scholarly journals Resistance in marine cyanobacteria differs against specialist and generalist cyanophages

2019 ◽  
Vol 116 (34) ◽  
pp. 16899-16908 ◽  
Author(s):  
Sophia Zborowsky ◽  
Debbie Lindell
Keyword(s):  
Phage Genome ◽  
Marine Cyanobacteria ◽  
Genome Replication ◽  
Genome Transcription ◽  
Infection Cycles ◽  
Resistance To Infection ◽  
Partial Genome ◽  
Stage Infection ◽  
Genome Degradation

Long-term coexistence between unicellular cyanobacteria and their lytic viruses (cyanophages) in the oceans is thought to be due to the presence of sensitive cells in which cyanophages reproduce, ultimately killing the cell, while other cyanobacteria survive due to resistance to infection. Here, we investigated resistance in marine cyanobacteria from the genera Synechococcus and Prochlorococcus and compared modes of resistance against specialist and generalist cyanophages belonging to the T7-like and T4-like cyanophage families. Resistance was extracellular in most interactions against specialist cyanophages irrespective of the phage family, preventing entry into the cell. In contrast, resistance was intracellular in practically all interactions against generalist T4-like cyanophages. The stage of intracellular arrest was interaction-specific, halting at various stages of the infection cycle. Incomplete infection cycles proceeded to various degrees of phage genome transcription and translation as well as phage genome replication in numerous interactions. In a particularly intriguing case, intracellular capsid assembly was observed, but the phage genome was not packaged. The cyanobacteria survived the encounter despite late-stage infection and partial genome degradation. We hypothesize that this is tolerated due to genome polyploidy, which we found for certain strains of both Synechococcus and Prochlorococcus. Our findings unveil a heavy cost of promiscuous entry of generalist phages into nonhost cells that is rarely paid by specialist phages and suggests the presence of unknown mechanisms of intracellular resistance in the marine unicellular cyanobacteria. Furthermore, these findings indicate that the range for virus-mediated horizontal gene transfer extends beyond hosts to nonhost cyanobacterial cells.

scholarly journals Proofreading-Deficient Coronaviruses Adapt for Increased Fitness over Long-Term Passage without Reversion of Exoribonuclease-Inactivating Mutations

mBio ◽  
2017 ◽  
Vol 8 (6) ◽  
Author(s):  
Kevin W. Graepel ◽  
Xiaotao Lu ◽  
James Brett Case ◽  
Nicole R. Sexton ◽  
Everett Clinton Smith ◽  
...  
Keyword(s):  
Rna Viruses ◽  
Hepatitis Virus ◽  
Nucleoside Analogues ◽  
High Fidelity ◽  
Genome Replication ◽  
Murine Hepatitis Virus ◽  
Replicase Proteins ◽  
Rna Genome ◽  
Inactivating Mutations

