scholarly journals Systematic Excision of Vector Sequences from the BAC-Cloned Herpesvirus Genome during Virus Reconstitution

1999 ◽  
Vol 73 (8) ◽  
pp. 7056-7060 ◽  
Author(s):  
Markus Wagner ◽  
Stipan Jonjić ◽  
Ulrich H. Koszinowski ◽  
Martin Messerle

ABSTRACT Recently the mouse cytomegalovirus (MCMV) genome was cloned as an infectious bacterial artificial chromosome (BAC) (M. Messerle, I. Crnković, W. Hammerschmidt, H. Ziegler, and U. H. Koszinowski, Proc. Natl. Acad. Sci. USA 94:14759–14763, 1997). The virus obtained from this construct is attenuated in vivo due to deletion of viral sequences and insertion of the BAC vector. We reconstituted the full-length MCMV genome and flanked the BAC vector with identical viral sequences. This new construct represents a versatile basis for construction of MCMV mutants since virus generated from the construct loses the bacterial sequences and acquires wild-type properties.

2001 ◽  
Vol 75 (12) ◽  
pp. 5692-5696 ◽  
Author(s):  
Heiko Adler ◽  
Martin Messerle ◽  
Ulrich H. Koszinowski

ABSTRACT We studied the in vivo biological properties of viruses reconstituted from the genome of murine gammaherpesvirus 68 (MHV-68) cloned as an infectious bacterial artificial chromosome (BAC). Recombinant virus RγHV68A98.01, containing BAC vector sequences, is attenuated in vivo as determined by (i) viral titers in the lungs during the acute phase of infection, (ii) the extent of splenomegaly, and (iii) the number of latently infected spleen cells reactivating virus in an ex vivo reactivation assay. Since the BAC vector sequences were flanked by loxP sites, passaging the virus in fibroblasts expressing Cre recombinase resulted in the generation of recombinant virus RγHV68A98.02, with biological properties comparable to those of wild-type MHV-68. On the basis of these data we conclude (i) that excision of BAC vector sequences from cloned MHV-68 genomes is critical for reconstitution of the wild-type phenotypic properties of this virus and (ii) that the BAC-cloned MHV-68 genome is suitable for the construction of mutants and mutant libraries whose phenotypes can be reliably assessed in vivo.


2008 ◽  
Vol 82 (10) ◽  
pp. 4955-4964 ◽  
Author(s):  
B. Costes ◽  
G. Fournier ◽  
B. Michel ◽  
C. Delforge ◽  
V. Stalin Raj ◽  
...  

ABSTRACT Koi herpesvirus (KHV) is the causative agent of a lethal disease in koi and common carp. In the present study, we describe the cloning of the KHV genome as a stable and infectious bacterial artificial chromosome (BAC) clone that can be used to produce KHV recombinant strains. This goal was achieved by the insertion of a loxP-flanked BAC cassette into the thymidine kinase (TK) locus. This insertion led to a BAC plasmid that was stably maintained in bacteria and was able to regenerate virions when permissive cells were transfected with the plasmid. Reconstituted virions free of the BAC cassette but carrying a disrupted TK locus (the FL BAC-excised strain) were produced by the transfection of Cre recombinase-expressing cells with the BAC. Similarly, virions with a wild-type revertant TK sequence (the FL BAC revertant strain) were produced by the cotransfection of cells with the BAC and a DNA fragment encoding the wild-type TK sequence. Reconstituted recombinant viruses were compared to the wild-type parental virus in vitro and in vivo. The FL BAC revertant strain and the FL BAC-excised strain replicated comparably to the parental FL strain. The FL BAC revertant strain induced KHV infection in koi carp that was indistinguishable from that induced by the parental strain, while the FL BAC-excised strain exhibited a partially attenuated phenotype. Finally, the usefulness of the KHV BAC for recombination studies was demonstrated by the production of an ORF16-deleted strain by using prokaryotic recombination technology. The availability of the KHV BAC is an important advance that will allow the study of viral genes involved in KHV pathogenesis, as well as the production of attenuated recombinant candidate vaccines.


2007 ◽  
Vol 81 (17) ◽  
pp. 9024-9033 ◽  
Author(s):  
Zhen Zhang ◽  
Jenny Rowe ◽  
Weijia Wang ◽  
Marvin Sommer ◽  
Ann Arvin ◽  
...  

ABSTRACT To efficiently generate varicella-zoster virus (VZV) mutants, we inserted a bacterial artificial chromosome (BAC) vector in the pOka genome. We showed that the recombinant VZV (VZVBAC) strain was produced efficiently from the BAC DNA and behaved indistinguishably from wild-type virus. Moreover, VZV's cell-associated nature makes characterizing VZV mutant growth kinetics difficult, especially when attempts are made to monitor viral replication in vivo. To overcome this problem, we then created a VZV strain carrying the luciferase gene (VZVLuc). This virus grew like the wild-type virus, and the resulting luciferase activity could be quantified both in vitro and in vivo. Using PCR-based mutagenesis, open reading frames (ORF) 0 to 4 were individually deleted from VZVLuc genomes. The deletion mutant viruses appeared after transfection into MeWo cells, except for ORF4, which was essential. Growth curve analysis using MeWo cells and SCID-hu mice indicated that ORF1, ORF2, and ORF3 were dispensable for VZV replication both in vitro and in vivo. Interestingly, the ORF0 deletion virus showed severely retarded growth both in vitro and in vivo. The growth defects of the ORF0 and ORF4 mutants could be fully rescued by introducing wild-type copies of these genes back into their native genome loci. This work has validated and justified the use of the novel luciferase VZV BAC system to efficiently generate recombinant VZV variants and ease subsequent viral growth kinetic analysis both in vitro and in vivo.


