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The East African : June 2nd 2014
30 The EastAfrican OUTLOOK MAY 31 - JUNE 6, 2014 S CI E N C E Scientists on the verge of a major breakthrough in malaria vaccine Initial tests have shown that it can enhance the ≥odents’ life p≥ospects by double By PAUL REDFERN Special Correspondent S cientists believe they could be on the verge of a major breakthrough in the ongoing battle to find a vaccine for malaria after studying a group of naturally resistant children in Tanzania. The study involving 785 chil- dren in Tanzania found that around six per cent possessed antibodies to a protein that is vital for the malaria parasite to complete its lifecycle within the human body. Initial tests on mice of a new vaccine known as PfSEA-1, which was produced as a result of research and tests into these antibodies, have shown that it can enhance the rodents’ life prospects by double from those who did not receive the vaccine. The vaccine works by trapping malaria parasites inside infected red blood cells so that they cannot emerge to infect other red blood cells. “Most vaccine candidates for malaria have worked by trying to prevent parasites from entering red blood cells,” said one of the key researchers, Prof Jonathan Kurtis, an immunologist at Brown University in the US, whose findings were published in the journal Science. “We’ve taken a different ap- proach. We’re sort of trapping the parasite in the burning 50PC DECREASE The parasite that causes the disease has long defied efforts to develop a vaccine. Picture: File house. We have found a way to block it from leaving the cell once it has entered. If it’s trapped in the red blood cells, it can’t go anywhere and it can’t do any further damage.” In 2012, about 200 million We have found a way to block the parasite from leaving the cell once it has entered.” Prof Jonathan Kurtis, Brown University people developed malaria after being bitten by the insect; some 600,000 died, 90 per cent of them in Africa and most of them children under five. The parasite that causes the disease has long defied efforts to develop a vaccine. When an infected female mos- quito bites a human, the microbe enters the victim’s bloodstream and makes for the liver, where it multiplies by the tens of thousands. From the liver, it goes back into the bloodstream, infecting and multiplying inside red blood cells. Eventually, it bursts out again, in a form called a schizont — infecting more blood cells and re-entering the bloodstream to infect the next hungry mosquito, in whose body it goes through a cycle even more complex. The bursting-out stage, which occurs about every 24 hours, produces the fever, chills, and aches that make the patient so miserable. “It’s like the worst flu you’ve ever had,” Prof Kurtis says. Until PfSEA-1, the most prom- ising vaccine was RTS,S. In a phase III clinical trial in 2012, this vaccine led to a 50 per cent decrease in the number of severe symptoms and blood levels of the parasite in children aged five months to 17 months. The research started because of evidence that even in malariastricken areas, some people have only mild symptoms of malaria or none at all, and they show only minimal levels of the parasite in blood samples. To find out why, Kurtis and colleagues compared the blood of people who are resistant to those who are not. The team examined a group of children in Tanzania who had been studied since shortly before their birth. In a study of about 450 chil- dren, about six per cent had antibodies to the protein; none of these children developed severe In a phase III clinical trial in 2012, PfSEA-1 led to a 50 per cent decrease in the number of severe symptoms and blood levels of the parasite in children aged five months to 17 months. The research started because of evidence that even in malaria-stricken areas, some people have only mild symptoms of malaria or none at all, and they show only minimal levels of the parasite in blood samples. malaria (defined as difficulty breathing, convulsions, high fever, low blood sugar, or severe anaemia). Initially, researchers took blood samples of 23 two-yearold children (the age at which resistance to malaria typically develops); 12 were resistant to the disease, as evidenced by the small number of parasites in their blood. To see whether these 12 had unique, protective antibodies, the team checked the blood plasma — the clear, antibodycontaining fluid from all chil- dren — against a set of Plasmodium genes known to be turned on when the parasite infects the blood. When the researchers subse- quently checked blood samples drawn from a group of teenagers in an unrelated study in Kenya, they