The Malaysian Insider :: Features
The Malaysian Insider :: Features |
| New vaccine approach imprisons malaria parasite in blood cells Posted: 22 May 2014 06:52 PM PDT The researchers said yesterday an experimental vaccine based on this idea protected mice in five trials and will be tested on lab monkeys beginning in the next four to six weeks. Dr Jonathan Kurtis, director of Rhode Island Hospital's Center for International Health Research, said if the monkey trials go well, a so-called Phase I clinical trial testing the vaccine in a small group of people could begin within a year and a half. Using blood samples and epidemiological data collected from hundreds of children in Tanzania, where malaria is endemic, by Drs Patrick Duffy and Michal Fried of the US National Institutes of Health, the researchers pinpointed a protein, dubbed PfSEA-1, that the parasites need in order to escape from inside red blood cells they infect as they cause malaria. The researchers then found that antibodies sent by the body's immune system to take action against this protein managed to trap the parasites inside the red blood cells, blocking the progression of the disease. Scientists have struggled for years to create an effective vaccine against malaria, a mosquito-borne disease that the UN World Health Organization estimates kills 627,000 people a year, mostly children in sub-Saharan Africa. "It's profoundly important to develop an effective malaria vaccine," said Dr Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases, calling the study "a novel and different type of an approach toward a vaccine". "Since the malaria parasite has such a complex replication cycle, there are multiple points in that replication cycle that are vulnerable to interference by an antibody or some response that can be induced by a vaccine," Fauci told Reuters. Microscopic malaria parasites are carried in the saliva of female mosquitoes and enter a person's bloodstream through the insect's bite. The parasites pass through the liver and infect red blood cells. They replicate wildly in these cells and cause them to rupture, flooding the body with more and more parasites. Two existing approaches to vaccine development have sought to block the parasites from entering the liver or red blood cells. The new approach instead tries to bottle them up inside the red blood cells – or, as Kurtis put it, "trap them inside a burning house". If the parasites remain trapped, they can be harmlessly gobbled up in the spleen by immune system cells called macrophages, Kurtis said. The researchers developed a vaccine that targeted PfSEA-1 and tried it on mice. In five experiments, vaccinated mice that were exposed to malaria had parasite levels four times lower than unvaccinated mice and survived twice as long afterward. The researchers then looked at blood samples from some of the Tanzanian children. Roughly one in 20 had naturally occurring levels of the antibodies that target PfSEA-1, and among these children there were no cases of severe malaria. The researchers also examined blood samples from 138 boys and men from a malaria-endemic area of Kenya. Those with detectable levels of naturally occurring antibodies to PfSEA-1 had 50% lower parasite levels than those who did not. Kurtis expressed hope about the prospects of a vaccine targeting this protein, but said the best future vaccine likely would combine this approach with others to attack the parasite on several fronts. He noted that there is currently no licensed vaccine for human parasitic infection. The study was published in the journal Science. – Reuters, May 23, 2014. |
| Little kiwi, huge extinct elephant bird were birds of a feather Posted: 22 May 2014 05:52 PM PDT Scientists yesterday identified the closest relative of New Zealand's famed kiwi, a shy chicken-sized flightless bird, as the elephant bird of Madagascar, a flightless giant that was 3 metres tall and went extinct a few centuries ago. The surprising findings, based on DNA extracted from the bones of two elephant bird species, force a re-evaluation of the ancestry of the group of flightless birds called ratites that reside in the world's southern continents, they added. The group, which boasts some of the world's largest birds, includes emus and cassowaries in Australia, rheas in South America, ostriches in Africa and kiwis in New Zealand. Ratites that have disappeared in recent centuries include the moa of New Zealand and the elephant bird. The researchers compared elephant bird DNA to the other birds and saw a close genetic link to the kiwi despite obvious differences in size, body shape and lifestyle – and the fact they lived about 11,500km apart. The largest elephant bird species weighed more than 275kg. Kiwis reach around 5kg. There has been a lively debate among bird experts about the origins of the ratites and how they came to live where they do. The world's first birds arose about 150 million years ago. Over the eons, some species lost the ability to fly but became large and formidable. Many scientists have thought the ancestors of today's ratites were already flightless when they were isolated in their current locations by the separation and drift of the southern continents over the past 130 million years. The new findings indicate the continents had already separated before ratite ancestors showed up, meaning the forebears of these flightless birds reached their current homes by flying. "It does seem a little ironic, but in fact it's the simplest explanation for the facts we observe," said Kieren Mitchell of the University of Adelaide's Australian Centre for Ancient DNA. Alan Cooper of University of Adelaide said the new data suggest that flying ratite ancestors dispersed around the world right after the mass extinction killed the dinosaurs 65 million years ago and before mammals became dominant. Mitchell said the researchers had expected to find that the elephant bird and ostrich were the most ancient lineages of ratite because Africa and Madagascar were the first landmasses to separate from what had been an ancient super-continent. Instead, they found that elephant birds and kiwis arose from a common ancestor around 50 million years ago after even New Zealand had become isolated. Previous research had suggested Australia's ratites as the kiwi's closest relatives. "If the common ancestor of kiwi and elephant birds lived on Madagascar, then kiwis must have flown to New Zealand. If this ancestor lived on New Zealand, then elephant birds must have flown to Madagascar," Mitchell said. "Or perhaps the common ancestor of both elephant birds and kiwis flew to their final locations from somewhere else entirely." The study was published in the journal Science. – Reuters, May 23, 2014. |
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