scholarly journals Insight into motility-dependent pathogenicity of the zoonotic spirochete Leptospira

2020 ◽  
Author(s):  
Jun Xu ◽  
Nobuo Koizumi ◽  
Shuichi Nakamura
Keyword(s):  
Host Tissue ◽  
Solid Surfaces ◽  
Host Cells ◽  
Bacterial Motility ◽  
Kidney Cells ◽  
Pathogenic Species ◽  
Tissue Surfaces ◽  
Crawling Motility ◽  
Insight Into ◽  
Host Tissues

AbstractBacterial motility is crucial for many pathogenic species in the process of invasion and/or dissemination. The spirochete bacteria Leptospira spp. cause symptoms, such as hemorrhage, jaundice, and nephritis, in diverse mammals including humans. Although loss-of-motility attenuate the spirochete, the mechanism of the motility-dependent pathogenicity is unknown. Here, focusing on that Leptospira spp. swim in liquid and crawl on solid surfaces, we investigated the spirochetal dynamics on the host tissues by infecting cultured kidney cells from various species with pathogenic and nonpathogenic leptospires. We found that, in the case of the pathogenic leptospires, a larger fraction of bacteria attached to the host cells and persistently traveled long distances using the crawling mechanism. Our results associate the kinetics and kinematic features of the spirochetal pathogens with their virulence.One Sentence SummaryAdhesivity and crawling motility over host tissue surfaces are closely related to the pathogenicity of a zoonotic spirochete.

scholarly journals An epidemic Zika virus isolate suppresses antiviral immunity by disrupting antigen presentation pathways

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ryan D. Pardy ◽  
Stefanie F. Valbon ◽  
Brendan Cordeiro ◽  
Connie M. Krawczyk ◽  
Martin J. Richer
Keyword(s):  
T Cell ◽  
Zika Virus ◽  
Cell Response ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cross Presentation ◽  
Cell Immunity ◽  
Asian Lineage ◽  
Insight Into ◽  
Host Tissues

AbstractZika virus (ZIKV) has emerged as an important global health threat, with the recently acquired capacity to cause severe neurological symptoms and to persist within host tissues. We previously demonstrated that an early Asian lineage ZIKV isolate induces a highly activated CD8 T cell response specific for an immunodominant epitope in the ZIKV envelope protein in wild-type mice. Here we show that a contemporary ZIKV isolate from the Brazilian outbreak severely limits CD8 T cell immunity in mice and blocks generation of the immunodominant CD8 T cell response. This is associated with a more sustained infection that is cleared between 7- and 14-days post-infection. Mechanistically, we demonstrate that infection with the Brazilian ZIKV isolate reduces the cross-presentation capacity of dendritic cells and fails to fully activate the immunoproteasome. Thus, our study provides an isolate-specific mechanism of host immune evasion by one Brazilian ZIKV isolate, which differs from the early Asian lineage isolate and provides potential insight into viral persistence associated with recent ZIKV outbreaks.

scholarly journals Mycobacterium tuberculosis adhesins: potential biomarkers as anti-tuberculosis therapeutic and diagnostic targets

Microbiology ◽  
2014 ◽  
Vol 160 (9) ◽  
pp. 1821-1831 ◽  
Author(s):  
Viveshree S. Govender ◽  
Saiyur Ramsugit ◽  
Manormoney Pillay
Keyword(s):  
Immune Response ◽  
Mycobacterium Tuberculosis ◽  
Control Strategies ◽  
Host Cells ◽  
Tuberculosis Control ◽  
Surface Molecules ◽  
Host Pathogen Interaction ◽  
Bacterial Aggregation ◽  
Insight Into

Adhesion to host cells is a precursor to host colonization and evasion of the host immune response. Conversely, it triggers the induction of the immune response, a process vital to the host’s defence against infection. Adhesins are microbial cell surface molecules or structures that mediate the attachment of the microbe to host cells and thus the host–pathogen interaction. They also play a crucial role in bacterial aggregation and biofilm formation. In this review, we discuss the role of adhesins in the pathogenesis of the aetiological agent of tuberculosis, Mycobacterium tuberculosis. We also provide insight into the structure and characteristics of some of the characterized and putative M. tuberculosis adhesins. Finally, we examine the potential of adhesins as targets for the development of tuberculosis control strategies.