2003 ◽  
Vol 77 (9) ◽  
pp. 5073-5083 ◽  
Author(s):  
W. L. William Chang ◽  
Peter A. Barry

ABSTRACT Rigorous investigation of many functions encoded by cytomegaloviruses (CMVs) requires analysis in the context of virus-host interactions. To facilitate the construction of rhesus CMV (RhCMV) mutants for in vivo studies, a bacterial artificial chromosome (BAC) containing an enhanced green fluorescent protein (EGFP) cassette was engineered into the intergenic region between unique short 1 (US1) and US2 of the full-length viral genome by Cre/lox-mediated recombination. Infectious virions were recovered from rhesus fibroblasts transfected with pRhCMV/BAC-EGFP. However, peak virus yields of cells infected with reconstituted progeny were 10-fold lower than wild-type RhCMV, suggesting that inclusion of the 9-kb BAC sequence impeded viral replication. Accordingly, pRhCMV/BAC-EGFP was further modified to enable efficient excision of the BAC vector from the viral genome after transfection into mammalian cells. Allelic exchange was performed in bacteria to substitute the cre recombinase gene for egfp. Transfection of rhesus fibroblasts with pRhCMV/BAC-Cre resulted in a pure progeny population lacking the vector backbone without the need of further manipulation. The genomic structure of the BAC-reconstituted virus, RhCMV-loxP(r), was identical to that of wild-type RhCMV except for the residual loxP site. The presence of the loxP sequence did not alter the expression profiles of neighboring open reading frames. In addition, RhCMV-loxP(r) replicated with wild-type kinetics both in tissue culture and seronegative immunocompetent macaques. Restriction analysis of the viral genome present within individual BAC clones and virions revealed that (i) RhCMV exhibits a simple genome structure and that (ii) there is a variable number of a 750-bp iterative sequence present at the S terminus.


2007 ◽  
Vol 81 (6) ◽  
pp. 2957-2969 ◽  
Author(s):  
Ryan D. Estep ◽  
Michael F. Powers ◽  
Bonnie K. Yen ◽  
He Li ◽  
Scott W. Wong

ABSTRACT Rhesus rhadinovirus (RRV) is closely related to Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) and causes KSHV-like diseases in immunocompromised rhesus macaques (RM) that resemble KSHV-associated diseases including multicentric Castleman's disease and non-Hodgkin's lymphoma. RRV retains a majority of open reading frames (ORFs) postulated to be involved in the pathogenesis of KSHV and is the closest available animal model to KSHV infection in humans. Here we describe the generation of a recombinant clone of RRV strain 17577 (RRV17577) utilizing bacterial artificial chromosome (BAC) technology. Characterization of the RRV BAC demonstrated that it is a pathogenic molecular clone of RRV17577, producing virus that behaves like wild-type RRV both in vitro and in vivo. Specifically, BAC-derived RRV displays wild-type growth properties in vitro and readily infects simian immunodeficiency virus-infected RM, inducing B cell hyperplasia, persistent lymphadenopathy, and persistent infection in these animals. This RRV BAC will allow for rapid genetic manipulation of the RRV genome, facilitating the creation of recombinant versions of RRV that harbor specific alterations and/or deletions of viral ORFs. This system will provide insights into the roles of specific RRV genes in various aspects of the viral life cycle and the RRV-associated pathogenesis in vivo in an RM model of infection. Furthermore, the generation of chimeric versions of RRV containing KSHV genes will allow analysis of the function and contributions of KSHV genes to viral pathogenesis by using a relevant primate model system.


Blood ◽  
2003 ◽  
Vol 102 (8) ◽  
pp. 2856-2861 ◽  
Author(s):  
Hongmin Sun ◽  
Tony L. Yang ◽  
Angela Yang ◽  
Xixi Wang ◽  
David Ginsburg

Abstract Coagulation factor V (FV) is a central regulator of the coagulation cascade. Circulating FV is found in plasma and within platelet α granules. The specific functions of these distinct FV pools are uncertain. We now report the generation of transgenic mice with FV gene expression restricted to either the liver or megakaryocyte/platelet lineage using bacterial artificial chromosome (BAC) constructs. Six of 6 independent albumin BAC transgenes rescue the neonatal lethal hemorrhage of FV deficiency. Rescued mice all exhibit liver-specific Fv expression at levels ranging from 6% to 46% of the endogenous Fv gene, with no detectable FV activity within the platelet pool. One of the 3 Pf4 BAC transgenes available for analysis also rescues the lethal FV null phenotype, with FV activity restricted to only the platelet pool (approximately 3% of the wild-type FV level). FV-null mice rescued by either the albumin or Pf4 BAC exhibit nearly normal tail bleeding times. These results demonstrate that Fv expression in either the platelet or plasma FV pool is sufficient for basal hemostasis. In addition, these findings indicate that the murine platelet and plasma FV pools are biosynthetically distinct, in contrast to a previous report demonstrating a plasma origin for platelet FV in humans.


2006 ◽  
Vol 8 (4) ◽  
pp. 1054-1063 ◽  
Author(s):  
Jun Arii ◽  
Orkash Hushur ◽  
Kentaro Kato ◽  
Yasushi Kawaguchi ◽  
Yukinobu Tohya ◽  
...  

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