Archive for the ‘Microbiology’ Category

Malaria drug treatment breakthrough

April 6, 2013 1 comment

An international study, involving researchers from Griffith University’s Eskitis Institute, has discovered a molecule which could form the basis of powerful new anti-malaria drugs.

Professor Vicky Avery from Griffith University’s Eskitis Institute is co-author of the paper “Quinolone-3-Diarylethers: a new class of drugs for a new era of malaria eradication” which has been published in the journal Science Translational Medicine.

“The 4(1H)-quinolone-3- diarylethers are selective potent inhibitors of the parasite mitochondrial cytochrome bc1 complex,” Professor Avery said.

“These compounds are highly active against the types of malaria parasites which infect humans, Plasmodium falciparum and Plasmodium vivax,” she said.

“What is really exciting about this study is that a new class of drugs based on the 4(1H)- quinolone-3- diarylethers would target the malaria parasite at different stages of its lifecycle.”

This provides the potential to not only kill the parasite in people who are infected, thus treating the clinical symptoms of the disease, but also to reduce transmission rates.

“Just one of these properties would be of great benefit but to achieve both would really make a difference in reducing the disease burden on developing nations,” Professor Avery said.

“There is also the real possibility that we could begin to impact on the incidence and spread of malaria, bringing us closer to the ultimate goal of wiping out malaria altogether.”

The selected preclinical candidate compound, ELQ-300, has been demonstrated to be very effective at blocking transmission in the mouse models.

There is a further benefit in that the predicted dosage in patients would be very low and it’s expected that ELQ-300, which has a long half-life, would provide significant protection.

The development of a new chemical class of anti-malarial drugs is very timely as the parasite is becoming increasing resistant to currently available treatments.

Eskitis Director Professor Ronald J Quinn AM said “I congratulate Professor Avery on her contribution to the discovery of this new class of anti-malarials. This is an exciting discovery that closely aligns with the Institute’s focus on global health and fighting diseases that burden the developing world. We are continuing to take the fight to malaria along a number of fronts, including targeting its many life cycle stages.”

Journal reference: Science Translational Medicine

A. Nilsen, A. N. LaCrue, K. L. White, I. P. Forquer, R. M. Cross, J. Marfurt, M. W. Mather, M. J. Delves, D. M. Shackleford, F. E. Saenz, J. M. Morrisey, J. Steuten, T. Mutka, Y. Li, G. Wirjanata, E. Ryan, S. Duffy, J. X. Kelly, B. F. Sebayang, A.-M. Zeeman, R. Noviyanti, R. E. Sinden, C. H. Kocken, R. N. Price, V. M. Avery, I. Angulo-Barturen, M. B. Jiménez-Díaz, S. Ferrer, E. Herreros, L. M. Sanz, F.-J. Gamo, I. Bathurst, J. N. Burrows, P. Siegl, R. K. Guy, R. W. Winter, A. B. Vaidya, S. A. Charman, D. E. Kyle, R. Manetsch, M. K. Riscoe, Quinolone-3-Diarylethers: A New Class of Antimalarial Drug. Sci. Transl. Med. 5, 177ra37 (2013).

Provided by: Griffith University

Innate immune system can kill HIV when a viral gene is deactivated

Human cells have an intrinsic capacity to destroy HIV. However, the virus has evolved to contain a gene that blocks this ability. When this gene is removed from the virus, the innate human immune system destroys HIV by mutating it to the point where it can no longer survive.

This phenomenon has been shown in test tube laboratory experiments, but now researchers at the University of North Carolina School of Medicine have demonstrated that the same phenomenon occurs in a humanized mouse model, suggesting a promising new target for tackling the virus, which has killed nearly 30 million people worldwide since it first appeared three decades ago.

A family of human proteins called APOBEC3 effectively restrict the growth of HIV and other viruses, but this action is fully counteracted by the viral infectivity factor gene (vif) in HIV. In the study, researchers intravenously infected humanized mice with HIV. They found that the most commonly transmitted strains of HIV are completely neutralized by APOBEC3 proteins when vif is removed from the virus.

