Absonifibula estuarina sp. n. (Monogenea: Diclidophoridae) parasite of juvenile Cynoscion guatucupa (Osteichthyes) from southwestern Atlantic Ocean

Absonifibula estuarina sp. n. (Diclidophoridae, Absonifibulinae), is described from the gills of juvenile striped weakfish, Cynoscion guatucupa (Cuvier), from the southwestern Atlantic, Argentinean coast. This marine fish migrates to estuarine areas to spawn where exclusively juveniles are found parasitized; adult fish in marine water were never found to be parasitized by this monogenean. A. estuarina sp. n. is characterized mainly by the pedunculate clamps dissimilar in size, the shape of anterior jaw with sclerite 'a' attached to a sub-trapezoidal lamellate extension and fused to sclerites 'c' and 'd'. It differs from Absonifibula bychowskyi Lawler & Overstreet, 1976, the only known species of the genus, in the shape and arrangement of the genital corona, which is armed with six similar hooks disposed in circle and the sub-trapezoidal shape of lamellate extension ('b'). The restriction to juvenile sciaenids is a shared feature among the Absonifibulinae indicating an estuary-dependent life cycle.

Structural organization of Trypanosoma cruzi

Since the initial description of Trypanosoma cruzi by Carlos Chagas in 1909, several research groups have used different microscopic techniques to obtain detailed information about the various developmental stages found in the life cycle of this intracellular parasite. This review describes the present knowledge on the organization of the most important structures and organelles found in the protozoan, such as the cell surface, flagellum, cytoskeleton, kinetoplast-mitochondrion complex, glycosome, acidocalcisome, contractile vacuole, lipid inclusions, the secretory pathway, endocytic pathway and the nucleus.

Light and electron microscopy of Myxobolus sciades n. sp. (Myxozoa), a parasite of the gills of the Brazilian fish Sciades herzbergii (Block, 1794) (Teleostei: Ariidae)

A myxosporean parasite in the gill lamellae of the freshwater teleost fish, Sciades herzbergii (Ariidae) (Block, 1794), from the Poti River (Northeast of Brazil) was described by light and electron microscopy studies. Polysporic histozoic cyst-like plasmodia containing several life-cycle stages, including mature spores, were observed. The spores were pyriform and uninucleate, measuring 9.15 ± 0.39 μm (n = 50) long, 4.36 ± 0.23 μm (n = 25) wide and 2.61 ± 0.31 μm (n = 25) thick. Elongated pyriform polar capsules (PC) were of equal size (4.44 ± 0.41 μm long and 1.41 ± 0.42 μm in diameter) and each contained a polar filament with 9-10 coils obliquely arranged in relation to the axis of PC. The PC wall was composed of two layers of different electron densities. Histological analysis revealed the close contact of the cyst-like plasmodia with the basal portion of the epithelial gill layer, which exhibited some alterations in the capillary vessels. Based on the morphological and ultrastructural differences, the similarity of the spore features to those of the genus Myxobolus and the specificity of this host to previously described species, we describe a new species named Myxobolus sciades n. sp. in this study.

Orthologues of the Drosophila melanogaster E75 molting control gene in the filarial parasites Brugia malayi and Dirofilaria immitis.

Filarial parasites cause debilitating diseases in humans and domesticated animals. Brugia malayi and Dirofilaria immitis are transmitted by mosquitoes and infect humans and dogs, respectively. Their life cycle is punctuated by a series of cuticular molts as they move between different hosts and tissues. An understanding of the genetic basis for these developmental transitions may suggest potential targets for vaccines or chemotherapeutics. Nuclear receptor (NR) proteins have been implicated in molting in the free-living nematode Caenorhabditis elegans and have well characterized roles in molting during larval development of Drosophila melanogaster. For example, the D. melanogaster E75 (NR1D3) NR gene is required for molting and metamorphosis, as well as egg chamber development in adult females. We have identified Bm-nhr-11and Di-nhr-6, B. malayi and D. immitis orthologues of E75. Both genes encode canonical nuclear receptor proteins, are developmentally regulated, and are expressed in a sex-specific manner in adults.

Role of the host cell's unfolded protein response in arenavirus infection.