found that blood containing the antibody had only about half as many parasites as did samples without it. Finally, Prof Kurtis and his colleagues used the antibody to develop a vaccine candidate that they gave to mice infected with a particularly lethal form of malaria. The vaccinated animals lived almost twice as long, The team, which published its results in the journal Science, said trials in primates and humans were now needed to fully assess the vaccine’s promise. “I think there’s fairly compel- ling evidence that this is a bona fide vaccine candidate,” Professor Kurtis said. “However, it’s an incredibly difficult parasite to attack. It’s had millions of years of evolution to co-opt and adapt to our immune responses — it really is a formidable enemy.” This latest study is one of many avenues being explored in the race to find a malaria vaccine. The most advanced remains the RTS,S vaccine, developed by GlaxoSmithKline. The drug company is seeking regulatory approval after Phase III clinical trials showed that the drug almost halved the number of malaria cases in young children and reduced by about 25 per cent the number of malaria cases in infants. Commenting on the research, Dr Ashley Birkett, director of the PATH Malaria Vaccine Initiative, said: “The identification of new targets on malaria parasites to support malaria vaccine development is a necessary and important endeavour. “While these initial results are promising with respect to prevention of severe malaria, a lot more data will be needed before this could be considered a leading vaccine approach — either alone or in combination with other antigens.” Kenya tu≥ns to two-dose ‘Rota≥ix’ to combat kille≥ dia≥≥hoea vi≥us By CHRISTABEL LIGAMI Special Correspondent KENYA WILL introduce a rotavirus vaccine – Rotarix – for newborn children in July to cut the number of diarrhoea cases and deaths resulting from the virus by half. The vaccine will target 1.4 mil- lion children under one year of age and will be given for free in both public and private hospitals. “The Rotarix vaccine will be given in two doses. The first dose will be given alongside the pentavalent vaccine which combines DPT/HepB/Hib 3 vaccine at week six after the baby is born,” said Collins Tabu, an epidemiologist in charge of policy direction on immu- nisation at the Ministry of Health. The second dose will be given in the 10th week or before the child is eight months old. The vaccine rollout is part of Kenya’s Action Plan for Pneumonia and Diarrhoea Prevention. Kenya joins Rwanda, Tanzania, Malawi and Ethiopia, which have also introduced the vaccine. Uganda plans to roll out the rotavirus vaccines next year while plans are still under way for Burundi. There are two orally adminis- tered rotavirus vaccines available and pre-qualified by the WHO: Rotarix and RotaTeq, found to prevent approximately 75 per cent of cases of rotavirus infection and 98 per cent of severe cases. Tanzania introduced a similar vaccine last year while Rwanda is using RotaTeq given as a three dose vaccine at six weeks, 10 weeks and 14 weeks. “Kenya chose the two doses be- cause the three-dose vaccine is almost two times the cost of the two dose vaccine and it’s not bulky to store,” he said. The Ministry of health, in part- nership with the Global Alliance for Vaccines and Immunisation (GAVI), $11.1m United Nations Children’s Fund (Unicef) and the World Health Organisation, has allocated $3.3 million for the second half of the year and $7.8 million for next year. The government has already procured one million vaccines for this year but has budgeted to have about three million doses for 2015. “Rotarix vaccines cost $20 per dose but GAVI has subsidised it to $3 per dose to be supplied by Glaxo SmithKline,” noted Dr Tabu. “No health facility will be re- Budget for the new vaccine, to cover half of 2014 and all of 2015 quired to charge for the vaccine but private hospitals will be allowed to charge a nominal fee of $1.1,” Dr Tabu said Diarrhoea is one of the world’s leading killers of children, and ro- tavirus is the most common cause of the deadly severe diarrhoea. According to the World Health Organisation, rotavirus is the leading cause of severe diarrhoea in children under five worldwide, killing more than 450,000 children each year and hospitalising millions more, second only to pneumonia, which kills around 1.2 million. More than 2,200 children die each day from rotavirus infection. Almost all of them are in developing countries. In Kenya, it is estimated that di- arrhoea kills about 5,000 children every year and up to 14 children in the country die from the disease every day.
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