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Infection Cycle (infection + cycle)
Selected AbstractsInhibition of HIV-1 IIIB and clinical isolates by human parotid, submandibular, sublingual and palatine salivaEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2002Jan G. M. Bolscher Human saliva is known to possess components that decrease the HIV-1 infectivity in vitro. The mechanism of how these components inhibit the infectivity is still not clear on the molecular level. The purpose of this study was to discriminate between serous and mucous components with respect to inhibitory capacity and site of action. We have used total saliva and saliva from the major (sero)mucous glands: submandibular gland, sublingual glands, and glands in the palate, in comparison with the serous parotid glands. HIV-1 IIIB and primary variants were incubated with saliva, and inhibition of HIV-1-infection was determined by analysing the cytopathic effect on MT-2 cells. Mucous saliva, as well as serous saliva, contained high molecular weight components that reduced HIV-1-infectivity, at least partially by entrapment of the virus particles. Lower molecular weight components in all types of saliva possessed strong HIV-1 neutralizing capacity. Using pro-viral DNA synthesis by reverse transcription as a discrimination point in the replication cycle, the results indicated that part of the saliva samples acted before, but others after, this point. In conclusion, saliva inhibits HIV-1-infection by the action of high molecular weight components in combination with low molecular weight components from serous as well as mucous saliva, affecting different stages of the infection cycle. [source] Reconstructing the replication complex of AcMNPVFEBS JOURNAL, Issue 24 2002Kathleen L. Hefferon Baculoviruses are well known for their large, circular, double-stranded DNA genomes. The type member, AcMNPV, is the best characterized and undergoes a succession of early, late and very late gene expression during its infection cycle. The viral genes involved in DNA replication have previously been identified and their products are required for the activation of late gene expression. In this study, we FLAG- and HA-tagged the replication late expression factors of AcMNPV, examined their expression and functional activities by CAT assay and Western blot analysis, and determined their subcellular localization in transfected cells by subcellular fractionation and immunofluorescent microscopy. We found that all replication LEFs with the exception of P143 and P35 resided in the nucleus of transfected cells. We further investigated the interactions among various replication LEFs using both yeast two-hybrid and coprecipitation strategies. A summary of the interactive properties of the replication LEFs is presented and a model for a putative AcMNPV replication complex is offered. [source] Mucosal challenge of Macaca nemestrina with simian immunodeficiency virus (SIV) following SIV nucleocapsid mutant DNA vaccination*JOURNAL OF MEDICAL PRIMATOLOGY, Issue 3-4 2000Robert J. Gorelick A simian immunodeficiency virus (SIV)(Mne) DNA clone was constructed that produces viruses containing a four amino acid deletion in the second zinc finger of the nucleocapsid (NC) domain of the Gag polyprotein. Viruses produced from this clone, although non-infectious both in vitro and in vivo, complete a majority of the steps in a single retroviral infection cycle. Eight pig-tailed macaques (Macaca nemestrina) were inoculated intramuscularly and subcutaneously three times over the course of 24 weeks with the NC mutant expressing DNA. These macaques, and four controls, were then challenged mucosally (intrarectally) with the homologous virus (SIV Mne CL E11S) and monitored for evidence of infection and clinical disease. Prior to challenge, a measurable humoral immune response was noted in four of eight immunized macaques. After challenge, all 12 macaques became infected, although four immunized animals greatly restricted their viral replication, and one immunized animal that controlled replication remains antibody negative. No disease has been evidence during the 46-week period of monitoring after challenge. [source] ULTRASTRUCTURAL CHARACTERIZATION OF THE LYTIC CYCLE OF AN INTRANUCLEAR VIRUS INFECTING THE DIATOM CHAETOCEROS CF. WIGHAMII(BACILLARIOPHYCEAE) FROM CHESAPEAKE BAY, USA,JOURNAL OF PHYCOLOGY, Issue 4 2009Yoanna Eissler Numerous microalgal species are infected by viruses that have the potential to control phytoplankton dynamics