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Comparison of a conserved region in fowlpox virus and vaccinia virus genomes and the translocation of the fowlpox virus thymidine kinase gene.

The DNA sequence of a clustered set of genes which are conserved in orthopoxviruses has been determined for the avipoxvirus, fowlpox virus. The arrangement of the genes in fowlpox virus is nearly identical to that in vaccinia virus, and genes which are overlapping in vaccinia virus overlap in fowlpox virus. One major difference exists however, as the thymidine kinase (TK) gene is absent in fowlpox virus from the position it occupies within this cluster of genes in vaccinia virus. Instead, in fowlpox virus there is a 32 bp non-coding region present between the genes that flank the TK gene in vaccinia virus. The fowlpox virus TK gene has been cloned and sequenced. The sequences immediately flanking the TK gene show no homology to any previously reported poxvirus gene. These results are discussed in terms of genome stability in poxviruses and the use of the TK gene as a non-essential region for the introduction of foreign genes into poxviruses.

Amino Acid Sequence

Activity of a fowlpox virus late gene promoter in vaccinia and fowlpox virus recombinants.

Characterization of a late promoter of fowlpox virus (FPV) and a study of its activity in FPV and vaccinia virus (VV) was carried out. The 5'-mRNA start site of the FPV late gene mapped to a TAAAT sequence near the translation start site (ATG). A cloned DNA fragment of FPV genome (PFL1) comprising of the 5'-end of the late gene was used to express the LacZ gene of E. coli in FPV and VV recombinants. A comparative analysis of beta-galactosidase (BG) expression from the LacZ gene under the control of the FPV promoter and a VV late promoter (PL11) was performed. Like FPV-PL11-LacZ and VV-PL11-LacZ constructs, FPV-PFL1-LacZ and VV-PFL1-LacZ virus recombinants expressed BG indicating that essential features of transcription were conserved in the two viruses. Furthermore, the LacZ transcripts originating from PFL1 in FPV and VV recombinants mapped to the expected TAAAT sequence. Time course analysis of BG expressed by VV and FPV recombinants suggested that although the transcription machinery in the two viruses was essentially conserved, subtle differences in the efficiency of transcription or translation may exist.

Animals

Recombinant fowlpox virus inducing protective immunity in non-avian species.

The natural host of fowlpox virus is limited to avian species. When inoculated into non-avian tissue culture cells, however, fowlpox virus can initiate an abortive infection. A fowlpox virus was engineered to express rabies virus glycoprotein. On inoculation of the recombinant virus into either avian (permissive) or non-avian (non-permissive) cells, the rabies glycoprotein was expressed as a membrane-associated antigen. Inoculation of the fowlpox virus recombinant into six different species of mammal resulted in specific immune responses to both fowlpox antigens and to rabies glycoprotein. In mice, cats and dogs the immune response was sufficient to protect against a live rabies virus challenge. The results demonstrate the utility of a fowlpox virus vector in immunizing non-avian species against rabies in the absence of productive viral replication of the fowlpox vector.

Animals

Analysis of the fowlpox virus genome region corresponding to the vaccinia virus D6 to A1 region: location of, and variation in, non-essential genes in poxviruses.

The DNA sequence of the fowlpox virus genome corresponding to the vaccinia virus D6 to A1 region has been determined. Translation of this sequence reveals fowlpoxvirus gene homologues corresponding to the D6, D7, D9, D10, D11, D12, D13 and A1 genes of vaccinia virus. In contrast, no gene homologue for the non-essential vaccinia virus D8 gene was present in fowlpox virus. Instead, a gene transcribed from the opposite strand to the vaccinia virus D8 gene showing no homology to any previously sequenced poxvirus gene was present. The amino terminus of the fowlpox virus D9 homologue had undergone substantial changes, including frameshifts which would be predicted to inactivate the gene. Insertion of a gene cartridge composed of the vaccinia virus p7.5 promoter and the lacZ gene into the fowlpox virus D8, D9 and D10 genes in vitro, followed by recombination into fowlpox virus, was carried out. Stable insertion mutants with the correct genotype were obtained for D8 and D9 which, when tested in chickens did not appear to have been attenuated. No stable insertion mutants were obtained for D10, indicating that this gene probably encodes a function which is essential for virus replication. The D8 and D9 genes of fowlpox virus represent useful insertion sites for the construction of recombinant fowlpox virus vaccines.

