Scientists Discover How Immune Cells Die During HIV Infection; Identify Potential Drug to Block AIDS

Research led by scientists at the Gladstone Institutes has identified the precise chain of molecular events in the human body that drives the death of most of the immune system's CD4 T cells as an HIV infection leads to AIDS. Further, they have identified an existing anti-inflammatory drug that in laboratory tests blocks the death of these cells -- and now are planning a Phase 2 clinical trial to determine if this drug or a similar drug can prevent HIV-infected people from developing AIDS and related conditions.

Two separate journal articles, published simultaneously today in Nature and Science, detail the research from the laboratory of Warner C. Greene, MD, PhD, who directs virology and immunology research at Gladstone, an independent biomedical-research nonprofit. His lab's Science paper reveals how, during an HIV infection, a protein known as IFI16 senses fragments of HIV DNA in abortively infected immune cells. This triggers the activation of the human enzyme caspase-1 and leads to pyroptosis, a fiery and highly inflammatory form of cell death. As revealed in the Nature paper, this repetitive cycle of abortive infection, cell death, inflammation and recruitment of additional CD4 T cells to the infection "hot zone" ultimately destroys the immune system and causes AIDS. The Nature paper further describes laboratory tests in which an existing anti-inflammatory inhibits caspase-1, thereby preventing pyroptosis and breaking the cycle of cell death and inflammation.
"Gladstone has made two important discoveries, first by showing how the body's own immune response to HIV causes CD4 T cell death via a pathway triggering inflammation, and secondly by identifying the host DNA sensor that detects the viral DNA and triggers this death response," said Robert F. Siliciano, MD, PhD, a professor of medicine at Johns Hopkins University, and a Howard Hughes Medical Institute investigator. "This one-two punch of discoveries underscores the critical value of basic science -- by uncovering the major cause of CD4 T cell depletion in AIDS, Dr. Greene's lab has been able to identify a potential new therapy for blocking the disease's progression and improving on current antiretroviral medications."
The research comes at a critical time, as so-called AIDS fatigue leads many to think that HIV/AIDS is solved. In fact, HIV infected an additional 2.3 million people last year, according to UNAIDS estimates, bringing the global total of HIV-positive people to 35.3 million. Antiretroviral medications (ARVs) can prevent HIV infections from causing AIDS, but they do not cure AIDS. Further, those taking ARVs risk both a latent version of the virus, which can rebound if ARVs are discontinued, and the premature onset of diseases that normally occur in aging populations. Plus, some 16 million people who carry the virus do not have access to ARVs, according to World Health Organization estimates.
Seeking solutions for all these challenges, the new Gladstone discovery builds on earlier research from Dr. Greene's lab, published in Cell in 2010. This study showed how HIV attempts, but fails, to productively infect most of the immune system's CD4 T cells. In an attempt to protect the body from the spreading virus, these immune cells then commit "cellular suicide," leading to the collapse of the immune system -- and AIDS.
After that research, the Gladstone scientists began to look for ways to prevent this process by studying exactly how the suicidal response is initiated. Working in the laboratory with human spleen and tonsil tissue, as well as lymph-node tissue from HIV-infected patients, the researchers found that these so-called abortive infections leave fragments of HIV's DNA in the immune cells. As described in Nature, pyroptosis ensues as immune cells rupture and release inflammatory signals that attract still more cells to repeat the death cycle.
"Our studies have investigated and identified the root cause of AIDS -- how CD4 T cells die," said Gladstone Staff Research Investigator Gilad Doitsh, PhD, who is the Nature paper's lead author, along with Nicole Galloway and Xin Geng, PhD. "Despite some 30 years of HIV research, this key HIV/AIDS process has remained pretty much a black box."
Once the scientists discovered this key process, as described in Nature, they began to investigate how the body senses the fragments of HIV's DNA in the first place, before alerting the enzyme caspase-1 to launch an immune response in the CD4 T cells. To identify the so-called DNA sensor, the scientists found a way to genetically manipulate CD4 T cells in spleen and tonsil tissue. In doing so, they discovered that reducing the activity of a protein known as IFI16 inhibited pyroptosis, explained Zhiyuan Yang, PhD, a Gladstone postdoctoral fellow who is one of the paper's two lead authors.
"This identified IFI16 as the DNA sensor, which then sends signals to caspase-1 and triggers pyroptosis," says Kathryn M. Monroe, PhD, the Science paper's other lead author, who completed the research while a postdoctoral fellow at Gladstone. "We can't block a process until we understand all of its steps -- so this discovery is critical to devising ways to inhibit the body's own destructive response to HIV. We have high hopes for the upcoming clinical trial."
The Phase 2 trial -- which will test an existing anti-inflammatory's ability to block inflammation and pyroptosis in HIV-infected people -- promises to validate a variety of expected advantages to this therapy. For example, by targeting the human body, or host, instead of the virus, the drug is likely to avoid the rapid emergence of drug resistance that often plagues the use of ARVs. The anti-inflammatory may also provide a bridge therapy for the millions without access to ARVs, while also reducing persistent inflammation in HIV-infected people already on ARVs. Many suspect this inflammation drives the early onset of aging-related conditions such as dementia and cardiovascular disease. By reducing inflammation, the drug might also prevent expansion of a reservoir of latent virus that hides in the body where it thwarts a cure for HIV/AIDS.
"This has been an absolutely fascinating voyage of discovery," said Dr. Greene, who is also a professor of medicine, microbiology and immunology at the University of California, San Francisco, with which Gladstone is affiliated. "Every time we turned over an 'experimental rock' in the studies, a new surprise jumped out."
 

