表达病毒关键基因获得病毒蛋白，这比培养病毒要安全的多，并且可以避免活病毒从实验室泄露造成公共安全事件。

 

目前，Novavax公司的禽流感疫苗已经进入临床第三期试验，前两期的试验结果喜人。Novavax公司的研究人员称，这些病毒样颗粒还能为筛选猪流感敏感药物做出贡献。

（生物通 小茜）

资料来自《The Scientist》

Researchers at Novavax have been developing vaccines for the H5N1 strain of avian flu, along with other strains of influenza, over the past few years using an approach built around virus-like particles (VLP)--viral membrane proteins in a matrix of lipids. Researchers from the company, with scientists from the Centers for Disease Control and Prevention (CDC), published a study last month in which they successfully protected mice against a reconstructed virus from the 1918 Spanish flu outbreak through intranasal immunization with H1N1 VLPs.

A new strain of H1N1 is likely causing the current outbreak of swine flu in North America, which this weekend led both the World Health Organization and the CDC to declare a public health emergency.

Gregory Poland, an immunologist and head of the Vaccine Research Group at the Mayo Clinic in Minnesota, said VLPs and other novel approaches to vaccine development, for combating influenza are exciting but untested. "The issue, from the perspective of influenza, is that none of these is approved," he said. In fact, the only FDA-approved VLP-based vaccines on the market are those developed to protect women from human papillomavirus.

Novavax's typical timeframe, going from DNA sequence to a testable product based on VLPs, is 10 to 12 weeks, according to the company's vice president for strategy, Thomas Johnston. "The way we develop vaccines allows us to move pretty quickly once DNA sequences are known," Johnston told The Scientist, adding that Novavax--like scores of other biotechs and pharmaceutical companies--received the sequence data for the new H1N1 strain of swine flu late last week. "We have begun our process for developing a vaccine."

Novavax's approach--which clones key viral genes, and uses insect cell cultures to produce the virus-like particles--is faster and safer than approaches that utilize live viral cells, said Gale Smith, Novavax's vice president for vaccine development. Because the latest strain of H1N1 is transmittable from human to human, manufacturing a live virus vaccine represents significant safety risks, he added.

But so might a relatively untested strategy. Novavax has two vaccine candidates in clinical trials: One, for H5N1, just completed Phase IIa trials, and a seasonal vaccine candidate is in Phase IIa trials now.

According to Andrea Sant, an immunologist at the University of Rochester, traditional approaches, such as the commonly used subunit vaccines that consist of non-viable viral protein extracts, could be enough. "I think it's not impossible to make a conventional vaccine for next fall," at the typical start of the flu season, she said.

Hildegund Ertl, an immunologist at the Wistar Institute in Philadelphia, cautioned that going the VLP route may be tricky because the approach is so new and relatively untested. "For a company that's in a pre-clinical stage for a new vaccine to think that their vaccine is going to help in this situation is very optimistic indeed," she told The Scientist. "I would stick to what we know about in case time is of the essence."

Ertl and Sant agreed that how swine flu plays out in the human population--how the virus mutates, moves between hosts, etc--over the next couple weeks will determine which vaccine development strategy will be most effective. "A lot will depend on what happens over the next month," Sant said.