ABSTRACT The coronavirus (CoV) RNA genome is the largest among the single-stranded positive-sense RNA viruses. CoVs encode a proofreading 3′-to-5′ exoribonuclease within nonstructural protein 14 (nsp14-ExoN) that is responsible for CoV high-fidelity replication. Alanine substitution of ExoN catalytic residues [ExoN(-)] in severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and murine hepatitis virus (MHV) disrupts ExoN activity, yielding viable mutant viruses with defective replication, up to 20-fold-decreased fidelity, and increased susceptibility to nucleoside analogues. To test the stability of the ExoN(-) genotype and phenotype, we passaged MHV-ExoN(-) 250 times in cultured cells (P250), in parallel with wild-type MHV (WT-MHV). Compared to MHV-ExoN(-) P3, MHV-ExoN(-) P250 demonstrated enhanced replication and increased competitive fitness without reversion at the ExoN(-) active site. Furthermore, MHV-ExoN(-) P250 was less susceptible than MHV-ExoN(-) P3 to multiple nucleoside analogues, suggesting that MHV-ExoN(-) was under selection for increased replication fidelity. We subsequently identified novel amino acid changes within the RNA-dependent RNA polymerase and nsp14 of MHV-ExoN(-) P250 that partially accounted for the reduced susceptibility to nucleoside analogues. Our results suggest that increased replication fidelity is selected in ExoN(-) CoVs and that there may be a significant barrier to ExoN(-) reversion. These results also support the hypothesis that high-fidelity replication is linked to CoV fitness and indicate that multiple replicase proteins could compensate for ExoN functions during replication. IMPORTANCE Uniquely among RNA viruses, CoVs encode a proofreading exoribonuclease (ExoN) in nsp14 that mediates high-fidelity RNA genome replication. Proofreading-deficient CoVs with disrupted ExoN activity [ExoN(-)] either are nonviable or have significant defects in replication, RNA synthesis, fidelity, fitness, and virulence. In this study, we showed that ExoN(-) murine hepatitis virus can adapt during long-term passage for increased replication and fitness without reverting the ExoN-inactivating mutations. Passage-adapted ExoN(-) mutants also demonstrate increasing resistance to nucleoside analogues that is explained only partially by secondary mutations in nsp12 and nsp14. These data suggest that enhanced resistance to nucleoside analogues is mediated by the interplay of multiple replicase proteins and support the proposed link between CoV fidelity and fitness. IMPORTANCE Uniquely among RNA viruses, CoVs encode a proofreading exoribonuclease (ExoN) in nsp14 that mediates high-fidelity RNA genome replication. Proofreading-deficient CoVs with disrupted ExoN activity [ExoN(-)] either are nonviable or have significant defects in replication, RNA synthesis, fidelity, fitness, and virulence. In this study, we showed that ExoN(-) murine hepatitis virus can adapt during long-term passage for increased replication and fitness without reverting the ExoN-inactivating mutations. Passage-adapted ExoN(-) mutants also demonstrate increasing resistance to nucleoside analogues that is explained only partially by secondary mutations in nsp12 and nsp14. These data suggest that enhanced resistance to nucleoside analogues is mediated by the interplay of multiple replicase proteins and support the proposed link between CoV fidelity and fitness.

Immunity toTrichuris murisin the laboratory mouse

2003 ◽  
Vol 77 (2) ◽  
pp. 95-98 ◽  
Author(s):  
K.J. Else ◽  
M.L. deSchoolmeester
Keyword(s):  
Laboratory Mouse ◽  
Mouse Strains ◽  
Chronic Infections ◽  
Trichuris Muris ◽  
Intestinal Nematode ◽  
Unique Model ◽  
Resistance To Infection ◽  
Laboratory Models ◽  
Strain Dependent

AbstractOf all the laboratory models of intestinal nematode infection,Trichuris murisin the mouse is arguably the most powerful. This is largely due to the fact that the ability to expel this parasite is strain dependent. Thus, most mouse strains readily expelT. muris. However certain mouse strains, and indeed some individuals within particular mouse strains, are unable to mount a protective immune response and harbour long term chronic infections. This unique model thus presents an opportunity to examine the immune events underlying both resistance to infection and persistent infection within the same host species, and in some cases, the same host strain.

scholarly journals Alphavirus RNA Genome Repair and Evolution: Molecular Characterization of Infectious Sindbis Virus Isolates Lacking a Known Conserved Motif at the 3′ End of the Genome

2000 ◽  
Vol 74 (20) ◽  
pp. 9776-9785 ◽  
Author(s):  
Jyothi George ◽  
Ramaswamy Raju
Keyword(s):  
Sindbis Virus ◽  
Repeat Sequence ◽  
Genome Replication ◽  
Sequence Element ◽  
Conserved Sequence ◽  
Long Term Stability ◽  
Nontranslated Region ◽  
Viral Promoters ◽  
Sequence Elements

