Vivax malaria may be evolving around natural defense ( 2.5 billion people worldwide are at risk )

Contact: Kevin Mayhood kevin.mayhood@case.edu 216-368-4442 Case Western Reserve University

3 gene mutations appear to be invasion mechanisms

             IMAGE:   Plasmodium vivax has traditionally infected red blood cells of hosts in the Duffy positive blood group but Duffy negative people have been resistant.

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CLEVELAND—Researchers at Case Western Reserve University and Cleveland Clinic Lerner Research Institute have discovered recent genetic mutations in a parasite that causes over 100 million cases of malaria annually—changes that may render tens of millions of Africans who had been considered resistant, susceptible to infection.

Peter A. Zimmerman, professor of international health, biology and genetics at the Case Western Reserve School of Medicine, and David Serre, a scientific staff member of the Genomic Medicine Institute at Lerner and assistant professor of genomics at Case Western Reserve, report their findings at the American Society of Tropical Medicine and Hygiene annual meeting today (11/15).

They and fellow researchers describe the changes in the Plasmodium vivax genome in papers scheduled to be published in the journal PLoS Neglected Tropical Disease on Nov. 21 and Dec. 5.

To learn the functions of the mutations, and whether the parasite is evolving around a natural defense, Zimmerman and Serre have received a $3.5 million grant from the National Institute of Allergy and Infectious Disease at the National Institutes of Health. They will begin their field study in early 2014.

“We’ve found a duplication of a gene known to enable the parasite to infect red blood cells and two possible additional components to a more complex red cell invasion mechanism,” Zimmerman said.

Researchers have long thought that P. vivax infects a person one way: a protein on the parasite, called the Duffy binding protein, latches onto a Duffy receptor on the surface of the person’s red blood cell and works itself through the membrane. People who lack the receptor are called Duffy negative and are resistant to infection.

But, during the last decade, reports of cases of Duffy negative patients with P. vivax infections have been on the rise in several parts of the world.

P. vivax has been called benign malaria because it is less lethal than malaria caused by Plasmodium falciparum. But unlike its cousin, P. vivax can hide from treatment in a host’s liver and repeatedly emerge to cause relapses of debilitating headaches, nausea and fever. This chronic malaria often triggers a cycle of poverty for sufferers left unable to work for long periods. By weakening the immune system, the disease contributes to death.

The Malaria Atlas Project estimates 2.5 billion people worldwide are at risk for P. vivax malaria.

P. vivax does not grow well in the laboratory, so to try to understand how the parasite lives and operates, the researchers gathered samples from malaria patients and focused on its genome.

They found a duplication of the Duffy binding protein in half of 189 P. vivax infection samples taken in Madagascar.  Other researchers’ prior efforts to sequence the P. vivax genome missed the duplication but all indications are it’s a recent change, Serre said.

“The way we date duplications is to compare differences between the two parts: the more different they are, the older they are,” he explained. “They accumulate mutations. The two parts of this duplication have, among 8,000 base pairs, only one difference.”

Often a second copy of a gene enables an organism to outmaneuver a defense, Serre continued. “Instead of making a supergene, a duplication is simpler for nature.”

The researchers suspect the mutation is spreading from Madagascar through travelers. They found the duplication in less than 10 percent of samples from Cambodia and Sudan.

The new components found on the P. vivax genome are two proteins that closely resemble binding proteins used by related malaria parasites to enter immature and mature red blood cells. Both were present in samples from Cambodia, Brazil, Mauritania and North Korea.

The new proteins were absent in a 2008 sequencing of P. vivax, which is used as a reference genome, suggesting the developments are recent.

“Binding proteins and receptors are locks and keys,” Zimmerman said. “If the parasite has one key and there’s one lock, you may be able to block that. But if it has more keys and there are more locks, there are multiple ways in.”

The researchers say the duplication may be a cause of the growing infections among Duffy negative people, but it’s too early to tell.

Zimmerman, Serre and colleagues aim to find the answer with the newly-funded research project. They’ll begin by studying blood samples taken from 1,500 patients at each of two locations in Madagascar.

They and colleagues have great concern that a loss of resistance to P. vivax infection will now enable the parasite to travel the 250 miles across the Mozambique Channel to Africa. There, falciparum malaria is wrecking havoc on a population that has for the most part lived P. vivax-free. In some regions of the continent, 100 percent of the population is Duffy negative.

