Inter Press Service - Tuesday, November 17, 1998
Andrew Nette

This month, medical researchers working simultaneously in Sydney, Melbourne and Canberra announced that what they call the Co-X-Gene vaccine has been tested successfully on monkeys, preventing HIV infection in the animals.

The Co-X-Gene still has to undergo more tests, some of them on humans. But there is already some speculation that work on it could help in the development of an AIDS cure that can be administered on a mass basis, similar to immunisation against polio and measles.

"Although we are cautious, this is one step in the process of developing a vaccine against HIV," says Dr Stephen Kent of the Melbourne-based McFarlane Burnet Centre for Medical Research.

Scientists at the Centre have been working on the vaccine with colleagues at Canberra's Australian National University (ANU) and the Commonwealth Scientific and Industrial Research Organisation.

The Co-X-Gene researchers say their animal test results showed that all traces of HIV disappeared from the monkeys' systems within one to two weeks. The vaccine will be tested on HIV infected people in Australia next year, with the possibility of mass trials following in Africa and Asia.

"What our vaccine does is induce T-cells against the disease that are more capable of fighting off the virus," says Kent. "To the extent that it does this, its stands a chance of totally eradicating the virus. That would be a cure."

T-cells make up one of the two "armies" of the human body's immune system. The other is composed of antibodies that seek to neutralise certain viruses and bacteria, but it is the T-cells that have proven much more effective in searching out and combating the HIV virus.

Some countries such as Thailand are known to be already conducting tests on possible HIV vaccines. But much of the current research regarding HIV has centered on combination therapies, drawing on a pool of around eight to nine drugs.

"These have shown great effectiveness in stabilising the condition of people with HIV, but they don't eradicating the virus completely in that once you stop taking them the virus comes back," says Dr David Beams of the Australian biotechnology company Virax, which holds the worldwide license to commercialise Co-X-Gene.

"They are also expensive," Kent also says of the combination drug therapies. "If you are taking three of these drugs they are in the order of somewhere between (10,000) to 15,000 dollars per year per patient. This is simply unaffordable for someone in place like Vietnam or China."

He adds, "What would be much better in terms of public health and from a global perspective would be a vaccine to prevent the disease. The eventual hope would be for this sort of vaccine to be incorporated into the sort of childhood vaccines that could delivered to everybody and would prevent HIV from taking hold."

But researchers stress that a possible vaccine is at least three to five years away from being licensed. As it is, trials for a therapeutic version of Co-X-Gene are scheduled to begin in Melbourne and Sydney only in early 1999, involving 30 to 40 people with HIV. A laboratory has already been built at ANU to produce the vaccine.

The trials will focus on assessing the vaccine's safety, and if successful will be expanded to larger groups. Says Beams: "I think it's highly significant because it will be the first test of this technology in people and one of the few trials of this style of vaccine in the world."

Scientists also are seeking funding for future trials of the vaccine on healthy humans in Africa and South-east Asia, where the virus has reached epidemic proportions.

The tests would involve thousands of subjects. According to Kent, mass testing "requires a country experiencing an epidemic of HIV". Among the possible areas of testing mentioned so far are Vietnam and Sub-Saharan Africa.

Co-X-Gene is particularly suitable for tropical countries as it did not require refrigeration and can be easily administered.

Although Beams will not comment on the likely cost of the vaccine, he anticipates it will be cheaper than current combination therapies. "The other thing is that if it's a cure then you don't have to keep taking it."

Funds for the tests would most likely come from overseas. The United States in particular is under pressure to support clinical trials on vaccines, especially in the developing world.

The World Health Organisation maintains that if present trends continue, more than 40 million people will be affected by HIV by year 2000, 90 percent of them living in parts of Africa and Asia.

There are also some indications that after successfully containing the spread of HIV, new risks are emerging in many Western countries.

News of a possible vaccine also comes amid concern by scientists over the appearance of drug resistant strains of HIV in Australia and overseas.

This threatens to undermine combination drug therapies that have proved so successful in slowing the disease's progress among people with HIV in the West, heightening concern among infectious disease specialists that the world may be entering a new phase in its battle against the disease.

According to some reports submitted during this year's 12th World AIDS Conference in Geneva, super strains of HIV resistant to many of the drugs currently available had been transmitted from person to person.

Comments Kent: "That is another reason why we need to develop vaccines because the virus is very tricky in its ability to develop resistance to drugs available."

There is little formal information on the incidence of drug- resistant strains of HIV. But data from the McFarlane Burnet Centre show that about one-fourth of people with HIV, over the period of six months of testing, will develop a resistance to combination drug therapies. (END/IPS/ap-he/an/cb/98)
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