Location: Endemic Poultry Viral Diseases ResearchTitle: Comparative molecular characterization of three Gallid alphaherpesvirus type 3 strains 301B/1, HPRS24, and SB-1
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2020
Publication Date: 1/30/2020
Citation: Kim, T.N., Volkening, J.D., Spatz, S.J. 2020. Comparative molecular characterization of three Gallid alphaherpesvirus type 3 strains 301B/1, HPRS24, and SB-1. Avian Diseases. 64(2):174-182. https://doi.org/10.1637/0005-2086-64.2.174.
Interpretive Summary: Marek’s disease is an economically important poultry disease and the causative agent, Marek’s disease virus (MDV), is highly infectious in chicken flocks. Vaccination is the most efficacious method to control Marek’s disease outbreak. However MDV virulence has evolved since the introduction of Marek’s disease vaccines. Gallid alphaherpesvirus 3 (GaHV-3) was shown to be an effective vaccine candidate against Marek’s disease, particularly when it is used as a bivalent vaccine in a mixture with Turkey herpesvirus vaccine. Previously we had shown that GaHV-3 strain 301B/1 elicits a better protective immune response when compared to GaHV-3 strain SB1. We now have determined the complete DNA sequence of 301B/1 using Illumina MiSeq sequencing technology. The 301B/1 genome and open reading frames are more highly homologous with the SB-1 genome than the HPRS24 genome or any other Gallid alphaherpesviruses. Only 18 out of 126 genes differ from those of SB-1, and 7 of the genes have single nucleotide polymorphisms in the coding sequences that contain amino acid substitutions. Remarkably, unlike the SB-1 genome, no avian retrovirus long terminal repeat sequences were found within the 301B/1 genome. This report describes a genomic analysis of GaHV-3 strain 301B/1 to develop as a vector vaccine platform.
Technical Abstract: Marek's disease (MD) is a highly contagious lymphoproliferative disease of chickens caused by Gallid alphaherpesvirus type 2. Gallid alphaherpesvirus type 3 (GaHV-3) strain 301B/1 was previously shown to be an effective MD vaccine with synergistic efficacy when used as a bivalent vaccine with turkey herpesvirus. Since the nucleotide sequences of only two GaHV-3 strains have been determined, we sought to sequence the 301B/1 genome using Illumina MiSeq technology. Phylogenomic analysis indicated that 301B/1 is more closely related to other GaHV-3 strains (SB-1 and HPRS24) than to virulent or attenuated strains of GaHV-2. One hundred and twenty-six open reading frames (ORFs) have been identified within the 301B/1 genome with 108 ORFs showing a high degree of similarity to homologs found in the genomes of SB-1 and HPRS24; 14 ORFs are highly homologous (> 90% identity) with the corresponding ORFs within the SB-1 genome. The R-LORF8 and R-LORF9 genes are the most dissimilar to the collinear genes found in the SB-1 genome but are highly homologous (99%–100% identity) with those within the HPRS24 genome. Overall the 301B/1 genome is most similar to the SB-1 virus genome (99.1%) and to a lesser degree with the HPRS24 virus genome (97.7%). However, six 301B/1 ORFs (UL47, UL48, UL52, pp38, ICP4, and US10) have been identified that contain nonsynonymous substitutions relative to homologs found in the SB-1 genome. Notably, unlike the avian retrovirus long terminal repeat sequences found within the SB-1 genome, none were identified within the 301B/1 genome.