Arenaviruses are enveloped RNA viruses with a nonlytic life cycle that cause acute and persistent infections. Here, we investigated the role of the host cell's unfolded protein response (UPR) in infection of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV). In mammalian cells, the endoplasmic reticulum (ER) chaperone protein GRP78/BiP functions as the principal sensor for the induction of the UPR and interacts with three mediators: kinase/endonuclease inositol-requiring protein 1 (IRE1), PKR-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Acute infection with LCMV resulted in a selective induction of the ATF6-regulated branch of the UPR, whereas pathways controlled by PERK and IRE1 were neither activated nor blocked. Expression of individual LCMV proteins revealed that the viral glycoprotein precursor (GPC), but not that of other viral proteins, was responsible for the induction of ATF6. Rapid downregulation of the viral GPC during transition from acute to persistent LCMV infection restored basal levels of UPR signaling. To address a possible role of ATF6 signaling in LCMV infection, we used cells deficient in site 2 protease (S2P), a metalloprotease required for the activation of ATF6. Cells deficient in S2P showed significantly lower levels of production of infectious virus during acute but not persistent infection, indicating a requirement for ATF6-mediated signaling for optimal virus multiplication. In summary, acute LCMV infection seems to selectively induce the ATF6-regulated branch of the UPR that is likely beneficial for virus replication and cell viability, but it avoids induction of PERK and IRE1, whose activation may be detrimental for virus and the host cell.

Anàlisi del Cicle de Vida (ACV) del Monoestearat de Glicerina a CRODA Ibérica, S.A. – Mevisa Site

L’estudi de l’Anàlisi del Cicle de Vida (ACV) ha estat realitzat a l’empresa CRODA Ibèrica S.A - Mevisa Site, en concret a la línia productiva on s’hi fabrica el monoestearat de glicerina utilitzant una eina informàtica comercial denominada SIMAPRO que analitza i compara els aspectes mediambientals d’un producte d’una manera sistemàtica i consistent seguint les recomanacions de les normes ISO 14040

Characterization of TcSTI-1, a homologue of stress-induced protein-1, in Trypanosoma cruzi

The life cycle of the protozoan Trypanosoma cruzi exposes it to several environmental stresses in its invertebrate and vertebrate hosts. Stress conditions are involved in parasite differentiation, but little is known about the stress response proteins involved. We report here the first characterization of stress-induced protein-1 (STI-1) in T. cruzi (TcSTI-1). This co-chaperone is produced in response to stress and mediates the formation of a complex between the stress proteins HSP70 and HSP90 in other organisms. Despite the similarity of TcSTI-1 to STI-1 proteins in other organisms, its expression profile in response to various stress conditions, such as heat shock, acidic pH or nutrient starvation, is quite different. Neither polysomal mRNA nor protein levels changed in exponentially growing epimastigotes cultured under any of the stress conditions studied. Increased levels of TcSTI-1 were observed in epimastigotes subjected to nutritional stress in the late growth phase. Co-immunoprecipitation assays revealed an association between TcSTI-1 and TcHSP70 in T. cruzi epimastigotes. Immunolocalization demonstrated that TcSTI-1 was distributed throughout the cytoplasm and there was some colocalization of TcSTI-1 and TcHSP70 around the nucleus. Thus, TcSTI-1 associates with TcHSP70 and TcSTI-1 expression is induced when the parasites are subjected to stress conditions during specific growth phase.

Hypomorphic mutation in the site-1 protease Mbtps1 endows resistance to persistent viral infection in a cell-specific manner.

The prototypic arenavirus lymphocytic choriomeningitis virus (LCMV), which naturally persists in rodents, represents a model for HIV, HBV, and HCV. Cleavage of the viral glycoprotein precursor by membrane-bound transcription factor peptidase, site 1 (Mbtps1 or site-1 protease), is crucial for the life cycle of arenaviruses and therefore represents a potential target for therapy. Recently, we reported a viable hypomorphic allele of Mbtps1 (woodrat) encoding a protease with diminished enzymatic activity. Using the woodrat allele, we examine the role of Mbtps1 during persistent LCMV infection. Surprisingly, Mbtps1 inhibition limits persistent but not acute viral infection and is associated with an organ/cell type-specific decrease in viral titers. Analysis of bone marrow-derived dendritic cells from woodrat mice supports their specific role in resolving persistent viral infection. These results support in vivo targeting of Mbtps1 in the treatment of arenavirus infections and demonstrate a critical role for dendritic cells in persistent viral infections.

Regulatory elements involved in the post-transcriptional control of stage-specific gene expression in Trypanosoma cruzi: a review

Trypanosoma cruzi, a protozoan parasite that causes Chagas disease, exhibits unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes, RNA editing and trans-splicing. In the absence of mechanism controlling transcription initiation, organized subsets of T. cruzi genes must be post-transcriptionally co-regulated in response to extracellular signals. The mechanisms that regulate stage-specific gene expression in this parasite have become much clearer through sequencing its whole genome as well as performing various proteomic and microarray analyses, which have demonstrated that at least half of the T. cruzi genes are differentially regulated during its life cycle. In this review, we attempt to highlight the recent advances in characterising cis and trans-acting elements in the T. cruzi genome that are involved in its post-transcriptional regulatory machinery.

