Posts Tagged ‘Medicine’

Helicobacter pylori and stomach lesions

Friday, July 18th, 2014

Helicobacter pylori Helicobacter pylori infection promotes stomach ulcers and cancer. How H. pylori initially interacts with and irritates gastric tissue is not well understood.

A new article describes how H. pylori rapidly identifies and colonizes sites of minor injuries in the stomach, almost immediately interferes with healing at those injury sites, and so promotes sustained gastric damage.

Smoking, alcohol, excessive salt intake, and non-steroidal anti-inflammatory drugs cause damage to the tissue lining the stomach, and are associated with stomach ulcers. Scientists asked whether H. pylori can sense and respond to such damage and so contribute to disease development.

The researchers induced small stomach lesions in mice and observed that H. pylori bacteria can rapidly detect the injury site and navigate toward it. Within minutes, accumulation of bacteria interferes with repair of the tissue damage.

To examine how the bacteria accomplish this, the researchers also studied mice with larger stomach lesions (ulcers) that were subsequently infected with H. pylori. They found that H. pylori preferentially colonizes stomach tissue at injured ulcer sites, and there impairs healing of the damaged tissue. Selective colonization requires both bacterial motility and chemotaxis (the ability to change direction of movement in response to environmental cues), and higher levels of bacterial accumulation cause slower healing. However, when extremely high levels of immotile or chemotaxis-deficient bacteria are added to damaged tissue, they can also slow healing.

While the signals that attract H. pylori (but not benign stomach bacteria) toward injured tissue are not yet known, the researchers hope that their ability to rapidly measure H. pylori accumulation at the injured site now provides an experimental set-up to determine the factor(s) involved.

 

Motility and Chemotaxis Mediate the Preferential Colonization of Gastric Injury Sites by Helicobacter pylori. (2014) PLoS Pathog 10(7): e1004275. doi:10.1371/journal.ppat.1004275

 

Honing in on enteric fever

Thursday, July 3rd, 2014

Salmonella typhimurium Enteric fever (typhoid), affects about 22 million people and causes about 200,000 deaths every year, according to conservative estimates. Enteric fever is spread by bacteria belonging to the Salmonella genus, with two sub-species – Salmonella Typhi and Salmonella Paratyphi A – being responsible for most cases of the disease. And although the number of cases of enteric fever has fallen significantly over recent decades, there is a clear need for a diagnostic test for Salmonella that is rapid, affordable and accurate. It is important to be able to distinguish between enteric fever caused by Salmonella Typhi and enteric fever caused by Salmonella Paratyphi A in order to ensure that the correct drugs are prescribed and to combat the development of antibiotic resistance.

The application of metabolomics is relatively new in infectious diseases research compared to the application of genomics and proteomics. Despite this, screening the metabolome in blood plasma has identified useful prognostic profiles of several diseases, including sepsis. One of the major benefits of this technique is that it utilizes a pattern of biomarkers (that is, the various metabolites), as opposed to relying on just one host biomarker, as has been the focus of previous approaches.

A new paper in eLife applies this promising new approach to this challenge. Instead of trying to detect Salmonella in the blood during infection, they used a technique called metabolomics. The basic idea of this approach is that infection leads to metabolic changes, such that a person with enteric fever (or any infection) could have a profile of metabolites in their blood that is different to the metabolite profile of a healthy person. The challenge, therefore, is to identify a ‘metabolic fingerprint’ that can be used to detect enteric fever with high levels of sensitivity and specificity.

 

eLife: Host-pathogen interactions: Honing in on enteric fever

 

Crossing the species barrier

Friday, June 20th, 2014

The number of pathogens known to infect humans is ever increasing. Whether such increase reflects improved surveillance and detection or actual emergence of novel pathogens is unclear. Nonetheless, infectious diseases are the second leading cause of human mortality and disability-adjusted life years lost worldwide. On average, three to four new pathogen species are detected in the human population every year. Most of these emerging pathogens originate from nonhuman animal species.

Zoonotic pathogens represent approximately 60% of all known pathogens able to infect humans. Their occurrence in humans relies on the human-animal interface, defined as the continuum of contacts between humans and animals, their environments, or their products. The human-animal interface has existed since the first footsteps of the human species and its hominin ancestors 6–7 million years ago, promoting the prehistoric emergence of now well-established human pathogens. These presumably include pathogens with roles in the origin of chronic diseases, such as human T-lymphotropic viruses and Helicobacter pylori, as well as pathogens causing major crowd diseases, such as the smallpox and measles viruses and Bordetella pertussis. Since prehistory, the human-animal interface has continued to evolve and expand, ever allowing new pathogens to access the human host and cross species barriers.

