BIOLOGY & SCIENCE

Tuesday, August 5, 2008

article : Dr. Anthony Fauci has reflects on 25 years of HIV

On the 25th anniversary of the first scientific article linking a retrovirus to AIDS, Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, reflects in an essay in Nature on his experience treating and studying HIV/AIDS for the past quarter century. Outlining the peaks and valleys of the scientific community’s journey so far, Dr. Fauci writes, “…we must learn from our mis-steps, build on our successes in treatment and prevention, and renew our commitment to developing the truly transforming tools that will one day put this scourge behind us.”

From the outset, AIDS was clearly more menacing than any other novel disease Dr. Fauci and his colleagues had previously encountered, he writes. The period when clinicians lacked the ability to diagnose and treat AIDS was the bleakest of his career. The discovery that HIV causes AIDS stimulated a burst of progress in both the clinic and the laboratory. But the 1987 debut of the first effective drug against HIV, zidovudine (AZT), generated excessive optimism, Dr. Fauci reflects, as the virus quickly and predictably developed drug resistance.

Eight years and thousands of AIDS deaths later, protease inhibitors launched a renaissance of anti-HIV drug development in 1995. Combination therapies dramatically cut the rate of AIDS deaths in the United States—but the developing world has continued to suffer from lack of access to effective treatments for HIV. Even more sobering, Dr. Fauci writes, “Treatment alone will never end the AIDS pandemic…around three people are newly infected for every person put on therapy.”

So what options remain? Dr. Fauci praises research aimed at finding a cure for HIV/AIDS and affirms that this work must continue, but he places considerable hope and energy in preventing HIV infection, most importantly through the development of a vaccine. In retrospect, he writes, the scientific community expected to achieve an HIV vaccine unrealistically quickly. He advises that the steps we must take toward this goal now involve basic research, interdisciplinary research and active fostering of innovation, especially among young investigators. Twenty-five years since the discovery of HIV, Dr. Fauci views the prospect of ending the HIV/AIDS pandemic with cautious optimism.

Source : NIH/National Institute of Allergy and Infectious Diseases

article : HIV infection stems from few viruses

A new study reveals the genetic identity of human immunodeficiency virus (HIV), the version responsible for sexual transmission, in unprecedented detail.

The finding provides important clues in the ongoing search for an effective HIV/AIDS vaccine, said researchers at the University of Alabama at Birmingham (UAB). The UAB team found that among billions of HIV variants only a few lead to sexual transmission.

Earlier studies have shown that a ‘bottleneck’ effect occurs where few versions of the virus lead to infection while many variants are present in the blood. The UAB study is the first to use genetic analysis and mathematical modeling to identify precisely those viruses responsible for HIV transmission.

George M. Shaw, M.D., Ph.D., professor in the UAB departments of Medicine and Microbiology and senior author on the report, said the research sheds new light on potential vulnerabilities in the virus at a time when science, medicine and society are still reeling from the failure of a major HIV vaccine clinical trial.

“We can now identify unambiguously those viruses that are responsible for sexual transmission of HIV-1. For the first time we can see clearly the face of the enemy,” said Shaw, a project leader with the Center for HIV/AIDS Vaccine Immunology. The center is a National Institutes of Health-sponsored consortium of researchers at UAB, Harvard Medical School in Boston, Oxford University in England, the University of North Carolina in Chapel Hill and Duke University in Durham, N.C.

The new HIV-1 findings are published online in the Proceedings of the National Academy of Sciences.

The new study was performed by sequencing many copies of the HIV envelope gene present in the viruses taken from 102 recently infected patients. The envelope gene encodes for a protein called Env that forms part of the outer covering of the virus, and is responsible for its infectiousness.

The researchers then used sophisticated mathematical models of HIV replication and genetic change to identify the virus or viruses responsible for transmission. In 80 percent of the newly infected patients, a single virus caused transmission, though each virus was different in each patient. In the other 20 percent of patients, two to five unique viruses caused transmission.

“Previously, researchers employed inexact methodologies that prevented precise identification of the virus that initiated infection,” said Brandon Keele, Ph.D., an instructor in UAB’s Department of Medicine and lead study investigator. “Our findings allow us to identify not only the transmitted virus, but also viruses that evolve from it.”

The UAB team said their work would lead to new research on how different HIV genes and proteins work together to make a virus biologically fit for transmission and for growth in the face of mounting immunity.

