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PubMed2002

Regulation of apoptosis in African swine fever virus-infected macrophages.

A number of viruses have evolved antiapoptotic mechanisms to promote infected-cell survival, either to ensure efficient productive viral replication or to promote long-term survival of virus-infected cells. Recent studies identified critical African swine fever virus genes involved in the complex regulation of ASFV-host interactions. Here we review the present knowledge of the recently identified ASFV genes with special attention to those which affect viral virulence, host range, and pathogenesis by regulating viral-induced apoptotic mechanisms.

African Swine Fever↗
PubMed2001

Evolution of cell recognition by viruses.

Evolution of receptor specificity by viruses has several implications for viral pathogenesis, host range, virus-mediated gene targeting, and viral adaptation after organ transplantation and xenotransplantation, as well as for the emergence of viral diseases. Recent evidence suggests that minimal changes in viral genomes may trigger a shift in receptor usage for virus entry, even into the same cell type. A capacity to exploit alternative entry pathways may reflect the ancient evolutionary origins of viruses and a possible role as agents of horizontal gene transfers among cells.

Animals↗
PubMed2000

Pseudotyping of glycoprotein D-deficient herpes simplex virus type 1 with vesicular stomatitis virus glycoprotein G enables mutant virus attachment and entry.

The use of herpes simplex virus (HSV) vectors for in vivo gene therapy will require the targeting of vector infection to specific cell types in certain in vivo applications. Because HSV glycoprotein D (gD) imparts a broad host range for viral infection through recognition of ubiquitous host cell receptors, vector targeting will require the manipulation of gD to provide new cell recognition specificities in a manner designed to preserve gD's essential role in virus entry. In this study, we have determined whether an entry-incompetent HSV mutant with deletions of all Us glycoproteins, including gD, can be complemented by a foreign attachment/entry protein with a different receptor-binding specificity, the vesicular stomatitis virus glycoprotein G (VSV-G). The results showed that transiently expressed VSV-G was incorporated into gD-deficient HSV envelopes and that the resulting pseudotyped virus formed plaques on gD-expressing VD60 cells, albeit at a 50-fold-reduced level compared to that of wild-type gD. This reduction may be related to differences in the entry pathways used by VSV and HSV or to the observed lower rate of incorporation of VSV-G into virus envelopes than that of gD. The rate of VSV-G incorporation was greatly improved by using recombinant molecules in which the transmembrane domain of HSV glycoprotein B or D was substituted for that of VSV-G, but these recombinant molecules failed to promote virus entry. These results show that foreign glycoproteins can be incorporated into the HSV envelope during replication and that gD can be dispensed with on the condition that a suitable attachment/entry function is provided.

Gene Targeting↗
PubMed2002

The genome of swinepox virus.

Swinepox virus (SWPV), the sole member of the Suipoxvirus genus of the Poxviridae, is the etiologic agent of a worldwide disease specific for swine. Here we report the genomic sequence of SWPV. The 146-kbp SWPV genome consists of a central coding region bounded by identical 3.7-kbp inverted terminal repeats and contains 150 putative genes. Comparison of SWPV with chordopoxviruses reveals 146 conserved genes encoding proteins involved in basic replicative functions, viral virulence, host range, and immune evasion. Notably, these include genes with similarity to genes for gamma interferon (IFN-gamma) receptor, IFN resistance protein, interleukin-18 binding protein, IFN-alpha/beta binding protein, extracellular enveloped virus host range protein, dUTPase, hydroxysteroid dehydrogenase, superoxide dismutase, serpin, herpesvirus major histocompatibility complex inhibitor, ectromelia virus macrophage host range protein, myxoma virus M011L, variola virus B22R, four ankyrin repeat proteins, three kelch-like proteins, five vaccinia virus (VV) A52R-like family proteins, and two G protein-coupled receptors. The most conserved genomic region is centrally located and corresponds to the VV region located between genes F9L and A38L. Within the terminal 13 kbp, colinearity is disrupted and multiple poxvirus gene homologues are absent or share a lower percentage of amino acid identity. Most of these differences involve genes and gene families with likely functions involving viral virulence and host range. Three open reading frames (SPV018, SPV019. and SPV020) are unique for SWPV. Phylogenetic analysis, genome organization, and amino acid identity indicate that SWPV is most closely related to the capripoxvirus lumpy skin disease virus, followed by the yatapoxvirus yaba-like disease virus and the leporipoxviruses. The gene complement of SWPV better defines Suipoxvirus within the Chordopoxvirinae subfamily and provides a basis for future genetic comparisons.

