Day: 03/23/2012

Hepatitis C virus: How genetic variability affects pathobiology of disease.

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As an RNA virus, hepatitis C virus (HCV) shows a characteristically high level of nucleotide diversity. Accumulation of nucleotide substitutions in the virus has resulted in diversification into quasispecies, subtypes and distinct genotypes. Pathobiological studies linking nucleotide and amino acid sequences with clinical findings have identified relationships between certain genotypes and characteristic biological properties. Genotype 3 HCV infection was found to be associated with a high level of liver steatosis. Genotypes 1 and 4 were found to be more resistant to interferon (IFN) based therapies than genotypes 2 and 3. Studies of genotype 1 sequences obtained from patients treated with IFN have identified a relationship between favorable response to interferon therapy and amino acid substitutions in the NS5A region (interferon response determining region; ISDR). Further studies have identified a relationship between the effect of IFN therapy and other regions of the NS5A protein. More recently, a relationship has been found between poor response to peg-IFN plus ribavirin combination therapy and substitutions at amino acid 70 and 91 in the core protein. Furthermore, a correlation between human genetic variation in the IL28B (IFN-lamda 3) locus and core amino acid substitutions has been characterized.

In this review we briefly summarize the discovery, classification and nomenclature of HCV genotypes and subtypes. We also discuss amino acid substitutions within specific regions that have been reported to be associated with outcome of IFN and peg-IFN plus ribavirin combination therapy.

Source: Journal of Gastroenterology and Hepatology

Treatment of chronic hepatitis B: Evolution over two decades.

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There has been a recent paradigm shift in the indications and endpoints of treatment for chronic hepatitis B (CHB). Hepatitis B e antigen (HBeAg)-negative disease is being increasingly recognized. Antiviral treatment for both HBeAg-positive and HBeAg-negative patients should aim at long-term suppression of HBV DNA, with the ultimate ideal endpoint of hepatitis B surface antigen (HBsAg) seroconversion. Conventional interferon alpha (IFN-α), the only agent licensed in 1991, has been superseded by pegylated IFN-α. HBeAg seroconversion using pegylated IFN-α is 33%, with only 25% of HBeAg-positive patients achieving undetectable HBV DNA by polymerase chain reaction (PCR) assay. Five nucleoside/nucleotide analogues have been licensed since 1998. Lamivudine, an L-nucleoside, is limited by the development of resistance in 76% of patients after 5 years of therapy. Telbivudine, another L-nucleoside, is more potent than lamivudine but resistance still develops in 25% of HBeAg-positive and 11% HBeAg-negative patients after 2 years. Adefovir, an acyclic phosphonate, is relatively weak, but is effective against lamivudine- and telbivudine- resistant mutations, for which it should be used in combination (add-on therapy) rather than substituted. Resistance to adefovir develops slowly, rising to 29% for HBeAg-negative patients by year 5, but more rapidly when used alone for lamivudine-resistant HBV. Currently the two first line nucleoside/nucleotides are entecavir and tenofovir. Entecavir, a cyclopentane (D-nucleoside), is very potent, with 94% of patients having undetectable HBV DNA after 5 years. Resistance develops in only 1.2% of treatment-naïve patients. Tenofovir, another acyclic nucleotide, is more potent with less renal toxicity compared to adefovir. It is effective against lamivudine-resistant mutations when used alone. No resistance to tenofovir has been described after its use for 3 years or longer, often for patients with human immunodeficiency virus/HBV co-infection. With these current, potent antiviral agents associated with very low rates of resistance, long-term HBV DNA suppression and possibly even reversal of cirrhosis can now be achieved in a proportion of patients. In addition, long-term treatment with these antiviral agents is associated with a reduced risk of development of hepatocellular carcinoma.

Source: Journal of Gastroenterology and Hepatology

 

The clinical implications of hepatitis B virus genotype: Recent advances.

