Homologies between herpesvirus of turkey and Marek's disease virus type-1 DNAs within two co-linearly arranged open reading frames, one encoding glycoprotein A

The genomes of two avian herpesviruses, Marek's disease virus type 1 (MDV1) and herpesvirus of turkey (HVT), share close homology only within certain DNA regions. One such homologous region of HVT DNA was cloned and sequenced. Two open reading frames (ORFs) were found in the long unique region, ORF1 encoding the glycoprotein A (gA), and ORF2 encoding a still unidentified protein. These two HVT-ORFs are located at almost the same positions as the homologous MDV1-ORFs. The nucleotide sequence homologies between HVT and MDV1 were 73% and 68% for ORF1 and ORF2, respectively. Both the 5'- and 3'-noncoding regions, however, are less conserved. The third letter within every codon of ORF1 and ORF2 showed a mismatch of greater than 50% between the two viruses. The amino acid (aa) sequence homologies between the corresponding putative viral proteins are 83% and 80% for ORF1 (gA) and ORF2, respectively. More than 90% homology was observed in the C-terminal region of ORF1 (gA). Furthermore, the deduced aa sequences for both of the ORFs in these two viruses showed considerable homology to two adjoining genes in herpes simplex virus type 1, the glycoprotein C and UL45 genes.     

Persistence of genomes of both herpesvirus of turkeys and Marek's disease virus in a chicken T-lymphoblastoid cell line

A cell line tentatively designated as MDCC-BO1(T), was established from spleen cells of an apparently healthy chicken inoculated with herpesvirus of turkey (HVT). BO1(T) cells were T lymphoblastoid cells and the more than 95% of them had Marek's disease (MD) tumor-associated surface antigen (MATSA). However, no viral internal antigens or membrane antigens could be demonstrated in them by immunofluorescence tests using chicken anti-HVT and -MD virus (MDV) sera. The virus could be rescued from BO1(T) cells by co-cultivation with chick embryo fibroblasts (CEF). The DNA of the rescued virus was characterized as HVT DNA by its sedimentation profile in a neutral glycerol gradient and its endonuclease Hind III cleavage-pattern. Ultrastructural studies on CEF infected with the rescued virus revealed the presence of HVT-like virions. However, DNA-DNA reassociation kinetics showed that the BO1(T) cells contained a few copies of NVT and also MDV genomes.     

Cloning of human papilloma virus genomic DNAs and analysis of homologous polynucleotide sequences.

The complete DNA genomes of four distinct human papilloma viruses (human papilloma virus subtype 1a [HPV-1a], HPV-1b, HPV-2a, and HPV-4) were molecularly cloned in Escherichia coli, using the certified plasmid vector pBR322. The restriction endonuclease patterns of the cloned HPV-1a and HPV-1b DNAs were similar to those already published for uncloned DNAs. Physical maps were constructed for HPV-2a DNA and HPV-4 DNA, since these viral DNAs had not been previously mapped. By using the cloned DNAs, the genomes of HPV-1a, HPV-2a, and HPV-4 were analyzed for nucleotide sequence homology. Under standard hybridization conditions (Tm = --28 degrees C), no homology was detectable among the genomes of these papilloma viruses, in agreement with previous reports. However, under less stringent conditions (i.e., Tm = --50 degrees C), stable DNA hybrids could be detected between these viral DNAs, indicating homologous segments in the genomes with approximately 30% base mismatch. By using specific DNA fragments immobilized on nitrocellulose filters, these regions of homology were mapped. Hybridization experiments between radiolabeled bovine papilloma virus type 1 (BPV-1) DNA and the unlabeled HPV-1a, HPV-2a, or HPV-4 DNA restriction fragments under low-stringency conditions indicated that the regions of homology among the HPV DNAs are also conserved in the BPV-1 genome with approximately the same degree of base mismatch.     

Electron microscope study of the base sequence homology between simian virus 40 and human papovavirus BK.

The base sequence homology between the genomes of simian virus 40 (SV40) and human papovavirus BK (BKV) was studied by the heteroduplex method of Ferguson and Davis (J. Mol. Biol. 94:135-149, 1975). When mounted for microscopy in 30% formamide (Tm-35 degrees C), BKV/SV40 heteroduplexes were an average of 92% double-stranded and contained only two small nonhomologous regions that mapped near the junctions between the early and late regions of the SV40 Genome. At higher formamide concentrations, the fraction of duplex DNA in the BKV/SV40 heteroduplexes decreased, indicating significant base mismatching in the homologous regions. The strongest regions of homology were located in the late region.     

Evolutionary relationships of the primate papovaviruses: base sequence homology among the genomes of simian virus 40, stump-tailed macaque virus, and SA12 virus.