Animals↗
PubMed1976

Evidence for host-dependent modification and restriction of bacteriophage DNA in Mycobacterium tuberculosis.

Wild isolates of Mycobacterium tuberculosis may be divided into the three internationally recognized phage types on the basis of susceptibility to mycobacteriophages DS6A, BK1 and D34. Strains of type A are lysed at high efficiency by DS6A only; type B is lysed by BK1 grown on Mycobacterium smegmatis ATCC607 and DS6A, while type C is lysed additionally by D34 grown on atypical Mycobacterium F130. Propagation of D34 on a C-strain (D34-C) or BK1 on a B-strain (BK1-B) has no effect on viral host-range. D34-C has an efficiency of plating (e.o.p.) of 10(-5) on type B strains and 10(-7) on A strains. BK1-B plates on A strains at an e.o.p. of 10(-5). BK1 recovered from and repropagated on an A strain (BK1-A) has an e.o.p. of 1-0 on strains of all classes. D34-B has an e.o.p. of 1-0 on strains of type B and C, while D34-A plates with high efficiency on types B and C and displayed an e.o.p. of 10(-4) on type A. Repropagation of these viruses on the M. tuberculosis strains originally lysed by them results in the restoration of their previous host range. Variations in plating efficiency cannot be explained by differences in viral absorption alone. These findings suggest that the three phage types of human tubercle bacilli are related by a hierarchical pattern of DNA restriction and modification in which the C pattern is included in the B, and both patterns are included in A-modified DNA. Viruses such as DS6A which are equally virulent for strains of all classes are not susceptible to host dependent restriction.

Bacteriophage Typing↗
PubMed2001

Genome of lumpy skin disease virus.

Lumpy skin disease virus (LSDV), a member of the capripoxvirus genus of the Poxviridae, is the etiologic agent of an important disease of cattle in Africa. Here we report the genomic sequence of LSDV. The 151-kbp LSDV genome consists of a central coding region bounded by identical 2.4 kbp-inverted terminal repeats and contains 156 putative genes. Comparison of LSDV with chordopoxviruses of other genera reveals 146 conserved genes which encode proteins involved in transcription and mRNA biogenesis, nucleotide metabolism, DNA replication, protein processing, virion structure and assembly, and viral virulence and host range. In the central genomic region, LSDV genes share a high degree of colinearity and amino acid identity (average of 65%) with genes of other known mammalian poxviruses, particularly suipoxvirus, yatapoxvirus, and leporipoxviruses. In the terminal regions, colinearity is disrupted and poxvirus homologues are either absent or share a lower percentage of amino acid identity (average of 43%). Most of these differences involve genes and gene families with likely functions involving viral virulence and host range. Although LSDV resembles leporipoxviruses in gene content and organization, it also contains homologues of interleukin-10 (IL-10), IL-1 binding proteins, G protein-coupled CC chemokine receptor, and epidermal growth factor-like protein which are found in other poxvirus genera. These data show that although LSDV is closely related to other members of the Chordopoxvirinae, it contains a unique complement of genes responsible for viral host range and virulence.

Animals↗
PubMed1998

Quasispecies and the implications for virus persistence and escape.

BACKGROUND: In the 1970s Manfred Eigen and colleagues proposed a new model of molecular evolution to explain adaptability and rapid evolution of simple replicons, as those that probably populated the earth at the onset of life. This model of evolution placed emphasis on mutant generation, to the point of invalidating the concept of wild-type genomes as a defined sequence of nucleotides. In striking similarity with the proposals for such early replicons, present-day RNA viruses consist of complex distributions of nonidentical but closely related genomes termed quasispecies. OBJECTIVES: To discuss indeterminations inherent to a quasispecies structure and to the analytical procedures to define it, biological implications of quasispecies, and the need to take into account this type of population structure, in order to design effective strategies to prevent and control diseases caused by highly variable viruses. RESULTS: Quasispecies have many biological implications, extending from viral pathogenesis to the emergence of new pathogens, rapid antigenic variation, and alterations in cell tropism, virulence, host range and viral gene expression. CONCLUSIONS: Diseases caused by highly variable RNA viruses prove very difficult to control and vaccine development against such viruses are largely unsuccessful. It is important to understand quasispecies composition and dynamics, as quasispecies are an important step in the natural history of RNA viruses.