by reducing host populations, preventing bloom formation, or causing the collapse of blooms. Here we describe a virus infecting the diatom Chaetoceros cf. wighamii Brightw. from the Chesapeake Bay. To characterize the morphology and lytic cycle of this virus, we conducted a time-course experiment, sampling every 4 h over 72 h following viral inoculation. In vivo fluorescence began to decline 16 h after inoculation and was reduced to <19% of control cultures by the end of experiment. TEM confirmed infection within the first 8 h of inoculation, as indicated by the presence of virus-like particles (VLP) in the nuclei. VLP were present in two different arrangements: rod-like structures that appeared in cross-section as paracrystalline arrays of hexagonal-shaped profiles measuring 12 ± 2 nm in diameter and uniformly electron-dense hexagonal-shaped particles measuring , 22,28 nm in diameter. Nuclei containing paracrystalline arrays were most prevalent early in the infection cycle, while cells containing VLP increased and then declined toward the end of the cycle. The proportion of nuclei containing both paracrystalline arrays and VLP remained relatively constant. This pattern suggests that rod-like paracrystalline arrays fragmented to produce icosahedral VLP. C. cf. wighamii nuclear inclusion virus (CwNIV) is characterized by a high burst size (averaged 26,400 viruses per infected cell) and fast generation time that could have ecological implications on C. cf. wighamii population control. [source] 2 Influence of mixed host populations on success of the parasitic dinoflagellate AmoebophryaJOURNAL OF PHYCOLOGY, Issue 2003T.-N. Armstrong Parasitic dinoflagellates of the genus Amoebophrya commonly infect bloom-forming dinoflagellates of Chesapeake Bay, including Akashiwo sanguinea and Karlodinium micrum. While different strains of Amoebophrya appear host specific, infective dinospores liberated from A. sanguinea do enter the cytoplasm of K. micrum, but fail to complete the infection cycle. Thus, in mixed-species dinoflagellate blooms, interference from inappropriate hosts may influence the success of Amoebophrya spp. To explore that possibility, we conducted laboratory studies to examine the effect of the toxic dinoflagellate K. micrum on success of Amoebophrya from A. sanguinea. Treatments consisted of A. sanguinea (1000/mL) plus corresponding dinospores (10,000/mL) in the presence of different K. micrum densities (0 to 100,000/mL). We also examined whether changes in parasite success were due to interaction with K. micrum cells, or from indirect effects of bacteria or dissolved substances present in K. micrum cultures. Success of Amoebophrya was unaffected by low densities of K. micrum, but decreased at high concentrations of K. micrum. Reduced parasite success appeared to result from combined effects of non-host cells and dissolved substances in K. micrum media. Results suggest that parasitism of A. sanguinea in Chesapeake Bay would be reduced when K. micrum is a major component of mixed-species blooms. [source] Infection of Arabidopsis thaliana leaves with Albugo candida (white blister rust) causes a reprogramming of host metabolismMOLECULAR PLANT PATHOLOGY, Issue 2 2000Hsueh-Mei Chou Albugo candida (Pers.) (O.) Kunze is a biotrophic pathogen which infects the crucifer Arabidopsis thaliana (L.) Heynh forming discrete areas of infection. Eight days after inoculation of leaves, white blisters became visible on the under surface of the leaf although no symptoms were apparent on the upper surface. By day 14, the region of leaf invaded by fungal mycelium had become chlorotic. Recently it has been hypothesized that an accumulation of soluble carbohydrates, following an increase in invertase activity, may trigger sugar signal transduction pathways leading to the repression of photosynthetic gene expression and to the induction of defence proteins. This hypothesis was investigated by quantifying localized changes in carbohydrate and photosynthetic metabolism and the expression of genes encoding photosynthetic and defence proteins. Quantitative imaging of chlorophyll fluorescence revealed that the rate of photosynthesis declined progressively in the invaded regions of the leaf. However, in uninfected regions of the infected leaf the rate of photosynthesis was similar to that measured in the control leaf until late on during the infection cycle when it declined. Images of nonphotochemical fluorescence quenching (NPQ) suggested that the capacity of the Calvin cycle had been reduced in