Five unique open reading frames of infectious laryngotracheitis virus are expressed during infection but are dispensable for virus replication in cell culture.
The chicken alphaherpesvirus infectious laryngotracheitis virus (ILTV) exhibits several unique genetic features including an internal inversion of a conserved part of the unique long genome region. At one end, this inversion is preceded by a cluster of five open reading frames (ORFs) of 335-411 codons, designated ORF A to ORF E, that are not present in any other known herpesvirus genome. In this report we analysed expression of these genes and identified the corresponding viral RNA and protein products. Northern blot analyses showed 3'-coterminal transcripts of ORFs A and B, and monocistronic mRNAs of ORFs C and D. ORF E is part of a 3'-coterminal transcription unit that includes the conserved glycoprotein H and thymidine kinase genes. Monospecific antisera obtained after immunization of rabbits with bacterial fusion proteins allowed detection of the protein products of ORF A (40 kDa), ORF B (34 kDa), ORF C (38 and 30 kDa), ORF D (41 kDa) and ORF E (44 kDa) in ILTV-infected cells. For functional analyses, five virus recombinants possessing deletions within the individual ORFs and concomitant insertions of a reporter gene cassette encoding green fluorescent protein were generated. All virus mutants were replication competent in cell culture, but exhibited reduced virus titres or plaque sizes when compared to wild-type ILTV. These findings indicate that the ILTV-specific ORF A to ORF E genes might be important for virus replication in the natural host organism.
Veits
Jutta
J
Institute of Molecular Biology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17493 Greifswald - Insel Riems, Germany.
Mettenleiter
Thomas C
TC
Institute of Molecular Biology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17493 Greifswald - Insel Riems, Germany.
Fuchs
Walter
W
Institute of Molecular Biology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17493 Greifswald - Insel Riems, Germany.
D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D015870:Gene Expression; D016679:Genome, Viral; D006566:Herpesviridae Infections / Q000662:veterinary / Q000821:virology; D001352:Herpesvirus 1, Gallid / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology; D016366:Open Reading Frames; D010957:Plasmids / Q000235:genetics; D011201:Poultry Diseases / Q000821:virology; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D017384:Sequence Deletion; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
D012333:RNA, Messenger; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins