HIV virus in disguise tricks immune system, Marie Larsson is Professor of Molecular Virology

Name: Marie LarssonTitle: Professor of Molecular Virology
Department: IKE

CONTACT

Phone: +46 (0)10-103 10 55
E-mail: marie.larsson@liu.se

Address:
Linköping University
Department of Clinical and Experimental Medicine
Virology
SE-581 85 Linköping
Sweden

Marie Larsson is Professor of Molecular Virology. Her research is in the area of immunovirology, specifically HIV research with focus on the immunomodulatory effect this virus has on dendritic cells and T cells. She has also ongoing projects exploring new adjuvants and vaccine constellations for cancer and virus. Furthermore, she is investigating the induction and sustainment of cancer associated inflammation and the deleterious effect this has on host immune defense.

Immunomodulatory effects of HIV-1’s interactions with DCs and T cells from

blood and mucosa
So far over 30 million people have died from HIV-1 infection (figure 1), the majority of them in the developing countries, and this epidemic is still cause for major concern. The existing antiretroviral therapy dampens the infection and the destruction of the immune system, i.e. AIDS, but does not cure the disease. Sadly, this therapy is not available to all HIV infected and is a very expensive lifelong commitment with severe side effects.

A vaccine blocking HIV infection is theDendritic cell sought-after solution but there is no hope that we will have such a vaccine in the near future. Instead we can hope for a therapy that induces a potent long lasting immune response consisting of CD4+ and CD8+ T cells, two types of control cells involved in the immune defense, that have proven to be important to control the infection. There exists a unique cell in all tissues in our bodies, the dendritic cell (DC) (Figure 2) with unique ability to activate T cells so they can perform their job in the body. DCs in the vaginal and rectal tissues are one of the first cells to encounter HIV during intercourse with an infected individual (Figure 3 and 4). Unfortunately, HIV hijacks the DCs, which makes this cell responsible for spreading the virus to interacting T cells in the body which provokes HIV-infection of T cells and cell death when it should be initiating immune responses to fight the infection.DC HIV

My research aspires to elucidate the mechanisms behind the immunomodulatory effects HIV exerts on DCs and on their ability to activate T cells. Focus will be on; Elucidation of the mechanisms involved in HIV’s binding to and uptake by DCs and the subsequent degradation that leads to DC antigen presentation of HIV peptides for activation of HIV specific T cells. Elucidation of the mechanisms responsible for the negative effects HIV exerts on DCs and if presence of HIV virions during DC T cell priming impairs the T cell function. Elucidate the effect opsonized HIV-1 exerts on immune cells such as DCs, NK cells and T cells. Identification of receptors and cells involved in the initial HIV infection of cervical mucosa and colorectal mucosa,  and potential microbiocides that can block the initial infection, and elucidation of why HIV affects the T cells in the gut to a higher extent than the T cells in blood.

HIV will continue to kill people and have a great impact on mankind until we have a drug that can stop this infection. My ambition is that the planed research will answer some basic questions regarding the role of DCs in HIV pathogenesis and induction of potent immune response against this virus. This knowledge will guide how a vaccine/therapy needs to be constructed in order to have high efficacy.

                                                             Mucosal transmission

                                                                Cervix

Cancer research

Elucidation the role of IL-1α and the microenvironment in development of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a common gastrointestinal malignancy with an exceptional poor prognosis and a mortality rate that nearly matches the rate of incidence. The cross-talk between PDAC and stroma cells, e.g. cancer associated fibroblasts (CAF), and immune cells, may create an environment with chronic inflammation augmenting tumor transformation and maintenance.