The researchers will conduct similar studies on P. vivax carrying the new proteins, in samples taken from Asia, Africa and South America.

In addition to studying patients, they plan to study the mutated parasites in the lab. Parasites that live a day or two could have enough time to invade new blood cells, but not many. Brian Grimberg, assistant professor of international health at the Case Western Reserve School of Medicine, is developing a scanning process that will enable the team to look through millions of red blood cells in a few minutes and spot newly infected cells. They will test the parasites in Duffy negative and Duffy positive red cells.

Zimmerman and Serre believe the work could help lead to a vaccine—that’s the overall goal. The mechanisms P. vivax uses to attach and enter a cell could be targets.

 

No idle chatter: Study finds malaria parasites ‘talk’ to each other – It Changes everything

Contact: Liz Williams williams@wehi.edu.au 61-405-279-095 Walter and Eliza Hall Institute

Melbourne scientists have made the surprise discovery that malaria parasites can ‘talk’ to each other – a social behaviour to ensure the parasite’s survival and improve its chances of being transmitted to other humans.

The finding could provide a niche for developing antimalarial drugs and vaccines that prevent or treat the disease by cutting these communication networks.

Professor Alan Cowman, Dr Neta Regev-Rudzki, Dr Danny Wilson and colleagues from the Walter and Eliza Hall Institute in collaboration with Professor Andrew Hill from the University of Melbourne’s Bio21 Institute and Department of Biochemistry and Molecular Biology showed that malaria parasites are able to send out messages to communicate with other malaria parasites in the body. The study was published today in the journal Cell.

Professor Cowman said the researchers were shocked to discover that malaria parasites work in unison to enhance ‘activation’ into sexually mature forms that can be picked up by mosquitoes, which are the carriers of this deadly disease.

“When Neta showed me the data, I was absolutely amazed, I couldn’t believe it,” Professor Cowman said. “We repeated the experiments many times in many different ways before I really started to believe that these parasites were signalling to each other and communicating. But we came to appreciate why the malaria parasite really needs this mechanism – it needs to know how many other parasites are in the human to sense when is the right time to activate into sexual forms that give it the best chance of being transmitted back to the mosquito.”

Malaria kills about 700,000 people a year, mostly children aged under five and pregnant women. Every year, hundreds of millions of people are infected with the malaria parasite, Plasmodium, which is transmitted through mosquito bites. It is estimated that half the world’s population is at risk of contracting malaria, with the disease being concentrated in tropical and subtropical regions including many of Australia’s near neighbours.

Dr Regev-Rudzki said the malaria parasites inside red blood cells communicate by sending packages of DNA to each other during the blood stage of infection. “We showed that the parasites inside infected red blood cells can send little packets of information from one parasite to another, particularly in response to stress,” she said.

The communication network is a social behaviour that has evolved to signal when the parasites should complete their lifecycle and be transmitted back to a mosquito, Dr Regev-Rudzki said. “Once they receive this information, they change their fate – the signals tell the parasites to become sexual forms, which are the forms of the malaria parasite that can live and replicate in the mosquito, ensuring the parasites survives and is transmitted to another human.”

Professor Cowman said he hopes to see the discovery pave the way to new antimalarial drugs or vaccines for preventing malaria. “This discovery has fundamentally changed our view of the malaria parasite and is a big step in understanding how the malaria parasite survives and is transmitted,” he said. “The next step is to identify the molecules involved in this signalling process, and ways that we could block these communication networks to block the transmission of malaria from the human to the mosquito. That would be the ultimate goal.”

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This project was supported by the National Health and Medical Research Council of Australia, Howard Hughes Medical Research Institute and the Victorian Government.

No Antibodies, No Problem

 

 

Researchers Identify How Mosquito Immune System Attacks Specific Infections

 

Researchers at the Johns Hopkins Bloomberg School of Public Health have determined a new mechanism by which the mosquitoes’ immune system can respond with specificity to infections with various pathogens, including the parasite that causes malaria in humans, using one single gene. Unlike humans and other animals, insects do not make antibodies to target specific infections. According to the Johns Hopkins researchers, mosquitoes use a mechanism known as alternative splicing to arrange different combinations of binding domains, encoded by the same AgDscam gene, into protein repertoires that are specific for different invading pathogens. The researchers’ findings were published October 18 in the journal Cell Host & Microbe and could lead to new ways to prevent the spread of a variety of mosquito born illnesses.