ABSTRACT The 3′ nontranslated region of the genomes of Sindbis virus (SIN) and other alphaviruses carries several repeat sequence elements (RSEs) as well as a 19-nucleotide (nt) conserved sequence element (3′CSE). The 3′CSE and the adjoining poly(A) tail of the SIN genome are thought to act as viral promoters for negative-sense RNA synthesis and genome replication. Eight different SIN isolates that carry altered 3′CSEs were studied in detail to evaluate the role of the 3′CSE in genome replication. The salient findings of this study as it applies to SIN infection of BHK cells are as follows: i) the classical 19-nt 3′CSE of the SIN genome is not essential for genome replication, long-term stability, or packaging; ii) compensatory amino acid or nucleotide changes within the SIN genomes are not required to counteract base changes in the 3′ terminal motifs of the SIN genome; iii) the 5′ 1-kb regions of all SIN genomes, regardless of the differences in 3′ terminal motifs, do not undergo any base changes even after 18 passages; iv) although extensive addition of AU-rich motifs occurs in the SIN genomes carrying defective 3′CSE, these are not essential for genome viability or function; and v) the newly added AU-rich motifs are composed predominantly of RSEs. These findings are consistent with the idea that the 3′ terminal AU-rich motifs of the SIN genomes do not bind directly to the viral polymerase and that cellular proteins with broad AU-rich binding specificity may mediate this interaction. In addition to the classical 3′CSE, other RNA motifs located elsewhere in the SIN genome must play a major role in template selection by the SIN RNA polymerase.

scholarly journals Bioengineered Acellular Vessel Implantation in a Patient with Chronic Limb-Threatening Ischemia: A Case Report and Discussion of Implications for Trauma

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Alexis L Lauria ◽  
Joseph M White ◽  
Alexander J Kersey ◽  
Paul W White ◽  
Todd E Rasmussen
Keyword(s):  
Case Report ◽  
Vascular Reconstruction ◽  
Vascular Trauma ◽  
Autologous Vein ◽  
Resistance To Infection ◽  
Vessel Implantation ◽  
Tissue Incorporation ◽  
Synthetic Grafts ◽  
The Ideal

The ideal conduit for vascular reconstruction is one that can be obtained “off the shelf” and demonstrates long-term patency, tissue incorporation and resistance to infection. Currently available conduits, such as autologous vein and synthetic grafts, are limited in one or more of these areas. The Human Acellular Vessel (HAV), a bioengineered, acellular blood vessel, can be obtained “off the shelf” and has shown promise in each of these properties. We describe a case in which the HAV was utilized for open bypass reconstruction in a patient with chronic limb-threatening ischemia who lacked alternative reconstructive options. The case is followed by a discussion of potential broader applications of this novel implant, specifically in the management of vascular trauma.  

scholarly journals The Bacteriophage HK97 gp15 Moron Element Encodes a Novel Superinfection Exclusion Protein

2012 ◽  
Vol 194 (18) ◽  
pp. 5012-5019 ◽  
Author(s):  
Nichole Cumby ◽  
Aled M. Edwards ◽  
Alan R. Davidson ◽  
Karen L. Maxwell
Keyword(s):  
Phage Genome ◽  
Sequence Similarity ◽  
Bacterial Protein ◽  
Bacterial Host ◽  
Related Phage ◽  
Superinfection Exclusion ◽  
Phage Dna ◽  
N Terminus ◽  
Resistance To Infection ◽  
Membrane Spanning

ABSTRACTA phage moron is a DNA element inserted between a pair of genes in one phage genome that are adjacent in other related phage genomes. Phage morons are commonly found within phage genomes, and in a number of cases, they have been shown to mediate phenotypic changes in the bacterial host. The temperate phage HK97 encodes a moron element, gp15, within its tail morphogenesis region that is absent in most closely related phages. We show that gp15 is actively expressed from the HK97 prophage and is responsible for providing the host cell with resistance to infection by phages HK97 and HK75, independent of repressor immunity. To identify the target(s) of this gp15-mediated resistance, we created a hybrid of HK97 and the related phage HK022. This hybrid phage revealed that the tail tube or tape measure proteins likely mediate the susceptibility of HK97 to inhibition by gp15. The N terminus of gp15 is predicted with high probability to contain a single membrane-spanning helix by several transmembrane prediction programs. Consistent with this putative membrane localization, gp15 acts to prevent the entry of phage DNA into the cytoplasm, acting in a manner reminiscent of those of several previously characterized superinfection exclusion proteins. The N terminus of gp15 and its phage homologues bear sequence similarity to YebO proteins, a family of proteins of unknown function found ubiquitously in enterobacteria. The divergence of their C termini suggests that phages have co-opted this bacterial protein and subverted its activity to their advantage.