Physical maps of the genomes of the two newly discovered primate papovaviruses, SA12 and stump-tailed macaque virus (STMV), were generated by restriction endonuclease analysis. The base sequence homologies among the genomes of SA12, stump-tailed macaque virus, and simian virus 40 (SV40) were studied by heteroduplex analysis. Heteroduplexes between SA12 and SV40 DNAs and stump-tailed macaque virus and SV40 DNAs were constructed and mounted for electron microscopy in various amounts of formamide to achieve a range of effective temperatures. At each effective temperature, the regions of duplex DNA in the heteroduplexes were measured and localized on the SV40 physical and functional maps. By analyzing the data from this study and rom our previous study (N. Newell, C. J. Lai, G. Khoury, and T. J. Kelly Jr., J. Virol. 25:193-201, 1978) on the base sequence homology between the genomes of BK virus and SV40, some general conclusions have been drawn concerning the evolutionary relationships among the genomes of the primate papovaviruses. The extent of homology among the viral genomes does not reflect the phylogenetic relationships of their hosts. At comparable effective temperatures Tm - 33 degrees C), the heteroduplexes between the DNAs of BK virus and SV40 contained the largest amount of duplex (about 90%). The heteroduplexes made between SA12 and SV40 DNAs were slightly less homologous, containing about 80% duplex. The heteroduplexes made between SV40 and stump-tailed macaque virus DNAs were only 20% duplex under the same conditions. When the various heteroduplexes were mounted for microscopy at effective temperatures greater than Tm - 33 degrees C, the fraction of the duplex DNA decreased in each case, indicating the existence of considerable base mismatching in the homologous regions. When specific coding or noncoding regions of the viral genomes were compared, the data indicated that the extent of sequence divergence differed markedly from one region to another. In all the heteroduplexes studied, there were two regions, located near the junctions between early and late regions on the SV40 map, which were essentially nonhomologous. All of the heteroduplexes studied showed significantly greater homology in the late region than in early region. Within the late region, the sequences coding for the major capsid polypeptide, VP1, were the most highly conserved.     

The genome of a very virulent Marek's disease virus

Here we present the first complete genomic sequence, with analysis, of a very virulent strain of Marek's disease virus serotype 1 (MDV1), Md5. The genome is 177,874 bp and is predicted to encode 103 proteins. MDV1 is colinear with the prototypic alphaherpesvirus herpes simplex virus type 1 (HSV-1) within the unique long (UL) region, and it is most similar at the amino acid level to MDV2, herpesvirus of turkeys (HVT), and nonavian herpesviruses equine herpesviruses 1 and 4. MDV1 encodes 55 HSV-1 UL homologues together with 6 additional UL proteins that are absent in nonavian herpesviruses. The unique short (US) region is colinear with and has greater than 99% nucleotide identity to that of MDV1 strain GA; however, an extra nucleotide sequence at the Md5 US/short terminal repeat boundary results in a shorter US region and the presence of a second gene (encoding MDV097) similar to the SORF2 gene. MD5, like HVT, encodes an ICP4 homologue that contains a 900-amino-acid amino-terminal extension not found in other herpesviruses. Putative virulence and host range gene products include the oncoprotein MEQ, oncogenicity-associated phosphoproteins pp38 and pp24, a lipase homologue, a CxC chemokine, and unique proteins of unknown function MDV087 and MDV097 (SORF2 homologues) and MDV093 (SORF4). Consistent with its virulent phenotype, Md5 contains only two copies of the 132-bp repeat which has previously been associated with viral attenuation and loss of oncogenicity.     

Inverted repeat regions of Marek''s disease virus DNA possess a structure similar to that of the a sequence of herpes simplex virus DNA and contain host cell telomere sequences.

The genomic structure of Marek's disease virus (MDV) is similar to those of the alphaherpesviruses herpes simplex virus (HSV) types 1 and 2. Sequence analysis of the junction region between the long component (L) and the short component (S) revealed the existence of an a-like sequence, similar in structure to the a sequence of HSV-1. Further study revealed that the MDV genome contains five copies of the a-like sequence within the long terminal repeat region as well as in the short terminal repeat region. The junction between the L and S components was found to contain 10 copies of the a-like sequence. Within the a-like sequence, a structure homologous to the DR2 of HSV was found to contain 17 copies of the telomeric sequence, GGGGTTA. There appears to be little to no sequence homology between the HSV a sequence and the MDV a-like sequence; however, the strong physical homology to its counterpart in HSV-1 suggests that the MDV a-like sequence may have the same functional homology (the domain for cleavage/packaging of the DNA into the viral capsids and for genomic inversion) as well.     