Journal References:

1. Gilad Doitsh, Nicole L. K. Galloway, Xin Geng, Zhiyuan Yang, Kathryn M. Monroe, Orlando Zepeda, Peter W. Hunt, Hiroyu Hatano, Stefanie Sowinski, Isa Muñoz-Arias, Warner C. Greene. Cell death by pyroptosis drives CD4 T-cell depletion in HIV-1 infection. Nature, 2013; DOI: 10.1038/nature12940
2. K. M. Monroe, Z. Yang, J. R. Johnson, X. Geng, G. Doitsh, N. J. Krogan, W. C. Greene. IFI16 DNA Sensor Is Required for Death of Lymphoid CD4 T Cells Abortively Infected with HIV. Science, 2013; DOI: 10.1126/science.1243640

Courtesy: ScienceDaily
 

TB Bacteria Mask Their Identity to Intrude Into Deeper Regions of Lungs

TB-causing bacteria appear to mask their identity to avoid recognition by infection-killing cells in the upper airways. The bacteria call up more permissive white blood cells in the deeper regions of the lungs and hitch a ride inside them to get into the host's body.

Flying under the radar: tuberculosis-causing mycobacteria initiate infection in the lower lung to evade pathogen-killing cells. (Credit: Ramakrishnan Lab/University of Washington)

Details on this finding are reported Dec. 16 in the advanced online edition of the journal Nature. The research was a collaboration between the University of Washington and the Seattle Biomedical Research Institute.
Dr. Lalita Ramakrishan, who studies how TB evades the body's immune system and manipulates the body's defenses for its own ends, is the senior author. She is a UW professor of microbiology, medicine and immunology. The lead author is C.J. Cambier of the UW Department of Immunology.
Ramakrishnan noted that the recent study also suggests an explanation for the longstanding observation that tuberculosis infections begin in the comparatively sterile lower lungs. In the upper respiratory tract, resident microbes and inhaled microbes of a variety of species signal their presence.
These tip-offs alert and attract many infection-fighting cells to the upper airways. The presence of other microbes in the upper airway may thereby help to keep TB infections at bay by creating a hostile environment.
Their presence may explain why TB is a less contagious disease than those caused by several other respiratory pathogens.
To cause disease, TB bacteria must sneak through this well-patrolled area and head for parts of the lungs where fewer microbiocidal cells are policing.
Almost like intruders wearing a stocking over their faces to keep surveillance cameras from clearly recording their features, the TB pathogens produce particular types of fatty substances, or lipids, on their cell surfaces.
These lipids, abbreviated as PDIM, are already known to be associated with bacterial virulence. The researchers showed that PDIM lipids function by masking the underlying molecular patterns that would reveal their dangerous nature to macrophages, a first-line defense of infection-fighting cells.
At the same time, a related lipid -- called PGL -- on the bacterium's cell surface promotes the recruitment of cells described as permissive macrophages. These clean-up cells engulf but don't kill the TB pathogens. Instead, they take them across the lung lining, deep into the lung tissue where the bacteria can establish an infection.
According to the researchers on this study, these mechanisms appear to allow certain TB pathogens to avoid detection by the pattern recognition receptors that enable some infection-fighting cells to spot a variety of different disease microbes through the pathogen-associated molecular patterns on or near their cell surface.
Like most other bacteria, TB pathogens have many of these telltale molecular patterns that should activate an immune response. However, TB pathogens have evolved mechanisms to circumvent tripping the alarm, in this case by physically masking the otherwise detectable pattern. This cover-up allows them to infect the airway initially by avoiding the infection-fighting cell populations that are detrimental to their survival, the researchers noted.
The TB pathogens then use the other lipid molecule, PGL, to co-opt a host chemical pathway that triggers the recruitment of the permissive macrophages.
The present study expands on earlier work in the Ramakrishan and collaborative labs, which helped describe the strategies by which TB pathogens manipulate host pathways for their own purposes after they enter certain host cells.
These include the secretion of proteins that help expand the niche for TB by recruiting macrophages to the early lung tubercles characteristic of the disease. The present study describes earlier stages in infection, when the pathogens first come in contact with their potential host at the surface of the lining of the lung.
"The current study suggests the manner in which the TB pathogens manipulate recruitment of the first responding macrophages to gain access to their preferred niche," the researchers noted.
"The choreographed entry involves two related TB cell lipids acting in concert to avoid one host pathway while inducing another," they wrote. The findings link the previously known, absolutely essential virulence factor on the surface of TB cells, PDIM, to the evasion of immune cell detection. They also might explain why a certain pathogen molecular pattern recognition system is dispensable in protecting against TB. On the other hand, PGL is not required on the surface of TB cells for them to infect the body.
Ramakrishnan noted that globally, a lot of samples of TB taken from infected patients do not have PGL. "However," she and her research team noted, "the importance of PGL in mediating TB virulence or transmission is underscored by its presence in many of the W-Beijing strains" of TB which are starting to rapidly appear in more patient samples, and which have predominated in outbreaks in North America.
Ramakrishnan explains that their findings suggest how PGL may play an important role in increasing TB's infectivity.
"The presence of PGL in ancestral strains of TB suggest it played an integral role in the evolution of TB infectivity," the researchers noted. "TB is an ancient disease and the enhanced infectivity conferred by PGL may have been essential for most of its history before human crowding, with its increased opportunity for transmission, made it dispensable."
The study findings, and previous work on TB, might also explain why smaller droplets of TB are more infectious than larger ones. Only the smaller droplets can make their way down into the lower airways. On the flip side, all it takes is 3 or fewer TB mycobacteria with PGL-producing ability to enter the lower lungs and start an infection.
 