Amino Acid Sequence

Cell-culture virus-neutralization test and enzyme-linked immunosorbent assay for evaluation of immunity in chickens against fowlpox.

Two serological tests--the virus-neutralization (VN) test in chicken embryo fibroblasts (CEF) using a cell-culture-adapted virus, and the enzyme-linked immunosorbent assay (ELISA)--were used for evaluating the immune response in chickens against fowlpox virus. The VN test was conducted in 96-well tissue-culture plates using a fowlpox virus that was adapted to induce cytopathic effects (CPE) in CEF in 48 hr. The ELISA was carried out with an antigen prepared by precipitation of a cell-culture-propagated virus suspension with ammonium sulfate and concentration by centrifugation. A 0.1 M acetate buffer, pH 5, was used as the sensitizing solution for maximum specific binding of the antigen to the microplate plastic well. No antibodies were detected by the VN test in 228 serum samples taken from chickens at irregular intervals between 1 and 39 weeks of age, even though the birds were vaccinated against fowlpox at 13 weeks of age. However, in sera collected 4 weeks after a sample of laying hens was challenged with fowlpox virus, VN titers of 1/10 to 1/40 were detectable. On the other hand, significant antibody reactions were detected by the ELISA on sera from chickens during the growing period, following vaccination and challenge. Although no maternal antibodies were found at 1 week of age, a continuous increase in the mean ELISA titers to fowlpox was demonstrated during the entire experimental period. This study showed that the ELISA was considerably more sensitive and practical than the VN test.

Animals

Construction of fowlpox virus vectors with intergenic insertions: expression of the beta-galactosidase gene and the measles virus fusion gene.

A DNA fragment from fowlpox virus cloned on a plasmid vector was modified to contain foreign DNA inserts within an intergenic region. In a first step, a 32-base-pair intergenic region from the fowlpox virus genome corresponding to the position of the thymidine kinase locus in the vaccinia virus genome was enlarged to 55 base pairs by site-directed mutagenesis. A unique restriction endonuclease site introduced upstream of the intergenic region was then used to insert various foreign DNA fragments. The lacZ gene encoding beta-galactosidase and the measles virus gene encoding the fusion protein were positioned downstream of two vaccinia virus p7.5 promoter elements in either a direct repeat or inverted repeat orientation. Foreign DNA inserts contained within the fowlpox virus sequence were transferred to the viral genome by homologous recombination occurring in cells infected with a fowlpox virus temperature-sensitive mutant and transfected with both wild-type viral DNA and plasmid DNA. Recombinant viruses were selected for the expression of beta-galactosidase activity by screening for blue plaques in the presence of a chromogenic substrate. Stable recombinants expressing both the lacZ gene and the unselected measles gene were obtained when the p7.5 promoter was present as an inverted repeat. However, when the p7.5 promoter was in the direct repeat orientation, viral recombinants which initially expressed both gene inserts readily deleted the lacZ gene flanked by the promoter repeat. The methods described enable precise insertion and deletion of foreign genes in the fowlpox virus genome and could be applied to other intergenic regions of the same virus as well as other poxviruses.

Amino Acid Sequence

Fowlpox virus: pathogenicity and vaccination of day-old chickens via the aerosol route.

Day-old chickens were given a single fowlpox virus vaccination (strain HP201) either via the aerosol or wing-web route. Both methods induced protective immunity against a wing-web or intravenous challenge with virulent fowlpox virus at 47 days old, although high titred virus preparations were required for successful aerosol vaccination. However, no clinical signs of infection were observed as a result of aerosol vaccination even if invasive strains of Escherichia coli were administered simultaneously. The use of aerosol fowlpox virus vaccination of day-old chicks has been shown to be a possible means of mass vaccination and could be applied to the use of fowlpox virus in recombinant vaccines.

Aerosols

Mapping of a major early/late gene of fowlpox virus.

