The authors wish to draw attention to the following errors in their article:

On page 15 an incorrect sequence database was referenced. The sentence ‘A set of eight pairs of overlapping HSV-1-specific primers (designed on the basis of HSV-1 strain 17 sequence; Genbank accession number NC001806) was used (McGeoch et al., 1988).’ should read ‘A set of eight pairs of overlapping HSV-1-specific primers (designed on the basis of HSV-1 strain 17 sequence; RefSeq accession number NC001806) was used (McGeoch et al., 1988).’

On Table 2 an incorrect symbol was used: ‘^$reported by Liuzzi et al., 2004’ should be replaced by ‘^♠reported by Liuzzi et al., 2004’. A corrected table can be found below.

On Table 3 the 5th column heading is incorrect: ‘BAY 57–1293 concentration, mg/ml’ should read ‘BAY 57–1293 concentration µg/ml’. A corrected table can be found below.

Table 2.

Observed frequency of BAY 57-1293 and other HPI-resistant variants in various laboratory isolates of HSV-1 and mutations in the helicase (UL5) protein

HPI	HSV-1 parental strain	Frequency*	Level of resistance, fold increase in ED₅₀ (example)	Amino acid substitution in HSV-1 UL5

BAY 57-1293^†	F	0.5–4.5 in 10⁶	>5 (n/s)	M355→T
	F	–	>150 (n/s)	K356→Q
	F	–	>400 (n/s)	G352→V
BAY 57-1293	SC16 crude	>1 in 10⁵^‡	15 (E cl-2)	M355→T
	SC16 crude	∼1 in 2×10⁶	125 (C cl-2)	K356→T^§
	SC16 cl-2	1 in 5×10⁶	80 (BAYr1)	A4→V^§K356→Q
	SC16 cl-2	1 in10⁶	4,000 (BAYr2)	G352→R^§
BAY 57-1293	PDK crude	1 in 4×10⁴^¶	50 (PDK crude-rm-1)	A199→T^§
	PDK cl-1	1 in 3×10⁶	50 (BAY-Pr1)	None
	PDK cl-1	1 in 3×10⁶	2,000 (BAY-Pr2)	K356→T^§
BILS 22 BS^♠	KOS	∼1 in 10⁶	38 (K138^r3)	G352→C
	KOS	∼1 in 10⁶	316 (K22^r5)	G352→V
	KOS	∼1 in10⁶	2,500 (K22^r1)	K356→N
T157602^$	n/s	∼1 in 10⁷	n/s (R1, R2 & R3)	n/s

Frequency expressed as observed number of drug-resistant plaque-forming units (PFU) in the total number of PFU screened;

†

reported by Kleymann et al., 2002;

‡

SC16 crude stock reproducibly contained >10× more drug-resistant variants than that observed for plaque-purified SC16 cl-2;

novel substitutions, not previously reported as BAY 57-1293-resistant mutations;

PDK crude stock reproducibly contained >70 × more drug-resistant variants than that observed for plaque-purified PDK cl-1;

♠

reported by Liuzzi et al., 2004;

reported by Spector et al., 1998. Bold type indicates the BAY 57-1293-resistant variants occurring at high frequency and the corresponding laboratory isolates in which they were detected. ED₅₀, 50% effective dose; HPI, helicase-primase inhibitor; HSV, herpes simplex virus; n/s, not specified.

Table 3.

A summary of BAY 57-1293-resistant variants showing the methods used for their selection

Parent virus	Variant clone	ED_50′ μg/ml	Fold-resistance	BAY 57-1293 concentration, μg/ml	Method of selection (protocol)

SC16 crude	E-cl-2	0.3*	15	0.1	Pre-incubated and replenished:24 h interval × 1 day
SC16 crude	C-cl-2	2.5*	125	1.0	Pre-incubated and replenished:24 h interval × 1 day
SC16 cl-2	BAYr1	0.8^†	80	0.1	One exposure
SC16 cl-2	BAYr2	40^†	4,000	1.0	Pre-incubated and replenished:24 h interval × 5 days
PDK crude	PDK cr-rm-1	2^‡	50	1.0	Pre-incubated and replenished:24 h interval × 1 day
PDK cl-1	BAY-Pr1	2^‡,§	50	0.3	One exposure
PDK cl-1	BAY-Pr2	79^§	2,000	0.3 & 10	Two exposures

Fifty percent effective dose (ED₅₀)data was determined by plaque reduction assay in Vero cells and was significantly different from respective wild-type in an un-paired 2-tailed t-test (P<0.001).

From Figure 6A;

†

from Figure 6B;

‡

from Figure 6C;

from Figure 6D.

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High Frequency of Spontaneous Helicase-Primase Inhibitor (BAY 57–1293) Drug-Resistant Variants in Certain Laboratory Isolates of HSV-1