Journal Reference:

1. C. J. Cambier, Kevin K. Takaki, Ryan P. Larson, Rafael E. Hernandez, David M. Tobin, Kevin B. Urdahl, Christine L. Cosma, Lalita Ramakrishnan. Mycobacteria manipulate macrophage recruitment through coordinated use of membrane lipids. Nature, 2013; DOI: 10.1038/nature12799

Courtesy: ScienceDaily
 

New -- And Reversible -- Cause of Aging: Naturally Produced Compound Rewinds Aspects of Age-Related Demise in Mice

Researchers have discovered a cause of aging in mammals that may be reversible.

Sirt1 protein, red, circles the cell's chromosomes, blue. (Credit: Ana Gomes)

The essence of this finding is a series of molecular events that enable communication inside cells between the nucleus and mitochondria. As communication breaks down, aging accelerates. By administering a molecule naturally produced by the human body, scientists restored the communication network in older mice. Subsequent tissue samples showed key biological hallmarks that were comparable to those of much younger animals.
"The aging process we discovered is like a married couple -- when they are young, they communicate well, but over time, living in close quarters for many years, communication breaks down," said Harvard Medical School Professor of Genetics David Sinclair, senior author on the study. "And just like with a couple, restoring communication solved the problem."
This study was a joint project between Harvard Medical School, the National Institute on Aging, and the University of New South Wales, Sydney, Australia, where Sinclair also holds a position.
The findings are published Dec. 19 in Cell.
Communication breakdown
Mitochondria are often referred to as the cell's "powerhouse," generating chemical energy to carry out essential biological functions. These self-contained organelles, which live inside our cells and house their own small genomes, have long been identified as key biological players in aging. As they become increasingly dysfunctional over time, many age-related conditions such as Alzheimer's disease and diabetes gradually set in.
Researchers have generally been skeptical of the idea that aging can be reversed, due mainly to the prevailing theory that age-related ills are the result of mutations in mitochondrial DNA -- and mutations cannot be reversed.
Sinclair and his group have been studying the fundamental science of aging -- which is broadly defined as the gradual decline in function with time -- for many years, primarily focusing on a group of genes called sirtuins. Previous studies from his lab showed that one of these genes, SIRT1, was activated by the compound resveratrol, which is found in grapes, red wine and certain nuts.
Ana Gomes, a postdoctoral scientist in the Sinclair lab, had been studying mice in which this SIRT1 gene had been removed. While they accurately predicted that these mice would show signs of aging, including mitochondrial dysfunction, the researchers were surprised to find that most mitochondrial proteins coming from the cell's nucleus were at normal levels; only those encoded by the mitochondrial genome were reduced.
"This was at odds with what the literature suggested," said Gomes.
As Gomes and her colleagues investigated potential causes for this, they discovered an intricate cascade of events that begins with a chemical called NAD and concludes with a key molecule that shuttles information and coordinates activities between the cell's nuclear genome and the mitochondrial genome. Cells stay healthy as long as coordination between the genomes remains fluid. SIRT1's role is intermediary, akin to a security guard; it assures that a meddlesome molecule called HIF-1 does not interfere with communication.
For reasons still unclear, as we age, levels of the initial chemical NAD decline. Without sufficient NAD, SIRT1 loses its ability to keep tabs on HIF-1. Levels of HIF-1 escalate and begin wreaking havoc on the otherwise smooth cross-genome communication. Over time, the research team found, this loss of communication reduces the cell's ability to make energy, and signs of aging and disease become apparent.
"This particular component of the aging process had never before been described," said Gomes.