In PDAC, more than 70% of the total tumor mass can consist of fibrotic stroma, which makes CAFs the major component in this cancer. PDAC inflammatory environment consists of many mediators, e.g. IL-1, COX-2, IL-6, and CXCL8, and some of these factors correlate to tumor development and poor prognosis. Of note, elevated expression of IL-1 in tumors has been associated with more aggressive disease. Several studies, including ours have reported that dendritic cells (DCs), one of the immune cells found in the tumor microenvironment, show phenotypic and functional abnormalities when isolated from tumor bearing animals and individuals with PDAC. Recent findings provided some evidence that the COX-2 metabolite PGE2 is involved in the upregulation of immunomodulatory factors in DCs impairing their T cell stimulatory ability. The aims are to examine the receptor-ligands and signaling pathways involved in the cross talk between stroma cells, i.e. CAFs, and PDAC cells giving rise to the inflammatory environment and creating an environment sustaining the PDAC. To examine the role IL-1 cytokine family and effects these cytokines cell signaling have on creating the inflammatory environment and in tumor development and survival. To examine whether neutralization of IL1 signaling pathway enhances the survival and quality of life for individuals with pancreatic cancer.

The information gained from the proposed research will help us understand the mechanisms underlying the development of PDAC and the effect this solid tumor exert on the body and may help designing therapies for PDAC.

Source: Linköping University

Scheduling tool a big help in healthcare

The HIV virus avoids the body’s immune cells by disguising itself using proteins that normally take part in the defence against infections. These are the findings of research conducted at the Division of Molecular Virology.

Professor Marie LarssonThese “complement proteins” are soluble molecules that attach themselves to foreign particles and those of the body in different patterns. These patterns help the immune system to identify and attack dangerous intruders such as viruses and bacteria.

Phd student Rada EllegårdInstead, HIV exploits the complement proteins present in all body fluids in order to make its way into the body tissues without being attacked. It was known previously that infections are much more effective if the virus is surrounded by the bodily fluids normally present in blood or sexual contagion than if it is isolated in a laboratory environment. In an article in the Journal of Immunology Marie Larsson, professor of molecular virology (left) and PhD student Rada Ellegård (right) provide an explanation of this phenomenon.

“The ability to use our complement proteins in this way is probably key to the success of HIV in being transmitted. We are currently carrying out further work to investigate these mechanisms in the male genital mucous membrane – the tissue where the virus infection takes place in sexual transmission,” says Ms Larsson.

The first thing HIV particles come into contact with is dendritic cells, immune cells that function as sentry posts. Their job is to identify viruses as dangerous and hostile to the body, and to respond by producing the substances that combat infections and moving to a lymph node to set a specific immune defence in motion.

In the case of HIV, this process does not seem to work very well. The disguise stops the dendritic cells recognising the virus, which instead establishes an infection in the mucous membrane and uses the movement to the lymph nodes as a way to spread around the whole body.

As more and more cells are infected and killed, the virus slowly breaks down our immune system. Without treatment this sequence of events leads to AIDS, a condition where the victim becomes extremely vulnerable to infection and where normally harmless viruses and bacteria become life-threatening.

Related content

Marie Larsson - research presentation >>

                                       HIV-illustration

When a virus is captured by a dendritic cell, it is recognised by a virus sensor that normally sets in motion infection reduction factors which inhibit the production of new virus particles (picture, left). HIV has the ability to clothe itself in complements, a type of protein present in our bodily fluids. In this way it can dampen the signals from the virus sensors and produce many new particles (picture, right).


Source: Linköping University

ALS progression linked to increased protein instability

The new study provides evidence that proteins linked to more severe forms of ALS are less stable structurally and more prone to form clusters or aggregates. Mutants of the superoxide dismutase (SOD) protein formed long, rod-shaped aggregates (shown here as red lattice), compared to the compact folded structure of wild-type SOD (purple ribbons). Credit: Image courtesy of the Getzoff and Tainer labs, The Scripps Research Institute.

A new study by scientists from The Scripps Research Institute (TSRI), Lawrence Berkeley National Laboratory (Berkeley Lab) and other institutions suggests a cause of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

"Our work supports a common theme whereby loss of protein stability leads to disease," said John A. Tainer, professor of structural biology at TSRI and senior scientist at Berkeley Lab, who shared senior authorship of the new research with TSRI Professor Elizabeth Getzoff.

Getzoff, Tainer and their colleagues, who focused on the effects of mutations to a gene coding for a protein called superoxide dismutase (SOD), report their findings this week in the online Early Edition of the Proceedings of the National Academy of Sciences. The study provides evidence that those proteins linked to more severe forms of the disease are less stable structurally and more prone to form clusters or aggregates.

