Identification and nucleotide sequence of the thymidine kinase gene of Shope fibroma virus.

The thymidine kinase (TK) gene of Shope fibroma virus (SFV), a tumorigenic leporipoxvirus, was localized within the viral genome with degenerate oligonucleotide probes. These probes were constructed to two regions of high sequence conservation between the vaccinia virus TK gene and those of several known eucaryotic cellular TK genes, including human, mouse, hamster, and chicken TK genes. The oligonucleotide probes initially localized the SFV TK gene 50 kilobases (kb) from the right terminus of the 160-kb SFV genome within the 9.5-kb BamHI-HindIII fragment E. Fine-mapping analysis indicated that the TK gene was within a 1.2-kb AvaI-HaeIII fragment, and DNA sequencing of this region revealed an open reading frame capable of encoding a polypeptide of 176 amino acids possessing considerable homology to the TK genes of the vaccinia, variola, and monkeypox orthopoxviruses and also to a variety of cellular TK genes. Homology matrix analysis and homology scores suggest that the SFV TK gene has diverged significantly from its counterpart members in the orthopoxvirus genus. Nevertheless, the presence of conserved upstream open reading frames on the 5' side of all of the poxvirus TK genes indicates a similarity of functional organization between the orthopoxviruses and leporipoxviruses. These data suggest a common ancestral origin for at least some of the unique internal regions of the leporipoxviruses and orthopoxviruses as exemplified by SFV and vaccinia virus, respectively.     

采用我国痘苗病毒天坛株载体表达单纯疱疹病毒Ⅰ型糖蛋白D

木文从单纯疱疹病毒Ⅰ型(HSV-1)基因组EcoRI H片段中分离出含有糖蛋白D(gD)基因的2.5kb DWA片段,插入带有痘苗病毒天坛株TK基因区段的pJC—2质粒p7.5k启动子的下游,转染TK~-143细胞,获得带有HSV-1 gD基因的重组痘苗病毒。采用HSV-1 gD单克隆抗体免疫胶体金技术进行电镜观察表明,重组痘苗病毒感染的细胞内有特异性HSV-1 gD抗原.重组病毒免疫家兔后6周可产生明显的HSV-1中和抗体。     

Multiple-cloning-site plasmids for the rapid construction of recombinant poxviruses

Plasmid vectors containing multiple cloning sites suitable for the rapid insertion of protein-coding sequences into poxviruses have been constructed. They are based on pUC plasmids and carry the thymidine kinase (TK) gene of vaccinia virus interrupted by a vaccinia virus promoter. Six unique restriction enzyme sites (BamHI, SalI/HincII, PstI, HindIII, EcoRI), located within 40 bp of vaccinia virus promoters transposed from the HindIII-F or HindIII-C fragment of the vaccinia virus genome, allow rapid insertion of foreign-protein-coding sequences into these plasmids. Such plasmids can be used to construct recombinant poxviruses expressing foreign proteins using marker-rescue recombination techniques and selection for TK negative viruses. Vaccinia viruses expressing the haemagglutinin (HA) gene of swine influenza virus, A/NJ/11/76 (H1N1), have been constructed.     

人癌胚抗原-重组痘苗病毒的构建和制备

痘苗病毒的基因组庞大,结构复杂而特殊,不可能将外源基因直接插入它的基因组,必须利用一种特殊的痘苗病毒质粒,才能构建成功重组痘苗病毒．在分析了痘苗病毒质粒ｐＪ１２０〔含有我国天花疫苗－痘苗病毒天坛株７６１的启动子和胸苷激酶（ｔｈｙｍｉｄｉｎｅｋｉｎａｓｅ,简称ＴＫ基因）,及含有人癌胚抗原（ｃａｒｃｉｎｏｅｍｂｒｙｎｉｃａｎｔｉｇｅｎ,简称ＣＥＡ）ｃＤＮＡ全序列的质粒ｐ９１０２３Ｂ－ｃｅａ－１７结构的基础上,设计出三步法构建了重组疫苗病毒质粒ｐＪ－ＣＥＡ．经酶切及ＰＣＲ鉴定ｐＪ－ＣＥＡ中ＣＥＡｃＤ－ＮＡ的存在,进一步用同源重组方法构建了表达人ＣＥＡ的重组痘苗病毒,并以人体成纤维细胞作为宿主细胞,对ＣＥＡ－重组痘苗病毒进行了大量培养．再次证实痘苗病毒是良好的真核表达载体,可以高效而准确地表达细胞膜糖蛋白ＣＥＡ．     