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Outcomes of chronic hepatitis B virus (HBV) infection are heterogeneous. Estimates of annual incidence of cirrhosis and hepatocellular carcinoma (HCC) are 2–10% and 1–3%, respectively. Several viral factors, including HBV genotype, viral load and specific viral mutations, have been associated with disease progression. Among these, HBV genotype is not only predictive of clinical outcomes but has also been associated with response to interferon treatment. Currently, at least 10 HBV genotypes and several subtypes have been identified; they have distinct geographic distribution. Acute infection with genotypes A and D results in higher rates of chronicity than genotypes B and C. Compared to genotype A and B cases, patients with genotypes C and D have lower rates of spontaneous hepatitis B e antigen (HBeAg) seroconversion; when this occurs, it tends to be delayed. HBV genotype C has a higher frequency of basal core promoter (BCP) A1762T/G1764A mutation, pre-S deletion and is associated with higher viral load than genotype B. Similarly, genotype D has a higher prevalence of BCP A1762T/G1764A mutation than genotype A. These observations suggest important pathogenic differences between HBV genotypes. These may contribute to more severe liver disease, including cirrhosis and HCC with genotypes C and D HBV infection. In addition, genotype A and B patients have better responses to interferon-based therapy than genotypes C and D, but there are few consistent differences for direct HBV antivirals. In conclusion, genotyping of chronic HBV infections can help practicing physicians identify those at risk of disease progression and determine optimal anti-viral therapy.

Source: Journal of Gastroenterology and Hepatology

 

Pancreatic exocrine insufficiency: Diagnosis and treatment.

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Pancreatic insufficiency is a major consequence of pancreatic diseases leading to a loss of pancreatic parenchyma, obstruction of the main pancreatic duct, decreased pancreatic stimulation, or acid-mediated inactivation of pancreatic enzymes. In addition, gastrointestinal and pancreatic surgical resections are frequent causes. Clinical manifestations include abdominal cramps, steatorrhea and malnutrition. Malnutrition, the main contributing factor of weight loss, has been related to a high morbidity and mortality secondary to an increased risk of malnutrition-related complications and cardiovascular events.

Assessments of exocrine pancreatic function, such as fecal fat quantification and 13C-triglyceride breath test, are the method of choice for diagnosis. In clinical practice, high-risk patient populations include those with severe necrotizing pancreatitis, gastrointestinal and pancreatic surgery, cancer of pancreas head, and those with pancreatic calcifications.

Apart from relief of maldigestion-related symptoms, the main goal of pancreatic enzyme substitution therapy is to ensure a normal nutritional status. Therapy of pancreatic insufficiency is based on the oral administration of exogenous pancreatic enzymes. Restriction of fat intake, though traditionally important in conventional treatment, should be reconsidered.

Enzyme substitution therapy should ideally mimic the physiological pattern of pancreatic exocrine secretion, and pancreatic enzymes in the form of enteric-coated minimicrospheres are considered as the most elaborated commercially available enzyme preparations. In general, pancreatic exocrine insufficiency in patients after surgery may be managed similarly to patients with chronic pancreatitis. This review focuses on current perspectives in diagnosis and treatment of pancreatic exocrine insufficiency and practical suggestions on its clinical management.

Source: Journal of Gastroenterology and Hepatology

Endoscopic Treatment Superior to Surgical for Infected Pancreatic Necrosis.

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In a small, randomized trial, endoscopic necrosectomy reduced interleukin-6 levels and resulted in much lower rates of major complications.

Infected pancreatic necrosis is one of the most serious complications of severe necrotizing pancreatitis. In the past, identification of infected necrosis led to immediate open debridement, with high mortality and morbidity. Now, these patients are often managed with targeted antibiotics, watchful waiting, and less-invasive procedures, including minimally invasive laparoscopic or retroperitoneal surgical debridement, percutaneous drainage and debridement, and endoscopic transgastric necrosectomy. However, whether one minimally invasive technique is better than another is unknown.

To compare outcomes of endoscopic versus surgical treatments, 22 patients with infected pancreatic necrosis were randomized to receive endoscopic transgastric necrosectomy or surgical necrosectomy in a multicenter trial. Surgical necrosectomy involved a video-assisted retroperitoneal debridement utilizing a laparoscope, a procedure previously shown to be superior to traditional open laparotomy.Endoscopic necrosectomy involved transgastric puncture of the walled-off necrosis with endoscopic ultrasound guidance, balloon dilation, and placement of 2 plastic stents and a nasocystic catheter. Irrigation through the catheter was performed for 24 hours with 1 L of normal saline, followed by dilation of the site to allow passage of a standard forward-viewing endoscope into the cavity to evacuate necrotic tissue. The procedure was repeated until the majority of the necrotic material was removed. All patients were treated with antibiotics. The primary endpoint was the proinflammatory response after necrosectomy, measured by serum interleukin (IL)-6 levels. Secondary endpoints were major complications and death.