Towards an understanding of the epigenetics of schistosomes: a comparative epigenomic study

As in perhaps all eukaryotes, schistosomes use a supplementary information transmitting system, the epigenetic inheritance system, to shape genetic information and to produce different phenotypes. In contrast to other important parasites, the study of epigenetic phenomena in schistosomes is still in its infancy. Nevertheless, we are beginning to grasp what goes on behind the epigenetic scene in this parasite. We have developed techniques of native chromatin immunoprecipitation (N-ChIP) and associated the necessary bioinformatics tools that allow us to run genome-wide comparative chromatin studies on Schistosoma mansoni at different stages of its life cycle, on different strains and on different sexes. We present here an application of such an approach to study the genetic and epigenetic basis for a phenotypic trait, the compatibility of S. mansoni with its invertebrate host Biomphalaria glabrata. We have applied the ChIP procedure to two strains that are either compatible or incompatible with their intermediate host. The precipitated DNA was sequenced and aligned to a reference genome and this information was used to determine regions in which both strands differ in their genomic sequence and/or chromatin structure. This procedure allowed us to identify candidate genes that display either genetic or epigenetic difference between the two strains.

NS2 Proteins of GB Virus B and Hepatitis C Virus Share Common Protease Activities and Membrane Topologies.

GB virus B (GBV-B), which is hepatotropic in experimentally infected small New World primates, is a member of the Hepacivirus genus but phylogenetically relatively distant from hepatitis C virus (HCV). To gain insights into the role and specificity of hepaciviral nonstructural protein 2 (NS2), which is required for HCV polyprotein processing and particle morphogenesis, we investigated whether NS2 structural and functional features are conserved between HCV and GBV-B. We found that GBV-B NS2, like HCV NS2, has cysteine protease activity responsible for cleavage at the NS2/NS3 junction, and we experimentally confirmed the location of this junction within the viral polyprotein. A model for GBV-B NS2 membrane topology was experimentally established by determining the membrane association properties of NS2 segments fused to green fluorescent protein (GFP) and their nuclear magnetic resonance structures using synthetic peptides as well as by applying an N-glycosylation scanning approach. Similar glycosylation studies confirmed the HCV NS2 organization. Together, our data show that despite limited amino acid sequence similarity, GBV-B and HCV NS2 proteins share a membrane topology with 3 N-terminal transmembrane segments, which is also predicted to apply to other recently discovered hepaciviruses. Based on these data and using trans-complementation systems, we found that intragenotypic hybrid NS2 proteins with heterologous N-terminal membrane segments were able to efficiently trans-complement an assembly-deficient HCV mutant with a point mutation in the NS2 C-terminal domain, while GBV-B/HCV or intergenotypic NS2 chimeras were not. These studies indicate that virus- and genotype-specific intramolecular interactions between N- and C-terminal domains of NS2 are critically involved in HCV morphogenesis. IMPORTANCE: Nonstructural protein 2 (NS2) of hepatitis C virus (HCV) is a multifunctional protein critically involved in polyprotein processing and virion morphogenesis. To gain insights into NS2 mechanisms of action, we investigated whether NS2 structural and functional features are conserved between HCV and GB virus B (GBV-B), a phylogenetically relatively distant primate hepacivirus. We showed that GBV-B NS2, like HCV NS2, carries cysteine protease activity. We experimentally established a model for GBV-B NS2 membrane topology and demonstrated that despite limited sequence similarity, GBV-B and HCV NS2 share an organization with three N-terminal transmembrane segments. We found that the role of HCV NS2 in particle assembly is genotype specific and relies on critical interactions between its N- and C-terminal domains. This first comparative analysis of NS2 proteins from two hepaciviruses and our structural predictions of NS2 from other newly identified mammal hepaciviruses highlight conserved key features of the hepaciviral life cycle.

High host-plant nitrogen content: a prerequisite for the evolution of ant-caterpillar mutualism?