The African Swine Fever Virus Thymidine Kinase Gene Is Required for Efficient Replication in Swine Macrophages and for Virulence in Swine

African swine fever virus (ASFV) replicates in the cytoplasm of infected cells and contains genes encoding a number of enzymes needed for DNA synthesis, including a thymidine kinase (TK) gene. Recombinant TK gene deletion viruses were produced by using two highly pathogenic isolates of ASFV through homologous recombination with an ASFV p72 promoter–β-glucuronidase indicator cassette (p72GUS) flanked by ASFV sequences targeting the TK region. Attempts to isolate double-crossover TK gene deletion mutants on swine macrophages failed, suggesting a growth deficiency of TK⁻ ASFV on macrophages. Two pathogenic ASFV isolates, ASFV Malawi and ASFV Haiti, partially adapted to Vero cells, were used successfully to construct TK deletion viruses on Vero cells. The selected viruses grew well on Vero cells, but both mutants exhibited a growth defect on swine macrophages at low multiplicities of infection (MOI), yielding 0.1 to 1.0% of wild-type levels. At high MOI, the macrophage growth defect was not apparent. The Malawi TK deletion mutant showed reduced virulence for swine, producing transient fevers, lower viremia titers, and reduced mortality. In contrast, 100% mortality was observed for swine inoculated with the TK⁺ revertant virus. Swine surviving TK⁻ ASFV infection remained free of clinical signs of African swine fever following subsequent challenge with the parental pathogenic ASFV. The data indicate that the TK gene of ASFV is important for growth in swine macrophages in vitro and is a virus virulence factor in swine.     

Vaccinia virus expression vector: coexpression of beta-galactosidase provides visual screening of recombinant virus plaques.

We constructed a plasmid coexpression vector that directs the insertion of a foreign gene of interest together with the Escherichia coli beta-galactosidase (beta gal) gene into the thymidine kinase (TK) locus of the vaccinia virus genome. Tissue culture cells that had been infected with vaccinia virus were transfected with a plasmid vector containing a foreign gene. TK- recombinants could be selected by a plaque assay on TK- cells in the presence of 5-bromodeoxyuridine and distinguished from spontaneous TK- mutants by the addition of a beta-gal indicator to the agarose overlay. Plaques that expressed beta-gal stained dark blue within several hours at 37 degrees C. Alternatively, TK- selection could be eliminated, and recombinant plaques could be readily identified solely by their blue color. The reverse procedure, in which the starting virus expresses beta-gal (i.e., forms blue plaques) and the desired recombinant has deleted the entire beta-gal gene (i.e., forms white plaques), is another alternative. Each protocol was tested by constructing vaccinia virus recombinants that express hepatitis B virus surface antigen.     

用lac基因筛选表达狂犬病毒糖蛋白的重组痘苗病毒

为了研制基因工程狂犬病疫苗,我国于1991年首次报道了在痘苗病毒天坛株中表达狂犬病毒糖蛋白,但报道中重组病毒的选择是先经人骨髓瘤细胞(TK-143)在诱变剂5-溴脱氧尿苷(BrudR)作用下通过标记拯救技术筛选出携带有同源基因的重组病毒,然后再利用重组病毒中携带的Lac基因为选择标记,通过噬斑纯化获得重组病毒,用这种选择方式获得的重组病毒,经过了TK-143细胞和BrudR,因此不宜发展成疫苗,本研究探索不经过TK-143细胞和BrudR,仅利用Lac基因为选择标记,直接在鸡胚细胞上通过噬斑纯化获得重组病毒,现将研究结果报道如下。     