“Without the vif gene, HIV can be completely destroyed by the body’s own immune system,” said J. Victor Garcia, PhD, professor of medicine at the UNC School of Medicine and senior author on the study. “These results suggest a new target for developing drugs fully capable of killing the virus.”

Garcia and his colleagues pioneered the humanized mouse model used for these studies. The aptly named “BLT” mouse is created by introducing human bone marrow, liver and thymus tissues into animals without an immune system of their own. The mice have a fully functioning human immune system and can be infected with HIV in the same manner as humans. In previous research, Garcia and his team have effectively prevented intravenous, rectal, vaginal and oral transmission of HIV in the mice with pre-exposure prophylaxis (PrEP).

For the current study, Garcia and his colleagues also infected BLT mice with another, highly harmful strain of the virus. The results show that this strain of HIV does continue to replicate, even without vif, but at a much slower rate and without harming the human immune system. Further, the researchers found that virus replication in this case was limited to one tissue—the thymus—in the entire body.

“These findings demonstrate a fundamental weakness in HIV,” said John F. Krisko, PhD, lead author on the study. “If this weakness can be exploited, it might eventually lead to a cure for HIV/AIDS,” Krisko said.


Journal reference:

John F. Krisko, Francisco Martinez-Torres, John L. Foster, J. Victor Garcia. HIV Restriction by APOBEC3 in Humanized MicePLoS Pathogens, 2013; 9 (3): e1003242 DOI: 10.1371/journal.ppat.1003242

Provided by University of North Carolina Health Care

New Vaccine-Design Approach Targets Viruses Such as HIV

A team led by scientists from The Scripps Research Institute (TSRI) and the International AIDS Vaccine Initiative (IAVI) has unveiled a new technique for vaccine design that could be particularly useful against HIV and other fast-changing viruses.

New Vaccien Design HIV

The report, which appears March 28, 2013, in Science Express, the early online edition of the journal Science, offers a step toward solving what has been one of the central problems of modern vaccine design: how to stimulate the immune system to produce the right kind of antibody response to protect against a wide range of viral strains. The researchers demonstrated their new technique by engineering an immunogen (substance that induces immunity) that has promise to reliably initiate an otherwise rare response effective against many types of HIV.

“We’re hoping to test this immunogen soon in mice engineered to produce human antibodies, and eventually in humans,” said team leader William R. Schief, who is an associate professor of immunology and member of the IAVI Neutralizing Antibody Center at TSRI.

Seeking a Better Way

For highly variable viruses such as HIV and influenza, vaccine researchers want to elicit antibodies that protect against most or all viral strains — not just a few strains, as seasonal flu vaccines currently on the market. Vaccine researchers have identified several of these broadly neutralizing antibodies from long-term HIV-positive survivors, harvesting antibody-producing B cells from blood samples and then sifting through them to identify those that produce antibodies capable of neutralizing multiple strains of HIV. Such broadly neutralizing antibodies typically work by blocking crucial functional sites on a virus that are conserved among different strains despite high mutation elsewhere.

However, even with these powerful broadly neutralizing antibodies in hand, scientists need to find a way to elicit their production in the body through a vaccine. “For example, to elicit broadly neutralizing antibodies called VRC01-class antibodies that neutralize 90 percent of known HIV strains, you could try using the HIV envelope protein as your immunogen,” said Schief, “but you run into the problem that the envelope protein doesn’t bind with any detectable affinity to the B cells needed to launch a broadly neutralizing antibody response.”

To reliably initiate that VRC01-class antibody response, Schief and his colleagues therefore sought to develop a new method for designing vaccine immunogens.