"The suggestion here is that strategies for stabilizing SOD proteins could be useful in treating or preventing SOD-linked ALS," said Getzoff.

Striking in the Prime of Life

ALS is notorious for its ability to strike down people in the prime of life. It first leapt into public consciousness when it afflicted baseball star Lou Gehrig, who succumbed to the disease in 1941 at the age of only 38. Recently, the ALS Association's Ice Bucket Challenge has enhanced public awareness of the disease.

ALS kills by destroying muscle-controlling neurons, ultimately including those that control breathing. At any one time, about 10,000 Americans are living with the disease, according to new data from the Centers for Disease Control and Prevention, but it is almost always lethal within several years of the onset of symptoms.

SOD1 mutations, the most studied factors in ALS, are found in about a quarter of hereditary ALS cases and seven percent of ordinary "sporadic" ALS cases. SOD-linked ALS has nearly 200 variants, each associated with a distinct SOD1 mutation. Scientists still don't agree, though, on just how the dozens of different SOD1 mutations all lead to the same disease.

One feature that SOD1-linked forms of ALS do have in common is the appearance of SOD clusters or aggregates in affected motor neurons and their support cells. Aggregates of SOD with other proteins are also found in affected cells, even in ALS cases that are not linked to SOD1 mutations.

In 2003, based on their and others' studies of mutant SOD proteins, Tainer, Getzoff and their colleagues proposed the "framework destabilization" hypothesis. In this view, ALS-linked mutant SOD1 genes all code for structurally unstable forms of the SOD protein. 
Inevitably some of these unstable SOD proteins lose their normal folding enough to expose sticky elements that are normally kept hidden, and they begin to aggregate with one another, faster than neuronal cleanup systems can keep up -- and that accumulating SOD aggregation somehow triggers disease.

Faster Clumping, Worse Disease

In the new study, the Tainer and Getzoff laboratories and their collaborators used advanced biophysical methods to probe how different SOD1 gene mutations in a particular genetic ALS "hotspot" affect SOD protein stability.

To start, they examined how the aggregation dynamics of the best-studied mutant form of SOD, known as SOD G93A, differed from that of non-mutant, "wild-type" SOD. To do this, they developed a method for gradually inducing SOD aggregation, which was measured with an innovative structural imaging system called SAXS (small-angle X-ray scattering) at Berkeley Lab's SIBYLS beamline.

"We could detect differences between the two proteins even before we accelerated the aggregation process," said David S. Shin, a research scientist in Tainer's laboratories at Berkeley Lab and TSRI who continues structural work on SOD at Berkeley.

The G93A SOD aggregated more quickly than wild-type SOD, but more slowly than an SOD mutant called A4V that is associated with a more rapidly progressing form of ALS.

Subsequent experiments with G93A and five other G93 mutants (in which the amino acid glycine at position 93 on the protein is replaced with a different amino acid) revealed that the mutants formed long, rod-shaped aggregates, compared to the compact folded structure of wild-type SOD. The mutant SOD proteins that more quickly formed longer aggregates were again those that corresponded to more rapidly progressing forms of ALS.

What could explain these SOD mutants' diminished stability? Further tests focused on the role of a copper ion that is normally incorporated within the SOD structure and helps stabilize the protein. Using two other techniques, electron-spin resonance (ESR) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS), the researchers found that the G93-mutant SODs seemed normal in their ability to take up copper ions, but had a reduced ability to retain copper under mildly stressing conditions -- and this ability was lower for the SOD mutants associated with more severe ALS.

"There were indications that the mutant SODs are more flexible than wild-type SOD, and we think that explains their relative inability to retain the copper ions," said Ashley J. Pratt, the first author of the study, who was a student in the Getzoff laboratory and postdoctoral fellow with Tainer at Berkeley Lab.

Toward New Therapies

In short, the G93-mutant SODs appear to have looser, floppier structures that are more likely to drop their copper ions -- and thus are more likely to misfold and stick together in aggregates.