Recombination between irradiated shuttle vector DNA and chromosomal DNA in African green monkey kidney cells

1990 ◽  
Vol 10 (1) ◽  
pp. 37-46
Author(s):  
J S Mudgett ◽  
W D Taylor
Keyword(s):  
Gamma Irradiation ◽  
Uv Light ◽  
Shuttle Vector ◽  
Monkey Kidney ◽  
Host Cells ◽  
Mammalian Host ◽  
Kidney Cells ◽  
African Green Monkey Kidney ◽  
Green Monkey ◽  
Chromosome Recombination

An autonomously replicating shuttle vector was used to investigate enhancement of plasmid-chromosome recombination in mammalian host cells by gamma irradiation and UV light. Sequences homologous to the shuttle vector were stably inserted into the genome of African green monkey kidney cells to act as the target substrate for these recombination events. The shuttle vector molecules were irradiated at various doses before transfection into the mammalian host cells that contained the stable insertions. The homologous transfer of the bacterial ampicillin resistance gene from the inserted sequences to replace a mutant ampicillin sensitivity gene on the shuttle vector was identified by the recovery of ampicillin-resistant plasmids after Hirt extraction and transformation into Escherichia coli host cells. Gamma irradiation increased homologous shuttle vector-chromosome recombination, whereas UV light did not increase the frequency of recombinant plasmids detected. Introducing specific double-strand breaks in the plasmid or prolonging the time of plasmid residence in the mammalian host cells also enhanced plasmid-chromosome recombination. In contrast, plasmid mutagenesis was increased by UV irradiation of the plasmid but did not change with time. The ampicillin-resistant recombinant plasmid molecules analyzed appeared to rise mostly from nonconservative exchanges that involved both homologous and possibly nonhomologous interactions with the host chromosome. The observation that similar recombinant structures were obtained from all the plasmid treatments and host cells used suggests a common mechanism for plasmid-chromosome recombination in these mammalian cells.

Morphogenetic properties of the skin axolotl limb regeneration

Development ◽  
1980 ◽  
Vol 58 (1) ◽  
pp. 265-288
Author(s):  
Jonathan M. W. Slack
Keyword(s):  
Limb Regeneration ◽  
Host Tissue ◽  
Tissue Formation ◽  
Cellular Composition ◽  
Posterior Half ◽  
Tail Bud ◽  
Threshold Theory ◽  
Anterior Side ◽  
Immunological Rejection ◽  
Host Tissues

A study has been made of the morphogenetic properties of anterior and posterior skin from the lower forelimb of the axolotl. The basic experiment consisted of a graft of a half cuff of skin from a donor to a host limb followed by a 2-week healing period, amputation through the graft, and a study of the resulting regenerate. Limbs with double posterior skin formed double posterior regenerates and, in contrast, limbs with double anterior skin formed normal or slightly hypomorphic regenerates. Posterior skin from post-metamorphic animals had a similar but weaker effect to that from ordinary axolotls. Immunological rejection of allografts could be completely avoided if the donor limb was transplanted to the flank of the host when both were at the stage of tail-bud embryos, and the skin graft was later carried out between the supernumerary limb and one of the host limbs. This technique was used to show that immunological rejection does not affect the formation of duplicates from the limbs with double posterior skin, and to facilitate the studies of the cellular provenance of the regenerate. The cellular composition of duplicate regenerates was studied by using both triploid donors and triploid hosts. It was shown that the posterior side of the duplications consisted wholly of host tissue and the anterior side consisted of mixed donor and host tissue. Formation of the duplicated regenerate therefore seems to involve positional reprogramming of both donor and host tissues together with metaplasia of the donor tissue. It was not possible to inhibit the duplication-inducing property of posterior skin by treatment with a variety of enzymes. A model based on the serial threshold theory of regeneration is advanced to explain the results.This model successfully accounts for the observed non-equivalence of anterior and posterior skin, and also explains the different regeneration behaviour of anterior and posterior half limbs, the limited regeneration of double anterior limbs, and the pattern expansion and contraction shown by regenerates from double posterior limbs.

scholarly journals Opsonization Modulates Rac-1 Activation during Cell Entry by Leishmania amazonensis

2002 ◽  
Vol 70 (8) ◽  
pp. 4571-4580 ◽  
Author(s):  
J. Morehead ◽  
I. Coppens ◽  
N. W. Andrews
Keyword(s):  
Cho Cells ◽  
Chinese Hamster ◽  
Cytochalasin D ◽  
Leishmania Amazonensis ◽  
Cell Entry ◽  
Butanedione Monoxime ◽  
Respiratory Burst Oxidase ◽  
Insight Into ◽  
Host Tissues