Animals↗
PubMed1995

Host-specific alterations in viral RNA accumulation and infection spread in a brome mosaic virus isolate with an expanded host range.

To facilitate studies of virus-host interaction and the determinants of viral host range, we constructed full-length cDNA clones to all three genomic RNAs of an unusual brome mosaic virus (BMV) isolate with an expanded host range. While other BMV strains, including the previously cloned M1 strain, systemically infect barley and other grasses but not legumes, the expanded-host-range isolate and the set of transcripts from its cDNA clones, designated the M2 strain of BMV, systemically infect both barley and cowpea line TVu-612, a legume. All reassorted combinations of M1 and M2 genomic RNAs were equally competent for replication in barley protoplasts and systemic infection of barley plants but showed widely varying levels of viral RNA accumulation in cowpea protoplasts and systemic infection in TVu-612 cowpea plants. Systemic infection levels were influenced by all three genomic RNAs. M2 RNA2 and M2 RNA3 made independent and additive contributions to the frequency with which reassortants infected TVu-612 systemically. The greater individual effect segregated with M2 RNA3, which encodes functions required for infection spread (the 3a movement protein and coat protein). M2 RNA3 also directed accelerated expansion of BMV lesions in inoculated TVu-612 leaves. If the inoculum contained M2 RNA3, the frequency with which reassortants infected TVu-612 systemically could be further enhanced by the presence of M2 RNA1 rather than M1 RNA1. RNA1 encodes the 1a RNA replication protein, and despite similar accumulation in barley protoplasts, in cowpea protoplasts all reassortants bearing M2 RNA1 accumulated positive- and negative-strand RNAs to levels at least six- to eightfold higher than reassortants bearing M1 RNA1. Overall, the results indicate that changes in several distinct virus functions contribute to adapting BMV-M2 to systemically infect TVu-612 cowpea.

Base Sequence↗
PubMed2006

Prevalence and evolution of core photosystem II genes in marine cyanobacterial viruses and their hosts.

Cyanophages (cyanobacterial viruses) are important agents of horizontal gene transfer among marine cyanobacteria, the numerically dominant photosynthetic organisms in the oceans. Some cyanophage genomes carry and express host-like photosynthesis genes, presumably to augment the host photosynthetic machinery during infection. To study the prevalence and evolutionary dynamics of this phenomenon, 33 cultured cyanophages of known family and host range and viral DNA from field samples were screened for the presence of two core photosystem reaction center genes, psbA and psbD. Combining this expanded dataset with published data for nine other cyanophages, we found that 88% of the phage genomes contain psbA, and 50% contain both psbA and psbD. The psbA gene was found in all myoviruses and Prochlorococcus podoviruses, but could not be amplified from Prochlorococcus siphoviruses or Synechococcus podoviruses. Nearly all of the phages that encoded both psbA and psbD had broad host ranges. We speculate that the presence or absence of psbA in a phage genome may be determined by the length of the latent period of infection. Whether it also carries psbD may reflect constraints on coupling of viral- and host-encoded PsbA-PsbD in the photosynthetic reaction center across divergent hosts. Phylogenetic clustering patterns of these genes from cultured phages suggest that whole genes have been transferred from host to phage in a discrete number of events over the course of evolution (four for psbA, and two for psbD), followed by horizontal and vertical transfer between cyanophages. Clustering patterns of psbA and psbD from Synechococcus cells were inconsistent with other molecular phylogenetic markers, suggesting genetic exchanges involving Synechococcus lineages. Signatures of intragenic recombination, detected within the cyanophage gene pool as well as between hosts and phages in both directions, support this hypothesis. The analysis of cyanophage psbA and psbD genes from field populations revealed significant sequence diversity, much of which is represented in our cultured isolates. Collectively, these findings show that photosynthesis genes are common in cyanophages and that significant genetic exchanges occur from host to phage, phage to host, and within the phage gene pool. This generates genetic diversity among the phage, which serves as a reservoir for their hosts, and in turn influences photosystem evolution.

Base Composition↗
PubMed1991

Molecular characterization of two bipartite geminiviruses causing squash leaf curl disease: role of viral replication and movement functions in determining host range.