scholarly journals Difficulties in demonstrating long term immunity in FeLV vaccinated cats due to increasing age-related resistance to infection

2012 ◽  
Vol 8 (1) ◽  
pp. 125 ◽  
Author(s):  
Stephen Wilson ◽  
Juliet Greenslade ◽  
Gillian Saunders ◽  
Catherine Holcroft ◽  
Lynn Bruce ◽  
...  
Keyword(s):  
Age Related ◽  
Resistance To Infection

scholarly journals Resistance to infection of long-term cryopreserved human aortic valve allografts

2016 ◽  
Vol 151 (5) ◽  
pp. 1251-1259 ◽  
Author(s):  
Viola Steffen ◽  
Georg Marsch ◽  
Karin Burgwitz ◽  
Christian Kuehn ◽  
Omke E. Teebken
Keyword(s):  
Aortic Valve ◽  
Resistance To Infection ◽  
Human Aortic Valve

scholarly journals Human Metapneumovirus Induces Formation of Inclusion Bodies for Efficient Genome Replication and Transcription

2017 ◽  
Vol 91 (24) ◽  
Author(s):  
Nicolás Cifuentes-Muñoz ◽  
Jean Branttie ◽  
Kerri Beth Slaughter ◽  
Rebecca Ellis Dutch
Keyword(s):  
Inclusion Body ◽  
Inclusion Bodies ◽  
Time Course ◽  
Human Metapneumovirus ◽  
Genome Replication ◽  
Body Formation ◽  
Inclusion Body Formation ◽  
Genome Transcription ◽  
Infected Cells ◽  
Transcription And Replication

ABSTRACT Human metapneumovirus (HMPV) causes significant upper and lower respiratory disease in all age groups worldwide. The virus possesses a negative-sense single-stranded RNA genome of approximately 13.3 kb encapsidated by multiple copies of the nucleoprotein (N), giving rise to helical nucleocapsids. In addition, copies of the phosphoprotein (P) and the large RNA polymerase (L) decorate the viral nucleocapsids. After viral attachment, endocytosis, and fusion mediated by the viral glycoproteins, HMPV nucleocapsids are released into the cell cytoplasm. To visualize the subsequent steps of genome transcription and replication, a fluorescence in situ hybridization (FISH) protocol was established to detect different viral RNA subpopulations in infected cells. The FISH probes were specific for detection of HMPV positive-sense RNA (+RNA) and viral genomic RNA (vRNA). Time course analysis of human bronchial epithelial BEAS-2B cells infected with HMPV revealed the formation of inclusion bodies (IBs) from early times postinfection. HMPV IBs were shown to be cytoplasmic sites of active transcription and replication, with the translation of viral proteins being closely associated. Inclusion body formation was consistent with an actin-dependent coalescence of multiple early replicative sites. Time course quantitative reverse transcription-PCR analysis suggested that the coalescence of inclusion bodies is a strategy to efficiently replicate and transcribe the viral genome. These results provide a better understanding of the steps following HMPV entry and have important clinical implications. IMPORTANCE Human metapneumovirus (HMPV) is a recently discovered pathogen that affects human populations of all ages worldwide. Reinfections are common throughout life, but no vaccines or antiviral treatments are currently available. In this work, a spatiotemporal analysis of HMPV replication and transcription in bronchial epithelial cell-derived immortal cells was performed. HMPV was shown to induce the formation of large cytoplasmic granules, named inclusion bodies, for genome replication and transcription. Unlike other cytoplasmic structures, such as stress granules and processing bodies, inclusion bodies are exclusively present in infected cells and contain HMPV RNA and proteins to more efficiently transcribe and replicate the viral genome. Though inclusion body formation is nuanced, it corresponds to a more generalized strategy used by different viruses, including filoviruses and rhabdoviruses, for genome transcription and replication. Thus, an understanding of inclusion body formation is crucial for the discovery of innovative therapeutic targets.

