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. 1998 Jul;72(7):5626–5637. doi: 10.1128/jvi.72.7.5626-5637.1998

FIG. 5.

FIG. 5

Absence of Rosco- or Olo-resistant variants of HSV after 11 passages in selective medium. HSV-1 strain KOS was passaged in medium containing either Olo, Rosco, or PAA as described in the text and in Table 1, footnote a. After 11 passages in culture, 1,000 PFU of each passage was used to infect 105 Vero cells in duplicate. One set of infected cells was treated with inhibitory concentrations of the selective drugs (100 μg of PAA/ml, 100 μM Rosco, or 150 μM Olo), while the other set was left untreated (medium without drug). Virus was harvested and titrated at 24 hpi. The medium in cultures treated with Olo was changed at 6 hpi. The percentage of resistant virus after each passage was calculated by using the formula percent resistance = 100 × (PFU in the presence of selection drug/PFU in medium without drug) and is plotted against the passage number. (A) Percentage of virus resistant to Olo, Rosco, or PAA. The percentage of virus resistant to Rosco in the four different Rosco passage series (ROSCO 1, 1b, 9, and 9b) was so low as to be indistinguishable on this scale. Therefore, only the ROSCO 1 selection series was plotted. (B) Percentage of virus resistant to Rosco at different passages in the four Rosco selection series. Note the expanded scale of the y axis. The percentage of virus resistant to Olo or PAA was higher than 0.2% from the first passage on. Thus, the Olo and PAA selection series could not be plotted on this graph. ROSCO 1, selection of HSV-1 KOS in high Rosco concentrations (75, 50, 30, 30, and 50 μM from passages 7 to 11, respectively); ROSCO 1b, selection of HSV-1 KOS in low Rosco concentrations (40, 30, 30, and 50 μM from passages 7 to 10, respectively); ROSCO 9, selection in high Rosco concentrations (75, 50, 30, 30, and 50 μM from passages 7 to 11, respectively) of an HSV-1 stock previously passaged nine times in Olo; ROSCO 9b, selection in low Rosco concentrations (40, 30, 30, and 50 μM from passages 7 to 10, respectively) of an HSV-1 stock previously passaged nine times in Olo. See Table 1 and the text for details.