While the breakdown of this process causes a rapid decline in mitochondrial function, other signs of aging take longer to occur. Gomes found that by administering an endogenous compound that cells transform into NAD, she could repair the broken network and rapidly restore communication and mitochondrial function. If the compound was given early enough -- prior to excessive mutation accumulation -- within days, some aspects of the aging process could be reversed.
Cancer connection
Examining muscle from two-year-old mice that had been given the NAD-producing compound for just one week, the researchers looked for indicators of insulin resistance, inflammation and muscle wasting. In all three instances, tissue from the mice resembled that of six-month-old mice. In human years, this would be like a 60-year-old converting to a 20-year-old in these specific areas.
One particularly important aspect of this finding involves HIF-1. More than just an intrusive molecule that foils communication, HIF-1 normally switches on when the body is deprived of oxygen. Otherwise, it remains silent. Cancer, however, is known to activate and hijack HIF-1. Researchers have been investigating the precise role HIF-1 plays in cancer growth.
"It's certainly significant to find that a molecule that switches on in many cancers also switches on during aging," said Gomes. "We're starting to see now that the physiology of cancer is in certain ways similar to the physiology of aging. Perhaps this can explain why the greatest risk of cancer is age. "
"There's clearly much more work to be done here, but if these results stand, then many aspects of aging may be reversible if caught early," said Sinclair.
The researchers are now looking at the longer-term outcomes of the NAD-producing compound in mice and how it affects the mouse as a whole. They are also exploring whether the compound can be used to safely treat rare mitochondrial diseases or more common diseases such as Type 1 and Type 2 diabetes. Longer term, Sinclair plans to test if the compound will give mice a healthier, longer life.
 

Journal Reference:

1. Ana P. Gomes, Nathan L. Price, Alvin J.Y. Ling, Javid J. Moslehi, Magdalene K. Montgomery, Luis Rajman, James P. White, João S. Teodoro, Christiane D. Wrann, Basil P. Hubbard, Evi M. Mercken, Carlos M. Palmeira, Rafael de Cabo, Anabela P. Rolo, Nigel Turner, Eric L. Bell, David A. Sinclair. Declining NAD Induces a Pseudohypoxic State Disrupting Nuclear-Mitochondrial Communication during Aging. Cell, 2013; 155 (7): 1624 DOI: 10.1016/j.cell.2013.11.037

Courtesy: ScienceDaily
 

First Step of Metastasis Halted in Mice With Breast Cancer

Cell biologists at Johns Hopkins have identified a unique class of breast cancer cells that lead the process of invasion into surrounding tissues. Because invasion is the first step in the deadly process of cancer metastasis, the researchers say they may have found a weak link in cancer's armor and a possible new target for therapy. A summary of their results will be published online in the journal Cell on Dec. 12.

A breast tumor (blue) uses leader cells (green) to invade muscle tissue (red) in a mouse. (Credit: Kevin Cheung, courtesy of Cell)

"Metastasis is what most threatens breast cancer patients, and we have found a way to stop the first part of the process in mice," says Andrew Ewald, Ph.D., assistant professor of cell biology at the Johns Hopkins School of Medicine.

Before metastasis occurs, single cells on the edge of a tumor, termed leader cells, form protrusions into the surrounding tissue, like someone dipping a toe in to test the water before deciding to venture farther, Ewald says. If the conditions are right, the leader cells act as guides, with many tumor cells following behind, as they escape the confines of the tumor into the healthy tissue beyond. Full metastasis occurs when the cells succeed in migrating to a new location -- the lungs, for example -- and set up shop, creating a new tumor.

Beginning with the idea that some cells in the tumor might be more invasive than others, Ewald's team grew mouse tumors in the laboratory in special 3-D gels that mimic the environment that surrounds breast tumors in human patients. Kevin Cheung, M.D., a medical oncology fellow in the Ewald lab, observed that the cancer cells infiltrated the gels in groups, with a few cells out in front and the rest following behind.