Along with other researchers in the field, Getzoff and Tainer suspect that deviant interactions of mutant SOD trigger inflammation and disrupt ordinary protein trafficking and disposal systems, stressing and ultimately killing affected neurons.

"Because mutant SODs get bent out of shape more easily," said Getzoff, "they don't hold and release their protein partners properly. By defining these defective partnerships, we can provide new targets for the development of drugs to treat ALS."

The researchers also plan to confirm the relationship between structural stability and ALS severity in other SOD mutants.

"If our hypothesis is correct," said Shin, "future therapies to treat SOD-linked ALS need not be tailored to each individual mutation -- they should be applicable to all of them."

Source: The Scripps Research Institute

Heart drug may help treat ALS, mouse study shows

In the top image, cells from a mouse model of amyotrophic lateral sclerosis caused normal healthy brain cells (green) to die. But when scientists blocked an enzyme in the cells from the mouse model, more of the normal cells and their branches survived (bottom). Credit: Nature Neuroscience

Digoxin, a medication used in the treatment of heart failure, may be adaptable for the treatment of amyotrophic lateral sclerosis (ALS), a progressive, paralyzing disease, suggests new research at Washington University School of Medicine in St. Louis.

ALS, also known as Lou Gehrig's disease, destroys the nerve cells that control muscles. This leads to loss of mobility, difficulty breathing and swallowing and eventually death. Riluzole, the sole medication approved to treat the disease, has only marginal benefits in patients.

But in a new study conducted in cell cultures and in mice, scientists showed that when they reduced the activity of an enzyme or limited cells' ability to make copies of the enzyme, the disease's destruction of nerve cells stopped. The enzyme maintains the proper balance of sodium and potassium in cells.

"We blocked the enzyme with digoxin," said senior author Azad Bonni, MD, PhD. "This had a very strong effect, preventing the death of nerve cells that are normally killed in a cell culture model of ALS."

The findings appear online Oct. 26 in Nature Neuroscience.

The results stemmed from Bonni's studies of brain cells' stress responses in a mouse model of ALS. The mice have a mutated version of a gene that causes an inherited form of the disease and develop many of the same symptoms seen in humans with ALS, including paralysis and death.

Efforts to monitor the activity of a stress response protein in the mice unexpectedly led the scientists to another protein: sodium-potassium ATPase. This enzyme ejects charged sodium particles from cells and takes in charged potassium particles, allowing cells to maintain an electrical charge across their outer membranes.

Maintenance of this charge is essential for the normal function of cells. The particular sodium-potassium ATPase highlighted by Bonni's studies is found in nervous system cells called astrocytes. In the ALS mice, levels of the enzyme are higher than normal in astrocytes.

Bonni's group found that the increase in sodium-potassium ATPase led the astrocytes to release harmful factors called inflammatory cytokines, which may kill motor neurons.

Recent studies have suggested that astrocytes may be crucial contributors to neurodegenerative disorders such as ALS, and Alzheimer's, Huntington's and Parkinson's diseases. For example, placing astrocytes from ALS mice in culture dishes with healthy motor neurons causes the neurons to degenerate and die.

"Even though the neurons are normal, there's something going on in the astrocytes that is harming the neurons," said Bonni, the Edison Professor of Neurobiology and head of the Department of Anatomy and Neurobiology.

How this happens isn't clear, but Bonni's results suggest the sodium-potassium ATPase plays a key role. When he conducted the same experiment but blocked the enzyme in ALS astrocytes using digoxin, the normal motor nerve cells survived. Digoxin blocks the ability of sodium-potassium ATPase to eject sodium and bring in potassium.

In mice with the mutation for inherited ALS, those with only one copy of the gene for sodium-potassium ATPase survived an average of 20 days longer than those with two copies of the gene. When one copy of the gene is gone, cells make less of the enzyme.

"The mice with only one copy of the sodium-potassium ATPase gene live longer and are more mobile," Bonni said. "They're not normal, but they can walk around and have more motor neurons in their spinal cords."

Many important questions remain about whether and how inhibitors of the sodium-potassium ATPase enzyme might be used to slow progressive paralysis in ALS, but Bonni said the findings offer an exciting starting point for further studies.

Source: Washington University School of Medicine