infected regions and that there was a complex metabolic heterogeneity within the infected leaf. A. candida also caused localized changes in the carbohydrate metabolism of the leaf; soluble carbohydrates accumulated in the infected region whereas the amount of starch declined. The reverse was seen in uninfected regions of the infected leaf; carbohydrates did not accumulate until late on during infection and the amount of starch increased as the infection progressed. There was an increase in the activity of invertases which was confined to regions of the leaf invaded by the fungal mycelium. The increase in apoplastic invertase activity was of host origin, as mRNA levels of the AT,FRUCT1 gene (measured by semiquantitative RT-PCR) increased 40-fold in the infected region. The increase in soluble invertase activity resulted from the appearance of a new isoform in the invaded region of the leaf. Current evidence suggests that this was of fungal origin. Northern blot analysis of cab and rbcS showed that photosynthetic gene expression was repressed in the infected leaf from 6 days after inoculation (DAI) when compared to control leaves. In contrast, there was no detectable induction of defence proteins in the infected leaf. These data are discussed in the context of the sugar-sensing hypothesis presented above. [source] Aggressiveness of Phytophthora infestans and phenotypic analysis of resistance in wild Petota accessions in EcuadorPLANT PATHOLOGY, Issue 4 2007M. G. Chacón The aggressiveness of four Phytophthora infestans isolates collected from wild and cultivated potato species (sect. Petota) and the level of resistance of nine Petota species were assessed in the highland tropics of Ecuador. For this, isolates of P. infestans were inoculated on whole plants of Petota species in the field and net house and six epidemiological components , infection frequency (IF), incubation period (IP), latent period (LP), lesion size (LS), lesion growth rate (LGR), and relative area under the lesion expansion curve (RAULEC) , were measured during a single infection cycle. Additionally, host specificity was determined by testing for a significant host by pathogen interaction using the same components. The results showed significant differences among isolates of the EC-1 clonal lineage for IP, IF, and RAULEC. Significant differences among isolates were not found for the other components measured. There were significant differences in resistance among the accessions of Petota hosts tested. RAULEC, LGR, LP, and LS were in general more adequate in differentiating among the more resistant and more susceptible accessions but the importance of each component varied with host species. There was slight and inconsistent evidence for the existence of host specificity in some isolates of Petota hosts. IP was the only component for which a significant host by isolate interaction was observed and in most cases the isolates had the greatest aggressiveness on their hosts of origin. [source] Qualitative and quantitative ultrastructural analysis of the membrane rearrangements induced by coronavirusCELLULAR MICROBIOLOGY, Issue 6 2010Mustafa Ulasli Summary Coronaviruses (CoV) are enveloped positive-strand RNA viruses that induce different membrane rearrangements in infected cells in order to efficiently replicate and assemble. The origin, the protein composition and the function of these structures are not well established. To shed further light on these structures, we have performed a time-course experiment in which the mouse hepatitis virus (MHV)-induced membrane rearrangements were examined qualitatively and quantitatively by (immuno)-electron microscopy. With our approach we were able to confirm the appearance of 6, previously reported, membranous structures during the course of a complete infection cycle. These structures include the well-characterized double-membrane vesicles (DMVs), convoluted membranes (CMs) and virions but also the more enigmatic large virion-containing vacuoles (LVCVs), tubular bodies (TBs) and cubic membrane structures (CMSs). We have characterized the LVCVs, TBs and CMSs, and found that the CoV-induced structures appear in a strict order. By combining these data with quantitative analyses on viral RNA, protein synthesis and virion release, this study generates an integrated molecular and ultrastructural overview of CoV infection. In particular, it provides insights in the role of each CoV-induced structure and reveals that LVCVs are ERGIC/Golgi compartments that expand to