At the International AIDS Vaccine conference in Bangkok yesterday (Tuesday), the same scientists announced that they now had two clues about how the Thailand trial may have worked.

The ‘€œclues’€ are two antibodies found in the blood of those involved in the trial.

The one antibody was high in those that didn’€™t get HIV and it attached itself to the same parts of the virus every time, suggesting that it could recognise the virus.

The other antibody had the opposite effect, being high in those infected and low in those not infected.

Antibodies are special cells in the body that recognize viruses that invade the body. These antibodies mobilise other cells in the body (CD8 cells) to kill these invaders.

From outside this tight scientific community, these findings seem small. But to those who have been trying to find a vaccine for the past 25 years, they are the cause of great excitement and optimism.

Dr Bart Haynes, scientific head of the Thai trial known as RV144, described the findings as ‘€œintriguing clues’€ that provide direction for future research.

Finding these clues was an intense process involving 35 scientists based at 20 different institutes, who sifted through about 4 000 blood samples.

Although the RV144 vaccine only protected 31 percent of the people involved in the trial after three years, its protective effect after one year was an impressive 60 percent.

Scientists are now trying to understand how to maintain the protective effect ‘€“ and a trial is due within two months to test this.

The RV144 trial combined two vaccines. The first aimed to prime people’€™s immune systems to recognise HIV, and the other, injected within six months of the first, aimed to boost their immune systems to fight infection.

By October, scientists will recruit a group of volunteers involved in the RV144 trial and give them another booster shot of the vaccine to see whether their immunity against HIV can be pushed up again.

In addition, they have grown a lot of the protective antibodies ‘€“ called IgG ‘€“ and plan to insert them into monkeys to see whether these can protect the monkeys from the monkey version of HIV.

Also in the pipeline are two further trials of the RV144 virus, aimed at testing the vaccine in people who are more exposed to HIV than those in the original trial.

The first trial involves men who have sex with men in Thailand, where the HIV rate is around 10 percent.

The second will be a large trial of mainly heterosexual South Africans, where the HIV rate amongst adults is almost 18 percent.

‘€œDifferent populations may have completely different results so it is important to test this,’€ said Colonel Jerome Kim from the US military, one of the original investigators. ‘€“ Health-e News Service.