 

Mosquitoes and other insects use their primitive innate immune systems to successfully fight infections with a broad spectrum of viruses, bacteria, fungi and parasites, despite the lack of antibodies that are part of the more sophisticated human immune system. The effectiveness of the human immune system is to a large degree based on the ability to produce an enormous variety of antibodies containing different immunoglobulin domains that can specifically tag and label a pathogen for destruction. This great variety of pathogen-binding antibodies is achieved by combining different immunoglobulin gene segments and further mutate them through mechanisms called somatic recombination and hypermutation. While mosquitoes also have genes encoding immunoglobulin domains, they lack these specific mechanisms to achieve pathogen recognition diversity.

 

The Johns Hopkins researchers discovered a different way by which mosquitoes can combine immunoglobulin domains of a single gene called AgDscam (Anopheles gambiae Down Syndrome Cell Adhesion Molecule) to produce a variety of pathogen-binding proteins. The AgDscam gene is subjected to a mechanism called alternative splicing that combines different immunoglobulin domains into mature AgDscam proteins, depending on which pathogen has infected the mosquito. The researchers showed that this alternative splicing is guided by the immune signal transducing pathways (analogous to electrical circuits) that they previously demonstrated to activate defenses against different malaria parasites and other pathogens. While alternative splicing of the AgDscam gene does not nearly achieve the degree of pathogen recognition diversity of human antibodies, it does nevertheless vastly increase the variety of pathogen binding molecules.

 

“Using antibodies to fight infection is like fishing with a harpoon—it’s very targeted. The mosquito’s innate immune system is more like fishing with a net—it catches a bit of everything,” explained George Dimopoulos, PhD, senior investigator of the study and professor with the Johns Hopkins Malaria Research Institute. “However, we discovered that immune pathway-guided alternative splicing of the AgDscam gene renders the mosquito’s immune net, so to speak, more specific than previously suspected. The mosquito’s immune system can come up with approximately 32,000 AgDscam protein combinations to target infections with greater specificity.”

 

Dimopoulos and his group are developing a malaria control strategy based on mosquitoes that have been genetically modified to possess an enhanced immune defense against the malaria parasite Plasmodium. One obstacle to this approach is the great variety of Plasmodium strains that may interact somewhat differently with the mosquito’s immune system.

 

“Some of these strains may not be detected by the engineered immune system proteins that mediate their killing. Our new discovery may provide the means to create genetically modified mosquitoes that can target a broader variety of parasite strains, like casting a net rather than shooting with a harpoon,” said Dimopoulos.

 

Malaria kills more than 800,000 people worldwide each year. Many are children.

 

“Anopheles NF-kB –Regulated Splicing Factors Direct Pathogen-Specific Repertoires of the Hypervariable Pattern Recognition Receptor AgDscam” was written by Yuemei Dong, Chris M. Cirimotich, Andrew Pike, Ramesh Chandra and George Dimopoulos.

 

The research was supported by grants from the National Institutes of Health/National Institute of Allergy and Infectious Disease, the Calvin A. and Helen H. Lang Fellowship, and the Johns Hopkins Malaria Research Institute.

 

Media contact: Tim Parsons, director of Public Affairs, at 410-955-7619 or tmparson@jhsph.edu.

 

 

 

 

Chloroquine makes comeback to combat malaria

global health

Malaria-drug monitoring over the past 30 years has shown that malaria parasites develop resistance to medicine, and the first signs of resistance to the newest drugs have just been observed. At the same time, resistance monitoring at the University of Copenhagen shows that the previously efficacious drug chloroquine is once again beginning to work against malaria. In time that will ensure cheaper treatment for the world’s poor.

Child being tested for malaria in Senegal

Scientists and healthcare personnel the world over fear that the malaria parasite will develop resistance to the current frontline treatment against malaria, Artemisinin-based Combination Therapies (ACTs). Therefore, it is especially good news that resistance monitoring at the University of Copenhagen shows that in several African countries, malaria parasites are succumbing to the formerly used drug chloroquine. The results have just been published in the American Journal of Tropical Medicine and Hygiene.

