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Ta, rabies

a revolution in the treatment of rabies might be in the offing. The world's first combination dna veterinary vaccine against rabies, produced by scientists from the Bangalore-based Indian Institute of Sciences (iisc), is ready for trials. This is good news for many countries, especially the poorer ones, where the disease is a serious public health problem.

Rabies is caused by a virus of the family Rhabdoviridae. dna vaccination, more precisely the dna-mediated immunisation, refers to the direct introduction of the dna's plasmid (by injection or particle bombardment) into the host organism's tissues. This plasmid causes expression of antigens (antibodies-producing substance) directly within the infected cells. In this sense, dna vaccination resembles a viral infection.

The iisc team first developed the dna vaccine by taking a gene from the rabies virus and introducing it into the bacteria. But the vaccine produced was effective only 50 to 70 per cent of the times. However, the cost of production was lesser than that for cell culture vaccine.

Then, scientists found that adding a small quantity of the modern cell culture vaccine enhances the potency of the dna vaccine, giving 100 per cent result while keeping the price of the vaccine low. The principle works for both human and veterinary vaccines and has shown positive results in mice and cattle. It took the team five years to develop the vaccine.

The scientists from iisc, led by P N Rangarajan, collaborated with the Indian Immunologicals Limited to design the vaccine. They say the vaccine can be developed into a novel, cost-effective vaccination strategy for combating rabies in particular, and infectious diseases in general. The vaccine works such that if a rabies-infected dog is vaccinated, his bite to a human will not transmit the disease.

"Since bringing out a human vaccine is going to take time, we are thinking of bringing out a veterinary combination rabies vaccine first. Moreover, there are less regulatory protocols for bringing out a veterinary vaccine than a human vaccine,' says Rangarajan.

He adds that since it is the world's first combination dna vaccine, the scientists have to demonstrate that it is non-toxic. "Animal toxicity studies are being carried out at the National Institute of Nutrition in Hyderabad. Once the vaccine proves non-toxic to animals, we would approach the drug controller to initiate human clinical trials. It would take two to three years to complete the human trials and if everything goes well, we may get the license for manufacturing,' he says.

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