Status of Marek's disease virus in established lymphoma cell lines: herpesvirus integration is common.

Six cell lines derived from Marek's disease lymphomas of chickens and turkeys were investigated for the status of Marek's disease virus (MDV) DNA. In the transformed T- and B-cell lines, viral DNA could be detected by conventional Southern blot hybridization, by Gardella gel electrophoresis, and by in situ hybridization of metaphase and interphase chromosomes. Integration of viral DNA into the host cell chromosome was observed in all cell lines. Two to 12 integration sites of viral DNA could be detected in metaphase chromosome spreads. The integration sites were characteristic for the individual cell lines and were preferentially located at the telomers of large- and mid-sized chromosomes or on minichromosomes. In four of six cell lines, a minor population of latently infected cells supported the lytic cycle of MDV, giving rise to linear virion DNAs. In one of these cell lines, a third species of MDV DNA could be detected with properties reminiscent of covalently closed circular DNA. The finding that MDV integrates regularly into the genomes of latently infected cells is crucial to understanding the molecular biology of herpesvirus-induced tumors in the natural host.     

The genome of turkey herpesvirus

Here we present the first complete genomic sequence of Marek's disease virus serotype 3 (MDV3), also known as turkey herpesvirus (HVT). The 159,160-bp genome encodes an estimated 99 putative proteins and resembles alphaherpesviruses in genomic organization and gene content. HVT is very similar to MDV1 and MDV2 within the unique long (UL) and unique short (US) genomic regions, where homologous genes share a high degree of colinearity and their proteins share a high level of amino acid identity. Within the UL region, HVT contains 57 genes with homologues found in herpes simplex virus type 1 (HSV-1), six genes with homologues found only in MDV, and two genes (HVT068 and HVT070 genes) which are unique to HVT. The HVT US region is 2.2 kb shorter than that of MDV1 (Md5 strain) due to the absence of an MDV093 (SORF4) homologue and to differences at the UL/short repeat (RS) boundary. HVT lacks a homologue of MDV087, a protein encoded at the UL/RS boundary of MDV1 (Md5), and it contains two homologues of MDV096 (glycoprotein E) in the RS. HVT RS are 1,039 bp longer than those in MDV1, and with the exception of an ICP4 gene homologue, the gene content is different from that of MDV1. Six unique genes, including a homologue of the antiapoptotic gene Bcl-2, are found in the RS. This is the first reported Bcl-2 homologue in an alphaherpesvirus. HVT long repeats (RL) are 7,407 bp shorter than those in MDV1 and do not contain homologues of MDV1 genes with functions involving virulence, oncogenicity, and immune evasion. HVT lacks homologues of MDV1 oncoprotein MEQ, CxC chemokine, oncogenicity-associated phosphoprotein pp24, and conserved domains of phosphoprotein pp38. These significant genomic differences in and adjacent to RS and RL regions likely account for the differences in host range, virulence, and oncogenicity between nonpathogenic HVT and highly pathogenic MDV1.     

Inducible permissive cells transformed by a temperature-sensitive polyoma virus: superinfection does not allow excision of the resident viral genome.

After exposure of mouse embryo cells to the early temperature-sensitive mutant tsP155 of polyoma virus (Py), a transformed cell line (Cyp line) that can be readily induced to synthesize Py by transfer to 33 degrees C was isolated at 39 degrees C (7). Virus production and synthesis of free viral DNA occurring after temperature shiftdown or superinfection with wild-type Py or both were studied in several clonal isolates of the Cyp cell line. Measurements of virus yields indicated that, although some could be induced more effectively than others, all cell clones behaved as highly permissive when subjected to superinfection. We analyzed the origin of free viral DNA accumulating in the superinfected cultures, taking advantage of (i) the unique physical properties of the low-molecular-weight DNA which, in the case of one of the Cyp clones, accumulates during temperature shiftdown, and (ii) the differences between resident and superinfecting viral genomes in their susceptibilities towards restriction endonucleases. At 33 degrees C, both viral genomes were found to accumulate in all clones studied whereas in the case of the clones with lower inducibility, the replication of the resident genome appeared to be enhanced by superinfection. At 39 degrees C, however, accumulation of the superinfecting genome was not accompanied by that of the resident genome, unless it had already been initiated before superinfection. These findings demonstrate that, when routinely cultivated at 39 degrees C, Cyp cells contain few viral DNA molecules readily available for autonomous replication and that, upon transfer to 33 degrees C, therefore, excision must first take place before the resident genome can accumulate as free viral DNA. Our findings also suggest that, unlike the P155 gene product provided by the resident viral genome upon induction, the allelic gene product supplied by the superinfecting genome may be less effective in triggering excision than in promoting replication.     