Identification, cloning and mapping of a major gene expressed during the early and late stages of infection with fowlpox virus is described. The gene is located within a 17.3 kb PstI fragment of the fowlpox virus genome and has an open reading frame of 501 bp. Analysis of the 5'-ends of mRNA transcribed from this gene showed that the start sites of both early and late transcripts map to the sequence TAAAT near the translation start site (ATG). This is the first poxvirus early/late gene described in which both early and late transcription start sites map to same DNA sequence. From northern hybridization analysis it was shown that the early function of this gene gives rise to the most abundant early mRNA coded by 17% of the fowlpox virus genome. The strong early function of this gene promoter will be useful in the construction of recombinant fowlpox viruses.

Base Sequence

Gene translocations in poxviruses: the fowlpox virus thymidine kinase gene is flanked by 15 bp direct repeats and occupies the locus which in vaccinia virus is occupied by the ribonucleotide reductase large subunit gene.

By sequencing a fragment of 7351 bp the fowlpox virus thymidine kinase gene has been found to map to a position within the equivalent of the vaccinia HindIII I fragment. The deduced gene arrangement in fowlpox virus is I3, X, TK, I5, I6, I7, I8, G1, indicating that the homologue of the vaccinia I4 gene has been replaced by two genes X and TK. The non-essential TK gene has therefore replaced another non-essential gene, I4 (the ribonucleotide reductase large subunit) in this region. The X/TK insertion in fowlpox virus is precisely flanked by direct repeats of 15 bp suggesting that the translocation event may have involved transposition. The % identities between the fowlpox virus and vaccinia virus proteins ranged between 58.5% and 31.3%.

Amino Acid Sequence

A 39,000 Mr immunodominant protein of fowlpox virus contains multiple copies of a 12 amino acid repeat sequence.

The nucleotide sequence of an unusual fowlpox virus gene which maps immediately upstream from the fowlpox virus 4b gene has been determined. The 34,000 Mr protein predicted to be encoded by the gene contains 11 copies of a 12 amino acid serine-rich repeat sequence. The seven amino-terminal copies of the repeat sequence are perfectly conserved but variation exists in the four carboxy-terminal copies. Three peptides were synthesized which contained either one copy of the repeat sequence, two copies of the repeat sequence or a hydrophilic amino-terminal region of the protein. All three peptides when injected with adjuvant into rabbits gave rise to antibodies which reacted strongly on Western blots of purified fowlpox virus proteins with a 39,000 Mr protein. When directly compared in Western blots the antipeptide sera were shown to recognize a protein comigrating with one of the two immunodominant proteins recognized by chicken anti-fowlpox virus sera taken 2 weeks post-infection. The virion protein is removed by treatment with sodium deoxycholate suggesting that it is located at or near the surface of the virus.

Amino Acid Sequence

Regulation of foreign gene in fowlpox virus by a vaccinia virus promoter.

A vaccinia virus promoter was evaluated for regulation of a foreign gene in fowlpox virus by a transient expression assay. Fowlpox virus-infected quail cells, transfected with plasmid DNA containing chloramphenicol acetyltransferase (CAT) gene ligated to a vaccinia virus promoter, expressed CAT activity. No CAT activity was detected either in uninfected cells or fowlpox virus-infected cells. These results indicated that a heterologous vaccinia virus promoter can regulate expression of a foreign gene in fowlpox virus.

Animals

Similar genetic organization between a region of fowlpox virus DNA and the vaccinia virus HindIII J fragment despite divergent location of the thymidine kinase gene.

DNA from Fowlpox virus, a member of the Avipoxvirus genus, has been found to hybridize to DNA from vaccinia virus, a member of the Orthopoxvirus genus. The greatest homology detected was around the region containing the vaccinia virus thymidine kinase locus. A 3.1-kbp fowlpox virus fragment that hybridizes to the vaccinia virus HindIII J fragment has been cloned and its sequence determined. Comparison of the nucleotide and deduced amino acid sequence to the cross hybridizing vaccinia fragment revealed extensive conservation of six open reading frames as well as a similar organization along the genome. Nevertheless a fowlpox virus gene corresponding to the vaccinia virus thymidine kinase gene was apparently lacking within the region studied and is probably located elsewhere in the genome. Despite this intriguing divergence, our results indicate that the Avipoxviruses are more closely related to the Orthopoxviruses than previously suspected.

