Different Linkages in Long and Short Regions of the Genomes of Duck Enteritis Virus Clone-03 and VAC Strains

The two types of the virus were found to be different, and duck enteritis virus (DEV) should be a separate member of the sub-family, Alphaherpesvirinae, according to new research from Harbin Veterinary Research Institute in China.

22 July 2011

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Xiaoli Liu and colleagues at the Division of Avian Infectious Diseases at Harbin Veterinary Research Institute have published their study on DEV in a recent issue of Virology Journal.

Duck enteritis virus (DEV) is an unassigned member in the family Herpesviridae, they explain in their paper. To demonstrate the evolutionary position of DEV in the family Herpesviridae, they described a 42,897-base-pair (bp) fragment. They also demonstrated a novel genomic organisation at one end of the long (L) region and in the entire short (S) region in the Clone-03 strain of DEV.

A 42,897-bp fragment located downstream of the LOFR11 gene was amplified from the Clone-03 strain of DEV by using 'targeted gene walking PCR'.

Lui and colleagues predicted 22 open reading frames (ORFs) and determined them in the following order: 5'-LORF11-RLORF1-ORF1-ICP4-S1-S2-US1-US10-SORF3-US2-MDV091.5-like-US3-US4-US5-US6-US7-US8-ORFx-US1-S2-S1-ICP4 -3'.

This was different from that of the published VAC strain, both in the linkage of the L region and S region, and in the length of the US10 and US7 proteins.

The MDV091.5-like gene, ORFx gene, S1 gene and S2 gene were first observed in the DEV genome, according to the Harbin researchers.

The lengths of DEV US10 and US7 were determined to be 311 and 371 amino acids, respectively, in the Clone-03 strain of DEV, and these were different from those of other strains.

The comparison of genomic organisation in the fragment with those of other herpesviruses showed that DEV possesses some unique characteristics, such as the duplicated US1 at each end of the US region, and the US5, which showed no homology with those of other herpesviruses. In addition, the results of phylogenetic analysis of ORFs in the represented fragment indicated that DEV is closest to its counterparts VZV (Varicellovirus) and other avian herpesviruses.

Lui and colleagues concluded that the molecular characteristics of the 42,897-bp fragment of clone-03 were different from those of the VAC strain. The phylogenetic analysis of genes in this region showed that DEV should be a separate member of the subfamily Alphaherpesvirinae.

Reference

Liu X., Z. Han, Y. Shao, Y. Li, H. Li, X. Kong and S. Liu. 2011. Different linkages in the long and short regions of the genomes of duck enteritis virus clone-03 and VAC strains. Virology Journal, 8:200. doi:10.1186/1743-422X-8-200