Crossing the Interspecies Barrier: Opening the Door to Zoonotic Pathogens. (2014) PLoS Pathog 10(6): e1004129. doi:10.1371/journal.ppat.1004129

Crossing the species barrier

In case you forgot – we’re still fighting vCJD

Friday, June 13th, 2014

Prions The first cases of Mad Cow disease in humans (properly called variant Creutzfeld Jakob Disease, vCJD) occurred in the late 1990s as the consequence of eating contaminated beef products. Since then, several cases of secondary infections caused by transfusions with blood from donors who subsequently developed vCJD have been reported, raising ongoing concerns about the safety of blood and blood products. A paper just published describes a new test that uses protein misfolding cyclic amplification (PMCA – like PCR for proteins) which can detect prions in blood samples from humans with vCJD and in animals at early stages of the (asymptomatic) incubation phase.

This test could be used to identify vCJD infected but asymptomatic individuals and/or for screening donated blood for the presence of the vCJD agent. In the UK, 1 out 2000 people could carry the vCJD agent. In the absence of a vCJD screen, the UK like most of the developed countries apply systematic measures aiming at mitigating the blood borne transmission risk of the disease. These measures have a substantial cost and increase the difficulty met by the blood banking system to provide certain blood products.

 

Preclinical Detection of Variant CJD and BSE Prions in Blood. (2014) PLoS Pathog 10(6):e1004202. doi: 10.1371/journal.ppat.1004202
The emergence of variant Creutzfeldt Jakob Disease (vCJD) is considered a likely consequence of human dietary exposure to Bovine Spongiform Encephalopathy (BSE) agent. More recently, secondary vCJD cases were identified in patients transfused with blood products prepared from apparently healthy donors who later went on to develop the disease. As there is no validated assay for detection of vCJD/BSE infected individuals the prevalence of the disease in the population remains uncertain. In that context, the risk of vCJD blood borne transmission is considered as a serious concern by health authorities. In this study, appropriate conditions and substrates for highly efficient and specific in vitro amplification of vCJD/BSE agent using Protein Misfolding Cyclic Amplification (PMCA) were first identified. This showed that whatever the origin (species) of the vCJD/BSE agent, the ovine Q171 PrP substrates provided the best amplification performances. These results indicate that the homology of PrP amino-acid sequence between the seed and the substrate is not the crucial determinant of the vCJD agent propagation in vitro. The ability of this method to detect endogenous vCJD/BSE agent in the blood was then defined. In both sheep and primate models of the disease, the assay enabled the identification of infected individuals in the early preclinical stage of the incubation period. Finally, sample panels that included buffy coat from vCJD affected patients and healthy controls were tested blind. The assay identified three out of the four tested vCJD affected patients and no false positive was observed in 141 healthy controls. The negative results observed in one of the tested vCJD cases concurs with results reported by others using a different vCJD agent blood detection assay and raises the question of the potential absence of prionemia in certain patients.

 

A new drug against MERS?

Friday, May 30th, 2014

MERS virus Before the emergence of the highly pathogenic severe acute respiratory syndrome-associated coronavirus (SARS-CoV) in 2003 only two circulating human coronaviruses (HCoVs), HCoV- 229E and HCoV-OC43 causing relatively mild common cold-like respiratory tract infections, were known, and coronaviruses have not been regarded as significant threat for human health. Now, more than ten years later, the emergence of another highly pathogenic coronavirus of zoonotic origin, the Middle East respiratory syndrome coronavirus (MERS-CoV) points to the need for effective drugs against coronaviruses. Viruses such as coronaviruses that replicate in the host cell cytoplasm have evolved to employ host cell-derived membranes to compartmentalize genome replication and transcription. Specifically for positive-stranded RNA viruses, accumulating knowledge concerning the involvement, rearrangement and requirement of cellular membranes for RNA synthesis specify the establishment of the viral replicase complex at host cell-derived membranes as an evolution- ary conserved and essential step in the early phase of the viral life cycle.

A new paper in PLoS Pathogens describe a small molecule inhibitor of coronavirus replication that specifically targets this membrane-bound RNA replication step and has broad antiviral activity against number of diverse coronaviruses including highly pathogenic SARS-CoV and MERS-CoV. Since resistance mutations appear in an integral membrane-spanning component of the coronavirus replicase complex, and since all positive stranded RNA viruses have very similar membrane-spanning or membrane-associated replicase components implicated in anchoring the viral replication complex to host cell-derived membranes, the data suggests that the membrane-bound replication step of the viral life cycle is a novel, vulnerable, and druggable target for antiviral intervention of a wide range of RNA virus infections.