From Weak to Strong

Joseph Jardine, a TSRI graduate student in the Schief laboratory, evaluated the genes of VRC01-producing B cells in order to deduce the identities of the less mature B cells — known as germline B cells — from which they originate. Germline B cells are major targets of modern viral vaccines, because it is the initial stimulation of these B cells and their antibodies that leads to a long-term antibody response.

In response to vaccination, germline B cells could, in principle, mature into the desired VRC01-producing B cells — but natural HIV proteins fail to bind or stimulate these germline B cells so they cannot get the process started. The team thus set out to design an artificial immunogen that would be successful at achieving this.

Jardine used a protein modeling software suite called Rosetta to improve the binding of VRC01 germline B cell antibodies to HIV’s envelope protein. “We asked Rosetta to look for mutations on the side of the HIV envelope protein that would help it bind tightly to our germline antibodies,” he said.

Rosetta identified dozens of mutations that could help improve binding to germline antibodies. Jardine then generated libraries that contained all possible combinations of beneficial mutations, resulting in millions of mutants, and screened them using techniques called yeast surface display and FACS. This combination of computational prediction and directed evolution successfully produced a few mutant envelope proteins with high affinity for germline VRC01-class antibodies.

Jardine then focused on making a minimal immunogen — much smaller than HIV envelope — and so continued development using the “engineered outer domain (eOD)” previously developed by Po-Ssu Huang in the Schief lab while Schief was at the University of Washington. Several iterative rounds of design and selection using a panel of germline antibodies produced a final, optimized immunogen — a construct they called eOD-GT6.

A Closer Look

To get a better look at eOD-GT6 and its interaction with germline antibodies, the team turned to the laboratory of Ian A. Wilson, chair of the Department of Integrative Structural and Computational Biology and a member of the IAVI Neutralizing Antibody Center at TSRI.

Jean-Philippe Julien, a senior research associate in the Wilson laboratory, determined the 3D atomic structure of the designed immunogen using X-ray crystallography — and, in an unusual feat, also determined the crystal structure of a germline VRC01 antibody, plus the structure of the immunogen and antibody bound together.

“We wanted to know whether eOD-GT6 looked the way we anticipated and whether it bound to the antibody in the way that we predicted — and in both cases the answer was ‘yes’,” said Julien. “We also were able to identify the key mutations that conferred its reactivity with germline VRC01 antibodies.”

Mimicking a Virus

Vaccine researchers know that such an immunogen typically does better at stimulating an antibody response when it is presented not as a single copy but in a closely spaced cluster of multiple copies, and with only its antibody-binding end exposed. “We wanted it to look like a virus,” said Sergey Menis, a visiting graduate student in the Schief laboratory.

Menis therefore devised a tiny virus-mimicking particle made from 60 copies of an obscure bacterial enzyme and coated it with 60 copies of eOD-GT6. The particle worked well at activating VRC01 germline B cells and even mature B cells in the lab dish, whereas single-copy eOD-GT6 did not.

“Essentially it’s a self-assembling nanoparticle that presents the immunogen in a properly oriented way,” Menis said. “We’re hoping that this approach can be used not just for an HIV vaccine but for many other vaccines, too.”

The next step for the eOD-GT6 immunogen project, said Schief, is to test its ability to stimulate an antibody response in lab animals that are themselves engineered to produce human germline antibodies. The difficulty with testing immunogens that target human germline antibodies is that animals typically used for vaccine testing cannot make those same antibodies. So the team is collaborating with other researchers who are engineering mice to produce human germline antibodies. After that, he hopes to learn how to drive the response, from the activation of the germline B cells all the way to the production of mature, broadly neutralizing VRC01-class antibodies, using a series of designed immunogens.

Schief also hopes they will be able to test their germline-targeting approach in humans sooner rather than later, noting “it will be really important to find out if this works in a human being.”

