http://www.mdpi.com/journal/pathogens Latest open access articles published in Pathogens at http://www.mdpi.com/journal/pathogens http://www.mdpi.com/2076-0817/2/2/383 Burkholderia mallei, the etiologic agent of glanders, are Category B select agents with biothreat potential, and yet effective therapeutic treatments are lacking. In this study, we showed that CpG administration increased survival, demonstrating protection in the murine glanders model. Bacterial recovery from infected lungs, liver and spleen was significantly reduced in CpG-treated animals as compared with non-treated mice. Reciprocally, lungs of CpG-treated infected animals were infiltrated with higher levels of neutrophils and inflammatory monocytes, as compared to control animals. Employing the B. mallei bioluminescent strain CSM001 and the Neutrophil-Specific Fluorescent Imaging Agent, bacterial dissemination and neutrophil trafficking were monitored in real-time using multimodal in vivo whole body imaging techniques. CpG-treatment increased recruitment of neutrophils to the lungs and reduced bioluminescent bacteria, correlating with decreased bacterial burden and increased protection against acute murine glanders. Our results indicate that protection of CpG-treated animals was associated with recruitment of neutrophils prior to infection and demonstrated, for the first time, simultaneous real time in vivo imaging of neutrophils and bacteria. This study provides experimental evidence supporting the importance of incorporating optimized in vivo imaging methods to monitor disease progression and to evaluate the efficacy of therapeutic treatment during bacterial infections. Pathogens 2013-05-23 2 2 Article 10.3390/pathogens2020383 383 401 2076-0817 2013-05-23 doi: 10.3390/pathogens2020383 Tiffany Mott R. Johnston Sudhamathi Vijayakumar D. Estes Massoud Motamedi Elena Sbrana Janice Endsley Alfredo Torres http://www.mdpi.com/2076-0817/2/2/364 Primary infection with varicella zoster virus (VZV) results in varicella (chickenpox) followed by the establishment of latency in sensory ganglia. Declining T cell immunity due to aging or immune suppressive treatments can lead to VZV reactivation and the development of herpes zoster (HZ, shingles). HZ is often associated with significant morbidity and occasionally mortality in elderly and immune compromised patients. There are currently two FDA-approved vaccines for the prevention of VZV: Varivax® (for varicella) and Zostavax® (for HZ). Both vaccines contain the live-attenuated Oka strain of VZV. Although highly immunogenic, a two-dose regimen is required to achieve a 99% seroconversion rate. Zostavax vaccination reduces the incidence of HZ by 51% within a 3-year period, but a significant reduction in vaccine-induced immunity is observed within the first year after vaccination. Developing more efficacious vaccines and therapeutics requires a better understanding of the host response to VZV. These studies have been hampered by the scarcity of animal models that recapitulate all aspects of VZV infections in humans. In this review, we describe different animal models of VZV infection as well as an alternative animal model that leverages the infection of Old World macaques with the highly related simian varicella virus (SVV) and discuss their contributions to our understanding of pathogenesis and immunity during VZV infection. Pathogens 2013-05-13 2 2 Review 10.3390/pathogens2020364 364 382 2076-0817 2013-05-13 doi: 10.3390/pathogens2020364 Kristen Haberthur Ilhem Messaoudi http://www.mdpi.com/2076-0817/2/2/357 Common marmosets (Callithrix jacchus) developed high levels of viremia, clinical signs including fever, weight loss, a decrease in activity and hematuria upon inoculation with dengue virus (DENV). Presence of DENV genome in urine samples and pathological changes in kidneys were examined in the present study. Levels of DENV genome were determined in 228 urine samples from 20 primary DENV-inoculated marmosets and in 56 urine samples from four secondary DENV-inoculated marmosets. DENV genome was detected in 75% (15/20) of marmosets after primary DENV infection. No DENV genome was detected in urine samples from the marmosets with secondary infection with homologous DENV (0%, 0/4). Two marmosets demonstrated hematuria. Pathological analysis of the kidneys demonstrated non-suppressive interstitial nephritis with renal tubular regeneration. DENV antigen-positive cells were detected in kidneys. In human dengue virus infections, some patients present renal symptoms. The results indicate that marmosets recapitulate some aspects of the involvement of kidneys in human DENV infection, and suggest that marmosets are potentially useful for the studies of the pathogenesis of DENV infection, including kidneys. Pathogens 2013-05-13 2 2 Article 10.3390/pathogens2020357 357 363 2076-0817 2013-05-13 doi: 10.3390/pathogens2020357 Meng Moi Tsutomu Omatsu Takanori Hirayama Shinichiro Nakamura Yuko Katakai Tomoyuki Yoshida Akatsuki Saito Shigeru Tajima Mikako Ito Tomohiko Takasaki Hirofumi Akari Ichiro Kurane http://www.mdpi.com/2076-0817/2/2/288 The influence of microorganisms growing as sessile communities in a large number of human infections has been extensively studied and recognized for 30–40 years, therefore warranting intense scientific and medical research. Nonetheless, mimicking the biofilm-life style of bacteria and