Animal trials of indigenous DNA vaccine soon

THIRUVANANTHAPURAM Sept. 21. India's first DNA vaccine is set to begin animal trials shortly and a novel anti-diarrhoeal vaccine is in the early stages of human trials. In both cases, Indian scientists have provided the research know-how and industries will be producing the vaccines.

The public sector Indian Immunologicals, based in Hyderabad, will be producing the anti-rabies DNA vaccine developed at the Indian Institute of Science (IISc). DNA vaccines are still very new. It was only a decade ago that scientists found that bare strips of DNA could act as a vaccine. The DNA carries information about one of the germ's proteins. Given as a vaccine, the DNA strips get taken up by the body's cells, which then start producing this protein. The protein prepares the immune system so that it is ready to pounce on the germ when it enters the body.

Although various DNA vaccines are currently being tested, none have yet come into general use. A DNA vaccine is attractive because it can be produced at less cost and, unlike conventional vaccines, does not require refrigeration. In India, about 30,000 people die of rabies each year and another 500,000 take preventive injections.

Researchers led by P.N. Rangarajan of the IISc found that a combination rabies vaccine would be effective when given as preventive therapy and also when injected after a person had been bitten. The combination vaccine has DNA strips carrying a rabies virus gene and also a little of a rabies vaccine produced through cell culture. Indian Immunologicals will initially be testing the DNA combination rabies vaccine on dogs. Apart from the vaccine's efficacy, its stability at different temperatures and its ability to tolerate temperature fluctuations have also to be established, according to a senior company executive.

The animal trials are expected to finish in a year's time and the company should then be in position to market the product as an animal vaccine. The animal trials would also provide the data needed to get permission for testing the DNA vaccine on humans.

Vaccine against rotavirus

Meanwhile, an Indian vaccine against rotavirus is already in the first phase of human trials. Rotavirus causes severe diarrhoea in children and claims half-a-million lives each year, 85 per cent of them in poor countries.

The first rotavirus vaccine was licensed in the United States in 1998 and withdrawn a year later after its use was linked to bowel obstruction in infants. Various groups are trying to develop alternative rotavirus vaccines.

Researchers at the All India Institute of Medical Sciences and at the IISc independently found naturally occurring rotavirus strains which did not cause diarrhoea in newborns and yet were capable of inducing immunity.

Investigations revealed that these rotavirus strains had genes from both cattle and human rotavirus varieties. Natural vaccination by the new strain had considerably reduced rotavirus diarrhoea in newborns in Bangalore, according to C. Durga Rao of the IISc.

The Indian rotavirus vaccine, carrying the two strains identified at AIIMS and IISc, is being produced by the Hyderabad-based Bharat Biotech. The vaccine has been developed under the Indo-US Vaccine Action Programme.

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