Looking for a molecular cause for the apparent "leadership" seen in the initiating cells, Cheung searched for proteins that were uniquely present in the leader cells. They identified one protein, cytokeratin 14, or K14, that was present in almost all leader cells but was very rare in the noninvasive parts of the tumor. When the team looked at tumors from mice that had other types of breast cancer -- some more prone to invasion and others less prone -- all had leader cells containing K14. The more invasive a tumor was, the more cells with K14 it had.

The team then grew breast tumors from 10 breast cancer patients in 3-D gels and found that the leader cells in these human tumors also contained K14. "Our research shows that the most invasive cells in breast tumors express K14 across all types of breast cancer," says Cheung. "Now we need to learn how to eliminate these leader cells from breast tumors in patients."

K14 is a protein that helps form the internal "skeleton" of many cell types, giving them structure and helping them to move. Although its presence in leader cells made its involvement in the invasion process seem likely, the investigators conducted further experiments to determine whether it was essential to the process or merely coincidental to it.

The researchers removed breast tumors from mice with breast cancer and divided them into an experimental group and a control group. Each group of tumors was exposed to viruses that had been reprogrammed to carry pieces of genetic material into the cells. The experimental group received genetic material designed to prevent the production of K14; the control group got genetic material that didn't affect the cells. The two groups of tumors were then transplanted into healthy mice, with experimental tumors on one side and control tumors on the other side of the same mouse.

After letting the tumors grow for some time, the team removed and examined them. As expected, in the control group, leader cells were present, contained K14 and were leading vigorous invasions into normal tissue. In the experimental tumors, whose cells had no K14, the tumor borders were smooth, with essentially no invasions occurring.

"We're still several years away from being able to use these insights to help patients with breast cancer, but we now know which tumor cells are the most dangerous, and we know some of the proteins they rely on to do their dirty work," says Ewald. "Just a few leader cells are sufficient to start the process of metastasis, and they require K14 to lead the invasion."

He also notes that K14 is present in cells within many other organs, so K14 may play a similar role in other types of cancer.

Journal Reference:

1. Kevin J. Cheung, Edward Gabrielson, Zena Werb, Andrew J. Ewald. Collective Invasion in Breast Cancer Requires a Conserved Basal Epithelial Program. Cell, 12 December 2013 DOI: 10.1016/j.cell.2013.11.029

Courtesy: ScienceDaily

Simple Mathematical Formula Describes Human Struggles

Would you believe that a broad range of human struggles can be understood by using a mathematical formula? From child-parent struggles to cyber-attacks and civil unrest, they can all be explained with a simple mathematical expression called a "power-law."

The manner in which a baby's cries escalate against its parent is comparable to the way riots in Poland escalated in the lead-up to the collapse of the Soviet Union. (Credit: © erllre / Fotolia)

In a sort of unified theory of human conflict, scientists have found a way to mathematically describe the severity and timing of human confrontations that affect us personally and as a society.

For example, the manner in which a baby's cries escalate against its parent is comparable to the way riots in Poland escalated in the lead-up to the collapse of the Soviet Union. It comes down to the fact that the perpetrator in both cases (e.g. baby, rioters) adapts quickly enough to escalate its attacks against the larger, but more sluggish entity (e.g. parent, government), who is unable, or unwilling, to respond quickly enough to satisfy the perpetrator, according to a new study published in Nature's Scientific Reports.

"By picking out a specific baby (and parent), and studying what actions of the parent make the child escalate or de-escalate its cries, we can understand better how to counteract cyber-attacks against a particular sector of U.S. cyber infrastructure, or how an outbreak of civil unrest in a given location (e.g. Syria) will play out, following particular government interventions," says Neil Johnson, professor of physics and the head of the interdisciplinary research group in Complexity, at the College of Arts and Sciences at the University of Miami (UM) and corresponding author of the study.

Respectively, the study finds some remarkable similarities between seemingly disconnected confrontations. For instance:

• The escalation of violent attacks in Magdalena, Colombia -- though completely cut off from the rest of the world -- is actually representative of all modern wars. Meanwhile, the conflict in Sierra Leone, Africa, has exactly the same dynamics as the narco-guerilla war in Antioquia, Colombia.
• The pattern of attacks by predatory traders against General Electric (GE) stock is equivalent to the pattern of cyber-attacks against the U.S. hi-tech electronics sector by foreign groups, which in turn mimics specific infants and parents.
• New insight into the controversial 'Bloody Sunday' attack by the British security forces, against civilians, on January 30,1972, reveals that Bloody Sunday appears to be the culmination of escalating Provisional Irish Republican Army attacks, not their trigger, hence raising new questions about its strategic importance.

The findings show that this mathematical formula of the form AB-C is a valuable tool that can be applied to make quantitative predictions concerning future attacks in a given confrontation. It can also be used to create an intervention strategy against the perpetrators and, more broadly, as a quantitative starting point for cross-disciplinary theorizing about human aggression, at the individual and group level, in both real and online worlds.

