Singapore scientists crack 'sneak tactics' of dengue virus

By Linette Lai, The Straits Times, 14 Jan 2014

SCIENTISTS in Singapore have discovered how the dengue virus manages to slip past the body's immune safeguards.

A team of researchers, led by Duke-NUS associate professor Ooi Eng Eong, believes its findings will help to develop a "more targeted" vaccine against the mosquito-borne virus.

There are four types of the dengue virus in Singapore and while catching one type makes you immune to that type, catching another type after that can cause even greater damage.

Typically, the body protects itself against repeat infections by producing antibodies, which latch on to viruses and mark them for destruction by white blood cells.

White blood cells destroy viruses by engulfing them, activating their internal defence mechanisms as they do so. Ordinarily, these cells would destroy a dangerous virus.

However, there is a second system in white blood cells which prevents their internal defences from over-reacting.

Dr Ooi's research shows that, during a subsequent infection with a different type, the dengue virus manages to activate the second system - effectively disabling the cell's internal defences.

The virus is thus able to safely enter the white blood cell and start multiplying.

Developing a vaccine that is able to stop the virus from doing this, said Dr Ooi, will be the key to stopping dengue from spreading within the body.

Dengue infections hit an all-time high in Singapore last year, with more than 22,000 cases and seven deaths reported. Worldwide, almost 400 million people are infected by the virus annually.

While several drug companies are testing potential dengue vaccines, success has been limited so far because a vaccine needs to be effective against all four strains of the virus.

"The fundamental problem that we are all working with is that we are constrained by the knowledge on dengue," said Dr Ooi. "The real need is to understand the whole process better, so that we can anticipate where the weak points are and where we should target our vaccine."