Amino Acid Sequence

Protection of chickens with a recombinant fowlpox virus expressing the Newcastle disease virus hemagglutinin-neuraminidase gene.

A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) strain Texas was generated. Immunoprecipitation with chicken anti-NDV serum confirmed authentic expression of the HN protein. Protection of chickens from infection with NDV was observed when birds were immunized with the recombinant HN fowlpox virus by the intramuscular route after one or two inoculations. Vaccination by the ocular route with a mixture of fowlpox recombinants expressing the fusion and HN proteins did not show added protection over that seen with the individual viruses.

Animals

A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) protects chickens against challenge by NDV.

The hemagglutinin-neuraminidase (HN) gene from the Beaudette C strain of Newcastle disease virus (NDV) has been expressed in a recombinant fowlpox virus vector. The HN gene, under the control of the vaccinia p7.5 promoter, was inserted into a nonessential gene in the terminal inverted repeats of fowlpox virus. Expression was demonstrated in tissue culture, a protein of the correct size for fully glycosylated HN protein being recognized by an HN-specific monoclonal antibody on Western blots. When the recombinant fowlpox virus was inoculated into chickens by intravenous or wing-web routes, antibody which recognizes HN from purified NDV virions was produced. Protective immunity to NDV was generated in the chickens; at the highest dose of vaccine 100% of the chickens tested were protected against challenge with a virulent strain of NDV.

Animals

Protective immunity against avian influenza induced by a fowlpox virus recombinant.

Fowlpox virus, the prototypic virus of the genus Avipoxvirus has a natural host range limited to avian species. As such, fowlpox virus provides a suitable candidate for the development of a species-specific recombinant viral vector. This paper reports the development of a fowlpox virus recombinant expressing the haemagglutinin molecule from a highly virulent avian influenza virus. On immunization of chickens and turkeys with the recombinant, protection is afforded against a lethal challenge with either the homologous or a heterologous influenza virus strain.

Animals

Comparison of the locations of homologous fowlpox and vaccinia virus genes reveals major genome reorganization.

We have derived a restriction enzyme map for the fowlpox virus FP9 strain. Sites for BamHI, PvuII, PstI and NcoI have been mapped mainly by Southern blotting. The size of the genome derived from the restriction maps (254 kb) corresponds to the figure of 260 +/- 8 kb determined from analysis of genomic DNA by pulsed-field electrophoresis. The map can be compared with a previously published map for a different strain of fowlpox virus using the PstI digest which is common to both studies. Some 65 kb of fowlpox virus sequence, in 11 blocks, as well as individual M13 clones have been aligned with the map. Where those blocks correspond with blocks of homologous genes in vaccinia virus, it is possible to compare the genomic locations for those genes in the two viruses. This comparison reveals that, whereas there are blocks of sequence within which genes exist in the same relative position in the two viruses, the genomic location of those sequence blocks differs widely between the two viruses.

Deoxyribonuclease BamHI

Newcastle disease virus fusion protein expressed in a fowlpox virus recombinant confers protection in chickens.

A cDNA copy of the RNA encoding the fusion (F) protein of Newcastle disease virus (NDV) strain Texas, a velogenic strain of NDV, was obtained and the sequence was determined. The 1,792-base-pair sequence encodes a protein of 553 amino acids which has essential features previously established for the F protein of virulent NDV strains. These include the presence of three strongly hydrophobic regions and pairs of dibasic amino acids in the pentapeptide Arg-Arg-Gln-Arg-Arg preceding the putative cleavage site. When inserted into a fowlpox virus vector, a glycosylated protein was expressed and presented on the surface of infected chicken embryo fibroblast cells. The F protein expressed by the recombinant fowlpox virus was cleaved into two polypeptides. When inoculated into susceptible birds by a variety of routes, an immunological response was induced. Ocular or oral administration of the recombinant fowlpox virus gave partial protection, whereas both intramuscular and wing-web routes of inoculation gave complete protection after a single inoculation.

Amino Acid Sequence