scholarly journals The Bacillus phage SPβ and its relatives: A temperate phage model system reveals new strains, species, prophage integration loci, conserved proteins and lysogeny management components

2021 ◽  
Author(s):  
Katharina Kohm ◽  
Valentina A. Floccari ◽  
Veronika T. Lutz ◽  
Birthe Nordmann ◽  
Carolin Mittelstaedt ◽  
...  
Keyword(s):  
Phage Genome ◽  
Genome Replication ◽  
Genome Packaging ◽  
Virion Release ◽  
Replication Strategy ◽  
Conserved Genes ◽  
Core Proteome ◽  
Bacillus Phage ◽  
Plaque Phenotype ◽  
Type Strains

The Bacillus phage SPβ has been known for about 50 years, but only a few strains are avalible. We isolated four new wild type strains of the SPbeta species. Phage vB_BsuS-Goe14 introduces its prophage into the spoVK locus, previously not observed to be used by SPβ-like phages. We could also reveal the SPβ-like phage genome replication strategy, the genome packaging mode, and the phage genome opening point. We extracted 55 SPβ-like prophages from public Bacillus genomes, thereby discovering three more integration loci and one additional type of integrase. The identified prophages resembled four new species clusters and three species orphans in the genus Spbetavirus. The determined core proteome of all SPβ-like prophages consists of 38 proteins. The integration cassette proved to be not conserved even though present in all strains. It consists of distinct integrases. Analysis of SPβ transcriptomes revealed three conserved genes, yopQ, yopR, and yokI, to be transcribed from a dormant prophage. While yopQ and yokI could be deleted from the prophage without activating the prophage, damaging of yopR led to a clear-plaque phenotype. Under the applied laboratory conditions, the yokI mutant showed an elevated virion release implying the YokI protein being a component of the arbitrium system.

scholarly journals Infection dynamics of porcine circovirus type 3 in longitudinally sampled pigs from four Spanish farms

2019 ◽  
Vol 184 (20) ◽  
pp. 619-619 ◽  
Author(s):  
Francini Klaumann ◽  
Florencia Correa-Fiz ◽  
Marina Sibila ◽  
José Ignacio Núñez ◽  
Joaquim Segalés
Keyword(s):  
Porcine Circovirus Type ◽  
Pairwise Distance ◽  
Porcine Circovirus ◽  
High Similarity ◽  
Distance Analysis ◽  
Infection Dynamics ◽  
Type 3 ◽  
Partial Genome ◽  
Sampling Times

Porcine circovirus type 3 (PCV-3) is a recently discovered virus in domestic pigs and wild boar. The virus has been described in pigs with different clinical/pathological presentations and healthy animals, but the dynamics of infection is currently unknown. The aim of this study was to longitudinally monitor PCV-3 infection in 152 pigs from four different healthy farms (A, B, C and D) by means of PCR in serum. The selected animals were sampled five (farm A) or six (farms B–D) times from weaning until the end of the fattening period. PCV-3 genome was found in pigs from all tested ages and farms; few animals had an apparent long-term infection (4–23 weeks). PCV-3 frequency of detection remained fairly uniform along tested ages within farms A and C, but was more variable among sampling times in farms B and D. Eight partial genome sequences were obtained from six different animals. Phylogenetic tree and pairwise distance analysis showed high similarity among sequences and with available genomes from different countries. This is the first study on PCV-3 infection dynamics in longitudinally sampled pigs. Most pigs got infection during their life, although PCV-3 did not appear to be linked with any specific age.

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