The genomes of two distinct, but highly homologous, bipartite geminiviruses have been identified in and cloned from extracts of squash leaf curl diseased field squash. These two squash leaf curl viruses (SqLCVs) have covalently closed, circular single-stranded DNA genomes with the same bipartite component organization characteristic of other whitefly-transmitted geminiviruses. Infectivity studies using virus preparations or cloned viral genomic components on different potential host plants demonstrated that these two SqLCVs have different host range phenotypes which can be explained by specific interactions among the different viral genomic components that act to influence viral replication and systemic movement in the plant. Analysis of Agrobacterium-inoculated leaf discs demonstrated that replication of the restricted virus was rescued in trans by the nonrestricted virus, providing an explanation for the mixtures of viral DNA components often found in particular hosts in the field. Sequence analysis of the common regions of these two SqLCVs identified a 13-base deletion in the restricted virus as compared to the nonrestricted virus, suggesting a potential sequence alteration likely to be involved in their host range phenotypic differences and strengthening the conclusion based on hybridization studies of their close evolutionary relationship. Also identified in the original field squash was a defective viral component which appeared to interfere with movement of the restricted SqLCV in its normally permissive hosts and accounted for another aspect of host range variation observed for this virus.

Base Sequence↗
PubMed2003

Molecular anatomy of Tupaia (tree shrew) adenovirus genome; evolution of viral genes and viral phylogeny.

Adenoviruses are globally spread and infect species in all five taxons of vertebrates. Outstanding attention is focused on adenoviruses because of their transformation potential, their possible usability as vectors in gene therapy and their applicability in studies dealing with, e.g. cell cycle control, DNA replication, transcription, splicing, virus-host interactions, apoptosis, and viral evolution. The accumulation of genetic data provides the basis for the increase of our knowledge about adenoviruses. The Tupaia adenovirus (TAV) infects members of the genus Tupaiidae that are frequently used as laboratory animals in behavior research dealing with questions about biological and molecular processes of stress in mammals, in neurobiological and physiological studies, and as model organisms for human hepatitis B and C virus infections. In the present study the TAV genome underwent an extensive analysis including determination of codon usage, CG depletion, gene content, gene arrangement, potential splice sites, and phylogeny. The TAV genome has a length of 33,501 bp with a G+C content of 49.96%. The genome termini show a strong CG depletion that could be due to methylation of these genome regions during the viral replication cycle. The analysis of the coding capacity of the complete TAV genome resulted in the identification of 109 open reading frames (ORFs), of which 38 were predicted to be real viral genes. TAV was classified within the genus Mastadenovirus characterized by typical gene content, arrangement, and homology values of 29 conserved ORFs. Phylogenetic trees show that TAV is part of a separate evolutionary lineage and no mastadenovirus species can be considered as the most related. In contrast to other mastadenoviruses a direct ancestor of TAV captured a DUT gene from its mammalian host, presumably controlling local dUTP levels during replication and enhance viral replication in non-dividing host tissues. Furthermore, TAV possesses a second DNA-binding protein gene, that is likely to play a role in the determination of the host range. In view of these data it is conceivable that TAV underwent evolutionary adaptations to its biological environment resulting in the formation of special genomic components that provided TAV with the ability to expand its host range during viral evolution.

Adenoviridae Infections↗
PubMed2000

Linkage of an alphavirus host-range restriction to the carbohydrate-processing phenotypes of the host cell.

The Sindbis virus mutant NE2G216 retains PE2 in place of E2 in its virion structure. NE2G216 is a host-range mutant that replicates with near-normal kinetics in vertebrate cells, but displays severely restricted growth in cultured mosquito cells (C6/36) due to defects in the virus maturation process. In this study we tested the hypothesis that the host-range phenotype of NE2G216 was linked to the differences in carbohydrate-processing phenotypes between vertebrate and arthropod cells. Arthropod cell-derived glycoproteins are distinguishable from those synthesized in vertebrate cells by the absence of complex- and hybrid-type N-linked oligosaccharides. To test our hypothesis we compared the growth of the wild-type virus, TRSB, NE2G216 and three PE2-containing, C6/36 cell-adapted variants, in vertebrate cells treated with 1-deoxymannojirimycin (1-dMM). 1-dMM inhibits the Golgi alpha-mannosidase I enzyme and limits oligosaccharide processing to high-mannose forms (Man(8-9)GlcNAc(2)). The growth of TRSB was not restricted by the action of 1-dMM; however, NE2G216 was restricted in a dose-dependent manner. In contrast, the growth of each PE2-containing, C6/36 cell-adapted mutant was enhanced by low concentrations of 1-dMM (up to 1500%) and was only slightly affected by the higher concentrations. These results demonstrate that virion maturation functions of NE2G216 are sensitive to the structure of cis-linked oligosaccharides, and indicate that the carbohydrate-processing phenotypes of the host cell can influence viral host-range and function as a selective pressure in alphavirus evolution.

