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Serial passage
About: Serial passage is a research topic. Over the lifetime, 1270 publications have been published within this topic receiving 46928 citations.
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TL;DR: A full-length HCV genome that replicates and produces virus particles that are infectious in cell culture (HCVcc) is described, suggesting that this in vitro system will aid in the search for improved antiviral compounds.
Abstract: Many aspects of the hepatitis C virus (HCV) life cycle have not been reproduced in cell culture, which has slowed research progress on this important human pathogen. Here, we describe a full-length HCV genome that replicates and produces virus particles that are infectious in cell culture (HCVcc). Replication of HCVcc was robust, producing nearly 10(5) infectious units per milliliter within 48 hours. Virus particles were filterable and neutralized with a monoclonal antibody against the viral glycoprotein E2. Viral entry was dependent on cellular expression of a putative HCV receptor, CD81. HCVcc replication was inhibited by interferon-alpha and by several HCV-specific antiviral compounds, suggesting that this in vitro system will aid in the search for improved antivirals.
2,305 citations
TL;DR: A helper-dependent packaging system for production of vectors that have large regions of the genome deleted, which should have great utility for the generation of adenovirus-based vectors with increased cloning capacity, increased safety and reduced immunogenicity.
Abstract: Adenoviruses are attractive vectors for the delivery of foreign genes into mammalian cells for gene therapy. However, current vectors retain many viral genes that, when expressed at low levels, contribute to the induction of a host immune response against transduced cells. We have developed a helper-dependent packaging system for production of vectors that have large regions of the genome deleted. Helper viruses were constructed with packaging signals flanked by loxP sites so that in 293 cells that stably express the Cre recombinase (293Cre), the packaging signal was efficiently excised, rendering the helper virus genome unpackageable. However, the helper virus DNA was replicated at normal levels and could thus express all of the functions necessary in trans for replication and packaging of a vector genome containing the appropriate cis-acting elements. Serial passage of the vector in helper virus-infected 293Cre cells resulted in an approximately 10-fold increase in vector titer per passage. The vector could be partially separated from residual helper virus by cesium chloride buoyant density centrifugation. Large scale preparations of vector yielded semi-purified stocks of approximately 10(10) transducing virions/ml, with < 0.01% contamination by the E1-deleted helper virus. This system should have great utility for the generation of adenovirus-based vectors with increased cloning capacity, increased safety and reduced immunogenicity.
779 citations
TL;DR: It is shown that ferrets and domestic cats are susceptible to infection by SARS coronavirus (SCV) and that they can efficiently transmit the virus to previously uninfected animals that are housed with them.
Abstract: There is now a choice of animal models for testing therapies against the human virus. The reservoir of the coronavirus isolated from patients with severe acute respiratory syndrome (SARS)1,2 is still unknown, but is suspected to have been a wild animal species. Here we show that ferrets (Mustela furo) and domestic cats (Felis domesticus) are susceptible to infection by SARS coronavirus (SCV) and that they can efficiently transmit the virus to previously uninfected animals that are housed with them. The observation that these two distantly related carnivores can so easily be infected with the virus indicates that the reservoir for this pathogen may involve a range of animal species.
528 citations
TL;DR: These findings suggest that there is a relatively tight constraint on the amount of DNA which can be packaged into virions and that exceeding the limit results in a sharply decreased rate of virus growth.
Abstract: Adenovirus vectors are extensively used for high-level expression of proteins in mammalian cells and are receiving increasing attention for their potential use as live recombinant vaccines and as transducing viruses for use in gene therapy. Although it is commonly argued that one of the chief advantages of adenovirus vectors is their relative stability, this has not been thoroughly investigated. To examine the genetic stability of adenovirus type 5 vectors and in particular to examine the relationship between genetic stability and genome size, adenovirus vectors were constructed with inserts of 4.88 (herpes simplex virus type 1 gB), 4.10 (herpes simplex virus type 1 gB), or 3.82 (LacZ) kb combined with a 1.88-kb E3 deletion or with a newly generated 2.69-kb E3 deletion. The net excess of DNA over the wild-type (wt) genome size ranged from 1.13 to 3.00 kb or 3.1 to 8.3%. Analysis of these vectors during serial passage in tissue culture revealed that when the size exceeded 105% of the wt genome length by approximately 1.2 kb (4.88-kb insert combined with a 1.88-kb deletion), the resulting vector grew very poorly and underwent rapid rearrangement, resulting in loss of the insert after only a few passages. In contrast, vectors with inserts resulting in viral DNA close to or less than a net genome size of 105% of that of the wt grew well and were relatively stable. In general, viruses with genomes only slightly above 105% of that of the wt were unstable and the rapidity with which rearrangement occurred correlated with the size of the insert. These findings suggest that there is a relatively tight constraint on the amount of DNA which can be packaged into virions and that exceeding the limit results in a sharply decreased rate of virus growth. The resultant strong selection for variants which have undergone rearrangement, generating smaller genomes, is manifested as genetic instability of the virus population.
519 citations
TL;DR: It is demonstrated that two products of this locus, pUL130 and pUL128, form a complex with gH and gL, but not gO, and an epithelial and endothelial cell tropic AD169 variant in which the UL131 ORF has been repaired, termed BADrUL131, produces virions that carry both gH-gL-gO and gH/gL/gO complexes.
Abstract: Human cytomegalovirus replicates in many different cell types, including epithelial cells, endothelial cells, and fibroblasts. However, laboratory strains of the virus, many of which were developed as attenuated vaccine candidates by serial passage in fibroblasts, have lost the ability to infect epithelial and endothelial cells. Their growth is restricted primarily to fibroblasts, due to mutations in the UL131-UL128 locus. We now demonstrate that two products of this locus, pUL130 and pUL128, form a complex with gH and gL, but not gO. The AD169 laboratory strain, which lacks a functional UL131 protein, produces virions containing only the gH-gL-gO complex. An epithelial and endothelial cell tropic AD169 variant in which the UL131 ORF has been repaired, termed BADrUL131, produces virions that carry both gH-gL-gO and gH-gL-pUL128-pUL130 complexes. Antibodies against pUL130 and pUL128 block infection of epithelial and endothelial cells by BADrUL131 and the fusion-inducing factor X clinical human cytomegalovirus isolate but do not affect the efficiency with which fibroblasts are infected.
485 citations