In the surgical group, 6 of the 10 patients who completed the procedure underwent video-assisted retroperitoneal debridement only, and 4 required laparotomy. In the endoscopy group, all 10 patients underwent transgastric necrosectomy and required a median of three procedures. IL-6 levels increased after surgical necrosectomy and decreased after endoscopic necrosectomy (P=0.004). At 6 months follow-up, patients in the endoscopy group versus the surgery group experienced fewer major complications or death (20% vs. 80%; P=0.03), including fewer incidences of new-onset major organ failure (0% vs. 50%), pancreatic fistula (10% vs. 70%), and the need for pancreatic enzyme replacement (0% vs. 50%). One endoscopy patient and four surgery patients died.

Comment: In this first study to compare two minimally invasive approaches to managing infected pancreatic necrosis, endoscopic necrosectomy reduced the proinflammatory response and resulted in lower mortality or major complications compared with surgical necrosectomy. Although initially planned as minimally invasive, the surgical approach required frequent conversion to an open procedure, which might explain the large differences in complications. Despite its small size, this study highlights the differences in outcomes between groups and reinforces the increasingly prominent role that endoscopic techniques are playing in the management of severe and necrotizing pancreatitis.

Source:  Journal Watch Gastroenterology

Bed-of-nails’ breast implant deters cancer cells.

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Would it be possible to engineer implant materials that might drive down that rate of relapse? Brown University biomedical scientists report some promising advances. The team has created an implant with a “bed-of-nails”surface at the nanoscale that deters cancer cells from dwelling and thriving. Made out of a common federally approved polymer, the implant is the first of its kind, based on a review of the literature, with modifications at the nanoscale that cause a reduction in the blood-vessel architecture on whichbreast cancer tumors depend — while also attracting healthy breast cells.

“We’ve created an (implant) surface with features that can at least decrease (cancerous) cell functions without having to use chemotherapeutics, radiation, or other processes to kill cancer cells,” said Thomas Webster, associate professor of engineering and the corresponding author on the paper in Nanotechnology. “It’s a surface that’s hospitable to healthy breast cells and less so for cancerous breast cells.”

Webster and his lab have been modifying various implant surfaces to promote the regeneration of bone, cartilage, skin, and other cells. In this work, he and Lijuan Zhang, a fourth-year graduate student in chemistry, sought to reshape an implant that could be used in breast reconstruction surgery that would not only attract healthy cells but also repel any lingering breast-cancer cells. The duo created a cast on a glass plate using 23-nanometer-diameter polystyrene beads and polylactic-co-glycolic acid (PLGA), a biodegradable polymer approved by the FDA and used widely in clinical settings, such as stitches. The result: An implant whose surface was covered with adjoining, 23-nanometer-high pimples. The pair also created PLGA implant surfaces with 300-nanometer and 400-nanometer peaks for comparison.

 

In lab tests after one day, the 23-nanometer-peak surfaces showed a 15-percent decrease in the production of a protein (VEGF) upon which endothelial breast-cancer cells depend, compared to an implant surface with no surface modification. The 23-nanometer surface showed greater reduction in VEGF concentration when compared to the 300-nanometer and 400-nanometer-modified implants as well.

It’s unclear why the 23-nanoneter surface appears to work best at deterring breast-cancer cells. Webster thinks it may have to do something with the stiffness of malignant breast cells. When they come into contact with the bumpy surface, they are unable to fully wrap themselves around the rounded contours, depriving them of the ability to ingest the life-sustaining nutrients that permeate the surface.

“This is like a bed-of-nails surface to them,” Webster said.

“I would guess that surface peaks less than 23 nanometers would be even better,” Webster added, although polystyrene beads with such dimensions don’t yet exist. “The more you can push up that cancerous cell, the more you keep it from interacting with the surface.”

The pair also found that the 23-nanometer semispherical surface yielded 15 percent more healthy endothelial breast cells compared to normal surface after one day of lab tests.

Webster and Zhang next plan to investigate why the nanomodified surfaces deter malignant breast cells, to create surface features that yield greater results, and to determine whether other materials can be used.

Source: Brown University

 

Possible new route to fight dengue virus pointed.

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Researchers have identified enzymes and biochemical compounds called lipids that are targeted and modified by the dengue virus during infection, suggesting a potential new approach to control the aggressive mosquito-borne pathogen.

Findings also suggest that medications used to treat high cholesterol and other lipid-related conditions might also inhibit dengue’s replication and could represent a potential new therapy. The researchers have identified how infected mosquito cells undergo changes to certain lipids in membranes and in biochemical sensors that alert cells of invading viruses.