1-Deoxynojirimycin↗
PubMed1999

Adaptation of the geminivirus bean yellow dwarf virus to dicotyledonous hosts involves both virion-sense and complementary-sense genes.

Bean yellow dwarf virus (BeYDV) and maize streak virus (MSV) belong to the geminivirus genus Mastrevirus and have host ranges confined to dicotyledonous and monocotyledonous species, respectively. To investigate viral determinants of host range specificity, chimeras were constructed by exchanging their coding and non-coding regions. BeYDV chimeras containing MSV ORF V1, ORF V2 or small intergenic region sequences, either individually or in various sequential combinations, replicated and produced virus particles in Nicotiana tabacum protoplasts. BeYDV chimeras containing MSV ORFs C1 and C2 and/or the large intergenic region were unable to replicate. None of the chimeras was able to systemically infect either N. benthamiana or maize. Complementation experiments using BeYDV chimeras containing MSV ORF V1 and/or ORF V2 suggest that expression of MSV movement protein and/or coat protein prevents BeYDV movement. The results demonstrate that factors involved in both viral DNA replication and virus movement are exclusively adapted to either monocotyledonous or dicotyledonous host backgrounds.

Adaptation, Physiological↗
PubMed1997

Virologic, immunologic, and clinical follow-up of a couple infected by the human immunodeficiency virus type one, group O.

The pathogenic course (virologic, immunologic, and clinical changes) of infection due to human immunodeficiency virus type one (HIV-1) group O viruses is unknown at present. To address this issue, serial HIV-1 isolates from a married couple (patients A and B) infected with a group O virus were analyzed to determine the temporal association between disease status and alterations in several parameters including plasma viral burden as measured by semiquantitative polymerase chain reaction, changes in CD4+ T cells, presence of neutralizing antibodies, and the ability to induce syncytia on the MT2 cells. For patient A who has been asymptomatic for at least 8 years, both the absence of syncytium-inducing (SI) variants and the presence of autologous and heterologous neutralizing antibodies correlated with a clinically healthier status. In contrast, a switch from NSI to SI variants was observed in patient B in 1990, followed by an expanded in vitro host range, increased viral burden, and a sharp decrease in CD4+ T cells 4 years later. Moreover, plasma obtained from this patient uniformly failed to neutralize both autologous and heterologous viruses. These observations in patient B correlated with a slightly unfavorable clinical status. Based on our preliminary results, it appears that the pathogenic course of infections due to group O viruses is similar to that reported previously for infections due to group M viruses.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Efficient virus-induced gene silencing in roots using a modified tobacco rattle virus vector.

Due to their capability of eliciting a form of posttranscriptional gene silencing (termed virus-induced gene silencing or VIGS), plant viruses are increasingly used as reverse-genetics tools for functional characterization of plant genes. RNA viruses have been shown to trigger silencing in a variety of host plants, including members of Solanacae and Arabidopsis (Arabidopsis thaliana). Several factors affect the silencing response, including host range and viral tropism within the plant. The work presented here demonstrates that a modified tobacco rattle virus (TRV) vector retaining the helper protein 2b, required for transmission by a specific vector nematode, not only invades and replicates extensively in whole plants, including meristems, but also triggers a pervasive systemic VIGS response in the roots of Nicotiana benthamiana, Arabidopsis, and tomato (Lycopersicon esculentum). This sustained VIGS response was exemplified by the silencing of genes involved in root development (IRT1, TTG1 [transparent testa glabra], RHL1 [root hairless1], and beta-tubulin), lateral root-meristem function (RML1 [root meristemless1]), and nematode resistance (Mi). Roots of silenced plants exhibit reduced levels of target mRNA and phenocopy previously described mutant alleles. The TRV-2b vector displays increased infectivity and meristem invasion, both key requirements for efficient VIGS-based functional characterization of genes in root tissues. Our data suggest that the TRV helper protein 2b may have an essential role in the host regulatory mechanisms that control TRV invasion.