biofilm-related infections has been an arduous task. Models used to study biofilms range from simple in vitro to complex in vivo models of tissues or device-related infections. These different models have progressively contributed to the current knowledge of biofilm physiology within the host context. While far from a complete understanding of the multiple elements controlling the dynamic interactions between the host and biofilms, we are nowadays witnessing the emergence of promising preventive or curative strategies to fight biofilm-related infections. This review undertakes a comprehensive analysis of the literature from a historic perspective commenting on the contribution of the different models and discussing future venues and new approaches that can be merged with more traditional techniques in order to model biofilm-infections and efficiently fight them. Pathogens 2013-05-13 2 2 Review 10.3390/pathogens2020288 288 356 2076-0817 2013-05-13 doi: 10.3390/pathogens2020288 David Lebeaux Ashwini Chauhan Olaya Rendueles Christophe Beloin http://www.mdpi.com/2076-0817/2/2/264 The Henipavirus genus contains two highly lethal viruses, the Hendra and Nipah viruses and one, recently discovered, apparently nonpathogenic member; Cedar virus. These three, negative-sense single-stranded RNA viruses, are hosted by fruit bats and use EphrinB2 receptors for entry into cells. The Hendra and Nipah viruses are zoonotic pathogens that emerged in the middle of 90s and have caused severe, and often fatal, neurologic and/or respiratory diseases in both humans and different animals; including spillover into equine and porcine species. Development of relevant models is critical for a better understanding of viral pathogenesis, generating new diagnostic tools, and assessing anti-viral therapeutics and vaccines. This review summarizes available data on several animal models where natural and/or experimental infection has been demonstrated; including pteroid bats, horses, pigs, cats, hamsters, guinea pigs, ferrets, and nonhuman primates. It recapitulates the principal features of viral pathogenesis in these animals and current knowledge on anti-viral immune responses. Lastly it describes the recently characterized murine animal model, which provides the possibility to use numerous and powerful tools available for mice to further decipher henipaviruses immunopathogenesis, prophylaxis, and treatment. The utility of different models to analyze important aspects of henipaviruses-induced disease in humans, potential routes of transmission, and therapeutic approaches are equally discussed. Pathogens 2013-04-09 2 2 Review 10.3390/pathogens2020264 264 287 2076-0817 2013-04-09 doi: 10.3390/pathogens2020264 Kévin Dhondt Branka Horvat http://www.mdpi.com/2076-0817/2/2/232 Acute respiratory tract infection (RTI) is a leading cause of morbidity and mortality worldwide and the majority of RTIs are caused by viruses, among which respiratory syncytial virus (RSV) and the closely related human metapneumovirus (hMPV) figure prominently. Host innate immune response has been implicated in recognition, protection and immune pathological mechanisms. Host-viral interactions are generally initiated via host recognition of pathogen-associated molecular patterns (PAMPs) of the virus. This recognition occurs through host pattern recognition receptors (PRRs) which are expressed on innate immune cells such as epithelial cells, dendritic cells, macrophages and neutrophils. Multiple PRR families, including Toll-like receptors (TLRs), RIG-I-like receptors (RLRs) and NOD-like receptors (NLRs), contribute significantly to viral detection, leading to induction of cytokines, chemokines and type I interferons (IFNs), which subsequently facilitate the eradication of the virus. This review focuses on the current literature on RSV and hMPV infection and the role of PRRs in establishing/mediating the infection in both in vitro and in vivo models. A better understanding of the complex interplay between these two viruses and host PRRs might lead to efficient prophylactic and therapeutic treatments, as well as the development of adequate vaccines. Pathogens 2013-04-03 2 2 Review 10.3390/pathogens2020232 232 263 2076-0817 2013-04-03 doi: 10.3390/pathogens2020232 Deepthi Kolli Thangam Velayutham Antonella Casola http://www.mdpi.com/2076-0817/2/2/209 Intestinal inflammation is widely recognized as a pivotal player in health and disease. Defined cytologically as the infiltration of leukocytes in the lamina propria layer of the intestine, it can damage the epithelium and, on a chronic basis, induce inflammatory bowel disease and potentially cancer. The current view thus dictates that blood cell infiltration is the instigator of intestinal inflammation and tumor-promoting inflammation. This is based partially on work in humans and mice showing that intestinal damage during microbially mediated inflammation activates phagocytic cells and lymphocytes that secrete inflammatory signals promoting tissue damage and tumorigenesis. Nevertheless, extensive parallel work in the Drosophila midgut shows that intestinal epithelium damage induces inflammatory signals and growth factors acting mainly in a paracrine manner to induce intestinal stem cell proliferation and tumor formation when genetically predisposed. This is accomplished without any apparent need to involve Drosophila