“The virus reorganizes the internal architecture of the cell to support its own needs,” said Purdue University research scientist Rushika Perera. “Many details are unknown. This is our first attempt to understand how the virus alters lipids as part of the infection process. Part of what we looked at in this work was how the virus changes the cell, and the next step will be to figure out why.”

 

The researchers uncovered new details of how the virus alters lipids in membranes surrounding structures inside cells called organelles, including the mitochondria, which provide energy critical for a cell to function, and theendoplasmic reticulum, where proteins and lipids are synthesized.

“Findings also show that important host enzymes are used by the virus and may be targets for future antiviral drugs,” said Richard J. Kuhn, a professor and head of Purdue’s Department of Biological Sciences and director of the Bindley Bioscience Center. “It turns out, the pills you take to control your cholesterol might have some capability to control dengue.”

The work was led by Perera in collaboration with researchers at Purdue’s Bindley Bioscience Center and the Pacific Northwest National Laboratory. Findings are detailed in a research paper to appear Thursday (March 22) in the journal PLoS Pathogens.

The findings could apply to viruses similar to dengue, including the West Nile virus, yellow fever and hepatitis C.

Dengue causes 50 million to 100 million infections per year and is considered one of the most aggressive mosquito-borne human pathogens worldwide. It is a leading cause of serious illness and death among children in some Asian and Latin American countries.

“Identifying pathways of infection will help us understand how these viruses work,” Kuhn said. “Many viruses, including dengue, dramatically alter a host cell upon infection, and in this paper we begin to dissect the precise changes that occur. Ultimately, we are trying to understand how the virus subverts and exploits the host and uses it for its own purpose, which is to replicate.”

The team learned specifically that an enzyme called fatty acid synthase, which cells use to synthesize lipids, is affected by the virus. Researchers showed that compounds inhibiting production of the enzyme also inhibit virus replication, suggesting drugs already on the market to treat diseases related to lipid synthesis and storage, including diabetes and cancer, also might be used to treat dengue, Kuhn said.

 

The research paper was written by Perera; Kuhn; Bindley researchers Catherine Riley, Amber S. Hopf-Jannasch and Jiri Adamec; and PNNL researchers Giorgis Isaac, Ronald J. Moore, Karl W. Weitz, Ljiljana Pasa-Tolic and Thomas O. Metz.

The researchers had previously studied a compound that inhibits the production of fatty acid synthase in human cells. In the new findings, the researchers showed that the virus commandeers some of the same enzymes in both mosquito and human cells, meaning the same compound could work to attack the virus in mosquito cells.

“This is important because it may be easier to control the virus in mosquitoes than in humans,” Kuhn said.

Globally, dengue has grown dramatically in recent decades, placing about half the world’s population at risk of infection. The infection causes flulike illness and occasionally develops into a potentially lethal complication called dengue hemorrhagic fever. Prompt medical care for this severe form of dengue virus infection has been shown to decrease mortality rates from more than 20 percent to less than 1 percent, according to the World Health Organization.

 

The research hinges on recent advances in two areas: high-resolution mass spectrometry and “informatics,” or using computers to process volumes of information.

“You generate a large quantity of data that has to be interpreted in terms of what molecules you are looking at,” Perera said. “The mass spectrometer takes hundreds of lipids and breaks them apart, and then a computer is needed to put it all back together and identify them. It’s only in the past five years or so that we’ve had the capability to do this with the required accuracy.”

The researchers also detail changes in the curvature of membranes, using another technique called cryoelectron microscopy, and pinpointed an isolated part of the cell where most of the virus replication takes place, a complex of membranes modified by the infection. The virus is thought to commandeer enzymes, relocating them to this region where virus replication factories are situated.

Because the research tools enable scientists to see how changes in membranes and signaling lipids alter how a cell functions, a long-term benefit of the research is learning how to use a virus as a tool to better understand cellular processes, Perera said.

Dengue virus causes ~50-100 million infections per year and thus is considered one of the most aggressive arthropod-borne human pathogen worldwide. During its replication, dengue virus induces dramatic alterations in the intracellular membranes of infected cells. This phenomenon is observed both in human and vector-derived cells. Using high-resolution mass spectrometry of mosquito cells, we show that this membrane remodeling is directly linked to a unique lipid repertoire induced by dengue virus infection. Specifically, 15% of the metabolites detected were significantly different between DENV infected and uninfected cells while 85% of the metabolites detected were significantly different in isolated replication complex membranes. Furthermore, we demonstrate that intracellular lipid redistribution induced by the inhibition of fatty acid synthase, the rate-limiting enzyme in lipid biosynthesis, is sufficient for cell survival but is inhibitory to dengue virus replication. Lipids that have the capacity to destabilize and change the curvature of membranes as well as lipids that change the permeability of membranes are enriched in dengue virus infected cells. Several sphingolipids and other bioactive signaling molecules that are involved in controlling membrane fusion, fission, and trafficking as well as molecules that influence cytoskeletal reorganization are also up regulated during dengue infection. These observations shed light on the emerging role of lipids in shaping the membrane and protein environments during viral infections and suggest membrane-organizing principles that may influence virus-induced intracellular membrane architecture.