Of course clinical trials are needed before such drugs could be used, so we’re still years away from this approach being put into practce. Just in time for the next emergent coronavirus maybe?

 

Targeting Membrane-Bound Viral RNA Synthesis Reveals Potent Inhibition of Diverse Coronaviruses Including the Middle East Respiratory Syndrome Virus. (2014) PLoS Pathog 10(5): e1004166. doi:10.1371/journal.ppat.1004166
Coronaviruses raise serious concerns as emerging zoonotic viruses without specific antiviral drugs available. Here we screened a collection of 16671 diverse compounds for anti-human coronavirus 229E activity and identified an inhibitor, designated K22, that specifically targets membrane-bound coronaviral RNA synthesis. K22 exerts most potent antiviral activity after virus entry during an early step of the viral life cycle. Specifically, the formation of double membrane vesicles (DMVs), a hallmark of coronavirus replication, was greatly impaired upon K22 treatment accompanied by near-complete inhibition of viral RNA synthesis. K22-resistant viruses contained substitutions in non-structural protein 6 (nsp6), a membrane-spanning integral component of the viral replication complex implicated in DMV formation, corroborating that K22 targets membrane bound viral RNA synthesis. Besides K22 resistance, the nsp6 mutants induced a reduced number of DMVs, displayed decreased specific infectivity, while RNA synthesis was not affected. Importantly, K22 inhibits a broad range of coronaviruses, including Middle East respiratory syndrome coronavirus (MERS–CoV), and efficient inhibition was achieved in primary human epithelia cultures representing the entry port of human coronavirus infection. Collectively, this study proposes an evolutionary conserved step in the life cycle of positive-stranded RNA viruses, the recruitment of cellular membranes for viral replication, as vulnerable and, most importantly, druggable target for antiviral intervention. We expect this mode of action to serve as a paradigm for the development of potent antiviral drugs to combat many animal and human virus infections.

 

New Broad-Spectrum Peptide Antibiotic Targets Biofilms

Friday, May 23rd, 2014

Biofilm Biofilms are structured multicellular communities of microorganisms associated with surfaces. They have been widely studied, in part because they cause at least 65% of all human infections, being particularly prevalent in device-related infections, on body surfaces and in chronic infections. Biofilms represent a major health problem worldwide due to their resistance to host defence mechanisms and to conventional antimicrobials, which generally target free-swimming (planktonic) bacteria. So there is an urgent need to identify compounds that effectively clear biofilm-related infections.

A new report in PLoS Pathogens identifies a potent anti-biofilm peptide that works by blocking (p)ppGpp, an important signal in biofilm development. The peptide had at least three effects on biofilms, which might reflect the role of (p)ppGpp in cells. First when added prior to initiation of biofilms it prevented biofilm formation, second it specifically led to cell death in biofilms at concentrations that were not lethal for planktonic (free-swimming) cells, and third it promoted biofilm dispersal even in maturing (2-day old) biofilms. This anti-biofilm strategy represents a significant advance in the search for new agents that specifically target many bacterial species.

 

Broad-Spectrum Anti-biofilm Peptide That Targets a Cellular Stress Response. (2014) PLoS Pathog 10(5): e1004152. doi:10.1371/journal.ppat.1004152
Bacteria form multicellular communities known as biofilms that cause two thirds of all infections and demonstrate a 10 to 1000 fold increase in adaptive resistance to conventional antibiotics. Currently, there are no approved drugs that specifically target bacterial biofilms. Here we identified a potent anti-biofilm peptide 1018 that worked by blocking (p)ppGpp, an important signal in biofilm development. At concentrations that did not affect planktonic growth, peptide treatment completely prevented biofilm formation and led to the eradication of mature biofilms in representative strains of both Gram-negative and Gram-positive bacterial pathogens including Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, methicillin resistant Staphylococcus aureus, Salmonella Typhimurium and Burkholderia cenocepacia. Low levels of the peptide led to biofilm dispersal, while higher doses triggered biofilm cell death. We hypothesized that the peptide acted to inhibit a common stress response in target species, and that the stringent response, mediating (p)ppGpp synthesis through the enzymes RelA and SpoT, was targeted. Consistent with this, increasing (p)ppGpp synthesis by addition of serine hydroxamate or over-expression of relA led to reduced susceptibility to the peptide. Furthermore, relA and spoT mutations blocking production of (p)ppGpp replicated the effects of the peptide, leading to a reduction of biofilm formation in the four tested target species. Also, eliminating (p)ppGpp expression after two days of biofilm growth by removal of arabinose from a strain expressing relA behind an arabinose-inducible promoter, reciprocated the effect of peptide added at the same time, leading to loss of biofilm. NMR and chromatography studies showed that the peptide acted on cells to cause degradation of (p)ppGpp within 30 minutes, and in vitro directly interacted with ppGpp. We thus propose that 1018 targets (p)ppGpp and marks it for degradation in cells. Targeting (p)ppGpp represents a new approach against biofilm-related drug resistance.

