DESLEY BLANCH : While cows cannot be infected with HIV the scientists learned they can produce HIV antibodies that protect against transmitting the disease. With HIV infection rates on the rise worldwide the hope is to create affordable creams which will prevent sexual infection. The project’s leader is Associate Professor Damian Purcell from the University of Melbourne who explains their notion of using cows in the context of using their milk to defend human cells against HIV.
ASSOCIATE PROFESSOR DAMIAN PURCELL : Cows actually are one of the world’s great systems for producing antibodies and proteins. In fact they’re the most efficient protein production system that we have with milk being a very common commercial product.
And the thing that was also of interest to us is that we’re developing vaccines in a hope to make a prophylactic vaccine that one day will be able to allow humans to raise antibodies and protect themselves against HIV infection. But we wondered whether we could vaccinate cows and that they might in fact see this vaccine that we have made and produce antibodies that would be concentrated at high levels into the milk as a production system.
DESLEY BLANCH : Yes, you injected cows with HIV proteins which doesn’t give the cow HIV, but how does the cow respond to that?
ASSOCIATE PROFESSOR DAMIAN PURCELL : Well, the cow sees the HIV outer proteins in a very special way that in fact humans don’t seem to be able to see. So they make antibodies that have a very powerful mechanism for inhibiting the virus from infecting and this turned out to be a really useful approach because during pregnancy the cows concentrate the antibodies that they make in their blood into the colostrum milk, the first milk, so that the calf can drink that milk normally and develop a rapid immunity. So we harvest some of that colostrum, that first milk, and it’s packed full of these antibodies against HIV that have this unique power at preventing the virus from infecting human cells.
DESLEY BLANCH : You talk about taking it from the first milk, the colostrum, but does that continue any longer than the first initial supply of colostrum?
ASSOCIATE PROFESSOR DAMIAN PURCELL : It does continue but at much, much lower levels. Really, in terms of highest concentrations which we would want to manufacture into a gel or a cream, ultimately for use in for example, women, the highest concentrations are really in the very first delivery of milk, that colostrum milk, which is a special, special form of milk that is packed with immune antibodies that are required, in fact, by the calf for its immunity. Without those, the calf is severely immune deficient in fact.
DESLEY BLANCH : I can think of this when I was a mother myself. They talked about this immunity that the first colostrum gave to your baby. It’s the same for cows obviously. But the key to the success for your research is to make these creams really cheap and easy to produce and you believe that that’s possible?
ASSOCIATE PROFESSOR DAMIAN PURCELL : Well, the beauty of this system is that we can take something that’s actually quite a difficult thing to manufacture which is our current HIV vaccines and we can turn micrograms of a vaccine protein into kilograms of active antibody.
So this is a very effective amplification system in the cow but it also is safe, because while we’ve got years of testing to go to prove that the human version of this vaccine works and is safe, we’re able to very quickly move forward with the cow, where the product is essentially a food product, a product from milk, and a product where we only really need to prove safety for a mucosal delivery, which means, smearing that into a susceptible cavity, like the rectum or the vagina where it can prevent the transmission of virus, so it doesn’t need to be injected or delivered in a complex mechanism like that.
DESLEY BLANCH : So this principle could apply to men as well as to women in a cream?
ASSOCIATE PROFESSOR DAMIAN PURCELL : We’re thinking about the possibility of delivering this for men as well. The advantage in fact is that it might be amenable as an ingestible product for men because normally, our digestible tract produces antibodies and all of the digestion enzymes don’t inactivate antibodies through passage through the gut. So if we can protect the antibodies in their passage through the stomach, the high acid environment, we believe that ultimately we can also deliver these throughout the alimentary canal of humans as well.
DESLEY BLANCH : So how far are you down the track? Have you proven that it works in all of these systems or just part of the systems?
ASSOCIATE PROFESSOR DAMIAN PURCELL : What we’ve done up till now is we’ve produced a small amount of these antibodies from an elite little bunch of cows which has given us enough to prove that these antibodies have remarkable power for killing HIV in the test tube.
So our next step is to take these results into animal studies, into mice that have been bred and genetically-engineered to become susceptible to HIV infection and into monkeys. So those studies are under way at the moment in partnership with other collaborating laboratories and we hope that within a year we should be able to have enough proof that these antibodies work in an animal system.
DESLEY BLANCH : So this is part of turning that milk into a treatment.
ASSOCIATE PROFESSOR DAMIAN PURCELL : Exactly, yes, there are already products on the market developed from cow antibodies. It’s not a concept that’s brand new in medicine; there are antibodies produced in cows, for example, that prevent travellers’ diarrhoea and these antibodies are made in very large scale and already available in pharmacies certainly in Australia and many parts of the world.
So what we’ve done here that’s a unique thing is that instead of having antibodies against travellers’ diarrhoea, these antibodies that we’ve produced are in response to our vaccines that we’re really developing ultimately for human vaccination but we’ve fast tracked those into a vaccination of a cow so that we can deliver those antibodies in a speedy fashion to women in particular, who might need these to protect themselves from HIV infection.
DESLEY BLANCH : This is really been about empowering women to protect themselves against HIV, isn’t it!
ASSOCIATE PROFESSOR DAMIAN PURCELL : Well, that’s the most important medical need I think at the moment, particularly in high risk countries, countries with high prevalence for HIV such as sub-Saharan Africa and perhaps some parts of New Guinea where, really women aren’t empowered to ask their partners to wear a condom which is also a very effective and cheap barrier to prevent HIV infection.
And something else that’s become apparent is there are in fact many communities where women know that they’re infected or they know their partner is infected and they want to actually conceive and have children. So there is a need for cheap methods to allow women to have children yet protect themselves from the risk of infection.
DESLEY BLANCH : But this product won’t help those who are already infected with HIV, will it?
ASSOCIATE PROFESSOR DAMIAN PURCELL : No, that’s right. It won’t prevent somebody from moving towards progression of their HIV disease if they already are infected. Those patients need to take the anti-viral drugs which are now very advanced and can stop the high levels of virus from replicating. So those drugs are really an essential therapy for anyone infected with HIV. This is an adjunct to prevent new infections.
DESLEY BLANCH : Well you said it would be a little while, but how long does the world have to wait for this technology to be available do you think?
ASSOCIATE PROFESSOR DAMIAN PURCELL : Well, this technology really I think is on the fast track, because what it has in its advantage is that the level of safety is much simpler because essentially we’re dealing with something we have a long history with in terms of exposure on our mucosal surfaces, for example, into our mouths or whatever. It’s essentially a food product and something that we can produce using an existing production system that the dairy industry is very efficient at producing milk at high quality and in also purifying these antibodies out of colostrum-type milk.
So we think within three years that we will have a stream of these antibodies available for human use.
DESLEY BLANCH : Damian Purcell is Associate Professor in the Department of Microbiology and Immunology at the University of Melbourne and leads the project that is using cows to produce milk that protects against HIV.