hemocytes. Therefore, recent work on Drosophila host defense to infection by expanding its main focus on systemic immunity signaling pathways to include the study of organ homeostasis in health and disease shapes a new notion that epithelially emanating cytokines and growth factors can directly act on the intestinal stem cell niche to promote “regenerative inflammation” and potentially cancer. Pathogens 2013-04-02 2 2 Review 10.3390/pathogens2020209 209 231 2076-0817 2013-04-02 doi: 10.3390/pathogens2020209 Stavria Panayidou Yiorgos Apidianakis http://www.mdpi.com/2076-0817/2/2/193 Vertical transmission from an infected cow to its fetus accounts for the vast majority of new Neospora caninum infections in cattle. A vaccine composed of a chimeric antigen named recNcMIC3-1-R, based on predicted immunogenic domains of the two microneme proteins NcMIC1 and NcMIC3, the rhoptry protein NcROP2, and emulsified in saponin adjuvants, significantly reduced the cerebral infection in non-pregnant BALB/c mice. Protection was associated with a mixed Th1/Th2-type cytokine response. However, the same vaccine formulation elicited a Th2-type immune response in pregnant mice and did not prevent vertical transmission or disease, neither in dams nor in offspring mice. In this study, an alternative vaccine formulation containing recNcMIC3-1-R emulsified in Freund’s incomplete adjuvant, a stimulator of the cellular immunity, was investigated. No protection against vertical transmission and cerebral infection in the pregnant mice and a very limited protective effect in the non-pregnant mice were observed. The vaccine induced a Th1-type immune response characterized by high IgG2a titres and strong IFN-γ expression, which appeared detrimental to pregnancy. Pathogens 2013-03-27 2 2 Article 10.3390/pathogens2020193 193 208 2076-0817 2013-03-27 doi: 10.3390/pathogens2020193 Thierry Monney Denis Grandgirard Stephen Leib Andrew Hemphill http://www.mdpi.com/2076-0817/2/1/177 β-defensins are small cationic antimicrobial peptides secreted by diverse cell types including colonic epithelial cells. Human β-defensins form an essential component of the intestinal lumen in innate immunity. The defensive mechanisms of β-defensins include binding to negatively charged microbial membranes that cause cell death and chemoattraction of immune cells. The antimicrobial activity of β-defensin is well reported in vitro against several enteric pathogens and in non-infectious processes such as inflammatory bowel diseases, which alters β-defensin production. However, the role of β-defensin in vivo in its interaction with other immune components in host defense against bacteria, viruses and parasites with more complex membranes is still not well known. This review focuses on the latest findings regarding the role of β-defensin in relevant human infectious and non-infectious diseases of the colonic mucosa. In addition, we summarize the most significant aspects of β-defensin and its antimicrobial role in a variety of disease processes. Pathogens 2013-03-19 2 1 Review 10.3390/pathogens2010177 177 192 2076-0817 2013-03-19 doi: 10.3390/pathogens2010177 Eduardo Cobo Kris Chadee http://www.mdpi.com/2076-0817/2/1/153 Epstein-Barr virus (EBV) is a ubiquitous herpesvirus infecting more than 90% of the adult population of the world. EBV is associated with a variety of diseases including infectious mononucleosis, lymphoproliferative diseases, malignancies such as Burkitt lymphoma and nasopharyngeal carcinoma, and autoimmune diseases including rheumatoid arthritis (RA). EBV in nature infects only humans, but in an experimental setting, a limited species of new-world monkeys can be infected with the virus. Small animal models, suitable for evaluation of novel therapeutics and vaccines, have not been available. Humanized mice, defined here as mice harboring functioning human immune system components, are easily infected with EBV that targets cells of the hematoimmune system. Furthermore, humanized mice can mount both cellular and humoral immune responses to EBV. Thus, many aspects of human EBV infection, including associated diseases (e.g., lymphoproliferative disease, hemophagocytic lymphohistiocytosis and erosive arthritis resembling RA), latent infection, and T-cell-mediated and humoral immune responses have been successfully reproduced in humanized mice. Here we summarize recent achievements in the field of humanized mouse models of EBV infection and show how they have been utilized to analyze EBV pathogenesis and normal and aberrant human immune responses to the virus. Pathogens 2013-03-14 2 1 Review 10.3390/pathogens2010153 153 176 2076-0817 2013-03-14 doi: 10.3390/pathogens2010153 Shigeyoshi Fujiwara Go Matsuda Ken-Ichi Imadome http://www.mdpi.com/2076-0817/2/1/130 Parasite life history may differ during coinfection compared to single infections, and the order of infection may be an important predictor of life history traits. We subjected laboratory mice (Mus musculus) to single and coinfections with Heligmosomoides bakeri and Hymenolepis microstoma and measured life history traits of worms and also hepatobiliary and morphological responses by the host. We found that fewer H. bakeri larvae established, and adult worms were shorter and produced fewer eggs during a coinfection where H. microstoma occurred first. H. microstoma grew more and released more eggs after simultaneous inoculation