ABSTRACT Lesions caused by Leishmania amazonensis normally heal, but relapses occur due to parasite persistence in host tissues. It has been proposed that infection of fibroblasts plays an important role in this process by providing the parasites with a safe haven in which to replicate. However, most previous studies have focused on the entry of Leishmania into macrophages, a process mediated by serum opsonins. To gain insight into a possible role of nonopsonic entry in the intracellular persistence of amastigotes, we examined the invasion of Chinese hamster ovary (CHO) cells. Amastigotes entered CHO cells by a cytochalasin D, genistein, wortmannin, and 2,3-butanedione monoxime-sensitive pathway and replicated within phagolysosomes. However, unlike most phagocytic processes described to date, amastigote internalization in CHO cells involved activation of the GTPases Rho and Cdc42 but not Rac-1. When uptake was mediated by fibronectin or when amastigotes were opsonized with immunoglobulin G and internalized by Fc receptor-expressing CHO cells, Rac-1 activation was restored and found to be required for parasite internalization. Given the essential role of Rac in assembly of the respiratory burst oxidase, invasion through this nonopsonic, Rac-1-independent pathway may play a central role in the intracellular survival of Leishmania in immune hosts.

scholarly journals Virus–Host Coevolution with a Focus on Animal and Human DNA Viruses

2019 ◽  
Vol 88 (1) ◽  
pp. 41-56 ◽  
Author(s):  
Győző L. Kaján ◽  
Andor Doszpoly ◽  
Zoltán László Tarján ◽  
Márton Z. Vidovszky ◽  
Tibor Papp
Keyword(s):  
Life Form ◽  
Eukaryotic Cell ◽  
Arms Race ◽  
Host Cells ◽  
Dna Viruses ◽  
Fitness Level ◽  
Cellular Life ◽  
Human Dna ◽  
Insight Into

Abstract Viruses have been infecting their host cells since the dawn of life, and this extremely long-term coevolution gave rise to some surprising consequences for the entire tree of life. It is hypothesised that viruses might have contributed to the formation of the first cellular life form, or that even the eukaryotic cell nucleus originates from an infection by a coated virus. The continuous struggle between viruses and their hosts to maintain at least a constant fitness level led to the development of an unceasing arms race, where weapons are often shuttled between the participants. In this literature review we try to give a short insight into some general consequences or traits of virus–host coevolution, and after this we zoom in to the viral clades of adenoviruses, herpesviruses, nucleo-cytoplasmic large DNA viruses, polyomaviruses and, finally, circoviruses.

RIBONUCLEASE ACTIVITY IN RUSTED WHEAT LEAVES

1961 ◽  
Vol 39 (4) ◽  
pp. 775-784 ◽  
Author(s):  
R. Rohringer ◽  
D. J. Samborski ◽  
C. O. Person
Keyword(s):  
Leaf Rust ◽  
Direct Evidence ◽  
Specific Activity ◽  
Host Tissue ◽  
Ribonuclease Activity ◽  
Rnase Activity ◽  
Rnase Inhibitor ◽  
Germination Medium ◽  
Wheat Leaves ◽  
Host Tissues

Extracts from primary leaves of Lee wheat were prepared at various days following inoculation with races of leaf rust and tested for ribonuclease (RNase) activity. As early as 24 hours after inoculation there was a marked increase in the specific activity of the enzyme in extracts of rusted host tissues. A further increase in activity was observed during later stages of infection, with the susceptible and resistant reacting tissue differing only in the degree of their response. Extracts from noninoculated control leaves exhibited a constant RNase activity throughout the period of observation. The germination medium and extracts from germinating uredospores contained comparatively little RNase activity. No direct evidence was obtained either for the possible release of the enzyme from particulate cellular fractions of the host tissue as a result of infection or for the removal of an RNase inhibitor in the host tissue responding to infection.

Mast cell response during the early phase of tuberculosis: an electron-microscopic study

1977 ◽  
Vol 23 (9) ◽  
pp. 1245-1251 ◽  
Author(s):  
Samuel Ratnam ◽  
Shobhitha Ratnam ◽  
B. K. Puri ◽  
Saroj Chandrasekhar
Keyword(s):  
Mast Cell ◽  
Mycobacterium Tuberculosis ◽  
Electron Microscope ◽  
Host Tissue ◽  
Tuberculous Infection ◽  
Electron Microscopic ◽  
Morphological Alterations ◽  
Dense Bodies ◽  
Large Numbers ◽  
Host Tissues

Guinea pig lungs were infected with Mycobacterium tuberculosis by intratracheal route and examined under electron microscope to investigate the morphological alterations of the organisms, if any, and the response of the host tissue. The bacilli showed no changes in their morphology, while the host tissues revealed several cells containing many electron-dense intracytoplasmic granules. These cells were predominantly seen during the 1st week of infection. The electron-dense bodies of these cells may be the ones observed by earlier workers and suggested to be the altered forms of tubercle bacilli. The present investigation, however, revealed them to be the granules of the mast cells. These cells were observed to respond to tuberculous infection during the first few days by appearing in large numbers crowded with intracytoplasmic granules and soon disintegrating as the result of subsequent degranulation. The above observation is presented and its significance discussed.

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