Following ocular infection of normal mice, herpes simplex virus type 1 (HSV-1) establishes a latent infection in the trigeminal ganglia (TG) with the complete absence of detectable infectious virus. In this study, the role of CD4+ and CD8+ T cell dependent immune responses is examined in relation to clearing infectious virus from the TG following HSV-1 ocular challenge. Nude mice, which lack T cells, and MHC(o/o) mice, which lack both MHC class I and MHC class II, were challenged ocularly with wild-type HSV-1. Over 70% of the TG from mice surviving the infection contained infectious virus, indicative of a chronic infection in these TG, rather than a latent infection. No infectious virus was detected in TGs from infected C57BL/6 parental mice. Ocular challenge Of CD4(o/o) A(β)(o/o), CD8(o/o) or β2m(o/o) mice resulted in latent rather than chronic infection. Similarly, when C57BL/6 mice were depleted for CD4+ or CD8+ T cells from 4 days before ocular challenge to 26 days after ocular challenge, no free virus was detected in TGs of challenged mice. In contrast, when mice were depleted of both their CD4+ and CD8+ T cells, over 90% of TGs were positive for free virus, suggesting that the lack of virus clearance was due to the combined lack of both CD4+ T cells and CD8+ T cells (i.e. in the presence of either CD4+ T cells or CD8+ T cells alone all of the infectious virus was cleaved and latency was established).
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