of both parasites compared to a single H. microstoma infection, despite similar worm numbers. Mouse small intestine mass, but not length, varied with coinfection and bile duct mass was largest when H. microstoma was given alone or first. Mouse serum alkaline phosphatase levels were greatest for mice infected with H. microstoma only but did not vary with number of scolices; no change in mouse serum alanine transaminase levels was observed. Overall, the order of coinfection influenced life history traits of both H. bakeri and H. microstoma, but changes in survival, growth, and reproduction with order of inoculation were not consistent between the two parasites. Pathogens 2013-03-01 2 1 Article 10.3390/pathogens2010130 130 152 2076-0817 2013-03-01 doi: 10.3390/pathogens2010130 Paul Clark W. Ward Samantha Lang Alaa Saghbini Deborah Kristan http://www.mdpi.com/2076-0817/2/1/105 Matrix metalloproteinases (MMPs) represent a large family of over twenty different secreted or membrane-bound endopeptidases, involved in many physiological (embryogenesis, precursor or stem cell mobilization, tissue remodeling during wound healing, etc.), as well as pathological (inflammation, tumor progression and metastasis in cancer, vascular pathology, etc.) conditions. For a long time, MMPs were considered only for the ability to degrade extracellular matrix (ECM) molecules (e.g., collagen, laminin, fibronectin) and to release hidden epitopes from the ECM. In the last few years, it has been fully elucidated that these molecules have many other functions, mainly related to the immune response, in consideration of their effects on cytokines, hormones and chemokines. Among others, MMP-2 and MMP-9 are endopeptidases of the MMP family produced by neutrophils, macrophages and monocytes. When infection is associated with leukocyte influx into specific organs, immunopathology and collateral tissue damage may occur. In this review, the involvement of MMPs and, in particular, of gelatinases in both protozoan and helminth infections will be described. In cerebral malaria, for example, MMPs play a role in the pathogenesis of such diseases. Also, trypanosomosis and toxoplasmosis will be considered for protozoan infections, as well as neurocysticercosis and angiostrongyloidosis, as regards helminthiases. All these situations have in common the proteolytic action on the blood brain barrier, mediated by MMPs. Pathogens 2013-02-19 2 1 Review 10.3390/pathogens2010105 105 129 2076-0817 2013-02-19 doi: 10.3390/pathogens2010105 Fabrizio Bruschi Barbara Pinto http://www.mdpi.com/2076-0817/2/1/92 The pathological prion protein, PrPSc, displays various sizes of aggregates. In this study, we investigated the conformation, aggregation stability and proteinase K (PK)-sensitivity of small and large PrPSc aggregates of mouse-adapted prion strains. We showed that small PrPSc aggregates, previously thought to be PK-sensitive, are resistant to PK digestion. Furthermore, we showed that small PrPSc aggregates of the Chandler scrapie strain have greater resistance to PK digestion and aggregation-denaturation than large PrPSc aggregates of this strain. We conclude that this strain consists of heterogeneous PrPSc. Pathogens 2013-02-18 2 1 Article 10.3390/pathogens2010092 92 104 2076-0817 2013-02-18 doi: 10.3390/pathogens2010092 Kazuo Kasai Yoshifumi Iwamaru Kentaro Masujin Morikazu Imamura Shirou Mohri Takashi Yokoyama http://www.mdpi.com/2076-0817/2/1/71 Costs and benefits of the immune response have attracted considerable attention in the last years among evolutionary biologists. Given the cost of parasitism, natural selection should favor individuals with the most effective immune defenses. Nevertheless, there exists huge variation in the expression of immune effectors among individuals. To explain this apparent paradox, it has been suggested that an over-reactive immune system might be too costly, both in terms of metabolic resources and risks of immune-mediated diseases, setting a limit to the investment into immune defenses. Here, we argue that this view neglects one important aspect of the interaction: the role played by evolving pathogens. We suggest that taking into account the co-evolutionary interactions between the host immune system and the parasitic strategies to overcome the immune response might provide a better picture of the selective pressures that shape the evolution of immune functioning. Integrating parasitic strategies of host exploitation can also contribute to understand the seemingly contradictory results that infection can enhance, but also protect from, autoimmune diseases. In the last decades, the incidence of autoimmune disorders has dramatically increased in wealthy countries of the northern hemisphere with a concomitant decrease of most parasitic infections. Experimental work on model organisms has shown that this pattern may be due to the protective role of certain parasites (i.e., helminths) that rely on the immunosuppression of hosts for their persistence. Interestingly, although parasite-induced immunosuppression can protect against autoimmunity, it can obviously favor the spread of other infections. Therefore, we need to think about the evolution of the immune system using a multidimensional trade-off involving immunoprotection, immunopathology and the parasitic strategies to escape the immune response. Pathogens 2013-02-13 2 1 