A SYNTHETIC vaccine against foot and mouth disease has triumphed in its first full trial. But despite its promise, it is unclear whether it will ever be used.
All existing vaccines consist of whole foot and mouth viruses that have been inactivated, but these can sometimes cause the disease. The new 鈥渃omponent鈥� vaccine, however, consists of a single protein that resembles part of the virus. During tests in Taiwan, it protected 20 out of 21 vaccinated pigs. 鈥淭hat鈥檚 better than conventional vaccines,鈥� says Alan Walfield of United Biomedical, the New York company that developed the vaccine.
The success of the trial will strengthen arguments for tackling outbreaks by vaccinating animals instead of resorting to mass slaughter, as Britain did last year. Critics of the slaughter policy point out that vaccination would mean the countryside can remain open. In 2001, the losses to Britain鈥檚 tourism industry were actually far greater than those sustained by the farming industry (New 杏吧原创, 1 December 2001, p 34).
Advertisement
British farmers opposed vaccination because countries that are free of disease won鈥檛 accept imports from those that resort to widespread vaccination. That鈥檚 because animals given conventional vaccines produce the same antibodies as animals with the disease, making it difficult to distinguish between infected and vaccinated animals.
Animals given the new vaccine, however, make antibodies only against its protein component. If antibodies against other parts of the virus are present, the animal must be infected. To reveal whether an animal has been vaccinated or exposed to the disease, United Biomedical has developed a test that has been submitted for approval in Europe and the US. But the company faces an uphill battle to persuade authorities to allow vaccination without banning trade. 鈥淲e have to change a lot of minds, but we hope it鈥檚 possible,鈥� says Walfield.
Ultimately, the decision as to whether vaccination can coexist with free trade in meat rests with the Paris-based World Organisation for Animal Health (OIE), which grants FMD-free status to countries. 鈥淚t represents a step forward,鈥� says a spokeswoman, 鈥渂ut there鈥檚 still a long way to go before such a process can be approved.鈥�
The vaccine is designed to protect against all so-called 鈥淥鈥� variants of the foot and mouth virus, including the pan-Asian strain that hit Britain. It is an amalgamation of the most common features of all 鈥淥鈥� strains. Although the vaccine works only in pigs at the moment, United Biomedical has begun tweaking it to make a vaccine that should also work in sheep and cattle.
鈥淚t seems they are provoking the right immune cells,鈥� says Alex Donaldson, head of Britain鈥檚 Institute for Animal Health鈥檚 Pirbright Laboratory in Surrey. 鈥淚t鈥檚 a step forward, and very encouraging. But a lot more needs to be done, and they must measure how soon you get protection and how long it lasts,鈥� he says. Walfield says that protection has already lasted the six months since the pigs were vaccinated, and could last longer. 鈥淲e don鈥檛 know yet,鈥� he says.
A spokesman for Britain鈥檚 Department for Environment, Food and Rural Affairs says component vaccines have so far proved disappointing. 鈥淏ut if these promising results are reproducible and applicable to other species, and can be adapted to the other six serotypes of the virus, then this would represent a major breakthrough.鈥�
