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Posts Tagged ‘infectiology

Neural Progenitor Cells As Reservoirs For HIV In The Brain

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Impaired brain function is a prominent and still unsolved problem in AIDS. Shortly after an individual becomes infected with HIV, the virus can invade the brain and persist in this organ for life. Many HIV-infected individuals experience disturbances in memory functions and movement, which can progress to serious dementia. How the virus causes brain disease is still unclear.


HI-Virus leaving a cell. (Credit: NIH)

Dr. Ruth Brack-Werner and her team at the Institute of Virology of the German Research Center for Environmental Health previously demonstrated that HIV invades not only brain macrophages but also astrocytes. Astrocytes are the most abundant cells in the brain. They perform many important activities which support functions of nerve cells and protect them from harmful agents. HIV-infected astrocytes normally restrain the virus and prevent its production. However, various factors can cause astrocytes to lose control over the virus, allowing the virus to replicate and to reach the brain. There HIV can infect other brain cells as well as immune cells that patrol the brain and may carry the virus outside the brain.

Thus astrocytes form a reservoir for HIV in infected individuals and represent a serious obstacle to elimination of the virus from infected individuals. Whether this also applies to other types of brain cells was unclear until now. In a study recently published in AIDS, Dr. Brack Werner, together with Ina Rothenaigner and colleagues present data indicating that neural progenitor cells can also form HIV reservoirs in the brain. Neural progenitor cells are capable of developing into different types of brain cells and have an enormous potential for repair processes in the brain.

Dr. Brack-Werner’s team used a multi-potent neural progenitor cell line, which can be grown and developed to different types of brain cells in the laboratory, for their studies. After exposing these neural progenitor cells to HIV, they examined the cultures for signs of virus infection for 115 days. HIV was found to persist in these cultures during the entire observation period.

The cultures released infectious HIV particles for over 60 days and contained information for production of HIV regulatory proteins- Tat, Rev and Nef- for even longer. Dr. Brack-Werner and her team also examined neural progenitor cell populations cells with persisting HIV for differences from uninfected cells. They found that HIV persistence had an influence on the expression of selected genes and on cell morphology, but did not prevent their development to astrocytes. Thus HIV persistence has the potential to change neural progenitor cells.

Dr. Brack-Werner’s summarizes, “Our study indicates that neural progenitor cells are potential reservoirs for HIV and that HIV persistence has the potential to change the biology of these cells.” In future studies the researchers are planning to investigate the influence of HIV infection on important functions of neural progenitor cells. These include migration to diseased regions of the brain and development of different types of brain cells. Subsequently they will investigate how HIV changes neural progenitor cells and, importantly, how to protect neural progenitor cells from harmful effects of the virus in HIV infected individuals.

AIDS. 2007 Nov 12;21(17):2271-81.
Long-term HIV-1 infection of neural progenitor populations.
Rothenaigner I, Kramer S, Ziegler M, Wolff H, Kleinschmidt A, Brack-Werner R.

GSF–National Research Center for Environment and Health, Institute of Molecular Virology, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.

BACKGROUND: HIV can reside in the brain for many years. While astrocytes are known to tolerate long-term HIV infection, the potential of other neural cell types to harbour HIV is unclear. OBJECTIVE: To investigate whether HIV can persist in neural progenitor cell populations. DESIGN: A multipotent human neural stem cell line (HNSC.100) was used to compare HIV infection in neural progenitor and astrocyte cell populations. METHODS: Expression of cellular genes/proteins was analysed by real-time reverse transcriptase PCR, Western blot, immunocytochemistry and flow cytometry. Morphological properties of cells were measured by quantitative fluorescent image analysis. Virus release by cells exposed to HIV-1IIIB was monitored by enzyme-linked immunosorbent assay for Gag. Proviral copy numbers were determined by real-time PCR and early HIV transcripts by reverse transcriptase PCR. Rev activity was determined with a fluorescent-based reporter assay. RESULTS: Progenitor populations differed from astrocyte populations by showing much lower glial fibrillary acidic protein (GFAP) production, higher cell-surface expression of the CXCR4 chemokine receptor, higher Rev activity and distinct cell morphologies. HIV-exposed progenitor cultures released moderate amounts of virus for over 2 months and continued to display cell-associated HIV markers (proviral DNA, early HIV transcripts) during the entire observation period (115 days). Differentiation of HIV-infected progenitor cells to astrocytes was associated with transient activation of virus production. Long-term HIV infection of progenitor populations led to upregulation of GFAP and changes in cell morphology. CONCLUSION: These studies suggest that neural progenitor populations can contribute to the reservoir for HIV in the brain and undergo changes as a consequence of HIV persistence.

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Written by huehueteotl

March 7, 2008 at 12:56 pm

Posted in HIV

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HIV Breakthrough: Protein That Fights Immunodeficiency Identified

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A Canada-U.S. research team has solved a major genetic mystery: How a protein in some people’s DNA guards them against killer immune diseases such as HIV. In an advance online edition of Nature Medicine, the scientists explain how the protein, FOX03a, shields against viral attacks and how the discovery will help in the development of a HIV vaccine.

 

Computer model of AIDS virus (HIV). (Credit: Produced by Richard Feldmann; courtesy of NIH/National Institute of Allergy and Infectious Diseases)

“HIV infection is characterised by the slow demise of T-cells, in particular central memory cells, which can mediate lifelong protection against viruses,” said lead researcher Rafick-Pierre Sékaly, a Université de Montréal professor and a researcher at the Centre Hospitalier de l’Université de Montréal and the French Institut national de la santé et de la recherche médicale (Inserm).

“Our group has found how the key protein, FOX03a, is vital to the survival of central memory cells that are defective in HIV-infected individuals even if they are treated,” added Dr. Sékaly, who produced his study with CHUM and Inserm colleagues including Elias El Haddad and Julien van Grevenynghe. Collaborators also included Jean-Pierre Routy, a McGill University Health Centre researcher and professor at McGill University and Robert S. Balderas, Vice-President of Research and Development at BD Biosciences of San Diego, CA.

Public support for the research came through Genome Canada and Génome Québec, among others, while private contributions came via a segment of BD (Becton, Dickinson and Company). “Public-private collaborations such as this play an important role in advancing medical research,” Robert S. Balderas. “BD Biosciences was pleased to provide powerful research instruments, reagents and technical expertise to support this breakthrough research.”

The breakthrough emerged by studying three groups of men: One HIV-negative sample, a second HIV-positive group whose infection was successfully controlled through tritherapy and a third group whose HIV did not show any symptoms. Called elite controllers, this third group fended off infection without treatment because their immune system, which would normally be attacked by HIV, maintained its resilient immune memory through the regulation of the FOX03a protein.

“Given their perfect resistance to HIV infection, elite controllers represent the ideal study group to examine how proteins are responsible for the maintenance of an immune system with good anti-viral memory,” said Dr. Haddad. “This is the first study to examine, in people rather than animals, what shields the body’s immune system from infection and to pinpoint the fundamental role of FOX03a in defending the body.”

Beyond HIV treatment, Dr. Sékaly said his team’s discovery offers promise for other immune diseases. “The discovery of FOX03a will enable scientists to develop appropriate therapies for other viral diseases that weaken the immune system,” he said, citing cancer, rheumatoid arthritis, hepatitis C, as well as organ or bone marrow transplant rejection.

Paul L’Archevêque, president and CEO of Génome Québec, lauded Dr. Sékaly’s team for their breakthrough and the people who volunteered for the study. “This discovery, the first such study in humans, is a major step forward in the understanding of how our immune system responds to life-threatening infections such as HIV. This advance stems directly from research co-financed by Génome Québec, which demonstrates the impact that genomic research can have in improving healthcare.”

This research was made possible by public and private institutions across Canada, the United States and France: the Université de Montréal, CHUM, Inserm, MUHC, Genome Canada, Génome Québec, Fonds de la recherche en santé du Québec, Canadian Institutes of Health Research, National Institutes of Health and BD Biosciences.

 

Nature Medicine Published online: 2 March 2008 | doi:10.1038/nm1728
Transcription factor FOXO3a controls the persistence of memory CD4+ T cells during HIV infection

Julien van Grevenynghe, Francesco A Procopio, Zhong He, Nicolas Chomont, Catherine Riou, Yuwei Zhang, Sylvain Gimmig, Genevieve Boucher, Peter Wilkinson, Yu Shi, Bader Yassine-Diab, Elias A Said, Lydie Trautmann, Mohamed El Far, Robert S Balderas, Mohamed-Rachid Boulassel, Jean-Pierre Routy, Elias K Haddad & Rafick-Pierre Sekaly

The persistence of central memory CD4+ T cells (TCM cells) is a major correlate of immunological protection in HIV/AIDS, as the rate of TCM cell decline predicts HIV disease progression. In this study, we show that TCM cells and effector memory CD4+ T cells (TEM cells) from HIV+ elite controller (EC) subjects are less susceptible to Fas-mediated apoptosis and persist longer after multiple rounds of T cell receptor triggering when compared to TCM and TEM cells from aviremic successfully treated (ST) subjects or from HIV donors. We show that persistence of TCM cells from EC subjects is a direct consequence of inactivation of the FOXO3a pathway. Silencing the transcriptionally active form of FOXO3a by small interfering RNA or by introducing a FOXO3a dominant-negative form (FOXO3a Nt) extended the long-term survival of TCM cells from ST subjects to a length of time similar to that of TCM cells from EC subjects. The crucial role of FOXO3a in the survival of memory cells will help shed light on the underlying immunological mechanisms that control viral replication in EC subjects.

Written by huehueteotl

March 4, 2008 at 4:33 pm

Gene Can Block The Spread Of HIV

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A team of researchers at the University of Alberta has discovered a gene that is able to block HIV, and in turn prevent the onset of AIDS. Stephen Barr, a molecular virologist in the Department of Medical Microbiology and Immunology, says his team has identified a gene called TRIM22 that can block HIV infection in a cell culture by preventing the assembly of the virus.

“When we put this gene in cells, it prevents the assembly of the HIV virus,” said Barr, a postdoctoral fellow. “This means the virus cannot get out of the cells to infect other cells, thereby blocking the spread of the virus.”

Barr and his team also prevented cells from turning on TRIM22 – provoking an interesting phenomenon: the normal response of interferon, a protein that co-ordinates attacks against viral infections, became useless at blocking HIV infection.

“This means that TRIM22 is an essential part of our body’s ability to fight off HIV. The results are very exciting because they show that our bodies have a gene that is capable of stopping the spread of HIV.”

One of the greatest challenges in battling HIV is the virus’ ability to mutate and evade medications. Antiretroviral drugs introduced during the late 1990s interfere with HIV’s ability to produce new copies of itself – and even they are beneficial, the drugs are unable to eradicate the virus. Barr and his team have discovered a gene that could potentially do the job naturally.

“There are always newly emerging drug-resistant strains of HIV so the push has been to develop more natural means of blocking the virus. The discovery of this gene, which is natural in our cells, might provide a different avenue,” said Barr. “The gene prevents the assembly of the virus so in the future the idea would be to develop drugs or vaccines that can mimic the effects of this gene.”

“We are currently trying to figure out why this gene does not work in people infected with HIV and if there is a way to turn this gene on in those individuals,” he added. “We hope that our research will lead to the design of new drugs, or vaccines that can halt the person-to-person transmission of HIV and the spread of the virus in the body, thereby blocking the onset of AIDS.”

The researchers are now investigating the gene’s ability to battle other viruses.

The Interferon Response Inhibits HIV Particle Production by Induction of TRIM22.

Barr SD, Smiley JR, Bushman FD (2008)

Abstract

Treatment of human cells with Type 1 interferons restricts HIV replication. Here we report that the tripartite motif protein TRIM22 is a key mediator. We used transcriptional profiling to identify cellular genes that were induced by interferon treatment and identified TRIM22 as one of the most strongly up-regulated genes. We confirmed, as in previous studies, that TRIM22 over-expression inhibited HIV replication. To assess the role of TRIM22 expressed under natural inducing conditions, we compared the effects of interferon in cells depleted for TRIM22 using RNAi and found that HIV particle release was significantly increased in the knockdown, implying that TRIM22 acts as a natural antiviral effector. Further studies showed that TRIM22 inhibited budding of virus-like particles containing Gag only, indicating that Gag was the target of TRIM22. TRIM22 did not block the release of MLV or EIAV Gag particles. Inhibition was associated with diffuse cytoplasmic staining of HIV Gag rather than accumulation at the plasma membrane, suggesting TRIM22 disrupts proper trafficking. Mutational analyses of TRIM22 showed that the catalytic amino acids Cys15 and Cys18 of the RING domain are required for TRIM22 antiviral activity. These data disclose a pathway by which Type 1 interferons obstruct HIV replication.

Written by huehueteotl

March 3, 2008 at 4:02 pm

Posted in HIV

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Dramatic Boost To Immune Response With Engineered Artificial ‘Cells’

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Using artificial cell-like particles, Yale biomedical engineers have devised a rapid and efficient way to produce a 45-fold enhancement of T cell activation and expansion, an immune response important for a patient’s ability to fight cancer and infectious diseases, according to an advance on line report in Molecular Therapy.

Stimulatory particles (red) bound to activated T-cells (blue) as seen by fluorescence microscopy. Scale bar = 10 µm (Credit: Fahmy-Steenblock/Yale)

The artificial cells, developed by Tarek Fahmy, assistant professor of biomedical engineering at Yale and his graduate student Erin Steenblock, are made of a material commonly used for biodegradable sutures. The authors say that the new method is the first “off-the-shelf” antigen-presenting artificial cell that can be tuned to target a specific disease or infection.

“This procedure is likely to make it to the clinic rapidly,” said senior author Fahmy. “All of the materials we use are natural, biodegradable already have FDA approval.”

Cancer, viral infections and autoimmune diseases have responded to immunotherapy that boosts a patient’s own antigen-specific T cells. In those previous procedures, a patient’s immune cells were harvested and then exposed to cells that stimulate the activation and proliferation of antigen-specific T-cells. The “boosted” immune cells were then infused back into the patient to attack the disease.

Limitations of these procedures include costly and tedious custom isolation of cells for individual patients and the risk of adverse reaction to foreign cells, according to the Yale researchers. They also pointed to difficulty in obtaining and maintaining sufficient numbers of activated T-cells for effective therapeutic response.

In the new system, the outer surface of each particle is covered in universal adaptor molecules that serve as attachment points for antigens — molecules that activate the patient’s T-cells to recognize and fight off the targeted disease — and for stimulatory molecules. Inside of each particle, there are slowly released cytokines that further stimulate the activated T-cells to proliferate to as much as 45 times their original number.

“Our process introduces several important improvements,” said lead author Steenblock. “First, the universal surface adaptors allow us to add a span of targeting antigen and co-stimulatory molecules. We can also create a sustained release of encapsulated cytokines. These enhancements mimic the natural binding and signaling events that lead to T-cell proliferation in the body. It also causes a fast and effective stimulation of the patient’s T-cells — particularly T-cells of the cytotoxic type important for eradicating cancer.”

“Safe and efficient T-cell stimulation and proliferation in response to specific antigens is a goal of immunotherapy against infectious disease and cancer,” said Fahmy. “Our ability to manipulate this response so rapidly and naturally with an “off the shelf” reproducible biomaterial is a big step forward.”

Fahmy was recently awarded a five-year National Science Foundation (NSF) Career Award for work on this process and ways of engineering biomaterials to manipulate immune responses to fight cancer and other diseases. His approach incorporates signals important for T-cell stimulation in biocompatible polymer particulates, and integrates all the signals needed for efficient T-cell stimulation.

According to the NSF, devices as such these offer ease and flexibility in targeting different types of T-cells, and is expected to lead to state of the art improvements in the preparation of a new generation of therapeutic systems.

 

Molecular Therapy (2008); doi:10.1038/mt.2008.8

Mechanisms of Immunization Against Cancer Using Chimeric Antigens

Manuel E Engelhorn1, José A Guevara-Patiño2, Taha Merghoub1, Cailian Liu1, Cristina R Ferrone3, Gabriele A Rizzuto1, Daniel H Cymerman1, David N Posnett1, Alan N Houghton1 and Jedd D Wolchok1

  1. 1The Swim Across America Laboratory, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
  2. 2Section of Surgery and Committee on Immunology, University of Chicago, Chicago, Illinois, USA
  3. 3Division of General Surgery, Massachusetts General Hospital, Boston, Massachusetts, USA

Correspondence: Jedd D Wolchok, Melanoma-Sarcoma Service, Ludwig Center for Cancer Immunotherapy, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Room Z-1462, New York, New York 10021, USA. E-mail: wolchokj@mskcc.org

Received 29 October 2007; Accepted 28 December 2007; Published online 26 February 2008.

Successful approaches to tumor immunotherapy must overcome the physiological state of tolerance of the immune system to self-tumor antigens. Immunization with appropriate variants of syngeneic antigens can achieve this. However, improvements in vaccine design are needed for efficient cancer immunotherapy. Here we explore nine different chimeric vaccine designs, in which the antigen of interest is expressed as an in-frame fusion with polypeptides that impact antigen processing or presentation. In DNA immunization experiments in mice, three of nine fusions elevated relevant CD8+ T-cell responses and tumor protection relative to an unfused melanoma antigen. These fusions were: Escherichia coli outer membrane protein A (OmpA), Pseudomonas aeruginosa exotoxin A, and VP22 protein of herpes simplex virus-1. The gains of immunogenicity conferred by the latter two are independent of epitope presentation by major histocompatibility complex class II (MHC II). This finding has positive implications for immunotherapy in individuals with CD4+ T-cell deficiencies. We present evidence that antigen instability is not a sine qua non condition for immunogenicity. Experiments using two additional melanoma antigens identified different optimal fusion partners, thereby indicating that the benefits of fusion vectors remain antigen specific. Therefore large fusion vector panels such as those presented here can provide information to promote the successful advancement of gene-based vaccines.

Written by huehueteotl

February 27, 2008 at 10:28 am

Where Immune Cells Really Do Fight Viruses

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Vaccines have led to many of the world’s greatest public health triumphs, but many deadly viruses, such as HIV, still elude the best efforts of scientists to develop effective vaccines against them. An improved understanding of how the immune system operates during a viral infection is critical to designing successful anti-virus vaccines. Scientists from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), have added an important dimension to this knowledge.
Focusing on mouse lymph nodes–bean-shaped organs that contain a variety of immune cells and are distributed throughout the body–the researchers discovered that immune cells confront viruses just inside of the lymph node and not deep within these organs as previously thought. The study, led by Jonathan Yewdell, M.D., Ph.D., chief of the NIAID Cellular Biology Section and his NIAID colleague, Heather Hickman, Ph.D., is described in Nature Immunology.