Review 10.3390/pathogens2010071 71 91 2076-0817 2013-02-13 doi: 10.3390/pathogens2010071 Gabriele Sorci Stéphane Cornet Bruno Faivre http://www.mdpi.com/2076-0817/2/1/55 Goblet cells reside throughout the gastrointestinal (GI) tract and are responsible for the production and preservation of a protective mucus blanket by synthesizing and secreting high molecular weight glycoproteins known as mucins. The concept of the mucus layer functioning as a dynamic protective barrier is suggested by studies showing changes in mucins in inflammatory conditions of the GI tract, by the altered goblet cell response in germ-free animals, and by the enhanced mucus secretion seen in response to infections. The mucin-containing mucus layer coating the GI epithelium is the front line of innate host defense. Mucins are likely to be the first molecules that invading pathogens interact with at the cell surface and thus, can limit binding to other glycoproteins and neutralize the pathogen. This review will focus on what is known about goblet cell response in various GI infections and the regulatory networks that mediate goblet cell function and mucin production in response to intestinal insults. In addition, we describe the current knowledge on the role of mucins in intestinal innate defense. It is the aim of this review to provide the readers with an update on goblet cell biology and current understanding on the role of mucins in host defense in enteric infections. Pathogens 2013-02-04 2 1 Review 10.3390/pathogens2010055 55 70 2076-0817 2013-02-04 doi: 10.3390/pathogens2010055 Janice Kim Waliul Khan http://www.mdpi.com/2076-0817/2/1/33 Malaria continues to exact a great human toll in tropical settings. Antimalarial resistance is rife and the parasite inexorably develops mechanisms to outwit our best drugs, including the now first-line choice, artesunate. Novel strategies to circumvent resistance are needed. Here we detail drug development focusing on heat shock protein 90 and its central role as a chaperone. A growing body of evidence supports the role for Hsp90 inhibitors as adjunctive drugs able to restore susceptibility to traditionally efficacious compounds like chloroquine. Pathogens 2013-02-04 2 1 Review 10.3390/pathogens2010033 33 54 2076-0817 2013-02-04 doi: 10.3390/pathogens2010033 Dea Shahinas Asongna Folefoc Dylan Pillai http://www.mdpi.com/2076-0817/2/1/13 Epithelial cells of the cornea and the conjunctiva constitutively produce antimicrobial peptides; however, the production of defensins by other cell types located around the eye has not been investigated. We analyzed the production of beta-defensins (hBD) and cathelicidin LL-37 during the infection of primary limbo-corneal fibroblasts with M. tuberculosis (MTB), M. abscessus (MAB), and M. smegmatis (MSM). The intracellular survival of each mycobacterium, the production of cytokines and the changes on the distribution of the actin filaments during the infection were also analyzed. Fibroblasts produce basal levels of hBD1 and LL-37 and under PMA stimulation they produce hBD2, hBD3 and overexpress hBD1 and LL-37. MAB induced the highest levels of hBD1 and LL-37 and intermediate levels of IL-6; however, MAB was not eliminated. In addition, MAB induced the greatest change to the distribution of the actin filaments. MTB also produced changes in the structure of the cytoskeleton and induced low levels of hBD1 and IL-6, and intermediate levels of LL-37. The balance of these molecules induced by MTB appeared to contribute to the non-replicative state observed in the limbo-corneal cells. MSM induced the lowest levels of hBD1 and LL-37 but the highest levels of IL-6; MSM was eliminated. The results suggest that mycobacterial infections regulate the production of antimicrobial peptides and cytokines, which in conjunction can contribute to the control of the bacilli. Pathogens 2013-02-04 2 1 Article 10.3390/pathogens2010013 13 32 2076-0817 2013-02-04 doi: 10.3390/pathogens2010013 Jorge Castañeda-Sánchez Blanca García-Pérez Ana Muñoz-Duarte Shantal Baltierra-Uribe Herlinda Mejia-López Carlos López-López Victor Bautista-De Lucio Atzín Robles-Contreras Julieta Luna-Herrera http://www.mdpi.com/2076-0817/2/1/1 Human bocavirus (HBoV) was identified as the second human parvovirus with pathogenic potential in 2005 in respiratory samples from children suffering from viral respiratory infections of unknown etiology. Since its first description, a large number of clinical studies have been performed that address the clinical significance of HBoV detection and the molecular biology of the virus. This review summarizes the most important steps taken in HBoV research to date and addresses open questions that need to be answered in the future to provide a better understanding of the role of a virus that is difficult to grow in cell culture and is suspected to be a pathogen, although it has not yet fulfilled Koch’s postulates. Pathogens 2013-01-11 2 1 Review 10.3390/pathogens2010001 1 12 2076-0817 2013-01-11 doi: 10.3390/pathogens2010001 Oliver Schildgen http://www.mdpi.com/2076-0817/1/2/156 Some key questions in Epstein-Barr virus (EBV) biology center on whether naturally occurring sequence differences in the virus affect infection or EBV associated diseases. Understanding the pattern of EBV sequence variation is also important for possible development of EBV vaccines. At present EBV isolates