“70% of the malaria parasites we found in Senegal are reacting once again to chloroquine. This is a trend we have also seen in Tanzania and Mozambique, and which other researchers have shown in Malawi. Our choice of drugs against malaria is limited and related, so when the malaria parasite once again reacts to a substance, it influences several treatment methods,” explains Michael Alifrangis, associate professor at the Center for Medical Parasitology at the University of Copenhagen. He and Magatte Ndiaye, PhD student at Université Cheikh Anta Diop in Senegal, are keeping an eye on the malaria parasite’s sensitivity to drugs by analyzing the parasites’ DNA.

Each well on this plate contains malaria parasite DNA from one patient. The orange wells indicate that the patient is infected with malaria parasites sensitive to chloroquine. This plate shows 88 patients from Senegal 2011.

Cheaper treatment for the poor in Africa

If healthcare personnel in developing countries can begin using chloroquine again, it will open up some promising perspectives. It will be possible to protect the currently used medicine and delay the reappearance of resistance, and it will also give a large group of patients access to cheaper treatment.

“Chloroquine costs only 25 US cents for a four-day cure, while the current and corresponding ACTs cost two dollars. Chloroquine was a fantastic malaria drug that lasted for 50 years. However, it was misused for malaria prevention and ordinary fever, and even mixed with cooking salt, so it can come as no surprise that the malaria parasite became resistant to the active ingredient,” explains Professor Ib Bygbjerg, M.D. He also points out that reuse will require correct drug use and the training of healthcare personnel to make more accurate diagnoses.

Correct use of drugs paralyzes the development of resistance

According to Professor Ib Bygbjerg, three factors determine the extent to which a malaria drug will work: 1) the size of the dose, 2) how sensitive the parasite is to the drug, and 3) the extent to which the patient has developed a natural immunity to malaria.

Chloroquine drug

“In the near future, chloroquine and other malaria drugs not currently on the market will presumably be able to be used again, if we use them correctly. This means that the drug must be given in combination with other medicine and only to patients who have already developed a certain immunity to malaria and are therefore not at high risk. At the same time, we must reserve ACTs for the most exposed non-immune groups such as children. Chloroquine is one of the few drugs that can be given to pregnant women at the beginning of their pregnancy,” points out Ib Bygbjerg, adding that the patient can be treated with a high dose for a short period, another benefit.

In order to maintain the positive development with chloroquine, it is therefore also important that – with the exception of pregnant women – travellers to malaria areas refrain from taking the drug. Otherwise the parasites will quickly develop resistance once again

The malaria species rampant in the Asia-Pacific region has been a significant driver of evolution of the human genome, a new study has shown.

‘Benign’ Malaria Key Driver of Human Evolution in Asia-Pacific

ScienceDaily (Sep. 4, 2012)

Professor Ivo Mueller led a study that showed the malaria species rampant in the Asia-Pacific region has been a significant driver of evolution of the human genome

An international team of researchers has shown that Plasmodium vivax malaria, the most prevalent malaria species in the Asia-Pacific, is a significant cause of genetic evolution that provides protection against malaria.

Their finding challenges the widely-accepted theory that Plasmodium falciparum, which causes the most lethal form of malaria, is the only malaria parasite capable of driving genome evolution in humans. The study was published today in the journal PLoS Medicine.

Professor Ivo Mueller from the Walter and Eliza Hall Institute and Barcelona Centre for International Health Research (CRESIB) led the study, with colleagues from the Papua New Guinea Institute of Medical Research, Centre of Global Health and Diseases, US, and the University of Western Australia.

Malaria is a devastating parasitic disease that kills up to one million people a year. It is a major cause of poverty and a barrier to economic development. Approximately half of the world’s population is at risk of malaria infection.

“Humans and malaria parasites have been co-evolving for thousands of years,” Professor Mueller said. “Malaria has been a major force in the evolution of the human genome, with gene mutations that provide humans with some protection against the disease being preserved through natural selection because they aid in survival.”

Professor Mueller said the study has challenged the perception that P. falciparum malaria is the only malaria species that affects human genome evolution. “It has long been assumed that Plasmodium falciparum, the species that causes the most severe disease and most deaths from malaria, is the most important driver of this gene selection in humans,” Professor Mueller said. “Our results suggest that P. vivax malaria, though until recently widely considered to be a ‘benign’ form of malaria, actually causes severe enough disease to provide evolutionary selection pressures in the Asia-Pacific.”

