Malaria vaccine gets a boostVaccine
double-act success in humans raises TB and HIV hopes.
By injecting human volunteers with one scrap of DNA and then another in a poxvirus, researchers have tricked their immune systems into producing enough cells to attack malaria. It's a major step towards an effective vaccine for the disease. Similar drug double-acts are also being tested against HIV, tuberculosis, and some cancers. , They are called heterologous prime-boost vaccinations. "This is the first time [such a vaccine] has been shown to work in humans," says Adrian Hill of the University of Oxford, UK, who led the study. Success against malaria raises hope for other diseases. The results come from the very earliest stage of safety testing. Further studies are now beginning in Africa where malaria kills some 3000 children each day. Hill's group is also testing the prime boost strategy against tuberculosis. It remains to be seen how effective the prime-boost vaccine is against real malaria infection, cautions DNA vaccine pioneer Stephen Hoffman at Celera Genomics in Rockville Maryland. He estimates it will reduce the likelihood of infection by 80% or so. Ultimately, malaria vaccines may consist of a mixture of prime-boost and other technologies. Two for T Normal vaccines encourage part of the immune system to produce antibodies - small molecules that smother free-living bugs and instruct other immune cells to devour them. But the pathogens that cause malaria, AIDS and tuberculosis dwell inside cells, safe from antibodies and conventional vaccines. Being malfunctioning human cells, cancer tumours are essentially the same. Only T cells - the immune system's other arm - can destroy such defective cells. The body produces tiny numbers of T cells when immunized with harmless viruses containing short fragments of the DNA of the disease-causing organism. "It was never even close to optimal," says DNA-vaccine pioneer Stephen Hoffman at Celera Genomics in Rockville Maryland. The prime-boost approach gets around this. Like giving a scent to ravenous hounds, initial vaccination with DNA from the malaria parasite Plasmodium falciparum followed by a dose of a harmless virus containing different malaria DNA, produces five to ten times more anti-malaria T cells. "We've achieved responses the likes of which have never been seen," says Hill. "We'd be quite happy with that outcome," says immunologist Harriet Robinson who is testing prime-boost vaccines against HIV at Emory University in Atlanta, Georgia. Similar numbers of desired T cells produced would control the HIV virus, she says. |
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© Nature News Service / Macmillan Magazines Ltd 2003 |