worldwide can be grouped into Type 1 and Type 2, a classification based on the EBNA2 gene sequence. Type 1 EBV is the most prevalent worldwide but Type 2 is common in parts of Africa. Type 1 transforms human B cells into lymphoblastoid cell lines much more efficiently than Type 2 EBV. Molecular mechanisms that may account for this difference in cell transformation are now becoming clearer. Advances in sequencing technology will greatly increase the amount of whole EBV genome data for EBV isolated from different parts of the world. Study of regional variation of EBV strains independent of the Type 1/Type 2 classification and systematic investigation of the relationship between viral strains, infection and disease will become possible. The recent discovery that specific mutation of the EBV EBNA3B gene may be linked to development of diffuse large B cell lymphoma illustrates the importance that mutations in the virus genome may have in infection and human disease. Pathogens 2012-11-08 1 2 Review 10.3390/pathogens1020156 156 174 2076-0817 2012-11-08 doi: 10.3390/pathogens1020156 Stelios Tzellos Paul Farrell http://www.mdpi.com/2076-0817/1/2/128 Salmonella spp. are a leading cause of human infectious disease worldwide and pose a serious health concern. While we have an improving understanding of pathogenesis and the host-pathogen interactions underlying the infection process, comparatively little is known about the survival of pathogenic Salmonella outside their hosts. This review focuses on three areas: (1) in vitro evidence that Salmonella spp. can survive for long periods of time under harsh conditions; (2) observations and conclusions about Salmonella persistence obtained from human outbreaks; and (3) new information revealed by genomic- and population-based studies of Salmonella and related enteric pathogens. We highlight the mechanisms of Salmonella persistence and transmission as an essential part of their lifecycle and a prerequisite for their evolutionary success as human pathogens. Pathogens 2012-10-24 1 2 Review 10.3390/pathogens1020128 128 155 2076-0817 2012-10-24 doi: 10.3390/pathogens1020128 Landon L. Waldner Keith D. MacKenzie Wolfgang Köster Aaron P. White http://www.mdpi.com/2076-0817/1/2/102 As obligate intracellular pathogens, viruses depend on the host cell machinery to complete their life cycle. Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic virus causally linked to the development of Kaposi’s sarcoma and several other lymphoproliferative malignancies. KSHV entry into cells is tightly regulated by diverse viral and cellular factors. In particular, KSHV actively engages cellular integrins and ubiquitination pathways for successful infection. Emerging evidence suggests that KSHV hijacks both actin and microtubule cytoskeletons at different phases during entry into cells. Here, we review recent findings on the early events during primary infection of KSHV and its closely related primate homolog rhesus rhadinovirus with highlights on the regulation of cellular cytoskeletons and signaling pathways that are important for this phase of virus life cycle. Pathogens 2012-10-22 1 2 Review 10.3390/pathogens1020102 102 127 2076-0817 2012-10-22 doi: 10.3390/pathogens1020102 Wei Zhang Shou-Jiang Gao http://www.mdpi.com/2076-0817/1/2/83 B-lymphocyte-induced maturation protein 1 (BLIMP1) exists as two major isoforms, α and β, which arise from alternate promoters. Inactivation of the full length BLIMP1α isoform is thought to contribute to B cell lymphomagenesis by blocking post-germinal centre (GC) B cell differentiation. In contrast, the shorter β isoform is functionally impaired and over-expressed in several haematological malignancies, including diffuse large B cell lymphomas (DLBCL). We have studied the influence on BLIMP1β expression of the Epstein-Barr virus (EBV), a human herpesvirus that is implicated in the pathogenesis of several GC-derived lymphomas, including a subset of DLBCL and Hodgkin’s lymphoma (HL). We show that BLIMP1β expression is increased following the EBV infection of normal human tonsillar GC B cells. We also show that this change in expression is accompanied by hypomethylation of the BLIMP1β-specific promoter. Furthermore, we confirmed previous reports that the BLIMP1β promoter is hypomethylated in DLBCL cell lines and show for the first time that BLIMP1β is hypomethylated in the Hodgkin/Reed-Sternberg (HRS) cells of HL. Our results provide evidence in support of a role for BLIMP1β in the pathogenesis of EBV-associated B cell lymphomas. Pathogens 2012-10-08 1 2 Article 10.3390/pathogens1020083 83 101 2076-0817 2012-10-08 doi: 10.3390/pathogens1020083 Katerina Vrzalikova Sarah Leonard Yichao Fan Andrew Bell Martina Vockerodt Patrik Flodr Kenneth L. Wright Martin Rowe Qian Tao Paul G. Murray http://www.mdpi.com/2076-0817/1/2/65 We previously proved that a histone deacetylase inhibitor (valproate, VPA) decreases the number of leukemic cells in bovine leukemia virus (BLV)-infected sheep. Here, we characterize the mechanisms initiated upon interruption of treatment. We observed that VPA treatment is followed by a decrease of the B cell counts and proviral loads (copies per blood volume). However, all sheep eventually relapsed after different periods of time and became refractory to further VPA treatment. Sheep remained persistently infected with BLV. B lymphocytes isolated throughout