Professor Mueller said that the research team was interested in whether P. vivax malaria might be the cause of the unusually high rates of Southeast Asian ovalocytosis (SAO), a hereditary red blood cell disorder, in the Asia-Pacific region. “SAO occurs in approximately 10 to 15 per cent of the population in parts of the South West Pacific and is caused by a hereditary mutation in a single copy of a gene that makes a red blood cell membrane protein. This is almost an absurdly high frequency when you consider that inheriting two copies of the mutation is invariably fatal, so we figured it must confer a strong advantage to the carriers,” he said.

The research team looked at the incidence of P. vivax and P. falciparum infections in three studies that included a total of 1975 children in Papua New Guinea aged 0-14 years. “We found that SAO-positive children were significantly protected against P. vivax infection, with 46 per cent reduction of clinical disease in infants with little or no immunity, and 52-55 per cent reduction in the risk of infection in older children. We also saw a significant decrease in parasite numbers in infants and older children, which is linked to a decrease in risk of clinical disease,” Professor Mueller said.

The finding could have dramatic implications for future malaria vaccine design and development, Professor Mueller said. “Studying the mechanisms that cause SAO-positive people to be protected against P. vivax malaria could help us to better understand the mechanics of infection and help us to identify better targets for a malaria vaccine,” he said.

The research was supported by the MalariaGEN Consortium, National Health and Medical Research Council of Australia, National Institutes of Health, the United States Department of Veterans Affairs’ Office of Research and Development, AusAID and the Victorian Government

http://www.sciencedaily.com/releases/2012/09/120904170922.htm

Supplementary approach to malaria – Decreased the prevalence of malaria by 34%

Contact: Charlotte Webber press@biomedcentral.com 44-020-763-19980 BioMed Central

Could a simple vitamin A and zinc supplement help protect young children from malaria” A randomized double blind trial reported in the open access publication, Nutrition Journal, would suggest the answer is yes.

Jean-Bosco Ouedraogo of the Institut de Recherche en Sciences de la Santé (IRSS) in Bobo Dioulasso, Burkina Faso, and colleagues explain that vitamin A and zinc play a critical role in the normal function of the immune system, and may even play a synergistic role for reducing the risk of infection including malaria caused by Plasmodium falciparum.

There are approximately 300 to 500 million new cases of malaria each year across the globe, primarily due to P. falciparum.,The vast majority of cases occur in sub-Saharan Africa and lead to the death o f about one million children each year. Emerging drug resistance and ineffective insecticides used in malaria control have hampered efforts to reduce these figures. Moreover, people living in malaria-endemic areas often suffer from malnutrition and deficiencies of micronutrients such as vitamin A and zinc, which have serious health consequences.

In order to understand how reducing micronutrient deficiencies might influence malaria incidence, the researchers undertook a trial with a single dose of 200,000 IU of vitamin A and daily 10 mg of zinc supplementation in children aged 6 to 72 months in the village of Sourkoudougou in Burkina Faso. Half were given placebo. They evaluated the children daily for signs of fever and analyzed blood samples for the presence of the malaria parasite in those children with fever.

The researchers found a significant effect of vitamin A and zinc supplementation on malaria incidence. “At the end of the study we observed a significant decrease in the prevalence malaria in the supplemented group (34%) compared to the placebo group (3.5%),” they explained. Supplementation also increased the time to onset of malarial symptoms and reduced the frequency of episodes. “Supplementation thus may play a key role in malaria control strategies for children in Africa,” they added.

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Notes to Editors:

1.  Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial Augustin N Zeba, Hermann Sorgho, Noel Rouamba, Issaka Zongo, Jeremie Rouamba, Robert T Guiguemde, Davidson H Hamer, Najat Mokhtar and Jean-Bosco Ouedraogo Nutrition Journal 2008, 7:7

Article available at journal website:http://www.nutritionj.com/

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Nutrition Journal aims to encourage scientists and physicians of all fields to publish results that challenge current models, tenets or dogmas. The journal invites scientists and physicians to submit work that illustrates how commonly used methods and techniques are unsuitable for studying a particular phenomenon. Nutrition Journal strongly promotes and invites the publication of clinical trials that fall short of demonstrating an improvement over current treatments. The aim of the journal is to provide scientists and physicians with responsible and balanced information in order to improve experimental designs and clinical decisions.

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