Statistics show that while the worldwide percentage of people infected with HIV has leveled off, the total number HIV cases is rising. In 2007, 33.2 million people were estimated to be living with HIV, 2.5 million people became newly infected and 2.1 million people died from AIDS, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization.

Source : University of Alabama at Birmingham

article : The Study finds unique HIV vaccine formula elicits strong immune responses

Today, Advanced BioScience Laboratories, Inc. (ABL) and the University of Massachusetts Medical School (UMMS) report that their unique HIV vaccine formulation was effective in eliciting strong and balanced immune responses in healthy human volunteers. The findings are published in the journal Vaccine (“Cross-subtype antibody and cellular immune responses induced by a polyvalent DNA prime–protein boost HIV-1 vaccine in healthy human volunteers,” Vaccine online, May 22, 2008) In light of these initial findings, additional assays on volunteers’ samples were done by researchers at the University of Alabama at Birmingham, independently confirming the presence of long lasting and high quality T cell responses against HIV antigens. Results from this confirmatory study are currently available online in the Journal of Virology (April 30, 2008).

In this phase I clinical trial, sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), volunteers first received three injections of a DNA vaccine which expresses protective antigens from the HIV virus, followed by two injections of a protein vaccine whose components matched those included in the DNA vaccine. The report in Vaccine is the first scientific article in which a “DNA prime-protein boost” combination vaccination method is tested in humans for HIV vaccine development. Scientists at ABL and UMMS and their collaborators discovered that this combination approach is highly effective in inducing strong antibody and cell-mediated immune responses in human volunteers.

“Given the challenges of developing a vaccine against HIV, scientists have long believed that a final, effective HIV vaccine will require the induction of balanced responses from both arms of human immune system. Our results demonstrate that it is feasible to use this combination approach to achieve this objective,” said Phillip Markham, PhD, of ABL, the Principal Investigator (PI) on this vaccine development effort, performed under contract to the NIAID.

One unique design underlying this combination HIV vaccine formulation is the use of a “cocktail” of five different envelope (Env) proteins collected from HIV viruses circulating in different parts of the world. Env is a key protective antigen and the goal was to elicit broad antibody responses against a wide range of HIV viruses in order to counter the issue of frequent HIV mutations. Indeed, the high titer antibodies found in volunteers’ sera were able to recognize each of a very diverse group of Env antigens that were included in this study. More significantly, the majority of volunteers developed positive neutralizing antibodies against a good portion of the five HIV subtypes included in the assay.

Shan Lu, MD, PhD, professor of medicine and biochemistry & molecular pharmacology at the University of Massachusetts Medical School and the co- Principal Investigator (co-PI) of the vaccine development program, describes the finding of neutralizing antibodies in this study as “a major step forward.”

“Previously, we didn’t know where to start. The neutralizing antibody titers in our study are still relatively low, but, these results are promising and open the door for future efforts to optimize HIV vaccine formulations in order to achieve a protective HIV vaccine,” said Dr. Lu.

The dominant approaches in the current HIV vaccine field rely on viral vector-based delivery systems, an approach that produced disappointing results in a recent efficacy trial. Drs. Markham and Lu believe their HIV vaccine strategy will offer an alternative approach to focus on the induction of protective antibodies for HIV vaccine development, while maintaining strong cell-mediated immune responses. In addition to NIH, the International AIDS Vaccine Initiative (IAVI) also provided funding support to part of the study. Researchers from Duke University Medical School also participated, as did Dr. Paul Goepfert at the University of Alabama-Birmingham.

Source : University of Massachusetts Medical School

article : Failed HIV drug gets second chance with addition of gold nanoparticles

Researchers at North Carolina State University have discovered that adding tiny bits of gold to a failed HIV drug rekindle the drug’s ability to stop the virus from invading the body’s immune system.

The addition of gold nanoparticles to a modified version of a drug designed in the 1990s to combat HIV – but discarded due to its harmful side effects – creates a compound that prevents the virus from gaining a cellular foothold, say Dr. Christian Melander, assistant professor of chemistry at NC State, and doctoral student T. Eric Ballard.

Their findings appear online in the Journal of the American Chemical Society.

The drug, a compound known as TAK-779, was originally found to bind to a specific location on human T-cells, which blocks the HIV virus’ entry to the body’s immune system. Unfortunately, the portion of the drug’s molecule that made binding possible had unpleasant side effects. When that portion of the molecule – an ammonium salt – was removed, the drug lost its binding ability.