treatment and relapse were responsive to VPA-induced apoptosis in cell culture. B cell proliferation is only marginally affected by VPA ex vivo. Interestingly, in four out of five sheep, ex vivo viral expression was nearly undetectable at the time of relapse. In two sheep, a new tumoral clone arose, most likely revealing a selection process exerted by VPA in vivo. We conclude that the interruption of VPA treatment leads to the resurgence of the leukemia in BLV-infected sheep and hypothesize that resistance to further treatment might be due to the failure of viral expression induction. The development of more potent HDAC inhibitors and/or the combination with other compounds can overcome chemoresistance. These observations in the BLV model may be important for therapies against the related Human T-lymphotropic virus type 1. Pathogens 2012-10-08 1 2 Article 10.3390/pathogens1020065 65 82 2076-0817 2012-10-08 doi: 10.3390/pathogens1020065 Nicolas Gillet Fabian Vandermeers Alix de Brogniez Arnaud Florins Annamaria Nigro Carole François Amel-Baya Bouzar Olivier Verlaeten Eric Stern Didier M. Lambert Johan Wouters Luc Willems http://www.mdpi.com/2076-0817/1/1/52 Although there is increasing evidence that aberrant expression of those enzymes which control protein arginine methylation contribute to carcinogenesis, their de-regulation by oncogenic viruses in primary cells has yet to be reported. We first show that the protein arginine methyltransferases, CARM1, PRMT1 and PRMT5 are strongly expressed in Hodgkin Reed-Sternberg (HRS) cells, and up-regulated in Hodgkin's lymphoma (HL) cell lines. Given that Epstein-Barr virus (EBV) can be detected in approximately 50% of primary HL, we next examined how EBV infection of germinal centre (GC) B cells, the presumptive precursors of HRS cells, modulated the expression of these proteins. EBV infection of GC B cells was followed by the up-regulation of CARM1, PRMT1 and PRMT5, and by the down-regulation of the arginine deiminase, PADI4. Latent membrane protein 1 (LMP1), the major EBV transforming gene was shown to induce PRMT1 in GC B cells and in a stably transfected B cell line. The recent development of compounds which inhibit PRMT-mediated reactions provides a compelling case for continuing to dissect the contribution of virus induced changes in these proteins to lymphomagenesis. Pathogens 2012-09-19 1 1 Article 10.3390/pathogens1010052 52 64 2076-0817 2012-09-19 doi: 10.3390/pathogens1010052 Sarah Leonard Naheema Gordon Nikki Smith Martin Rowe Paul G. Murray Ciarán B. Woodman http://www.mdpi.com/2076-0817/1/1/37 EBNA1, a nuclear protein expressed in all EBV-associated neoplasms is indispensable for the maintenance of the viral episomes in latently infected cells. EBNA1 may induce genetic alterations by upregulating cellular recombinases, production of reactive oxygen species (ROS) and affecting p53 levels and function. All these changes may contribute to tumorigenesis. In this overview we focus, however, on the epigenetic alterations elicited by EBNA1 by drawing a parallel between EBNA1 and the FoxA family of pioneer transcription factors. Both EBNA1 and FoxA induce local DNA demethylation, nucleosome destabilization and bind to mitotic chromosomes. Local DNA demethylation and nucleosome rearrangement mark active promoters and enhancers. In addition, EBNA1 and FoxA, when associated with mitotic chromatin may “bookmark” active genes and ensure their reactivation in postmitotic cells (epigenetic memory). We speculate that DNA looping induced by EBNA1-EBNA1 interactions may reorganize the cellular genome. Such chromatin loops, sustained in mitotic chromatin similarly to the long-distance interactions mediated by the insulator protein CTCF, may also mediate the epigenetic inheritance of gene expression patterns. We suggest that EBNA1 has the potential to induce patho-epigenetic alterations contributing to tumorigenesis. Pathogens 2012-09-17 1 1 Review 10.3390/pathogens1010037 37 51 2076-0817 2012-09-17 doi: 10.3390/pathogens1010037 Hans Helmut Niller Janos Minarovits http://www.mdpi.com/2076-0817/1/1/30 As new platforms for high-risk strains of human papillomavirus (HR HPV) testing are introduced into the clinical laboratory, it is important to verify their performance and agreement. In this validation study, post-aliquot cervical cytopathology specimens (n = 226) were used to analyze agreement between the Invader HPV ASR assay (Hologic) and the recently FDA-approved Cobas 4800 high-risk HPV assay (Roche). Residual sample from 92 Invader positive and 134 Invader negative samples were analyzed with the Cobas 4800 test. Discordant results were further analyzed by Linear Array HPV genotype testing (Roche). To assess intra- and inter-run precision, 31 Invader positive samples were run in duplicate on the Cobas 4800 by different operators over multiple days and purchased HR HPV DNA control was run in ten replicates. Cross-contamination during cytology processing was evaluated by spiking 6 Invader negative samples with different volumes of Acrometrix HPV High Risk Positive Control and analyzed on the Cobas with 4 negative samples in between. There was significant discordance between the assays (p < 0.001; exact McNemar X2 test), with overall agreement of 82%. Of the 92 Invader positive samples, 58 (63%) were positive with the Cobas assay, while 34 (37%) were negative. Of the 134 Invader