Journal Reference:

1. Neil F. Johnson, Pablo Medina, Guannan Zhao, Daniel S. Messinger, John Horgan, Paul Gill, Juan Camilo Bohorquez, Whitney Mattson, Devon Gangi, Hong Qi, Pedro Manrique, Nicolas Velasquez, Ana Morgenstern, Elvira Restrepo, Nicholas Johnson, Michael Spagat, Roberto Zarama. Simple mathematical law benchmarks human confrontations.Scientific Reports, 2013; 3 DOI: 10.1038/srep03463

Courtesy: ScienceDaily

New Strain of Bird Flu Packs a Punch Even After Becoming Drug-Resistant

 Researchers at the Icahn School of Medicine at Mount Sinai reported that a virulent new strain of influenza -- the virus that causes the flu -- appears to retain its ability to cause serious disease in humans even after it develops resistance to antiviral medications. The finding was included in a study that was published today in the journal Nature Communications.

This negatively-stained transmission electron micrograph (TEM) captured some of the ultrastructural details exhibited by the new influenza A (H7N9) virus. (Credit: CDC/Cynthia S. Goldsmith and Thomas Rowe)

It is not uncommon for influenza viruses to develop genetic mutations that make them less susceptible to anti-flu drugs. However, these mutations usually come at a cost to the virus, weakening its ability to replicate and to spread from one person to another.

Initial reports suggested that H7N9, an avian strain of influenza A that emerged in China last spring, could rapidly develop a mutation that made it resistant to treatment with the antiviral medication Tamiflu (oseltamivir). However, patients in whom drug resistance developed often had prolonged, severe infections and poor clinical outcomes. No vaccine is currently available to prevent H7N9, which infected at least 135 people and caused 44 deaths during the outbreak. In the absence of a vaccine, antiviral drugs are the only means of defense for patients who are infected with new strains of the flu.

"In this outbreak, we saw some differences in the behavior of H7N9 and other avian influenza strains that can infect humans, beginning with the rapid development of antiviral resistance in some people who were treated with oseltamivir and the persistence of high viral loads in those patients," said lead investigator Nicole Bouvier, MD, Assistant Professor of Medicine, Infectious Diseases at the Icahn School of Medicine at Mount Sinai.

Specifically, the investigators found that a drug-resistant H7N9 virus retained its ability to replicate in human respiratory cells and was comparable to a non-resistant form of the virus in producing severe illness in animal models. And although H7N9 appears to have a limited ability to spread readily from human to human, transmissibility in animal models was comparable between drug-susceptible and drug-resistant strains. "Transmission was inefficient for both of the H7N9 viruses that we tested in our experiments," said Dr. Bouvier. "But surprisingly, transmission of the drug-resistant virus was no less efficient than that of the drug-sensitive version."

"Many of the people infected with H7N9 during the outbreak in China were elderly or had other conditions that predisposed them to severe influenza illness," observed Dr. Bouvier. "Nevertheless, our study suggests that flu viruses can indeed develop drug-resistant mutations without suffering a penalty in terms of their own fitness."

Older antiviral drugs such as amantadine are no longer effective in treating most strains of the flu that infect humans. Newer antiviral drugs called neuraminidase inhibitors block an enzyme that helps the virus replicate. These drugs include Tamiflu, a pill, and Relenza (zanamivir), a powder that is inhaled. Both medications have drawbacks: flu viruses can develop resistance to the medications in people who take them, and, in many parts of the world, neither drug is available in an intravenous form to treat those with severe infections.

"Our study underscores the need to develop a bigger arsenal of antiviral drugs and vaccines, which will allow us to outsmart the influenza virus," said Dr. Bouvier. "Researchers at Mount Sinai are actively engaged in identifying new targets for drug therapy and are working to develop a universal vaccine that will prevent multiple strains of influenza."

Journal Reference:

1. Rong Hai, Mirco Schmolke, Victor H. Leyva-Grado, Rajagowthamee R. Thangavel, Irina Margine, Eric L. Jaffe, Florian Krammer, Alicia Solórzano, Adolfo García-Sastre, Peter Palese, Nicole M. Bouvier. Influenza A(H7N9) virus gains neuraminidase inhibitor resistance without loss of in vivo virulence or transmissibility. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3854

Courtesy: ScienceDaily

Researchers Block Replication of AIDS Virus

A multidisciplinary team of scientists from Spanish universities and research centres, among which is the University of Valencia, has managed to design small synthetic molecules capable of joining to the genetic material of the AIDS virus and blocking its replication.