The first authors of the paper, “Rational HIV immunogen design to target specific germline B cell receptors,” were Jardine, Julien and Menis. Co-authors were Takayuki Ota and Devin Sok of the Nemazee and Burton laboratories at TSRI, respectively; Travis Nieusma of the Ward laboratory at TSRI; John Mathison of the Ulevitch laboratory at TSRI; Oleksandr Kalyuzhniy and Skye MacPherson, researchers in the Schief laboratory from IAVI and TSRI, respectively; Po-Ssu Huang and David Baker of the University of Washington, Seattle; Andrew McGuire and Leonidas Stamatatos of the Seattle Biomedical Research Institute; and TSRI principal investigators Andrew B. Ward, David Nemazee, Ian A. Wilson, and Dennis R. Burton, who is also head of the IAVI Neutralizing Center at TSRI.

Story Source:

The above story is reprinted from materials provided by Scripps Research Institute.

Journal Reference:

Joseph Jardine, Jean-Philippe Julien, Sergey Menis, Takayuki Ota, Oleksandr Kalyuzhniy, Andrew McGuire, Devin Sok, Po-Ssu Huang, Skye MacPherson, Meaghan Jones, Travis Nieusma, John Mathison, David Baker, Andrew B. Ward, Dennis R. Burton, Leonidas Stamatatos, David Nemazee, Ian A. Wilson, and William R. Schief. Rational HIV Immunogen Design to Target Specific Germline B Cell Receptors. Science, 28 March 2013 DOI: 10.1126/science.1234150

The Bacteria That Make Insects Eat Their Own Brains

September 5, 2012 Leave a comment

As far as bacteria are concerned, other living creatures are just another niche to exploit, which means that pretty much every animal and plant has a set of bacterial pathogens that come along with it. These bacteria have made the animal in question their speciality, and are highly adapted to live inside their hosts. While these bacteria often make the host ill, or less fit, or sometimes dead, the longer they live with their host, overall, the less they damage it. After all, it’s no help to the bacteria if their home drops down dead right after they’ve moved in.

A great example of this appeared in PLoS Pathogens this month (reference 1), concerning the bacteria Wolbachia. These bacteria infect insects and other arthropods and are much beloved of journalists (well, compared to other insect bacteria at least) because one of their effects is to stop insects producing male offspring (so only female survive to pass on the bacterial genome), which gives journalists the opportunity to write silly headlines.

An electron micrograph of an insect cell, with three Wolbachia bacteria inside (the large circular blobs with white lines surrounding them). Image from reference 2. (up)

As well as passing from females onto their offspring, Wolbachia can also be transmitted horizontally, that is between insects in the same generation. In its normal host the Wolbachia is not hugely damaging (apart from removing all males from the population) but when transmitted to a new species it causes various unpleasant nervous system complications, often leading to death. Clearly, the bacteria are more virulent when they encounter a new species. However when the bacterial infection was closely examined, it was found that infected individuals of both species contained the same number of bacteria. It wasn’t just that the new species couldn’t respond to the infection, it was in fact the way they responded that was doing the damage.

As it turns out, the reason Wolbachia are more dangerous in new species isn’t because the bacteria go wild in the unexplored territory, rather it’s because the new host doesn’t know how to deal with them. The insects that are used to dealing with the presence of the bacteria have developed ways to contain the infection, or just tolerate it. New species however, tend to panic, particularly as the bacteria tend to congregate in the gonads (sex organs) and the central nervous system, which even insects understand are bad places to have bacteria.

As the bacteria are found inside cells, the best way for an insect immune system to get rid of them, is by destroying the cells that house the bacteria. Which, as previously mentioned, are mainly the gonads and the central nervous system. When the Wolbachia get into a new species, the first response of the insect is to quickly and efficiently destroy any cells which have bacteria inside them. As a consequence the unfortunate insect basically destroys its own brain, leading to various unpleasant symptoms and death.

