Chinese scientists may have found the key to creating effective vaccines for the world’s deadly viruses – by breaking two taboos in traditional vaccinology.
An experiment by a research team at Beijing’s Peking University was hailed as “revolutionary” in the field in a paper published in the latest issue of Science magazine on Friday.
The scientists broke two of the field’s taboos first by creating a vaccine using a live, fully infectious virus, and then by injecting the substance into infected animals dying of the same virus.
The animals were cured after receiving the injection, according to the paper.
This breakthrough promises to simplify the process of producing vaccines, which may help scientists develop effective vaccines or even cures for various viruses – such bird flu, Sars, Ebola and HIV – within weeks of an outbreak.
The live virus used in the vaccine used by the researchers had its genetic code tweaked to disable the viral strains’ self-replication mechanism. But it was kept fully infectious to allow the host animal cells to generate immunity.
Using live viruses in their fully infectious form was considered taboo, as viruses spread rapidly. Vaccines sold and used widely today generally contain either dead or weakened forms of viruses.
Live viruses used in vaccines approved for clinical use have typically had their physical structure altered to weaken them. But this has affected the vaccines’ effectiveness. Vaccines also do not exist for many of the world’s deadly viruses.
Zhou Demin, a professor at Peking University’s School of Pharmaceutical Sciences, and the study’s lead scientist, said researchers had been facing a losing battle against viruses.
“Now we have a new weapon … that can mow down nearly any kind of virus and their mutations. It can shift the battle,” Zhou told the South China Morning Post.
In theexperiment reported in Science magazine, Zhou’s team made the vaccine using live bird flu virus.
They jabbed the vaccine into mice, guinea pigs and ferrets. The virus invaded the hosts and created havoc in cells, but they did not reproduce themselves.
The immune system fought back and picked out the virus in each cell, one after another. By the end of the third day the last strain of the virus was gone, leaving no trace behind except a permanent memory in the host’s immune system, which provided immunity.
The researchers then injected the vaccine into mice suffering from the flu. The animals recovered quickly and returned to full health.
Analysis showed that the man-made virus had recombined with the wild virus so that the combined virus was unable to reproduce, too.
“The vaccine is not just a vaccine, but also a drug,” Zhou said.
The bird flu virus in the vaccine had more than a 99 per cent similarity to its natural cousin.
The researchers tweaked as few as three genome bases in the virus’ DNA. A typical virus has hundreds of thousands of such bases.
A virus needs food and amino acids, the building blocks of proteins found in animals and plants, is one source of food. A wild virus will eat almost any amino acid, but the genetically tweaked virus in Zhou’s vaccine would accept only a special kind of man-made amino acid.
The unnatural amino acid can be produced only in a laboratory: it does not exist in the body of animals or humans.
“So after you inject these viruses into the host they will not be able to reproduce themselves due to the lack of a [suitable] amino acid, and they will ‘starve’ to death in the end,” Zhou said.
Zhou’s team produced the virus in a man-made cell line. The cells were filled with the unnatural amino acid. The virus would then find comfort in these man-made cells and reproduce in large numbers, like cars rolling off a production line.
Zhou has envisioned a likely use for the vaccine technology in the near future, such as a time when a nation is hit by an outbreak of something like severe acute respiratory syndrome.
Researchers would quickly isolate the unknown viral strain from patients and modify three genetic bases in the virus. The modified virus would then be used to vaccinate the general population. All this could be done within a few weeks.
The vaccine could also be injected into patients already suffering from the viral infection.
“The side effect is so small that the recipient would hardly feel anything,” Zhou said.
He said he believed the technology would benefit patients “soon”.
The team had acquired international patents for the technology and they were in contact with some vaccine manufacturers so that trials in humans could be carried out, he said.
In the past, vaccine development has been a long and complicated process, requiring researchers to know exactly the physical structures of a virus and its behaviour.
However, that would not be necessary using the new method, which requires only the modification of a few genetic bases that exist in the DNA of almost any virus.
Professor Meng Songdong, a researcher at the Chinese Academy of Sciences’ Key Laboratory of Pathogenic Microbiology and Immunology, said the work by Zhou’s team was a “new approach” and “something never thought of by others before”.
Meng, who was not involved in the study, added: “It shed a new light on how to deal with the virus.”
However, he raised concerns about whether the live virus vaccine could be used on humans in the near future.
The man-made virus might undergo unexpected mutations that broke the link of control initially created by researchers, he said.
And the recombination of a man-made virus with wild types might not always produce the good results that had been reported by Zhou’s team, Meng added.
“The chances are the exchange of genetic information will make [the virus] even deadlier, even more productive,” Meng said.
“I doubt health authorities in any country, especially China, will vaccinate the public with a live virus.”