Cellular transformation by subgenomic feline sarcoma virus DNA

The genome of the Snyder-Theilen strain of feline sarcoma virus (ST-FeSV) is a 4.3-kilobase-pair (kbp) RNA molecule that contains a 1.5-kbp cellular insertion (fes gene) flanked by feline leukemia virus sequences at its 5' end (1.6 kbp) and 3' end (1.2 kbp) (Sherr et al., J. Virol. 34:200-212, 1980). DNA transfection techniques have been utilized to determine the regions of the ST-FeSV genome involved in malignant transformation. I have found that the 3.7-kbp 5'-end fragment of the ST-FeSV provirus (which corresponds to the 3.4-kbp 5'-end fragment of the viral genome) is sufficient to transform NIH/3T3 fibroblasts. Enzymes that cleave the ST-FeSV provirus DNA within the feline leukemia virus gag gene sequences or within the fes gene abolished the transforming activity. Preservation of the proviral large terminal repeats was also required for transformation. Transformed NIH/3T3 cells obtained by transfection of total or subgenomic ST-FeSV DNA expressed normal levels of the ST-FeSV gene product ST P85 and of its associated protein kinase activity. Furthermore, these cells contained high levels of phosphotyrosine residues, a biochemical marker associated with cellular transformation induced by certain retroviruses including ST-FeSV. These results, taken together, strongly support the concept that only those ST-FeSV proviral sequences necessary for ST P85 expression are involved in malignant transformation.     

Infectious poxvirus vectors have capacity for at least 25 000 base pairs of foreign DNA

To test the capacity of poxviruses for added foreign DNA, a recombinant was constructed that contains 24 700 bp of bacteriophage λ DNA inserted within the vaccinia virus thymidine kinase (TK) gene. The recombinant is stable, infectious and replicates in tissue culture at the same rate and to the same titer as standard vaccinia virus. This size flexibility of the poxvirus genome and the lack of stringent packaging requirements are useful features for an infectious eukaryotic cloning vector.     

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.     

Vaccinia virus encodes a thymidylate kinase gene: sequence and transcriptional mapping

The nucleotide sequence and deduced amino acid sequence of a vaccinia virus gene from the SalI F fragment are shown. The predicted polypeptide shares 42% amino acid identity over a 200 amino acid region with Saccharomyces cerevisiae thymidylate kinase (TmpK) and has low homology with herpes simplex virus deoxypyrimidine kinase. Northern blotting and S1 nuclease protection showed that the TmpK gene is transcribed early during infection and mapped the mRNA 5' end to immediately upstream of the second inframe ATG codon of the open reading frame (ORF). The encoded polypeptide is predicted to be 204 amino acids long (23.2 kD) and is almost colinear with yeast TmpK. Vaccinia virus possesses genes for TK and TmpK, separated by 57 kilobases of DNA, which are co-ordinately expressed and the encoded enzymes perform sequential steps in the same biochemical pathway.     

Mapping of the vaccinia virus DNA polymerase gene by marker rescue and cell-free translation of selected RNA

The previous demonstration that a phosphonoacetate (PAA)-resistant (PAAr) vaccinia virus mutant synthesized an altered DNA polymerase provided the key to mapping this gene. Marker rescue was performed in cells infected with wild-type PAA-sensitive (PAAs) vaccinia by transfecting with calcium phosphate-precipitated DNA from a PAAr mutant virus. Formation of PAAr recombinants was measured by plaque assay in the presence of PAA. Of the 12 HindIII fragments cloned in plasmid or cosmid vectors, only fragment E conferred the PAAr phenotype. Successive subcloning of the 15-kilobase HindIII fragment E localized the marker within a 7.5-kilobase BamHI-HindIII fragment and then within a 2.9-kilobase EcoRI fragment. When the latter was digested with ClaI, marker rescue was not detected, suggesting that the PAAr mutation mapped near a ClaI site. The sensitive ClaI site was identified by cloning partial ClaI-EcoRI fragments and testing them in the marker rescue assay. The location of the DNA polymerase gene, about 57 kilobases from the left end of the genome, was confirmed by cell-free translation of mRNA selected by hybridization to plasmids containing regions of PAAr vaccinia DNA active in marker rescue. A 100,000-dalton polypeptide that comigrated with authentic DNA polymerase was synthesized. Correspondence of the in vitro translation product with purified vaccinia DNA polymerase was established by peptide mapping.     

