Doctors modify yoghurt bacteria to combat HIV infection
PM - Wednesday, 18 January , 2006 18:26:00
Reporter: Toni Hassan
HAMISH FITZSIMMONS: Doctors in the United States have modified a friendly bacteria found in humans and yoghurt, and discovered, that at least under laboratory conditions, the bacteria can neutralise the deadly HIV virus.
The results published today in the international journal Nature, pave the way for clinical trials this year using monkeys.
Scientists envisage the modified bacteria may one day be incorporated into yoghurts or be taken in tablet form to deliver an HIV blocking drug straight to a woman's vagina.
A single dose could potentially provide a week's worth of protection from HIV infection, as Toni Hassan reports.
TONI HASSAN: What makes this development exciting is how it differs from the approach of existing Human Immuno-deficiency virus drugs.
Existing drugs inhibit proteins in human cells that HIV requires in order to make copies of itself. The existing drugs limit the damage once the HIV is already in human cells. But there are no drugs to prevent the entry of the AIDS virus entering cells after sexual intercourse.
BHARAT RAMRATNAM: Once HIV enters, the game is pretty much over. The person becomes infected. So this is very much a strategy to prevent infection.
TONI HASSAN: Dr Bharat Ramratnam is an HIV specialist at Brown Medical School on Rhode Island. He's one of a team in the US that has genetically modified a good bug found in yoghurt and human stomachs - lactococcus lactic - to release a protein that stops HIV infection.
BHARAT RAMRATNAM: Yoghurt has been used for a bazillion years as a therapeutic. We're just sort of changing the mould a little and saying that let's make the yoghurt better and let's make it a drug machine.
And the thing that's probably not obvious to most people is that this "bug" already resides in us. Lactobacilli… our gastro-intestinal tract is full of bacteria and these bacteria live happily. They don't attack us. They in most cases don't cause disease. They actually probably have some health effects.
So we chose one of these bugs called Lactobacillus and we changed its genetic composition so that in addition to all the things that the Lactobacillus does, it also secretes a protein and that protein happens to be anti-viral or anti-HIV in activity.
TONI HASSAN: The lab results published today are of course just that and will now be tested on macaque monkeys.
The modified bacteria will be placed in what's called mucosal surfaces in vaginas and rectums of monkeys to test if the protein can in fact target and block HIV in infected semen.
Dr Ramaratnam again.
BHARAT RAMRATNAM: The principle is there. I think the concept is fairly scientifically sound, but the entire question which can only be answered through the animal studies is how much drug is produced by these bacteria and how long they last?
TONI HASSAN: How much of the bug would you initially need? I mean, you know, are we're talking about the equivalent of truckloads of yoghurt?
BHARAT RAMRATNAM: No, that's the wonderful things about this. The bacteria obviously multiply and so what we're going to do in our macaque studies is to dose the animals differently.
We're able to then figure out how many of these bacteria are say, still present at six hours, 12 hours, 24 hours, a week. And those data will tell us whether or not this is indeed a strategy that's worth pursuing.
TONI HASSAN: The modified bacteria could be also given in capsule form, with the active bacteria lining a woman's vagina to protect her from infection. Another application is a gel that would need to be smeared on the mucosal surface before sex. Given that HIV AIDS is its mostly deadly in the developing world, the new therapeutic approach could be a profound answer for people at risk.
HAMISH FITZSIMMONS: Toni Hassan reporting.
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