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Title: Comparative genomic sequence analysis of the Marek’s disease vaccine strain SB-1

Author
item Spatz, Stephen
item SCHAT, KAREL - Cornell University

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2011
Publication Date: 2/20/2011
Citation: Spatz, S.J., Schat, K.A. 2011. Comparative genomic sequence analysis of the Marek’s disease vaccine strain SB-1. Virus Genes. 42:331-338.

Interpretive Summary: The nucleotide sequence of the vaccine strain SB-1 was determined. Many differences were identified compared to as similar virus known as HPRS24. Interestingly, SB-1 protect against virulent Marek’s disease virus challenge while HPRS24 does not. A bioinformatic analysis shed light onto why the SB-1 strain is more protective.

Technical Abstract: Marek’s disease virus (MDV) is one of the most oncogenic herpesviruses known and induces a rapid onset T-cell lymphoma and demyelinating disease in chickens. Since the 1970s, the disease has been controlled through mass vaccination with meleagrid herpesvirus type 1 (MeHV-1). Over time the efficacy of the vaccine decreased, and in the 1980s a divalent vaccine consisting of MeHV-1 and a non-oncogenic gallid herpesvirus type 3 (GaHV-3) strain known as SB-1 was introduced to control this costly pathogen. The complete DNA sequence of this strain was recently determined using 454 pyrosequencing. The genome consists of 165,994 bp with an overall gene organization typical of avian class E herpesviruses. A total of 521 open reading frames (>25 amino acids) were examined for homology to protein sequences present in GenBank (E-values <0.9). Of the 128 ORF hits, 75 ORFs showed homology to well characterized alphaherpesviral proteins of the unique long region (UL1 through UL54), the unique short region (US1, US10, US2, US3, US6, US7 and US8) and ICP4 within the repeat long regions. Overall, the gene organization is more similar to that of MeHV-1 and gallid herpesvirus type 2 than to gallid herpesvirus type 1. Phylogenetically, this strain partitions in its own branch along with the GaHV-3 strain HPRS24. In comparison between the two GaHV-3 strains, 21 ORFs differ in the number of predicted amino acids; of these, eight (UL3.5, UL5, UL9, UL28, UL30, UL36, UL37 and UL50) encode well characterized alphaherpesviral proteins.