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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

How Herpesvirus Invades Nervous System


Northwestern Medicine scientists have identified a component of the herpesvirus that “hijacks” machinery inside human cells, allowing the virus to rapidly and successfully invade the nervous system upon initial exposure.

Led by Gregory Smith, associate professor in immunology and microbiology at Northwestern University Feinberg School of Medicine, researchers found that viral protein 1-2, or VP1/2, allows the herpesvirus to interact with cellular motors, known as dynein. Once the protein has overtaken this motor, the virus can speed along intercellular highways, or microtubules, to move unobstructed from the tips of nerves in skin to the nuclei of neurons within the nervous system.

This is the first time researchers have shown a viral protein directly engaging and subverting the cellular motor; most other viruses passively hitch a ride into the nervous system.

“This protein not only grabs the wheel, it steps on the gas,” says Smith. “Overtaking the cellular motor to invade the nervous system is a complicated accomplishment that most viruses are incapable of achieving. Yet the herpesvirus uses one protein, no others required, to transport its genetic information over long distances without stopping.”

Herpesvirus is widespread in humans and affects more than 90 percent of adults in the United States. It is associated with several types of recurring diseases, including cold sores, genital herpes, chicken pox, and shingles. The virus can live dormant in humans for a lifetime, and most infected people do not know they are disease carriers. The virus can occasionally turn deadly, resulting in encephalitis in some.

Until now, scientists knew that herpesviruses travel quickly to reach neurons located deep inside the body, but the mechanism by which they advance remained a mystery.

Smith’s team conducted a variety of experiments with VP1/2 to demonstrate its important role in transporting the virus, including artificial activation and genetic mutation of the protein. The team studied the herpesvirus in animals, and also in human and animal cells in culture under high-resolution microscopy. In one experiment, scientists mutated the virus with a slower form of the protein dyed red, and raced it against a healthy virus dyed green. They observed that the healthy virus outran the mutated version down nerves to the neuron body to insert DNA and establish infection.

“Remarkably, this viral protein can be artificially activated, and in these conditions it zips around within cells in the absence of any virus. It is striking to watch,” Smith says.

He says that understanding how the viruses move within people, especially from the skin to the nervous system, can help better prevent the virus from spreading.

Additionally, Smith says, “By learning how the virus infects our nervous system, we can mimic this process to treat unrelated neurologic diseases. Even now, laboratories are working on how to use herpesviruses to deliver genes into the nervous system and kill cancer cells.”

Smith’s team will next work to better understand how the protein functions. He notes that many researchers use viruses to learn how neurons are connected to the brain.

“Some of our mutants will advance brain mapping studies by resolving these connections more clearly than was previously possible,” he says.

Story Source:

The above story is reprinted from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Sofia V. Zaichick, Kevin P. Bohannon, Ami Hughes, Patricia J. Sollars, Gary E. Pickard, Gregory A. Smith. The Herpesvirus VP1/2 Protein Is an Effector of Dynein-Mediated Capsid Transport and Neuroinvasion. Cell Host & Microbe, 2013; 13 (2): 193 DOI: 10.1016/j.chom.2013.01.009

Nanoparticles Laced With Bee Venom Selectively Destroy HIV Virus


Nanoparticles carrying a toxin found in bee venom can destroy human immunodeficiency virus (HIV) while leaving surrounding cells unharmed, researchers at Washington University School of Medicine in St. Louis have shown. The finding is an important step toward developing a vaginal gel that may prevent the spread of HIV, the virus that causes AIDS.

“Our hope is that in places where HIV is running rampant, people could use this gel as a preventive measure to stop the initial infection,” says Joshua L. Hood, MD, PhD, a research instructor in medicine.

The study appears in the current issue of Antiviral Therapy.

Bee venom contains a potent toxin called melittin that can poke holes in the protective envelope that surrounds HIV, and other viruses. Large amounts of free melittin can cause a lot of damage. Indeed, in addition to anti-viral therapy, the paper’s senior author, Samuel A. Wickline, MD, the J. Russell Hornsby Professor of Biomedical Sciences, has shown melittin-loaded nanoparticles to be effective in killing tumor cells.

Nanoparticles (purple) carrying melittin (green) fuse with HIV (small circles with spiked outer ring), destroying the virus’s protective envelope. Molecular bumpers (small red ovals) prevent the nanoparticles from harming the body’s normal cells, which are much larger in size.

The new study shows that melittin loaded onto these nanoparticles does not harm normal cells. That’s because Hood added protective bumpers to the nanoparticle surface. When the nanoparticles come into contact with normal cells, which are much larger in size, the particles simply bounce off. HIV, on the other hand, is even smaller than the nanoparticle, so HIV fits between the bumpers and makes contact with the surface of the nanoparticle, where the bee toxin awaits.

“Melittin on the nanoparticles fuses with the viral envelope,” Hood says. “The melittin forms little pore-like attack complexes and ruptures the envelope, stripping it off the virus.”

According to Hood, an advantage of this approach is that the nanoparticle attacks an essential part of the virus’ structure. In contrast, most anti-HIV drugs inhibit the virus’s ability to replicate. But this anti-replication strategy does nothing to stop initial infection, and some strains of the virus have found ways around these drugs and reproduce anyway.

“We are attacking an inherent physical property of HIV,” Hood says. “Theoretically, there isn’t any way for the virus to adapt to that. The virus has to have a protective coat, a double-layered membrane that covers the virus.”

Beyond prevention in the form of a vaginal gel, Hood also sees potential for using nanoparticles with melittin as therapy for existing HIV infections, especially those that are drug-resistant. The nanoparticles could be injected intravenously and, in theory, would be able to clear HIV from the blood stream.

“The basic particle that we are using in these experiments was developed many years ago as an artificial blood product,” Hood says. “It didn’t work very well for delivering oxygen, but it circulates safely in the body and gives us a nice platform that we can adapt to fight different kinds of infections.”

Since melittin attacks double-layered membranes indiscriminately, this concept is not limited to HIV. Many viruses, including hepatitis B and C, rely on the same kind of protective envelope and would be vulnerable to melittin-loaded nanoparticles.

While this particular paper does not address contraception, Hood says the gel easily could be adapted to target sperm as well as HIV. But in some cases people may only want the HIV protection.

“We also are looking at this for couples where only one of the partners has HIV, and they want to have a baby,” Hood says. “These particles by themselves are actually very safe for sperm, for the same reason they are safe for vaginal cells.”

While this work was done in cells in a laboratory environment, Hood and his colleagues say the nanoparticles are easy to manufacture in large enough quantities to supply them for future clinical trials.

Journal referrence:

Hood JL, Jallouck AP, Campbell N, Ratner L, Wickline SA. Cytolytic nanoparticles attenuate HIV-1 infectivityAntiviral Therapy. Vol. 19: 95 – 103. 2013

Source:

Washington University in St. Louis

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