A single drug-resistance mutation in HSV-1 UL52 primase points to a difference between two helicase-primase inhibitors in their mode of interaction with the antiviral target.
OBJECTIVE
To investigate the mechanism of action of the helicase-primase inhibitors (HPIs) BAY 57-1293 and BILS 22 BS by selection and characterization of drug-resistant herpes simplex virus (HSV)-1 mutants.


METHODS
HSV-1 mutants were selected using BAY 57-1293 in Vero cells. Resistance mutations identified in the UL5 helicase or UL52 primase genes were validated by marker transfer. Cross-resistance to the structurally distinct BILS 22 BS was measured by ID(50) determinations.


RESULTS
(i) A single mutation (UL52: A899T) confers 43-fold resistance to BAY 57-1293, but does not confer any resistance to BILS 22 BS. (ii) A double mutant (UL52: A899T and UL5: K356T) is 2500-fold resistant to BAY 57-1293, which is more than 17 times the sum of fold-resistance due to the individual mutations, UL52: A899T (43-fold) and UL5: K356T (100-fold). (iii) Virus containing the single helicase mutation and the double mutant with mutations in both helicase and primase showed equal resistance to BILS 22 BS (70-fold).


CONCLUSIONS
By measuring the relative inhibitory concentrations required to overcome particular mutations in the helicase and primase proteins, evidence was obtained that BAY 57-1293 interacts with both components of the helicase-primase complex to achieve maximum potency, whereas for BILS 22BS, this may not be the case. Furthermore, our observations suggest that BAY 57-1293 interacts simultaneously with UL5 and UL52. Overall, the results suggest that these two potent HPIs interact differently with the helicase-primase complex.
Biswas
Subhajit
S
Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
Kleymann
Gerald
G
Swift
Mihaiela
M
Tiley
Laurence S
LS
Lyall
Jonathan
J
Aguirre-Hernández
Jesús
J
Field
Hugh J
HJ
D000998:Antiviral Agents / Q000494:pharmacology*; D004265:DNA Helicases / Q000037:antagonists & inhibitors* / Q000235:genetics*; D019915:DNA Primase / Q000037:antagonists & inhibitors* / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D024882:Drug Resistance, Viral / Q000235:genetics*; D018259:Herpesvirus 1, Human / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D011725:Pyridines / Q000494:pharmacology*; D013449:Sulfonamides; D013844:Thiazoles / Q000494:pharmacology*; D014764:Viral Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics*
D000998:Antiviral Agents; C529368:BILS 22 BS; D011725:Pyridines; D013449:Sulfonamides; D013844:Thiazoles; D014764:Viral Proteins; C453221:pritelivir; D019915:DNA Primase; C062021:helicase-primase, Human herpesvirus 1; D004265:DNA Helicases