The results are significant, the authors say, as they observed in detail the interaction of viruses and immune cells inside a living organism, in this case, mice. Combining expertise from disciplines such as imaging, immunology, virology and other specialties, the scientists first extracted and then purified specific T cells–killer T cells–from mice. Killer T cells, which attack and kill infected or cancerous cells, are major weapons in the immune system arsenal. The scientists labeled the T cells with a fluorescent marker, injected them back into the mice, and then infected the animals with vaccinia virus, the virus used to make smallpox vaccine, engineered to express a brilliantly colored protein.

Using a multiphoton microscope, a highly specialized microscope that enables scientists to peer into a living organism, the scientists could now look into the lymph nodes of the infected mice and see that the viruses had infected cells just inside the lymph node surface, triggering a swarm of T cells. These virus-specific T cells form an elaborate and dynamic communications network that activates them to divide and travel to the site of viral infection, where they kill virus-infected cells.

“A key challenge in viral vaccine research is developing strategies for immunizing against lethal viruses such as HIV that have eluded the standard vaccine approaches,” notes Dr. Yewdell. “We have contributed a page to the handbook of understanding how to rationally design vaccines to elicit a T-cell response.” According to the NIAID team, pinpointing where in the lymph node immune cells fight the virus should help efforts to design effective anti-virus vaccines.

Nat Immunol. 2008 Feb;9(2):155-65. Epub 2008 Jan 13.
Direct priming of antiviral CD8+ T cells in the peripheral interfollicular region of lymph nodes.

Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.

It is uncertain how antiviral lymphocytes are activated in draining lymph nodes, the site where adaptive immune responses are initiated. Here, using intravital microscopy we show that after infection of mice with vaccinia virus (a large DNA virus) or vesicular stomatitis virus (a small RNA virus), virions drained to the lymph node and infected cells residing just beneath the subcapsular sinus. Naive CD8+ T cells rapidly migrated to infected cells in the peripheral interfollicular region and then formed tight interactions with dendritic cells, leading to complete T cell activation. Thus, antigen presentation at the lymph node periphery, not at lymphocyte exit sites in deeper lymph node venules, as dogma dictates, has a dominant function in antiviral CD8+ T cell activation.

Written by huehueteotl

February 7, 2008 at 1:13 pm

Posted in HIV

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Novel Vaccine Concept Against AIDS Or Cervical Cancer

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Creating vaccines to protect people against viral diseases like AIDS, cervical cancer and infectious hepatitis is a delicate balancing act: If the immune system’s response to the vaccine is too strong, toxic side effects can kill the patient. If it’s not strong enough, the virus will spread faster than the immune system can kill it.

A new vaccine design strategy developed by scientists at The Wistar Institute Vaccine Center could be the answer. The secret is using a herpes simplex protein called glycoprotein D to block a specific receptor molecule on antigen-presenting cells, or APCs. These sentinel cells monitor the body for foreign antigens — molecules that can stimulate an immune response — from invading viruses.

https://i0.wp.com/content.answers.com/main/content/wp/en-commons/f/f2/Herpes_simpex_virus.jpg

Herpes-simplex-virus

When they detect viral antigens, APCs signal the body’s immune system to activate T cells to attack and destroy cells infected with the virus. At the same time, they also send inhibitory signals to prevent overreaction by the immune system. One of thee inhibitory signals is blocked by glycoprotein D from herpes virus.

In a study that will be published February 6 in Nature Medicine and is available online, Wistar scientists showed that vectors, which are vaccine delivery systems, made by fusing the glycoprotein D with genes from target antigens increase the immune system’s response to those antigens in cell cultures and laboratory mice. The researchers used antigens from HIV, the virus that causes AIDS, and from HPV-16, a human papilloma virus that causes cervical cancer.

Hildegund C.J. Ertl, M.D., director of The Wistar Institute Vaccine Center and senior author of the study, says using glycoprotein D to deliver antigens has a major advantage over other vaccine approaches. “It allows us to lower the dose but still get a stronger immune response,” she says.