That’s when the researchers turned to gold as the answer. The element is non-reactive in the human body, and would be the perfect “scaffold” to attach molecules of the drug to in the absence of the ammonium salt, holding the drug molecules together and concentrating their effect.

“The idea is that by attaching these individual molecules of the drug with a weak binding ability to the gold nanoparticle, you can magnify their ability to bind,” Melander says.

The researchers’ theory proved correct. They started with a modified version of TAK-779, which didn’t include the harmful ammonium salt. After testing, they found that attaching 12 molecules of the modified drug (SDC-1721) to one nanoparticle of gold restored the drug’s ability to prevent HIV infection in primary cultured patient cells. When only one molecule of the drug was attached to the gold nanoparticle, the compound was unable to prevent HIV infection, indicating that the multivalency of the drug was important for its activity.

“We’ve discovered a non-harmful way to improve the strength and efficacy of an important drug,” Melander says. “There’s no reason to think that this same process can’t be used with similar effect on other existing drugs.”

Source : North Carolina State University

article : Scientists image a single HIV particle being born

A mapmaker and a mathematician may seem like an unlikely duo, but together they worked out a way to measure longitude – and kept millions of sailors from getting lost at sea. Now, another unlikely duo, a virologist and a biophysicist at Rockefeller University, is making history of their own. By using a specialized microscope that only illuminates the cell’s surface, they have become the first to see, in real time and in plain view, hundreds of thousands of molecules coming together in a living cell to form a single particle of the virus that has, in less than 25 years, claimed more than 25 million lives: HIV.

This work, published in the May 25 advanced online issue of Nature, may not only prove useful in developing treatments for the millions around the globe still living with the lethal virus but the technique created to image its assembly may also change the way scientists think about and approach their own research.

“The use of this technique is almost unlimited,” says Nolwenn Jouvenet, a postdoc who spearheaded this project under the direction of HIV expert Paul Bieniasz and cellular biophysicist Sandy Simon, who has been developing the imaging technique since 1992. “Now that we can actually see a virus being born, it gives us the opportunity to answer previously unanswered questions, not only in virology but in biology in general.”

Unlike a classical microscope, which shines light through a whole cell, the technique called total internal reflection microscopy only illuminates the cell’s surface where HIV assembles. “The result is that you can see, in exquisite detail, only events at the cell surface. You never even illuminate anything inside of the cell so you can focus on what you are interested in seeing the moment it is happening,” says Simon, professor and head of the Laboratory of Cellular Biophysics.

When a beam of light passes through a piece of glass to a cell’s surface, the energy from the light propagates upward, illuminating the entire cell. But when that beam is brought to a steeper angle, the light’s energy reflects off the cell’s surface, illuminating only the events going on at its most outer membrane. By zeroing in at the cell’s surface, the team became the first to document the time it takes for each HIV particle, or virion, to assemble: five to six minutes. “At first, we had no idea whether it would take milliseconds or hours,” says Jouvenet. “We just didn’t know.”

“This is the first time anyone has seen a virus particle being born,” says Bieniasz, who is an associate professor and head of the Laboratory of Retrovirology at Rockefeller and a scientist at the Aaron Diamond AIDS Research Center. “Not just HIV,” he clarifies, “any virus.”

To prove that what they were watching was virus particles assembling at the surface (rather than an already assembled virion coming into their field of view from inside the cell), the group tagged a major viral protein, called the Gag protein, with molecules that fluoresce, but whose color would change as they packed closer together. Although many different components gather to form a single virion, the Gag protein is the only one necessary for assembly. It attaches to the inner face of the cell’s outer membrane and when enough Gag molecules flood an area, they coalesce in a way that spontaneously forms a sphere.

Simon, Bieniasz and Jouvenet found that the Gag molecules are recruited from the inside of the cell and travel to the cell’s surface. When enough Gag molecules get close and start bumping into each other, the cell’s outer membrane starts to bulge outward into a budding virion and then pinches off to form an individual, infectious particle. At this point, the researchers showed that the virion is a lone entity, no longer exchanging resources with the cell. By using tricks from optics and physiology, they were able to watch the steps of viral assembly, budding, and even scission off the cell surface. With such a view they can start to describe the entire lifeline in the birth of the virus.

“I think that you can begin to understand events on a different level if you actually watch them happen instead of inferring that they might occur using other techniques,” says Bieniasz. “This technique and this collaboration made that possible.”

Source : Rockefeller University