Animals↗
PubMed2025

Broad geographical circulation of a novel vesiculovirus in bats in the Mediterranean region.

Bats are the natural reservoirs for a variety of emerging and re-emerging viruses. Among them, rabies virus (genus Lyssavirus, family Rhabdoviridae) is one of the first and most emblematic described in these animals. Since its first description, several new bat lyssaviruses have been regularly identified. In addition to lyssaviruses, other bat rhabdoviruses have also been discovered, including members of the genera Vesiculovirus, Ledantevirus and, more recently, Alphanemrhavirus and Tupavirus. However, the family Rhabdoviridae is one of the most abundant and diverse viral families, with 434 officially recognized species, divided into 5 subfamilies and 56 different genera. The number of rhabdoviruses associated with bats is therefore probably higher than that currently available. In this study, we first developed and validated a combined nested RT-qPCR technique (pan-rhabdo RT-nqPCR) dedicated to the broad detection of animal rhabdoviruses. After validation, this technique was used for a large retrospective screening of archival bat samples (n = 1962), including blood (n = 816), brain (n = 723) and oral swab (n = 423). These samples were collected from various bat species over a 12-year period (2007-2019) in 9 different countries in Europe and Africa. A total of 23 samples (1.2%) from bat species Miniopterus schreibersii, Rhinolophus euryale and Rhinolophus ferrumequinum tested positive for rhabdovirus infection, including 17 (2.1%) blood and 6 (1.4%) oral swab samples, all collected from bats originating from the Mediterranean region. Complete virus genome sequences were obtained by next-generation sequencing for most of the positive samples. Molecular and phylogenetic analysis of these sequences demonstrated that the virus isolates, named Mediterranean bat virus (MBV), were closely related and represented a new species, Mediterranean vesiculovirus, within the genus Vesiculovirus. MBV was more specifically related to other bat vesiculoviruses previously described from China and North America, together clustering into a distinct group of bat viruses within this genus. Interestingly, our results suggest that MBV is widespread, at least in the western part of the Mediterranean region, where it circulates in the blood of several bat species. These results expand the host range and viral diversity of bat vesiculoviruses, and pave the way for further studies to determine the transmission route and dissemination dynamics of these viruses in bat colonies, as well as to assess their potential threat to public health.

Animals↗
PubMed1996

Green fluorescent protein expressed in living mosquitoes--without the requirement of transformation.

Mosquitoes transmit viruses, protozoa and nematodes that are major causes of morbidity and mortality in humans. Details of arthropod anatomy and development, and the replication and development of pathogens in the arthropod vector, have relied upon examination of dissected or histologically processed material. We constructed a double-subgenomic Sindbis (dsSIN) virus expressing green fluorescent protein to demonstrate the potential of this protein for studying pathogen development in living arthropods. We were able to observe dissemination of virus, and furthermore, it was possible to observe components of the nervous system of mosquito larvae in extraordinary detail and record this on video tape. Although green fluorescent protein has been used as a reporter gene in a number of organisms, expression has relied upon transformation of cells or embryos. Transformation technology has limited applicability, thus we have described an alternative system that, due to the broad host range and viral tropisms of dsSIN viruses, may be useful to scientists in a range of disciplines. Green fluorescent protein may also provide a non-lethal selection method for use in transgenic arthropod research.

Animals↗
PubMed1985

Mapping of a vaccinia host range sequence by insertion into the viral thymidine kinase gene.

A vaccinia virus mutant deleted of ca. 18 kilobase pairs at the left-hand end of the genome is unable to multiply on many human cell lines. To determine whether all or some of the deleted sequences were responsible for the host range property, the corresponding region from wild-type DNA was cloned in three pieces into a vaccinia transplacement vector containing the thymidine kinase gene on the HindIII J fragment. The next step was to transfer these pieces to the genome of the host range deletion mutant by in vivo homologous recombination around the thymidine kinase locus. Transfer of one 5.2-kilobase-pair EcoRI fragment was found to restore a wild-type phenotype on the host range mutant, thus demonstrating that only a small portion of the 18-kilobase-pair deletion contains the host range function(s). This result also illustrates that the method initially devised for inserting foreign genes into vaccinia virus DNA is useful for studies of the vaccinia genome.

Cell Line↗