This achievement has been obtained for the first time in the world by a group of researcher led by José Gallego from Universidad Católica de Valencia "San Vicente Mártir." The University of Valencia, the Príncipe Felipe Research Centre, and the Instituto de Salud Carlos III have participated. The work has been recently published by Angewandte Chemie International Edition.
The newly designed synthetic molecules inhibit the output of genetic material of the virus from the infected cell nucleus to the cytoplasm, thus the virus replication is blocked and avoids the infection of other cells.
The genetic material of the AIDS virus, or HIV-1, is formed by ribonucleic acid (RNA), and encodes several proteins that allow it to penetrate the human cells and reproduce within them. The new virus inhibitors, called terphenyls, developed by this group of scientists, were designed by computer to reproduce the interactions of one of the proteins encoded by the virus, the viral protein Rev.
In this way, the terphenyls join Rev's receptor in the viral RNA, preventing the interaction between the protein and its RNA receptor. This interaction is necessary for the virus genetic material to leave the infected cell nucleus and, thus, it is essential for the survival of HIV-1. The fact that the terphenyls block the virus genetic material output of the cell prevents the infection of other cells.
This discovery is the result of a close collaboration between three research groups throughout several years. Thus, the scientists of the Universitat Católica de Valencia were in charge of the computational design and verified experimentally that the terphenyls were capable of joining the Rev receptor in the viral RNA and inhibit the interaction between this RNA and the protein.
For its part, the molecules were synthesised in professor Santos Fustero's organic Chemistry laboratory in the Príncipe Felipe Research Centre and the University of Valencia. Also, through experiments with cells infected by the virus, the group of José Alcamí in the Instituto de Salud Carlos III demonstrated that the inhibitors block the replication of the HIV-1 and inhibit the function of the Rev protein, confirming this way the validity of the models generated by computer.
Traditionally, pharmaceutical companies have focused on the development of medicines that act on target proteins, as the approach to the receptors made out of RNA is considerably complex.
Although several natural antibiotics act at the bacterial ribosomal RNA level, up to now designing by computer a new synthetic chemical entity capable of joining RNA target and have a relevant pharmacological effect was not possible. The terphenyl structures identified in this research could open new ways to approach other therapeutic targets formed by nucleic acids.
On the other hand, the infection by HIV affected 34 million people worldwide in 2010, according to the World Health Organisation (WHO). The emergence of resistance to the current antiretroviral therapies and the lack of an effective vaccine highlight the necessity of identifying the new medicines that act on other virus targets. Rev protein constitutes one of this alternative targets, but so far they it has not been possible to develop antiviral agents based in their inhibition.
The results of this research have been the objectives of a patent application, and the three laboratories involved in the research keep their collaboration with the objective of improving the pharmacological properties of new Rev inhibitors.
 

 Journal Reference:

1. Luis González-Bulnes, Ignacio Ibáñez, Luis M. Bedoya, Manuela Beltrán, Silvia Catalán, José Alcamí, Santos Fustero, José Gallego. Structure-Based Design of an RNA-Bindingp-Terphenylene Scaffold that Inhibits HIV-1 Rev Protein Function. Angewandte Chemie International Edition, 2013; DOI: 10.1002/anie.201309856

Courtesy: ScienceDaily
 

Methylation Signaling Controls Cancer Growth

A study led by researchers at Boston University School of Medicine (BUSM) demonstrates a new mechanism involving a signaling protein and its receptor that may block the formation of new blood vessels and cancer growth. The findings are published in the December issue of Science Signaling.

gnaling protein produced by damaged cells, which binds to one of its receptors VEGFR-2, located on the surface of blood vessel cells. Once VEGF is bound to its receptor, it is activated and sends a biochemical signal to the inside of the blood vessel cell to initiate angiogenesis. There are currently multiple Federal Drug Administration-approved medications that target this process. However these medications are limited by insufficient efficacy and the development of resistance.

The researchers demonstrated that a biochemical process called methylation, which can regulate gene expression, also affects VEGFR-2, and this can lead to angiogenesis. Using multiple methods, the researchers were able to interfere with the methylation process of VEGFR-2 and subsequently block angiogenesis and tumor growth.

"The study points to the methylation of VEGFR-2 as an exciting, yet unexplored drug target for cancer and ocular angiogenesis, ushering in a new paradigm in anti-angiogenesis therapy," said Nader Rahimi, PhD, associate professor of pathology, BUSM, who served as the study's senior investigator.

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The above story is based on materials provided by Boston University Medical Center, via EurekAlert!, a service of AAAS. 

Courtesy: ScienceDaily

Gene Mutation for Excessive Alcohol Drinking Found

Researchers have discovered a gene that regulates alcohol consumption and when faulty can cause excessive drinking. They have also identified the mechanism underlying this phenomenon.