The carpenter ant, Camponotus pennsylvanicus. Many species of Camponotus are infected with Wolbachia. Image from reference 3. (up)

Even in insects, the immune system is vital to defend animals from bacterial, fungal, and viral attacks. However it’s fascinating to see the cases where the immune system (even ‘primitave’ immune systems that consist of nothing more than infected cells quickly being removed) can lead to issues by over-reacting to a threat. The best response to the Wolbachia is for the insects to learn to deal with it, rather than to attempt to launch counter-attacks which can be damaging for the animal as a whole.


Adopted from: Rat Lab blog

1: Le Clec’h W, Braquart-Varnier C, Raimond M, Ferdy JB, Bouchon D, & Sicard M (2012). High virulence of wolbachia after host switching: when autophagy hurts. PLoS pathogens, 8 (8) PMID22876183

2: (2004) Genome Sequence of the Intracellular Bacterium Wolbachia. PLoS Biol 2(3): e76. doi:10.1371/journal.pbio.0020076

3: Wernegreen JJ (2004) Endosymbiosis: Lessons in Conflict Resolution. PLoS Biol 2(3): e68. doi:10.1371/journal.pbio.0020068




Biologists Produce Potential Malarial Vaccine from Algae

May 25, 2012 1 comment

Biologists at the University of California, San Diego have succeeded in engineering algae to produce potential candidates for a vaccine that would prevent transmission of the parasite that causes malaria, an achievement that could pave the way for the development of an inexpensive way to protect billions of people from one of the world’s most prevalent and debilitating diseases. Initial proof-of-principle experiments suggest that such a vaccine could prevent malaria transmission.

(up) The edible algae Chlamydomonas, seen here at UC San Diego, can be grown in ponds anywhere in the world. (Credit: SD-CAB)

Malaria is a mosquito-borne disease caused by infection with protozoan parasites from the genus Plasmodium. It affects more than 225 million people worldwide in tropical and subtropical regions, resulting in fever, headaches and in severe cases coma and death. While a variety of often costly antimalarial medications are available to travelers in those regions to protect against infections, a vaccine offering a high level of protection from the disease does not yet exist.

The use of algae to produce malaria proteins that elicited antibodies against Plasmodium falciparum in laboratory mice and prevented malaria transmission was published May 16 in the online, open-access journal PLoS ONE. The development resulted from an unusual interdisciplinary collaboration between two groups of biologists at UC San Diego — one from the Division of Biological Sciences and San Diego Center for Algae Biotechnology, which had been engineering algae to produce bio-products and biofuels, and another from the Center for Tropical Medicine and Emerging Infectious Diseases in the School of Medicine that is working to develop ways to diagnose, prevent and treat malaria.

Part of the difficulty in creating a vaccine against malaria is that it requires a system that can produce complex, three-dimensional proteins that resemble those made by the parasite, thus eliciting antibodies that disrupt malaria transmission. Most vaccines created by engineered bacteria are relatively simple proteins that stimulate the body’s immune system to produce antibodies against bacterial invaders. More complex proteins can be produced, but this requires an expensive process using mammalian cell cultures, and the proteins those cells produce are coated with sugars due to a chemical process called glycosylation.

“Malaria is caused by a parasite that makes complex proteins, but for whatever reason this parasite doesn’t put sugars on those proteins,” said Stephen Mayfield, a professor of biology at UC San Diego who headed the research effort. “If you have a protein covered with sugars and you inject it into somebody as a vaccine, the tendency is to make antibodies against the sugars, not the amino acid backbone of the protein from the invading organism you want to inhibit. Researchers have made vaccines without these sugars in bacteria and then tried to refold them into the correct three-dimensional configuration, but that’s an expensive proposition and it doesn’t work very well.”

Instead, the biologists looked to produce their proteins with the help of an edible green alga, Chlamydomonas reinhardtii, used widely in research laboratories as a genetic model organism, much like the fruit fly Drosophila and the bacterium E. coli. Two years ago, a UC San Diego team of biologists headed by Mayfield, who is also the director of the San Diego Center for Algae Biotechnology, a research consortium seeking to develop transportation fuels from algae, published a landmark study demonstrating that many complex human therapeutic proteins, such as monoclonal antibodies and growth hormones, could be produced by Chlamydomonas.