Source: Purdue University

 

 

 

Hubble Zooms in On Double Nucleus in Andromeda Galaxy.

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A new Hubble Space Telescope image centers on the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy, the only galaxy outside the Milky Way visible to the naked eye and the only other giant galaxy in the local group.

This is the sharpest visible-light image ever made of the nucleus of an external galaxy.

The event horizon, the closest region around the black hole where light can still escape, is too small to be seen, but it lies near the middle of a compact cluster of blue stars at the center of the image. The compact cluster of blue stars is surrounded by the larger “double nucleus” of M31, discovered with the Hubble Space Telescope in 1992. The double nucleus is actually an elliptical ring of old reddish stars in orbit around the black hole but more distant than the blue stars. When the stars are at the farthest point in their orbit they move slower, like cars on a crowded freeway. This gives the illusion of a second nucleus.

The blue stars surrounding the black hole are no more than 200 million years old, and therefore must have formed near the black hole in an abrupt burst of star formation. Massive blue stars are so short-lived that they would not have enough time to migrate to the black hole if they were formed elsewhere.

Astronomers are trying to understand how apparently young stars were formed so deep inside the black hole’s gravitational grip and how they survive in an extreme environment.

The fact that young stars are also closely bound to the central black hole in our Milky Way galaxy suggests this may be a common phenomenon in spiral galaxies.

Tod R. Lauer of the National Optical Astronomy Observatory in Tucson, Ariz., assembled this image of the nuclear region by taking several blue and ultraviolet light exposures of the nucleus with Hubble’s Advanced Camera for Surveys high-resolution channel, each time slightly moving the telescope to change how the camera sampled the region. By combining these pictures, he was able to construct an ultra-sharp view of the galaxy’s core.

Lauer is presenting these Hubble observations this week at the meeting of the American Astronomical Society in Austin, Texas.

 

Source: http://www.sciencedaily.com

 

Meta-Analysis: Cervical Cancer Screening Strategies Can’t Be Applied to Anal Cancer Prevention .

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Among men who have sex with men (MSM), rates of progression from high-grade anal intraepithelial neoplasia to anal cancer appear too low to warrant generalized anal cancer screening, according to a meta-analysis in the Lancet Oncology.

The analysis included over 50 studies of anal human papillomavirus (HPV) prevalence and cytological abnormalities among MSM, mostly in North America. The prevalence of high-risk HPV was high (reaching 35% among HIV-positive men), as was the prevalence of high-grade intraepithelial neoplasia (nearly 30% overall). However, using limited data, researchers calculated that the “theoretical” rate of progression from high-grade anal intraepithelial neoplasia to anal cancer was just 1 in 600/year among HIV-positive men and 1 in 4000/year in HIV-negative men.

Noting that “rates of progression to [anal] cancer seem to be substantially lower than they are for cervical pre-cancerous lesions,” the researchers conclude that “approaches to cervical cancer screening cannot be simply extrapolated to anal cancer prevention.”

And in his HIV and ID Observations blog, Dr. Paul Sax writes: “Just because we can screen for pre-cancerous lesions, doesn’t mean we should.”

Source: Lancet Oncology

TB Incidence Dropping in U.S., Resistance Rates Steady, Epidemiology Shifting .

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The incidence of new cases of tuberculosis in the U.S. dropped to 3.4 per 100,000 population in 2011, the lowest rate in over 50 years of national reporting, according to an MMWR article. The proportion with multidrug-resistant disease remained unchanged from the 2009 rate of 1.3%.

Among TB patients with a known HIV serostatus, 7.9% were coinfected.

The number of cases among foreign-born persons exceeded that among the U.S.-born, as it has every year since 2001. And for the first time Asians surpassed Hispanics as the largest ethnic group among people with TB.

Nationally, incidence rates ranged from a low of 0.7 in Maine to 9.3 in Alaska. Four states accounted for half the cases: California, Florida, New York, and Texas.

Source: MMWR