negative samples, 6 (4%) were positive with the Cobas while 128 (96%) were negative. The observed discordance may be attributed to the previously described false positive rate of the Invader ASR assay. The Cobas 4800 high-risk HPV assay is a viable new tool for use in the clinical setting to identify high-risk HPV. Pathogens 2012-09-12 1 1 Article 10.3390/pathogens1010030 30 36 2076-0817 2012-09-12 doi: 10.3390/pathogens1010030 Isabella W. Martin Heather B. Steinmetz Claudine L. Lefferts Larry J. Dumont Laura J. Tafe Gregory J. Tsongalis http://www.mdpi.com/2076-0817/1/1/12 Using a strategy of gene deletion mutagenesis, we have examined the roles of genes putatively involved in lipopolysaccharide biosynthesis in the virulent facultative intracellular bacterial pathogen, Francisella tularensis subspecies tularensis, strain SCHU S4 in LPS biosynthesis, protein glycosylation, virulence and immunogenicity. One mutant, ∆wbtI, did not elaborate a long chain O-polysaccharide (OPS), was completely avirulent for mice, and failed to induce a protective immune response against challenge with wild type bacteria. Another mutant, ∆wbtC, produced a long chain OPS with altered chemical and electrophoretic characteristics. This mutant showed markedly reduced glycosylation of several known glycoproteins. Additionally this mutant was highly attenuated, and elicited a protective immune response against systemic, but not respiratory challenge with wild type SCHU S4. A third mutant, ∆kdtA, produced an unconjugated long chain OPS, lacking a detectable core structure, and which was not obviously expressed at the surface. It was avirulent and elicited partial protection against systemic challenge only. Pathogens 2012-09-10 1 1 Article 10.3390/pathogens1010012 12 29 2076-0817 2012-09-10 doi: 10.3390/pathogens1010012 Susan M. Twine Evguenii Vinogradov Helena Lindgren Anders Sjostedt J. Wayne Conlan http://www.mdpi.com/2076-0817/1/1/3 Several members of the staphylococcal phenol-soluble modulin (PSM) peptide family exhibit pronounced capacities to lyse eukaryotic cells, such as neutrophils, monocytes, and erythrocytes. This is commonly assumed to be due to the amphipathic, α-helical structure of PSMs, giving PSMs detergent-like characteristics and allowing for a relatively non-specific destruction of biological membranes. However, the capacities of PSMs to lyse synthetic phospholipid vesicles have not been investigated. Here, we analyzed lysis of synthetic phosphatidylcholine (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC) vesicles by all Staphylococcus aureus and S. epidermidis PSMs. In addition, we investigated the lytic capacities of culture filtrates obtained from different S. aureus PSM deletion mutants toward POPC vesicles. Our results show that all staphylococcal PSMs have phospholipid vesicle-lysing activity and the capacity of S. aureus culture filtrate to lyse POPC vesicles is exclusively dependent on PSMs. Notably, we observed largely differing capacities among PSM peptides to lyse POPC vesicles. Interestingly, POPC vesicle-lytic capacities did not correlate with those previously seen for the lysis of eukaryotic cells. For example, the β-type PSMs were strongly lytic for POPC vesicles, but are known to exhibit only very low lytic capacities toward neutrophils and erythrocytes. Thus our results also suggest that the interaction between PSMs and eukaryotic membranes is more specific than previously assumed, potentially depending on additional structural features of those membranes, such as phospholipid composition or yet unidentified docking molecules. Pathogens 2012-07-20 1 1 Article 10.3390/pathogens1010003 3 11 2076-0817 2012-07-20 doi: 10.3390/pathogens1010003 Anthony C. Duong Gordon Y. C. Cheung Michael Otto http://www.mdpi.com/2076-0817/1/1/1 Infection ranks alongside cardiovascular disease as the major cause of human death across the world. Word Health Organization data for 2002 shows that 26% of all deaths, almost 15 million in number, were due to infectious disease with HIV/AIDS, TB and malaria being the top three responsible infections. A significant proportion of these deaths were due to lower respiratory infections and diarrheal diseases in children. The worldwide morbidity associated with infectious disease is incalculable. When considered along with the consequences of infection in animals, it is hard to imagine any other disease that has such a significant impact on our lives―on health systems, on agriculture and on world economics. Our understanding of the agents responsible for infections―bacteria, fungi, parasites, prions and viruses―has an interesting history that heralds the great developments in modern biology and demonstrates how an understanding of disease pathogenesis can lead to successful prophylactic and therapeutic interventions. Van Leeuwenhoek’s first observation of bacteria under the light microscope, John Snow’s investigations tracing the source of a cholera epidemic in Victorian London’s Soho and Pasteur’s vaccines for rabies and anthrax contributed to an acceptance of the germ theory of disease and to the rational, scientific application of this knowledge to develop innovative disease control measures ranging from hygienic practices to antibiotics. [...] Pathogens 2011-09-29 1 1 Editorial 10.3390/pathogens1010001 1 2 2076-0817 2011-09-29 doi: 10.3390/pathogens1010001 Lawrence S. Young