Saturday 23 June 2012

Discovery raises hopes of cure for dengue fever

Singapore scientists find antibody that can destroy virus at a faster rate
By Poon Chian Hui, The Straits Times, 22 Jun 2012

SCIENTISTS in Singapore have uncovered a powerful antibody that can stifle and kill the dengue virus in two hours, in a finding that opens the door to a cure for the mosquito-borne infection.

Currently, there are no drugs or vaccines on the market that can counter dengue fever.

But this newly identified antibody, which is naturally present in humans, has been shown in mice to destroy the virus at a much faster rate than other dengue-fighting compounds around.

It appears to be effective against subtype 1 of the virus DENV1, which accounts for up to half of dengue cases in Singapore.

The landmark findings were published yesterday in international journal Science Translational Medicine. The study was carried out by scientists from the National University of Singapore's Yong Loo Lin School of Medicine, Duke-NUS Graduate Medical School and the Defence Medical & Environmental Research Institute at DSO National Laboratories.

Over two years, the team studied groups of cells extracted from about 200 patients who had recovered from dengue fever after being treated at Tan Tock Seng Hospital. They pinpointed an antibody that can stick to the virus, and lock it down so it does not attack other cells.

Principal investigator Paul Macary from the university's medical school said the antibody leads to a 50,000-fold reduction of the virus in two hours. It also works in a very small amounts.

'Essentially this means that this antibody is a million times better than any small molecule compounds that had ever been made for dengue,' said Associate Professor Macary, who is from the microbiology department.

He said that the antibody will be produced when a person gets infected, 'but the scale of the response is too small for it to have an impact on the infection'.

By injecting a larger amount of it into the patient, however, the recovery can be accelerated.

Side effects are likely to be minimal as the compound is already present in the body, he added.

There have been some 1,700 cases of dengue so far this year, according to the latest figures from the Ministry of Health.

In all, Singapore receives about 5,000 cases annually. During epidemics, the number can go as high as 15,000 cases a year.

Globally, the World Health Organisation estimates that there are 50 million to 100 million dengue infections every year.

Dengue patients usually become ill within a week of being bitten by an infected mosquito.

It takes about two weeks for patients to recover. But some go on to develop dengue haemorrhagic fever, which can kill.

Associate Professor Leo Yee Sin, clinical director of the Communicable Disease Centre at Tan Tock Seng Hospital, said treatment for dengue 'has been stagnant for many years'.

At hospitals, patients are monitored and given supportive treatment. For example, they will be put on drips to provide them with fluids, or receive blood platelets.

'This has been the traditional way of treating dengue for many decades - we let the body fight the infection on its own,' said Prof Leo.

The research team will be starting clinical trials in the next year or so, and a therapy is expected to be available within the next six to eight years.

Developing a vaccine may be next on the list. The team also hopes to uncover antibodies for the other dengue subtypes within the next two years.

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