That got James Gregory, a postdoctoral researcher in Mayfield’s laboratory, wondering if a complex protein to protect against the malarial parasite could also be produced by Chlamydomonas. Two billion people live in regions where malaria is present, making the delivery of a malarial vaccine a costly and logistically difficult proposition, especially when that vaccine is expensive to produce. So the UC San Diego biologists set out to determine if this alga, an organism that can produce complex proteins very cheaply, could produce malaria proteins that would inhibit infections from malaria.

“It’s too costly to vaccinate two billion people using current technologies,” explained Mayfield. “Realistically, the only way a malaria vaccine will ever be used is if it can be produced at a fraction of the cost of current vaccines. Algae have this potential because you can grow algae any place on the planet in ponds or even in bathtubs.”

Collaborating with Joseph Vinetz, a professor of medicine at UC San Diego and a leading expert in tropical diseases who has been working on developing vaccines against malaria, the researchers showed that the proteins produced by the algae, when injected into laboratory mice, made antibodies that blocked malaria transmission from mosquitoes.

“It’s hard to say if these proteins are perfect, but the antibodies to our algae-produced protein recognize the native proteins in malaria and, inside the mosquito, block the development of the malaria parasite so that the mosquito can’t transmit the disease,” said Gregory.

“This paper tells us two things: The proteins that we made here are viable vaccine candidates and that we at least have the opportunity to produce enough of this vaccine that we can think about inoculating two billion people,” said Mayfield. “In no other system could you even begin to think about that.”

The scientists, who filed a patent application on their discovery, said the next steps are to see if these algae proteins work to protect humans from malaria and then to determine if they can modify the proteins to elicit the same antibody response when the algae are eaten rather than injected.

Other UC San Diego scientists involved in the discovery were Fengwu Li from Vinetz’s laboratory and biologists Lauren Tomosada, Chesa Cox and Aaron Topol from Mayfield’s group. The basic technology that led to the development was supported by the Skaggs family. The research was supported by grants from the National Institute of Allergy and Infectious Diseases and the San Diego Foundation. The California Energy Commission supported work on recombinant protein production for biofuels use, and this technology helped enabled these studies.

Story Source:

The above story is reprinted from materials provided by University of California – San Diego.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Gregory JA, Li F, Tomosada LM, Cox CJ, Topol AB, et al.Algae-Produced Pfs25 Elicits Antibodies That Inhibit Malaria TransmissionPLoS ONE, 2012 DOI:10.1371/journal.pone.0037179

Drug Found for Parasite That Is Major Cause of Death Worldwide

Research by a collaborative group of scientists from UC San Diego School of Medicine, UC San Francisco and Wake Forest School of Medicine has led to identification of an existing drug that is effective against Entamoeba histolytica. This parasite causes amebic dysentery and liver abscesses and results in the death of more than 70,000 people worldwide each year.

(up) Entamoeba histolytica cyst. (Credit: UC San Diego School of Medicine)

Using a high-throughput screen for drugs developed by the research team, they discovered that auranofin — a drug approved by the US Food and Drug Administration 25 years ago for rheumatoid arthritis — is very effective in targeting an enzyme that protects amebae from oxygen attack (thus enhancing sensitivity of the amebae to reactive oxygen-mediated killing).

The results of the work, led by Sharon L. Reed, MD, professor in the UCSD Departments of Pathology and Medicine and James McKerrow, MD, PhD, professor of Pathology in the UCSF Sandler Center for Drug Discovery, will be published in the May 20, 2012 issue of Nature Medicine.

Entamoeba histolytica is a protozoan intestinal parasite that causes human amebiasis, the world’s fourth leading cause of death from protozoan parasites. It is listed by the National Institutes of Health as a category B priority biodefense pathogen. Current treatment relies on metronidazole, which has adverse effects, and potential resistance to the drug is an increasing concern.

