By SIMON COLLINS science reporter
Scientists in Auckland and Seattle have recreated part of the original ancestor of the HIV virus in an attempt to make a vaccine to stop the virus spreading.
Although still in the early stages, the team believes its vaccine has the best chance of any that have been developed so far to contain HIV/Aids, which has killed 28 million people worldwide.
More than one in every three people in Zambia, Zimbabwe and Botswana have been infected by the virus, and the average human life in Botswana has been chopped back from 60 years to the early forties.
Auckland University Professor Allen Rodrigo said the virus was mutating so quickly that any vaccine based on one of the current strains would quickly become ineffective.
The virus changes by about 1 per cent a year - about 4 million times faster than genes in any plant or animal species.
Dr Rodrigo and a colleague, Dr Howard Ross, decided the only way to tackle such a constantly changing prey was to track down the common element in all the varieties of the virus found in the Western world - their original common ancestor.
They figured out the likely structure of that ancestor by collecting the full genetic sequences of all the main existing strains and arranging them in a "tree", with each branch made up of strains with similar genetic sequences.
Then they arranged the branches themselves in groups of similar sequences, leading back ultimately to the original "trunk".
The project required huge computing power to work out the most likely "tree" that could have produced the various current arrangements of the 10,000 basic genetic elements, labelled A, C, G and T, which make up the virus's nine genes and the spaces between them.
Professor Jim Mullins at the University of Washington in Seattle then took the genetic sequence of part of the "trunk" and made all the actual chemical compounds, or proteins, which that sequence would have produced in the original HIV "ancestor".
He injected this artificial HIV virus into rabbit cells, and the cells developed antibodies which fought off the latest natural strains of the virus. "It does seem to protect [against the virus]," Dr Rodrigo said.
"This is very preliminary data. We have a synthetic vaccine of a synthetic virus that appears to create antibodies that can neutralise some of the kinds of HIV.
"I hope it will be broader than the existing vaccines that people are now trialling."
The US National Institutes of Health have funded the project to the tune of US$500,000 ($835,000) a year, and the team is now seeking the institute's support for further laboratory tests and animal trials.
Dr Rodrigo said the team created only part of the original ancestor virus for safety reasons.
"The part that we worked with only has a small genome 2400 nucleotides [genetic elements] long," he said.
"The total virus is only 10,000 nucleotides long, so there was no difficulty getting to the full virus.
"We have taken the step of not doing that because conceivably that virus could be some master virus or some virulent form and it would be a danger to do that.
"But theoretically there is nothing to stop you doing that. Theoretically there is nothing to stop you doing any other organism."
Dr Rodrigo believes the resulting vaccine will also be only partial, not eliminating HIV but weakening it so that people with the virus can live longer and, most importantly, not pass it on when they have children.
"The best strategy would be to immunise everyone with the hope that it would [weaken the virus] in people who get infected and prolong their lifespan," he said.
"The situation is dire in the developing world and that is where we feel the greatest effort needs to be directed."
Back to the beginning for Aids team
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