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Infectious measles virus from cloned cDNA.

ABSTRACT: The study of measles virus (MV) and of negative strand RNA viruses in general has been hampered by the lack of an experimental system for genetic manipulation. Here we describe a procedure for generating infectious MV from cloned MV cDNA. First we assembled a genetically marked DNA copy of the MV genome in plasmids, under the control of phage T3 or T7 promoters, allowing production of transcripts almost identical to the MV genome or antigenome. Incubation of these linearized plasmid DNAs with the appropriate phage polymerase and only two ribonucleoside triphosphates yielded committed transcription complexes. Microinjection of these complexes into the cytoplasm of helper cells which provide the proteins necessary for MV genome encapsidation and transcription/replication, reproducibly give rise to lytic MVs. The transcripts of one of these viruses were analysed by sequencing after reverse transcription followed by DNA amplification, and found to contain the genetic tags. The described procedure permits the analysis of a negative strand RNA virus with the same genetic tools previously applicable only to positive strand RNA viruses and retroviruses.

SUBMITTER: Ballart I

PROVIDER: S-EPMC551677 | biostudies-other | 1990 Feb

REPOSITORIES: biostudies-other

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Infectious measles virus from cloned cDNA.

Ballart I I Eschle D D Cattaneo R R Schmid A A Metzler M M Chan J J Pifko-Hirst S S Udem S A SA Billeter M A MA

The EMBO journal 19900201 2

The study of measles virus (MV) and of negative strand RNA viruses in general has been hampered by the lack of an experimental system for genetic manipulation. Here we describe a procedure for generating infectious MV from cloned MV cDNA. First we assembled a genetically marked DNA copy of the MV genome in plasmids, under the control of phage T3 or T7 promoters, allowing production of transcripts almost identical to the MV genome or antigenome. Incubation of these linearized plasmid DNAs with th ...[more]

PMID: 2303032

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Project description:We developed a reverse genetics system for infectious pancreatic necrosis virus (IPNV), a prototype virus of the Birnaviridae family, with the use of plus-stranded RNA transcripts derived from cloned cDNA. Full-length cDNA clones of the IPNV genome that contained the entire coding and noncoding regions of RNA segments A and B were constructed. Segment A encodes a 106-kDa precursor protein which is cleaved to yield mature VP2, nonstructural protease, and VP3 proteins, whereas segment B encodes the RNA-dependent RNA polymerase VP1. Plus-sense RNA transcripts of both segments were prepared by in vitro transcription of linearized plasmids with T7 RNA polymerase. Transfection of chinook salmon embryo (CHSE) cells with combined transcripts of segments A and B generated infectious IPNV particles 10 days posttransfection. Furthermore, a transfectant virus containing a genetically tagged sequence was generated to confirm the feasibility of this system. The presence and specificity of the recovered virus were ascertained by immunofluorescence staining of infected CHSE cells with rabbit anti-IPNV serum and by nucleotide sequence analysis. In addition, 3'-terminal sequence analysis of RNA from the recovered virus showed that extraneous nucleotides synthesized at the 3' end during in vitro transcription were precisely trimmed or excluded during replication, and hence these were not incorporated into the genome. An attempt was made to determine if RNA-dependent RNA polymerase of IPNV and infectious bursal disease virus (IBDV), another birnavirus, can support virus rescue in heterologous combinations. Thus, CHSE cells were transfected with transcripts derived from IPNV segment A and IBDV segment B and Vero cells were transfected with transcripts derived from IBDV segment A and IPNV segment B. In either case, no infectious IPNV or IBDV particles were generated even after a third passage in cell culture, suggesting that viral RNA-dependent RNA polymerase is species specific. However, the reverse genetics system for IPNV that we developed will greatly facilitate studies of viral replication and pathogenesis and the design of a new generation of live attenuated vaccines.

Project description:Many recent outbreaks of infectious bursal disease in commercial chicken flocks worldwide are due to the spread of very virulent strains of infectious bursal disease virus (vvIBDV). The molecular determinants for the enhanced virulence of vvIBDV compared to classical IBDV are unknown. The lack of a reverse genetics system to rescue vvIBDV from its cloned cDNA hampers the identification and study of these determinants. In this report we describe, for the first time, the rescue of vvIBDV from its cloned cDNA. Two plasmids containing a T7 promoter and either the full-length A- or B-segment cDNA of vvIBDV (D6948) were cotransfected into QM5 cells expressing T7 polymerase. The presence of vvIBDV could be detected after passage of the transfection supernatant in either primary bursa cells (in vitro) or embryonated eggs (in vivo), but not QM5 cells. Rescued vvIBDV (rD6948) appeared to have the same virulence as the parental isolate, D6948. Segment-reassorted IBDV, in which one of the two genomic segments originated from cDNA of classical attenuated IBDV CEF94 and the other from D6948, could also be rescued by using this system. Segment-reassorted virus containing the A segment of the classical attenuated isolate (CEF94) and the B segment of the very virulent isolate (D6948) is not released until 15 h after an in vitro infection. This indicates a slightly retarded replication, as the first release of CEF94 is already found at 10 h after infection. Next to segment reassortants, we generated and analyzed mosaic IBDVs (mIBDVs). In these mIBDVs we replaced the region of CEF94 encoding one of the viral proteins (pVP2, VP3, or VP4) by the corresponding region of D6948. Analysis of these mIBDV isolates showed that tropism for non-B-lymphoid cells was exclusively determined by the viral capsid protein VP2. However, the very virulent phenotype was not solely determined by this protein, since mosaic virus containing VP2 of vvIBDV induced neither morbidity nor mortality in young chickens.

Project description:Measles virus (MeV) is the most contagious human virus. Unlike most respiratory viruses, MeV does not directly infect epithelial cells upon entry in a new host. MeV traverses the epithelium within immune cells that carry it to lymphatic organs where amplification occurs. Infected immune cells then synchronously deliver large amounts of virus to the airways. However, our understanding of MeV replication in airway epithelia is limited. To model it, we use well-differentiated primary cultures of human airway epithelial cells (HAE) from lung donors. In HAE, MeV spreads directly cell-to-cell forming infectious centers that grow for ~3-5 days, are stable for a few days, and then disappear. Transepithelial electrical resistance remains intact during the entire course of HAE infection, thus we hypothesized that MeV infectious centers may dislodge while epithelial function is preserved. After documenting by confocal microscopy that infectious centers progressively detach from HAE, we recovered apical washes and separated cell-associated from cell-free virus by centrifugation. Virus titers were about 10 times higher in the cell-associated fraction than in the supernatant. In dislodged infectious centers, ciliary beating persisted, and apoptotic markers were not readily detected, suggesting that they retain functional metabolism. Cell-associated MeV infected primary human monocyte-derived macrophages, which models the first stage of infection in a new host. Single-cell RNA sequencing identified wound healing, cell growth, and cell differentiation as biological processes relevant for infectious center dislodging. 5-ethynyl-2'-deoxyuridine (EdU) staining located proliferating cells underneath infectious centers. Thus, cells located below infectious centers divide and differentiate to repair the dislodged infected epithelial patch. As an extension of these studies, we postulate that expulsion of infectious centers through coughing and sneezing could contribute to MeV's strikingly high reproductive number by allowing the virus to survive longer in the environment and by delivering a high infectious dose to the next host.

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Infectious measles virus from cloned cDNA.

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Infectious measles virus from cloned cDNA.

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