Malaria vax passes hurdle

A malaria vaccine for infants and children -- the group most vulnerable to the disease -- may be heading to phase III trials, according to authors of two studies published online today (Dec. 8) in the New England Journal of Medicine. "The research results show we are one important step closer to malaria joining diseases like small pox or polio that have been either controlled or eliminated by vaccine," said Christian Loucq, director of linkurl:PATH Malaria Vaccine Initiative;http://path.org/ during a press conference this morning. The search for a malaria vaccine has been stymied by the complex nature of the malaria parasite, its ability to evade the immune system, and constant exposure to malaria in regions of Africa, said Joe Cohen, Vice President of R&D for Vaccines for Emerging Diseases & HIV at GlaxoSmithKline(GSK). Cohen co-invented the vaccine, RTS,S/AS, in 1987, but it took more than a decade to make the vaccine most effective through adjuvant development. In 2001, GSK teamed up with the PATH Malaria Vaccine Initiative, established through a grant from the Bill and Melinda Gates Foundation, to push forward malaria vaccine efforts, focusing on RTS,S/AS. RTS,S/AS triggers an immune response to attack Plasmodium falciparum, the most deadly species of the malaria parasite, once it enters the bloodstream. RTS,S/AS fuses the surface protein that helps the parasite invade human liver cells, with a with hepatitis B virus antigen, preventing it from multiplying and maturing. The researchers developed two forms of adjuvants to help to train the immune system to recognize the surface of the malaria parasite, and to stimulate the immune system to attack the cells. Early clinical studies in 2004 and 2005 using one form of adjuvant, AS02, found that the vaccine slashed infection rates by 35 % in children ages one to four. A phase I/II study last year provided preliminary evidence that the vaccine could also work in infants, reducing clinical rates of malaria by 65 % in three months from follow-up. The studies reported today reaffirm the previous findings that RTS,S/AS can offer protection against malaria for infants and young children, paving the way for phase III trials. In one of studies published today researchers tested whether the vaccine would interfere with the protective properties of other vaccines, namely those for Diptheria, Tetanus, Pertussis and haemophilus influenzae B as well as oral polio vaccine in 340 infants under 12 months. Around 65% of infants who received RTS, S/AS vaccine, also made with the AS02 adjuvant, were protected against first malaria infection six months after receiving the third dose of vaccine. The second trial tested the vaccine with a different adjuvant, AS01, in 894 children between the ages of 5-17 months from Kenya and Tanzania in a double-blind randomized clinical trial to test the safety and efficacy of the RTS, S/AS with a second adjuvant system, AS01. Recent studies suggested AS01 to be more immunogenic than AS02. Children received either three doses of RTS, S/AS01 or control, rabies vaccine; the vaccine appeared to reduce clinical malaria episodes by 53 % for up to eight months. Pending regulatory approvals, the researchers hope to push the RTS,S/AS01 into phase III trials in infants and children in early 2009.**__Related stories:__***linkurl: Whole-organism malaria vaccine?;http://www.the-scientist.com/article/display/22525/ [6th December 2004]*linkurl:Malaria vaccines get real;http://www.the-scientist.com/article/display/22453/ [15th October 2004]*linkurl:Malaria drug muddle;http://www.the-scientist.com/article/display/20867/ [15th November 2002]

Malaria vax passes hurdle

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