 

Oncolytic virotherapy – in pets?

Friday, May 16th, 2014

Oncolytic viruses Oncolytic virotherapy – using viruses to treat cancer – is a hot topic. Earlier this week the media was reporting a new clinical trial where researchers seeming cured multiple myeloma in one patient by giving her a huge dose of measles vaccine (NHS Choices: Measles virus used to treat bone marrow cancer). But cancer is among the top fatal diseases in domestic and feral dogs and cats too. Incidence of canine or feline cancer ranges from 1% to 2% and cancer currently accounts for about half of the deaths of domestic animals older than 10 years. The most common forms of cancer in dogs and cats are skin, lymphoma, mammary, bone, connective tissue, and oral cancers. The traditional and established methods for pet cancer treatment include surgery, radiation therapy, chemotherapy, hyperthermia and photodynamic therapy. However, the available treatment options for pets with advanced-stage disease are limited and the prognosis for such animals is very poor.

The first clinical studies with vaccinia and adenovirus for canine cancer therapy are underway and data on clinical effectiveness is awaited. As for oncolytic virotherapy of human cancers, the most important challenges for the successful clinical use of OVs in veterinary practice are reduction of viral toxicity, optimization of virus delivery to tumor, and enhancement of viral spread throughout the tumor mass. So will it catch on?

 

Oncolytic Virotherapy of Canine and Feline Cancer. Viruses 2014, 6(5), 2122-2137; doi:10.3390/v6052122
Cancer is the leading cause of disease-related death in companion animals such as dogs and cats. Despite recent progress in the diagnosis and treatment of advanced canine and feline cancer, overall patient treatment outcome has not been substantially improved. Virotherapy using oncolytic viruses is one promising new strategy for cancer therapy. Oncolytic viruses (OVs) preferentially infect and lyse cancer cells, without causing excessive damage to surrounding healthy tissue, and initiate tumor-specific immunity. The current review describes the use of different oncolytic viruses for cancer therapy and their application to canine and feline cancer.

 

 

Emerging Disease or Emerging Diagnosis?

Tuesday, May 6th, 2014

Toward the end of the 20th century, deadly microbes seemed to be springing up out of nowhere: Lassa virus in 1969, Ebola virus in 1976 and HIV in the 1980s. Public health officials classified them as “emerging diseases,” meaning they are newly introduced or rising rapidly in human populations. Recent data, however, suggest these viruses may instead have been circulating widely for hundreds or thousands of years. We may not be contending with emerging disease at all, but emerging diagnosis of ancient and frequent disease. This paradigm shift has implications towards countering these viruses now before they become global threats.

Further delay before the end of smallpox virus?

Friday, May 2nd, 2014

Smallpox vaccine Variola, the virus that causes smallpox, is on the agenda of the upcoming meeting of the World Health Assembly (WHA), the governing body of the World Health Organization. The decision to be made is whether the last known remaining live strains of the virus should be destroyed. An international group of scientists argue in an opinion piece published on May 1st in PLOS Pathogens that the WHA should not choose destruction, because crucial scientific questions remain unanswered and important public health goals unmet.

Smallpox was declared eradicated in 1980, the only human pathogen for which successful eradication has been achieved to date. Since then, limited research focusing on diagnostic, antiviral and vaccine development, under close direction and oversight, has continued in two high-security laboratories – one in Russia and one in the US – the only places that are known still to have live variola strains. The justification for this research is that smallpox might re-appear via intentional release. Indeed, recent advances in synthetic biology make the possibility of re-creating the live virus from scratch more plausible.

Summarizing the focus and the achievements of the research on live variola over the past several decades, the authors of the PLOS Pathogens article mention several new smallpox vaccines (the ones widely used prior to eradication would not meet today’s stricter safety standards for routine use) and two new drug candidates that, based on research so far, appear to be promising antivirals against the virus that causes smallpox. However, both of these drug candidates have not yet been licensed for use against the disease. “Despite these considerable advances, they argue that “the research agenda with live variola virus is not yet finished”.

Are We There Yet? The Smallpox Research Agenda Using Variola Virus. (2014) PLoS Pathog 10(5): e1004108. doi:10.1371/journal.ppat.1004108

Should Remaining Stockpiles of Smallpox Virus Be Destroyed?