The amount of nitrogen required to complete an insect's life cycle may vary greatly among species that have evolved distinct life history traits. Myrmecophilous caterpillars in the Lycaenidae family produce nitrogen-rich exudates from their dorsal glands to attract ants for protection, and this phenomenon has been postulated to shape the caterpillar's host-plant choice. Accordingly, it was postulated that evolution towards myrmecophily in Lycaenidae is correlated with the utilization of nitrogen-rich host plants. Although our results were consistent with the evolutionary shifts towards high-nutrient host plants serving as exaptation for the evolution of myrmecophily in lycaenids, the selection of nitrogen-rich host plants was not confined to lycaenids. Butterfly species in the nonmyrmecophilous family Pieridae also preferred nitrogen-rich host plants. Thus, we conclude that nitrogen is an overall important component in the caterpillar diet, independent of the level of myrmecophily, as nitrogen can enhance the overall insect fitness and survival. However, when nitrogen can be obtained through alternative means, as in socially parasitic lycaenid species feeding on ant brood, the selective pressure for maintaining the use of nutrient-rich host plants is relaxed, enabling the colonization of nitrogen-poor host plants.

Antibodies against the Plasmodium falciparum glutamate-rich protein from naturally exposed individuals living in a Brazilian malaria-endemic area can inhibit in vitro parasite growth

The glutamate-rich protein (GLURP) is an exoantigen expressed in all stages of the Plasmodium falciparum life cycle in humans. Anti-GLURP antibodies can inhibit parasite growth in the presence of monocytes via antibody-dependent cellular inhibition (ADCI), and a major parasite-inhibitory region has been found in the N-terminal R0 region of the protein. Herein, we describe the antiplasmodial activity of anti-GLURP antibodies present in the sera from individuals naturally exposed to malaria in a Brazilian malaria-endemic area. The anti-R0 antibodies showed a potent inhibitory effect on the growth of P. falciparum in vitro, both in the presence (ADCI) and absence (GI) of monocytes. The inhibitory effect on parasite growth was comparable to the effect of IgGs purified from pooled sera from hyperimmune African individuals. Interestingly, in the ADCI test, higher levels of tumour necrosis factor alpha (TNF-α) were observed in the supernatant from cultures with higher parasitemias. Our data suggest that the antibody response induced by GLURP-R0 in naturally exposed individuals may have an important role in controlling parasitemia because these antibodies are able to inhibit the in vitro growth of P. falciparum with or without the cooperation from monocytes. Our results also indicate that TNF-α may not be relevant for the inhibitory effect on P. falciparum in vitro growth.

Surface-expressed enolases of Plasmodium and other pathogens

Enolase is the eighth enzyme in the glycolytic pathway, a reaction that generates ATP from phosphoenol pyruvate in cytosolic compartments. Enolase is essential, especially for organisms devoid of the Krebs cycle that depend solely on glycolysis for energy. Interestingly, enolase appears to serve a separate function in some organisms, in that it is also exported to the cell surface via a poorly understood mechanism. In these organisms, surface enolase assists in the invasion of their host cells by binding plasminogen, an abundant plasma protease precursor. Binding is mediated by the interaction between a lysine motif of enolase with Kringle domains of plasminogen. The bound plasminogen is then cleaved by specific proteases to generate active plasmin. Plasmin is a potent serine protease that is thought to function in the degradation of the extracellular matrix surrounding the targeted host cell, thereby facilitating pathogen invasion. Recent work revealed that the malaria parasite Plasmodium also expresses surface enolase, and that this feature may be essential for completion of its life cycle. The therapeutic potential of targeting surface enolases of pathogens is discussed.

Malaria vector species in Colombia: a review

Here we present a comprehensive review of the literature on the vectorial importance of the major Anopheles malaria vectors in Colombia. We provide basic information on the geographical distribution, altitudinal range, immature habitats, adult behaviour, feeding preferences and anthropophily, endophily and infectivity rates. We additionally review information on the life cycle, longevity and population fluctuation of Colombian Anopheles species. Emphasis was placed on the primary vectors that have been epidemiologically incriminated in malaria transmission: Anopheles darlingi, Anopheles albimanus and Anopheles nuneztovari. The role of a selection of local, regional or secondary vectors (e.g., Anopheles pseudopunctipennis and Anopheles neivai) is also discussed. We highlight the importance of combining biological, morphological and molecular data for the correct taxonomical determination of a given species, particularly for members of the species complexes. We likewise emphasise the importance of studying the bionomics of primary and secondary vectors along with an examination of the local conditions affecting the transmission of malaria. The presence and spread of the major vectors and the emergence of secondary species capable of transmitting human Plasmodia are of great interest. When selecting control measures, the anopheline diversity in the region must be considered. Variation in macroclimate conditions over a species' geographical range must be well understood and targeted to plan effective control measures based on the population dynamics of the local Anopheles species.