The study showed that normal mice show no interest in alcohol and drink little or no alcohol when offered a free choice between a bottle of water and a bottle of diluted alcohol.
However, mice with a genetic mutation to the gene Gabrb1 overwhelmingly preferred drinking alcohol over water, choosing to consume almost 85% of their daily fluid as drinks containing alcohol -- about the strength of wine.
The consortium of researchers from five UK universities -- Newcastle University, Imperial College London, Sussex University, University College London and University of Dundee -- and the MRC Mammalian Genetics Unit at Harwell, funded by the Medical Research Council (MRC), Wellcome Trust and ERAB, publish their findings today in Nature Communications.
Dr Quentin Anstee, Consultant Hepatologist at Newcastle University, joint lead author said: "It's amazing to think that a small change in the code for just one gene can have such profound effects on complex behaviours like alcohol consumption.
"We are continuing our work to establish whether the gene has a similar influence in humans, though we know that in people alcoholism is much more complicated as environmental factors come into play. But there is the real potential for this to guide development of better treatments for alcoholism in the future."
Identifying the gene for alcohol preference
Working at the MRC Mammalian Genetics Unit, a team led by Professor Howard Thomas from Imperial College London introduced subtle mutations into the genetic code at random throughout the genome and tested mice for alcohol preference. This led the researchers to identify the gene Gabrb1 which changes alcohol preference so strongly that mice carrying either of two single base-pair point mutations in this gene preferred drinking alcohol (10% ethanol v/v -- about the strength of wine), over water.
The group showed that mice carrying this mutation were willing to work to obtain the alcohol-containing drink by pushing a lever and, unlike normal mice, continued to do so even over long periods. They would voluntarily consume sufficient alcohol in an hour to become intoxicated and even have difficulty in coordinating their movements.
The cause of the excessive drinking was tracked down to single base-pair point mutations in the gene Gabrb1, which codes for the beta 1 subunit, an important component of the GABA_A receptor in the brain. This receptor responds to the brain's most important inhibitory chemical messenger (GABA) to regulate brain activity. The researchers found that the gene mutation caused the receptor to activate spontaneously even when the usual GABA trigger was not present.
These changes were particularly strong in the region of the brain that controls pleasurable emotions and reward, the nucleus accumbens, as Dr Anstee explains: "The mutation of the beta1 containing receptor is altering its structure and creating spontaneous electrical activity in the brain in this pleasure zone, the nucleus accumbens. As the electrical signal from these receptors increases, so does the desire to drink to such an extent that mice will actually work to get the alcohol, for much longer than we would have expected."
Professor Howard Thomas said: "We know from previous human studies that the GABA system is involved in controlling alcohol intake. Our studies in mice show that a particular subunit of GABA_A receptor has a significant effect and most importantly the existence of these mice has allowed our collaborative group to investigate the mechanism involved. This is important when we come to try to modify this process first in mice and then in man."
Huge burden of alcohol addiction
Initially funded by the MRC, the 10-year project aimed to find genes affecting alcohol consumption. Professor Hugh Perry, Chair of the MRC's Neurosciences and Mental Health Board, said: "Alcohol addiction places a huge burden on the individual, their family and wider society. There's still a great deal we don't understand about how and why consumption progresses into addiction, but the results of this long-running project suggest that, in some individuals, there may be a genetic component. If further research confirms that a similar mechanism is present in humans, it could help us to identify those most at risk of developing an addiction and ensure they receive the most effective treatment."
The project was led by Professor Howard Thomas from Imperial College London and initiated at the MRC Mammalian Genetics Unit. The consortium now involves researchers at five UK universities -- Imperial College London, Newcastle University, Sussex University, University College London and the University of Dundee. Senior investigators are Dr Quentin Anstee at Newcastle University and Dr Susanne Knapp at Imperial College London (joint lead authors); Professor Dai Stephens at Sussex University; Professor Trevor Smart at University College London; Professor Jeremy Lambert and Dr Delia Belelli at the University of Dundee; and Professor Steve Brown at the MRC Mammalian Genetics Unit.
 

Journal Reference:

1. Quentin M. Anstee, Susanne Knapp, Edward P. Maguire, Alastair M. Hosie, Philip Thomas, Martin Mortensen, Rohan Bhome, Alonso Martinez, Sophie E. Walker, Claire I. Dixon, Kush Ruparelia, Sara Montagnese, Yu-Ting Kuo, Amy Herlihy, Jimmy D. Bell, Iain Robinson, Irene Guerrini, Andrew McQuillin, Elizabeth M.C. Fisher, Mark A. Ungless, Hugh M.D. Gurling, Marsha Y. Morgan, Steve D.M. Brown, David N. Stephens, Delia Belelli, Jeremy J. Lambert, Trevor G. Smart, Howard C. Thomas. Mutations in the Gabrb1 gene promote alcohol consumption through increased tonic inhibition. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3816

Courtesy: ScienceDaily