African swine fever virus encodes two genes which share significant homology with the two largest subunits of DNA-dependent RNA polymerases.

A random sequencing strategy applied to two large SalI restriction fragments (SB and SD) of the African swine fever virus (ASFV) genome revealed that they might encode proteins similar to the two largest RNA polymerase subunits of eukaryotes, poxviruses and Escherichia coli. After further mapping by dot-blot hybridization, two large open reading frames (ORFs) were completely sequenced. The first ORF (NP1450L) encodes a protein of 1450 amino acids with extensive similarity to the largest subunit of RNA polymerases. The second one (EP1242L) codes for a protein of 1242 amino acids similar to the second largest RNA polymerase subunit. Proteins NP1450L and EP1242L are more similar to the corresponding subunits of eukaryotic RNA polymerase II than to those of vaccinia virus, the prototype poxvirus, which shares many functional characteristics with ASFV. ORFs NP1450L and EP1242L are mainly expressed late in ASFV infection, after the onset of DNA replication.     

Structure of the heterogeneous L-S junction region of human cytomegalovirus strain AD169 DNA

The genome of human cytomegalovirus strain AD169 contains a region of heterogeneity located at the junction between the long (L) and short (S) components of the viral DNA. Twelve cloned L-S junction fragments were studied by using the restriction enzymes HaeII and XhoI. The region of heterogeneity was localized within a single HaeII restriction fragment. The enzyme XhoI was used to subdivide this region and revealed the presence of three types of heterogeneity within the junction fragments. Each of the cloned junction fragments contained one of the following fragments: 0.553, 0.95, or 1.35 kilobase pairs (referred to as class I heterogeneity). Class II heterogeneity was defined as the presence of tandem duplications of class I fragments. In addition, a variable number (0 to 5) of a 0.2-kbp fragment (class III heterogeneity) was observed. Mapping of these fragments with partial XhoI digestions revealed that the class I and class III heterogeneous fragments were adjacent. The DNA sequence of the smallest cloned L-S junction fragment was determined and analyzed. This junction fragment contained a single 0.553-kbp XhoI fragment and no copies of the 0.2-kbp fragment. The 0.553-kbp XhoI fragment was similar in structure to the a-sequences of herpes simplex virus types 1 and 2. In addition, a region of homology was found between the a sequences of herpes simplex virus types 1 and 2 and the 0.553-kbp XhoI fragment from the human cytomegalovirus junction.     

Identification of the gene encoding Marek''s disease herpesvirus A antigen.

The gene encoding the glycoprotein Marek's disease herpesvirus A antigen (MDHV-A) precursor polypeptide pr47 was delineated by using Northern blot (RNA blot) analysis and hybrid selection of its mRNA with cloned MDHV DNA, cell-free translation of the mRNA, and immunoprecipitation of the polypeptide. The resulting piece of DNA with strongly positive hybrid selection results was a 2.2-kilobase-pair (kbp) PvuII-EcoRI restriction fragment localized to the center of the 18.3-kbp MDHV BamHI B fragment of the total virus genome. The localization was specific since no other small restriction subfragment of the larger BamHI B fragment was able to hybrid select significant MDHV-A mRNA and the gene mapped only in the BamHI B fragment of the total virus genome. Northern blot analysis confirmed the localization of the MDHV-A gene on the 2.2-kbp fragment and detected its mRNA as a 1.8-kilobase species, a size consistent with encoding a 47-kilodalton polypeptide. This is the first report of an MDHV gene being mapped to the MDHV viral genome. This opens the way for the use of recombinant DNA technology to study the nature of the gene encoding a secreted virus-specific glycoprotein that could possibly be involved in immunoprevention, immunosuppression, or immunoevasion, immune phenomena known or speculated to be involved in this oncogenic herpesvirus system.     

Palindromic structure and polypeptide expression of 36 kilobase pairs of heterogeneous Epstein-Barr virus (P3HR-1) DNA.

