China
Africa
Explore chapters and articles related to this topic
Changes Associated with CNS Infections Caused by the Herpesvirus Varicella Zoster Virus (VZV) and Models of VZV Neurotropism
Published in Sunit K. Singh, Daniel Růžek, Neuroviral Infections, 2013
The VZV genome sequence (derived by Davison and Scott 1986) shows coding potential for some 68-70 viral proteins or open reading frames (ORFs), which are assumed to be made in a virus-producing infection. Of the 68 ORFs, three (ORFs 62, 63, and 64) lie in the repeated sequences bounding the short region and are therefore duplicated (Davison and Scott 1986). Virus gene expression is highly regulated (Reichelt et al. 2009), divided into three temporal classes. The first proteins made function in transcription and adaptation of the host environment to virus replication. This includes a protein termed 1E62 (from ORF62 and 71) that recruits the cellular transcriptional machinery to the viral genome. The second wave of proteins made include those involved in nucleotide metabolism and viral DNA replication. Finally, virus assembly and structural proteins are made, followed by death of the host cell. Several viral proteins coordinate innate and adaptive immune evasion strategies that determine host pathogenesis (see, for review, Abendroth et al. 2010). ORFs are functionally annotated on the basis of the analyses of VZV mutants or from extrapolations from orthologous characterized proteins in HSV-1, because most VZV protein sequences have conserved domains to their better-studied HSV-1 counterparts and are collinearly arranged in the same order and directional orientation on the genomes (Cohen 2010 b). Indeed, it is recognized that 41 of the ORFs are conserved in all mammalian herpesviruses, and the arrangement of these genes is used, in part, to dictate the virus subfamily a particular herpesvirus belongs to. These 41 ORFs encode basic functions required for herpesvirus growth, such as capsid proteins, DNA replication machinery, and RNA regulation. To date, approximately half the VZV ORFs have been mutated and analyzed in the context of recombinant viruses (Cohen 2010 b). VZV mutants are generated either by using a series of overlapping cosmids (Cohen and Seidel 1993; Niizuma et al. 2003; Zerboni et al. 2005) or by “recombineering” of VZV genomes maintained as bacterial artificial chromosomes maintained in Escherichia coli (Nagaike et al. 2004; Tischer et al. 2007). Alignment of VZV and HSV reveals that VZV has six genes with no equivalent in HSV-1, named ORFs S/L, 1, 2, 13 (a thymidylate synthase), 32, and 57. All appear to be not required for growth in culture. On the other hand, nine HSV genes have no equivalent protein in VZV, and it is particularly interesting that VZV lacks an equivalent to the HSV-1 glycoprotein gD, which is the essential receptor binding protein dictating HSV infection. VZV gE glycoprotein has apparently evolved to be one of the major VZV receptor binding proteins (Li et al. 2010, 2007): while HSV-1 gE is not essential for replication of HSV, VZV gE is essential for infectivity. VZV also lacks the HSV-1 neurovirulence factor ICP34.5 and the HSV-1 ICP47 modulator of major histocompatibility complex I restricted antigen presentation, and it is of interest how VZV compensates for the lack of these proteins and activities.
How to discover new antibiotic resistance genes?
Published in Expert Review of Molecular Diagnostics, 2019
Linda Hadjadj, Sophie Alexandra Baron, Seydina M. Diene, Jean-Marc Rolain
To perform mutagenesis directly into the chromosome of bacteria, recombineering (recombination-mediated genetic engineering) strategies have been developed. Recombineering is an in vivo method based on genetic engineering through homologous recombination that allows the manipulations of bacterial genomes [39–41]. This method is effective but requires multiple steps to create a chromosomal ‘hybrid’. A method named REPLACR-mutagenesis, involving fewer steps, has been recently described [42]. Recently, the CRISPR-Cas12a-assisted recombineering method has been developed to generate point mutations, deletions and insertions in an E. coli genome [43]. This technique is faster and more efficient but is also more expensive. The mutagenesis process is successful but can be only used on genes already known to be involved in AR.
Blocking CTLA-4 while priming with a whole cell vaccine reshapes the oligoclonal T cell infiltrate and eradicates tumors in an orthotopic glioma model
Published in OncoImmunology, 2018
Cameron S. Field, Martin K. Hunn, Peter M. Ferguson, Christiane Ruedl, Lindsay R. Ancelet, Ian F. Hermans
Inbred C57BL/6 mice and the CD45.1 congenic strain B6.SJL-PtprcaPep3b/BoyJArc were purchased from Jackson Laboratories, Bar Harbor, Maine. Also used were: CD1d-deficient mice;24 an F1 cross of OT-II mice that express a TCR specific for the I-Ab-restricted epitope of chicken ovalbumin,25 with the CD45.1 congenic strain; I-Aα-deficient (MHC-II deficient) mice;26 TAP1-deficient mice;27 IFNγ-deficient mice;28 and CD11b-DTR transgenic mice. The latter line was generated via BALB/c ES cells transfected with recombineered bacterial artificial chromosome (BAC) clones (CD11b: RP23-373D19, BACPAC Resources Children's Hospital Oakland, USA) carrying insertions of human DTR sequence with its polyadenylation site in the initiation codons replacing the first coding exons of the CD11b gene. Recombineering was performed using RED/ET recombination kits following the instructions of the manufacturer (Gene Bridges GmbH, Heidelberg, Germany). Sce1 linearized BACs were electroporated in ES cells and those ES cell clones containing intact BAC sequences (i.e. both vector ends and middle modification verified by PCR) were selected for further transgenesis. Experiments were conducted in F1 crosses between CD11b-DTR and C57BL/6 mice. All animals were maintained by the Biomedical Research Unit at the Malaghan Institute of Medical Research. The Victoria University Animal Ethics Committee approved all experimental protocols (reference 2012R15M). Mice were 6–12 weeks of age and matched for age and gender.
Bacteriophages as tools for biofilm biocontrol in different fields
Published in Biofouling, 2021
Camila Mendes Figueiredo, Marilia Silva Malvezzi Karwowski, Romeu Cassiano Pucci da Silva Ramos, Nicoly Subtil de Oliveira, Lorena Caroline Peña, Everdan Carneiro, Renata Ernlund Freitas de Macedo, Edvaldo Antonio Ribeiro Rosa
In strictly lytic phages, allelic exchange is seriously limited by low natural recombination frequencies, which is more common in temperate phages. Within the bacterial cell, proteins derived from recombination (e.g. lambda Red and Rac RecE/RecT) avoid the degradation of phage templates and enable annealing with the phage genetic material. This is called ‘in vivo recombineering’ and increases the recombination frequency and efficacy (Marinelli et al. 2012).