Natural polymorphism of UL23 thymidine kinase and UL30 DNA polymerase among herpes simplex virus type1 and 2 strains

Abstract number: O336

Burrel S., Deback C., Le Labousse B., Conan F., Agut H., Boutolleau D.

Objectives: Genotypic detection of herpes simplex virus (HSV) resistance to antivirals is based on thymidine kinase (UL23) and DNA polymerase (UL30) gene sequencing. The interpretation of results requires distinguishing resistance mutations from natural interstrain sequence variations. The objective of this work was to assess extensively the natural polymorphism of pUL23 and pUL30 among HSV strains.

Methods: Three laboratory strains (KOS, G-HSV-2, MH2) and 54 clinical isolates (27 HSV-1 and 27 HSV-2) were studied. Forty strains were collected from patients who had not received any previous anti-HSV treatment, and 14 strains exhibited acyclovir and foscarnet phenotypic susceptibility using a plaque reduction assay. The entire open reading frame of UL23 and UL30 genes was sequenced. Nucleotide and amino acid sequences were compared with that of reference strains from Genbank: accession numbers X14112 (HSV-1 strain 17) and Z86099 (HSV2 strain HG52).

Results: The interstrain identity of UL23 gene ranged from 99.3% to 100% at the nucleotide level in the 57 HSV strains investigated. There were 19 and 11 variant nucleotides for HSV-1 and HSV-2 strains, respectively. Overall, 19 amino acid changes were identified for HSV-1 strains and 7 amino acid changes for HSV-2 strains (that is, 5.1% and 1.9% of the total codons of the protein, respectively). The analysis of UL30 gene showed >99.5% interstrain identity among all HSV strains. Surprisingly, in HSV-1 strains, 113 variant nucleotides were evidenced, of which 72% produced silent mutations, whereas in HSV-2 strains, only 28 were evidenced, of which 32% produced silent mutations. Thirty and 18 amino acid changes distributed across UL30 DNA polymerase were described for HSV-1 and HSV-2 strains, respectively, corresponding to 2.4% and 1.3% of the total codons of the protein. Of note, one HSV-2 isolate harboured a deletion at codons 1106–1111 in the C-terminal region of pUL30. For both viral proteins, 71 out of 74 amino acid changes identified lied within nonconserved regions.

Conclusion: Our results show that UL23 thymidine kinase and UL30 DNA polymerase are highly conserved among HSV strains, with a weaker variability for HSV-2 strains. Beside previously described mutations, a number of previously undescribed natural variations were identified. This work provides the natural polymorphism map of pUL23 and pUL30 among both HSV-1 and HSV-2 strains that will be helpful for HSV genotypic antiviral resistance testing.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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