accommodate an increasing production of viral particles. [source] The Conservation Relevance of Epidemiological Research into Carnivore Viral Diseases in the SerengetiCONSERVATION BIOLOGY, Issue 3 2007SARAH CLEAVELAND conservación de carnívoros; investigación epidemiológica; moquillo; rabia; Serengeti Abstract:,Recent outbreaks of rabies and canine distemper in wildlife populations of the Serengeti show that infectious disease constitutes a significant cause of mortality that can result in regional extirpation of endangered species even within large, well-protected areas. Nevertheless, effective management of an infectious disease depends critically on understanding the epidemiological dynamics of the causative pathogen. Pathogens with short infection cycles cannot persist in small populations in the absence of a more permanent reservoir of infection. Development of appropriate interventions requires detailed data on transmission pathways between reservoirs and wildlife populations of conservation concern. Relevant data can be derived from long-term population monitoring, epidemic and case-surveillance patterns, genetic analyses of rapidly evolving pathogens, serological surveys, and intervention studies. We examined studies of carnivore diseases in the Serengeti. Epidemiological research contributes to wildlife conservation policy in terms of management of endangered populations and the integration of wildlife conservation with public health interventions. Long-term, integrative, cross-species research is essential for formulation of effective policy for disease control and optimization of ecosystem health. Resumen:,Brotes recientes de rabia y moquillo en poblaciones silvestres del Serengeti muestran que las enfermedades infecciosas constituyen una causa significativa de mortandad que puede resultar en la extirpación regional de especies en peligro, aun en áreas extensas bien protegidas. Sin embargo, el manejo efectivo de una enfermedad infecciosa depende críticamente del entendimiento de la dinámica epidemiológica del patógeno. Los patógenos con ciclo infeccioso corto no pueden persistir en poblaciones pequeñas en ausencia de un reservorio de la infección más permanente. El desarrollo de intervenciones adecuadas requiere de datos detallados de las vías de transmisión entre reservorios y poblaciones de vida silvestre de preocupación para la conservación. Se pueden derivar datos importantes del monitoreo de poblaciones a largo plazo, de patrones de epidemias y de estudios de caso, del análisis genético de patógenos que evolucionan rápidamente, de muestreos sexológicos y de estudios de intervención. Examinamos estudios de enfermedades de carnívoros en el Serengeti. La investigación epidemiológica contribuye a las políticas de conservación de vida silvestre en términos de la gestión de poblaciones en peligro y de la integración de la conservación con intervenciones de salud pública. La investigación a largo plazo e integradora es esencial para la formulación de políticas efectivas para el control de enfermedades y la optimización de la salud del ecosistema. [source] How will plant pathogens adapt to host plant resistance at elevated CO2 under a changing climate?NEW PHYTOLOGIST, Issue 3 2003Sukumar Chakraborty Summary , , To better understand evolution we have studied aggressiveness of the anthracnose pathogen, Colletotrichum gloeosporioides, collected from Stylosanthes scabra pastures between 1978 and 2000 and by inoculating two isolates onto two cultivars over 25 sequential infection cycles at ambient (350 ppm) and twice-ambient atmospheric CO2 in controlled environments. , , Regression analysis of the field population showed that aggressiveness increased towards a resistant cultivar, but not towards a susceptible cultivar, that is no longer grown commercially. , , Here we report for the first time that aggressiveness increased on both cultivars after a few initial infection cycles at twice-ambient CO2 as isolates adapted to combat enhanced host resistance, while at ambient CO2 this increased steadily for most cycles as both cultivars selected for increased aggressiveness. Genetic fingerprint and karyotype of isolates changed for some CO2 -cultivar combinations, but these were not related to changed aggressiveness. , , At 700 ppm fecundity increased for both isolates, and this increased population size, in combination with a conducive microclimate for anthracnose from an enlarged plant canopy under elevated CO2, could accelerate pathogen evolution. [source] | |||||||||||||