Monoclonal antibodies with specificity for three different serotypes of Marek's disease viruses in chickens

A total of 50 antibody-secreting hybridoma cells against Marek's disease virus (MDV) and turkey herpesvirus (HVT) have been produced. Eleven hybridomas were used for serotyping a panel of 15 pathogenic and nonpathogenic strains of MDV and HVT, representing three serotypes. The antibodies from the culture medium have fluorescence antibody (FA) titers of up to 100 and those from mouse ascitic fluid have titers ranging from 10(4) to 10(6). Monoclonal antibody T81 is type-common, i.e., it reacts at equal titer with all MDV and HVT tested. Of the remaining 10 antibodies, eight react only with pathogenic and attenuated strains of MDV (presumably serotype 1), one reacts only with nonpathogenic MDV (presumably) serotype 2), and one reacts only with strains of HVT (presumably serotype 3). Two hybridomas belong to IgG2a and IgG2b subclasses, respectively, and the remaining nine belong to IgG1 subclass. None of the antibodies specific for MDV strains reacted with homologous viruses in serum neutralization (SN), agar gel precipitin (AGP), or membrane immunofluorescence tests. Antibody L78, which is specific for HVT, was reactive with its homologous virus in the SN test; antibody from the culture medium showed an SN titer of 10 and that from mouse ascites a titer of 10,000. None of the antibodies specific for MDV or HVT reacted with other avian or mammalian herpesviruses, avian leukosis viruses (ALV), reticuloendotheliosis viruses (REV), or Marek's disease tumor-associated surface antigen (MATSA) expressed in a lymphoblastoid cell line, MDCC-MSB-1.     

Nucleic Acid Homology of Murine Type-C Viral Genes

The nucleic acid sequence homology between various murine, endogenous type-C viruses (three host range classes of BALB/c virus, the AT-124 virus, and the CCL 52 virus) and two laboratory strains of murine leukemia virus (Rauscher and Kirsten) was determined by DNA:RNA hybridization. The viral sequences exhibit varying degrees of partial homology. DNA:DNA hybridizations were performed between [³H]DNA probes prepared from N- and X-tropic BALB/c endogenous viruses and cellular DNAs from BALB/c, NIH Swiss, and AKR inbred mouse strains as well as from California feral mice and the Asian mouse subspecies Mus musculus molossinus and M. musculus castaneus. All of these strains of mice are shown to possess multiple (six to seven per haploid genome), partially related copies of type-C virogenes in their DNAs. Thermal melting profiles of the DNA:RNA and DNA:DNA hybrids suggest that the partial homology of the viral nucleic acid sequences is the result of base alterations throughout the viral genomes, rather than the loss of discrete segments of viral sequences.     

Latent Marek's disease virus can be activated from its chromosomally integrated state in herpesvirus-transformed lymphoma cells.

Marek's disease virus (MDV), a lymphotropic herpesvirus, induces T-cell lymphomas in chicken, its natural host. The lymphoma cells are latently infected with MDV but the viral contribution to the transformed phenotype is not understood. To investigate the virus-cell interaction, we focused on the status of MDV in the transformed cells. By the use of highly sensitive fluorescent in situ hybridization with metaphase chromosomes, we found (i) MDV DNA to be randomly integrated at multiple sites in the chromosomes of primary lymphoma cells from chicken tissues; (ii) extrachromosomal, circular MDV genomes were absent and linear virion DNA was usually not detectable in the latently infected lymphoma cells; (iii) the pattern of integration sites revealed the clonal origin of the tumour cells; which (iv) was retained in in vitro established cell lines derived from primary lymphomas; (v) activation of the lytic phase of MDV's life cycle occurred in vitro suggesting that MDV can escape from its integrated status by an unknown mechanism.     

Polyoma genome in hamster BHK-21-C13 cells: integration into cellular DNA and induction of the viral replication.

When grown at 39.5 degrees C, BHK-21 C-13 cells transformed by A gene mutants of polyoma virus contain viral sequences that are predominantly associated with cellular DNA pelleted in the Hirt lysis procedure. At this temperature, in cells that are inducible for viral DNA replication (Folk, 1973), the majority of the viral genomes are covalently joined with cellular DNA's containing repetitious sequences. Upon a shift to 31 degrees C, free viral genomes appear and are replicated. Coupled with the replication of the free viral genomes at 31 degrees C is an increase in the viral genomes associated with cellular DNA.     

An X-linked gene affecting mouse cell DNA synthesis also affects production of unintegrated linear and supercoiled DNA of murine leukemia virus.

