Experts working on vaccine to fight AIDS in China

By Tan Ee Lyn

HONG KONG, Jan 21 (Reuters) - Scientists in Hong Kong and China are working on an AIDS vaccine to protect against three variants of HIV sweeping across south and west China, Hong Kong and Taiwan.

Chen Zhiwei, director of the new AIDS Institute in Hong Kong, said scientists have been using gene sequencing to track how HIV viruses in China are evolving, and their geographical spread.

Two closely-related HIV variants had spread through intravenous drug users (IDUs) from southwestern Yunnan province; one to as far as Xinjiang in the northwest, and the second to Guangdong in the south.

The third variant is in Yunnan and southern Guangxi province, which Chen said is passed mainly through heterosexual sex.

Chen, who worked alongside famous HIV/AIDS scientist David Ho in the U.S. before heading the Hong Kong institute, said collaborating scientists in the U.S. and China have designed a vaccine based on the two HIV variants spreading among IDUs and they hope to test it in animals by the end of this year.

"If you want to make a vaccine, it is better to have a local strain as a target to work on," Chen said in an interview with Reuters.

Asked if the experimental vaccine may confer protection against the third variant that is transmitted chiefly through sex, Chen said: "That's what we want to know. There is about 60-70 percent identity between the subtypes. If viruses are very closely related, chances of cross protection are better."

The HIV variants circulating in south and west China are very similar to those found in Myanmar, Vietnam, Cambodia, Thailand and India, as well as in Taiwan and Hong Kong, he said.

"The epidemic in China has evolved over time. Previously, the major risk factors were IDUs and the tragic story of blood donation in central China. But after these people got infected, they passed it to their spouses, friends and these are in the general population," Chen said.

"After 2006, heterosexual sex has been playing the major role in transmission of the virus. Infections have gone up in the general population and from mother to child."

The presence of these variants in Taiwan and Hong Kong also could be a tell-tale sign of the travelling routes of drug users in the region, Chen said.

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The AIDS Institute hopes to help set up HIV screening centres in China, which is estimated to have about 700,000 people living with HIV/AIDS, up from an earlier estimate of 650,000.

Chen also spoke about hundreds of thousands of HIV/AIDS patients in central China, who contracted the virus in the 1990s from unsanitary blood donations.

Despite free antiretroviral drugs provided by the government, some 30 percent of these patients have developed full-blown AIDS - which Chen attributed to drug resistance.

Antiretroviral drugs help keep the HIV virus in check and can prevent the progression to AIDS. But regimens can be complicated and sufferers can easily develop drug resistance if they miss doses - meaning they will then have to resort to stronger, more expensive, and in China, often unavailable drugs. (Editing by Sanjeev Miglani)