FIG 4.

Duration and lack of reactivation is affected in the absence of CD28, CTLA4, and PD-L1 in infected mice. Corneas from CD28^−/−, CD28^−/− CTLA4^−/−, PD-L1^−/−, and WT mice were scarified before ocular infection and infected ocularly with 2 × 10⁵ PFU per eye of KOS virus as described for Fig. 1. On day 28 p.i., TG from infected mice were harvested for explant reactivation. (A) Reactivated explant TG. Individual TGs from infected mice were incubated in 1.5 ml of tissue culture medium at 37°C, and the presence of infectious virus was monitored for 20 days as described in Materials and Methods. For CD28^−/− and CD28^−/− CTLA4^−/− infected mice, 34 TG from 17 mice were used. For PD-L1^−/− infected mice, 20 TG from 10 mice were used, and 38 TG from 19 mice were used for WT mice. The results are shown as the number of TG that reactivated daily. Each point represents the mean ± SEM from infected CD28^−/− mice (11 TG), CD28^−/− CTLA4^−/− mice (10 TG), PD-L1^−/− mice (4 TG), and WT mice (31 TG). (B) Percentage of TG that did not reactivate after 20 days of explant. Not all TG reactivated during the 20-day monitoring period. In CD28^−/− infected mice, 23/34 TG did not reactivate; in CD28^−/− CTLA4^−/− infected mice, 24/34 TG did not reactivate; in PD-L1^−/− infected mice, 16/20 TG did not reactivate; and in WT infected mice, 7/38 TG did not reactivate. The numbers of TG that did not reactivate are shown as percentages of total TG used per mouse strain. (A) Number of reactivated explant TG. (B) Percentage of explant TG that were not reactivated.