“Because auranofin has already been approved by the FDA for use in humans, we can save years of expensive development,” said Reed. “In our studies in animal models, auranofin was ten times more potent against this parasite than metronidazole.”

In a mouse model of amebic colitis and a hamster model of amebic liver abscess, the drug markedly decreased the number of parasites, damage from inflammation, and size of liver abscesses.

“This new use of an old drug represents a promising therapy for a major health threat, and highlights how research funded by the National Institutes of Health can benefit people around the world,” said Reed. The drug has been granted “orphan-drug” status (which identifies a significant, newly developed or recognized treatment for a disease which affects fewer than 200,000 persons in the United States) and UC San Diego hopes to conduct clinical trials in the near future.

This work was supported by the Sandler Foundation and US National Institute of Allergy and Infectious Diseases grant 5U01AI077822-02, with additional support from R01 GM050389.

Story Source:

The above story is reprinted from materials provided byUniversity of California, San Diego Health Sciences, via Newswise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Anjan Debnath, Derek Parsonage, Rosa M Andrade, Chen He, Eduardo R Cobo, Ken Hirata, Steven Chen, Guillermina García-Rivera, Esther Orozco, Máximo B Martínez, Shamila S Gunatilleke, Amy M Barrios, Michelle R Arkin, Leslie B Poole, James H McKerrow, Sharon L Reed. A high-throughput drug screen for Entamoeba histolytica identifies a new lead and targetNature Medicine, 2012; DOI: 10.1038/nm.2758

Notre Dame researchers report fundamental malaria discovery

February 11, 2012 1 comment

A team of researchers led by Kasturi Haldar and Souvik Bhattacharjee of the University of Notre Dame’s Center for Rare and Neglected Diseases has made a fundamental discovery in understanding how malaria parasites cause deadly disease.

The researchers show how parasites target proteins to the surface of the red blood cell that enables sticking to and blocking blood vessels. Strategies that prevent this host-targeting process will block disease.

The research findings appear in the Jan. 20 edition of the journal Cell, the leading journal in the life sciences. The study was supported by the National Institutes of Health.

Malaria is a blood disease that kills nearly 1-3 million people each year. It is caused by a parasite that infects red cells in the blood. Once inside the cell, the parasite exports proteins beyond its own plasma membrane border into the blood cell. These proteins function as adhesins that help the infected red blood cells stick to the walls of blood vessels in the brain and cause cerebral malaria, a deadly form of the disease that kills over half a million children each year.

In all cells, proteins are made in a specialized cell compartment called the endoplasmic reticulum (ER) from where they are delivered to other parts of the cell. Haldar and Bhattacharjee and collaborators Robert Stahelin at the Indiana University School of Medicine – South Bend (who also is an adjunct faculty member in Notre Dame’s Department of Chemistry and Biochemistry), and David and Kaye Speicher at the University of Pennsylvania’s Wistar Institute discovered that for host-targeted malaria proteins the very first step is binding to the lipid phosphatidylinositol 3-phosphate, PI(3)P, in the ER.

This was surprising for two reasons. Previous studies suggested an enzyme called Plasmepsin V that released the proteins into the ER was also the export mechanism. However, Haldar, Bhattacharjee and colleagues discovered that binding to PI(3)P lipid which occurs first is the gate keeper to control export and that export can occur without Plasmepsin V action. Further, in higher eukaryotic cells (such as in humans), the lipid PI(3)P is not usually found within the ER membrane but rather is exposed to the cellular cytoplasm.

Haldar and Bhattacharjee are experts in malaria parasite biology and pathogenesis. Stahelin is an expert in PI(3)P lipid biology, and David and Kaye Speicher are experts in proteomics and a method called mass spectrometry.

Story Source:

The above story is reprinted (with editorial adaptations by MedicalXpress staff) from materials provided by University of Notre Dame (news : web)