Glycoprotein D is part of the herpes viral envelope and is expressed on the surface of cells infected with the herpes simplex virus. Glycoprotein D binds to a receptor molecule called HVEM (herpes virus entry mediator) on antigen-presenting cells. By locking onto the HVEM receptor, glycoprotein D prevents HVEM from binding to another molecule called BTLA on T and B lymphocytes — white blood cells that attack disease-causing pathogens.

Binding between HVEM and BTLA is the first step in an inhibitory signaling pathway that reduces the immune system’s response to the presence of a virus. Blocking this inhibitory pathway allows the body to mount a stronger immune response by generating more antigen-specific CD8+ T cells to attack cells infected with the virus.

The researchers found that fusing HIV and HPV antigens to glycoprotein D enhances the immune response to those antigens. Mice injected with vaccines that included antigens fused to glycoprotein D generated more virus-killing CD8+ T cells than mice injected with the same vaccines and antigens, but without the glycoprotein D carrier protein.

Researchers also inoculated identical strains of laboratory mice with vaccines containing genes for the cancer-causing proteins E7, E6 and E5 from the HPV-16 virus. One group of animals received HPV-16 genes spliced into the genetic code for glycoprotein D; another group received the same antigens without glycoprotein D. Ten to 14 days later, both groups of animals were injected with a fast-growing tumor cell line that normally generates extensive tumors in mice within 14 days.

Mice that received vaccines with the glycoprotein D-antigen combination were fully protected against cancer, says Wistar’s Marcio Lasaro, Ph.D., lead author of the study. However, mice inoculated with vaccines containing the same HPV-16 genes, but without glycoprotein D, developed tumors after being inoculated with the same tumor cell line.

“It’s important to point out that the molecules we targeted in mice are similar to those in humans, and all the basic in-vitro studies in the paper were done with human molecules, making it likely that the method will also work in people,” Lasaro says.

Ertl says the ability of the glycoprotein D carrier protein to enhance the immune response could be particularly important to the development of a long-sought vaccine for AIDS. “The problem with HIV vaccines is that they might look good in mice and primates, but comparable doses in humans are too toxic,” she says. “If you lower the dose to avoid toxic side effects, you don’t get the immune response you need.” She believes that using glycoprotein D may solve that problem.

Ertl and her colleagues are planning future studies to further elucidate the mechanism behind the carrier protein’s effectiveness. If studies in research animals continue to be positive, they hope to conduct human clinical studies with HIV and HPV vaccines currently under development at The Wistar Institute Vaccine Center.

The Wistar Institute has filed for patent protection on the glycoprotein D carrier protein technology.

 

Nature Medicine Published online: 13 January 2008 | doi:10.1038/nm1704

Targeting of antigen to the herpesvirus entry mediator augments primary adaptive immune responses

Marcio O Lasaro, Nia Tatsis, Scott E Hensley, J Charles Whitbeck, Shih-Wen Lin, John J Rux, E John Wherry, Gary H Cohen, Roselyn J Eisenberg, Hildegund C Ertl

Interactions between the herpesvirus entry mediator (HVEM) and the B- and T-lymphocyte attenuator (BTLA) inhibit B and T cell activation. HVEM-BTLA interactions are blocked by herpes simplex virus (HSV) glycoprotein D (gD) through binding of its N-terminal domain to the BTLA binding site of HVEM. In this study, we inserted viral antigens into the C-terminal domain of gD and expressed these antigens with plasmid or E1-deleted (replication-defective) adenovirus vectors. Viral antigens fused to gD induced T and B cell responses to the antigen that were far more potent than those elicited by the same antigen expressed without gD. The immunopotentiating effect required binding of the gD chimeric protein to HVEM. Overall, the studies demonstrate that targeting of antigen to the BTLA binding site of HVEM augments the immunogenicity of vaccines.