To identify specific cellular factors which could be required during the synthesis of retroviral DNA, we have studied the replication of murine leukemia virus in mouse cells temperature sensitive for cell DNA synthesis (M. L. Slater and H. L. Ozer, Cell 7:289-295, 1976) and in several of their revertants. This mutation has previously been mapped on the X chromosome. We found that a short incubation of mutant cells at a nonpermissive temperature (39 degrees C) during the early part of the virus cycle (between 0- to 20-h postinfection) greatly inhibited virus production. This effect was not observed in revertant or wild-type cells. Molecular studies by the Southern transfer procedure of the unintegrated viral DNA synthesized in these cells at a permissive (33 degrees C) or nonpermissive temperature revealed that the levels of linear double-stranded viral DNA (8.8 kilobase pairs) were nearly identical in mutant or revertant cells incubated at 33 or 39 degrees C. However, the levels of two species of supercoiled viral DNA (with one or two long terminal repeats) were significantly lower in mutant cells incubated at 39 degrees C than in mutant cells incubated at 33 degrees C or in revertant cells incubated at 39 degrees C. Pulse-chase experiments showed that linear viral DNA made at 39 degrees C could not be converted into supercoiled viral DNA in mutant cells after a shift down to 33 degrees C. In contrast, such conversion was observed in revertant cells. Restriction endonuclease analysis did not detect differences in the structure of linear viral DNA made at 39 degrees C in mutant cells as compared to linear viral DNA isolated from the same cells at 33 degrees C. However, linear viral DNA made at 39 degrees C in mutant cells was poorly infectious in transfection assays. Taken together, these results strongly suggest that this X-linked gene, affecting mouse cell DNA synthesis, is operating in the early phase of murine leukemia virus replication. It seems to affect the level of production of unintegrated linear viral DNA only slightly while greatly reducing the infectivity of these molecules. In contrast, the accumulation of supercoiled viral DNA and subsequent progeny virus production are greatly reduced. Our pulse-chase experiments suggest that the apparent, but not yet identified, defect in linear viral DNA molecules might be responsible for their subsequent impaired circularization.     

Neutralization Studies with Marek''s Disease Virus and Turkey Herpesvirus

Use of Marek's disease virus (MDV) in a neutralization test presents several problems, which are described, making this potentially useful test difficult. To obviate these difficulties, a plaque reduction test has been designed based on cross-neutralization of turkey herpesvirus (HVT) by serum-neutralizing MDV. The technique for such a neutralization test is outlined. Kinetics of development of neutralizing antibodies in chickens inoculated with HVT and MDV are described. The neutralization test can be used to evaluate viability of HVT vaccines and the possible role of neutralizing antibodies in the protection afforded by vaccination against MDV-induced tumors.     

Human polyomavirus JC virus genome.

The complete DNA sequence of the human JC virus, which was found to consist of 5,130 nucleotide pairs, is presented. The amino acid sequence of six proteins could be deduced: the early, nonstructural proteins, large T and small t antigens; the late capsid proteins, VP1, VP2, and VP3; and the agnogene product encoded within the late leader sequence, called the agnoprotein in simian virus 40. The extent of homology between JC virus DNA and the genomes of simian virus 40 (69%) and BK virus (75%) confirmed the close evolutionary relationship of these three polyomaviruses. The sequences showing the greatest divergence in these viral DNAs occurred within the tandem repeats located to the late side of the replication origins.     

Processing of glycoprotein gB related to neutralization of Marek's disease virus and herpesvirus of turkeys

The glycoprotein gB related to neutralization of Marek's disease virus (MDV) and herpesvirus of turkeys (HVT) is composed of several glycosylated polypeptides, which were immunoprecipitated with monoclonal antibodies and rabbit antiserum cross-reactive to MDV-gB and HVT-gB, and analyzed by SDS-polyacrylamide gel electrophoresis. The present pulse-chase experiments showed that the precursor forms of MDV- and HVT-gB were glycoproteins with molecular weights of 110K to 115K (gp115/110) and 115K (gp115), respectively. These precursor forms were processed to smaller gB's (gp63 and gp50 for MDV; gp62, gp52, and gp48 for HVT), at least in part by sialylation. The proteins synthesized in the presence of tunicamycin were two polypeptides of 88K and 83K in MDV-infected cells and a 90K polypeptide in HVT-infected cells, indicating the presence of unglycosylated precursor forms of MDV- and HVT-gB. Differences between virulent and avirulent MDV's and between HVT's with and without protective activity against Marek's disease were observed in the processed forms of MDV- and HVT-gB, especially at the processing step of sialylation.