Among the Epstein-Barr virions (EBV) produced by the P3HR-1 (HR-1) cell line are a defective subpopulation with rearranged viral DNA designated heterogeneous DNA (het DNA). These defective virions are responsible for the capacity of HR-1 virus to induce early antigen in Raji c cells and for trans activation of latent EBV in X50-7 cells. Virions with het DNA are independent replicons which pass horizontally from cell to cell rather than being partitioned vertically. We analyzed the structure and defined several polypeptide products of het DNA to understand these remarkable biologic properties. A 36-kilobase-pair (kbp) stretch of het DNA was cloned (as two EcoRI fragments of 20 and 16 kbp) from virions released from a cellular subclone of HR-1 cells. The unusual aspect of the 20-kbp fragment was the linkage of sequences of BamHI-M and BamHI-B', which are not adjacent on the standard EBV genome. The 16-kbp fragment was a palindrome in which at least two additional recombinations on each side of the palindrome had linked regions of the standard EBV genome which are not normally contiguous. The 20-kbp het DNA fragment was attached to at least one and possibly both ends of the 16-kbp het DNA fragment. We identified antigenic polypeptides produced in COS-1 cells after gene transfer of various cloned het DNA fragments. The 20-kbp fragment encoded a cytoplasmic antigen of about 95 kilodaltons (kDa). The 16-kbp fragment encoded antigens located in the nucleus, nuclear membrane, and cytoplasm. These were represented by several polypeptides, the most prominent of which were about 55, 52, and 36 kDa. The 36-kDa polypeptide was localized to a 2.7-kbp BamHI fragment which had homology to standard BamHI-W and BamHI-Z. Another polypeptide of 50 kDa found in the nucleus was mapped to the 7.1-kbp BamHI het DNA fragment which spans the EcoRI site linking the 20- and 16-kbp fragments of het DNA. Thus, HR-1 het DNA encodes several discrete polypeptide products, one or more of which could be responsible for the unusual biologic properties of the virus. The composition, regulation, and ultimately the expression of some of these products relative to standard EBV is probably altered by the genomic rearrangements of het DNA.     

Novel swine virulence determinant in the left variable region of the African swine fever virus genome

Previously we have shown that the African swine fever virus (ASFV) NL gene deletion mutant E70DeltaNL is attenuated in pigs. Our recent observations that NL gene deletion mutants of two additional pathogenic ASFV isolates, Malawi Lil-20/1 and Pr4, remained highly virulent in swine (100% mortality) suggested that these isolates encoded an additional virulence determinant(s) that was absent from E70. To map this putative virulence determinant, in vivo marker rescue experiments were performed by inoculating swine with infection-transfection lysates containing E70 NL deletion mutant virus (E70DeltaNL) and cosmid DNA clones from the Malawi NL gene deletion mutant (MalDeltaNL). A cosmid clone representing the left-hand 38-kb region (map units 0.05 to 0.26) of the MalDeltaNL genome was capable of restoring full virulence to E70DeltaNL. Southern blot analysis of recovered virulent viruses confirmed that they were recombinant E70DeltaNL genomes containing a 23- to 28-kb DNA fragment of the Malawi genome. These recombinants exhibited an unaltered MalDeltaNL disease and virulence phenotype when inoculated into swine. Additional in vivo marker rescue experiments identified a 20-kb fragment, encoding members of multigene families (MGF) 360 and 530, as being capable of fully restoring virulence to E70DeltaNL. Comparative nucleotide sequence analysis of the left variable region of the E70DeltaNL and Malawi Lil-20/1 genomes identified an 8-kb deletion in the E70DeltaNL isolate which resulted in the deletion and/or truncation of three MGF 360 genes and four MGF 530 genes. A recombinant MalDeltaNL deletion mutant lacking three members of each MGF gene family was constructed and evaluated for virulence in swine. The mutant virus replicated normally in macrophage cell culture but was avirulent in swine. Together, these results indicate that a region within the left variable region of the ASFV genome containing the MGF 360 and 530 genes represents a previously unrecognized virulence determinant for domestic swine.