Written by huehueteotl

February 4, 2008 at 10:09 am

Clues For HIV Vaccine Design

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Two simple changes in its outer envelope protein could render the AIDS virus vulnerable to attack by the immune system, according to research from Kenya and the Fred Hutchinson Cancer Research Center.

The results could provide important clues for designing an effective AIDS vaccine, which is badly needed to decrease the number of new HIV infections, now estimated at about 2.5 million per year worldwide.

Although most people infected with HIV produce antibodies against the virus within several weeks following infection, these antibodies rarely prevent the infection from progressing to symptomatic AIDS.

While studying a group of women at risk of HIV in Mombasa, Julie Overbaugh and colleagues noticed that one woman carried an AIDS virus that was easily inactivated by antibodies. They initially described this case in 2007 in the Journal AIDS.

Analyzing this woman’s virus, they found that it contains mutations in four amino acids in the envelope protein, two of which, when introduced into unrelated strains of HIV in the laboratory, conferred sensitivity to inactivation by a number of antibodies produced in people infected with HIV.

The researchers propose that these mutations cause a change in the overall structure of the envelope protein that results in exposure to the immune system of regions that are normally hidden. If further research confirms this idea, vaccines containing envelope proteins that include these mutations might be able to stimulate an antibody response that would protect against infection with HIV.

PLoS Med 5(1): e9 doi:10.1371/journal.pmed.0050009

Blish CA, Nguyen MA, Overbaugh J (2008)

Enhancing Exposure of HIV-1 Neutralization Epitopes through Mutations in gp41.

BackgroundThe generation of broadly neutralizing antibodies is a priority in the design of vaccines against HIV-1. Unfortunately, most antibodies to HIV-1 are narrow in their specificity, and a basic understanding of how to develop antibodies with broad neutralizing activity is needed. Designing methods to target antibodies to conserved HIV-1 epitopes may allow for the generation of broadly neutralizing antibodies and aid the global fight against AIDS by providing new approaches to block HIV-1 infection. Using a naturally occurring HIV-1 Envelope (Env) variant as a template, we sought to identify features of Env that would enhance exposure of conserved HIV-1 epitopes.

Methods and Findings

Within a cohort study of high-risk women in Mombasa, Kenya, we previously identified a subtype A HIV-1 Env variant in one participant that was unusually sensitive to neutralization. Using site-directed mutagenesis, the unusual neutralization sensitivity of this variant was mapped to two amino acid mutations within conserved sites in the transmembrane subunit (gp41) of the HIV-1 Env protein. These two mutations, when introduced into a neutralization-resistant variant from the same participant, resulted in 3- to >360-fold enhanced neutralization by monoclonal antibodies specific for conserved regions of both gp41 and the Env surface subunit, gp120, >780-fold enhanced neutralization by soluble CD4, and >35-fold enhanced neutralization by the antibodies found within a pool of plasmas from unrelated individuals. Enhanced neutralization sensitivity was not explained by differences in Env infectivity, Env concentration, Env shedding, or apparent differences in fusion kinetics. Furthermore, introduction of these mutations into unrelated viral Env sequences, including those from both another subtype A variant and a subtype B variant, resulted in enhanced neutralization susceptibility to gp41- and gp120-specific antibodies, and to plasma antibodies. This enhanced neutralization sensitivity exceeded 1,000-fold in several cases.

Conclusions

Two amino acid mutations within gp41 were identified that expose multiple discontinuous neutralization epitopes on diverse HIV-1 Env proteins. These exposed epitopes were shielded on the unmodified viral Env proteins, and several of the exposed epitopes encompass desired target regions for protective antibodies. Env proteins containing these modifications could act as a scaffold for presentation of such conserved domains, and may aid in developing methods to target antibodies to such regions.

Written by huehueteotl

January 7, 2008 at 3:44 pm

Posted in HIV

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