Importance of NKT cells in resistance to herpes simplex virus, fate of virus-infected neurons, and level of latency in mice.

Herpes simplex virus type 1 (HSV-1) produces acute mucocutaneous infections, spread to sensory ganglia, and establishment of latency. In addition, neurovirulent strains have potential to invade the central nervous system (CNS), with potentially a lethal outcome. Early activation of defenses at all stages is essential to limit virus load and reduce the risk of neuronal damage, extensive zosteriform skin lesions, and catastrophic spread to the CNS. NKT cells respond rapidly, and we have shown previously that CD1d-deficient mice are compromised in controlling a neuroinvasive isolate of HSV-1. We now compare infection in Jalpha18 GKO and CD1d GKO mice, allowing direct assessment of the importance of invariant Valpha14(+) NKT cells and deduction of the role of the CD1d-restricted NKT cells with diverse T-cell receptors. The results indicate that both subsets of NKT cells contribute to virus control both in the afferent phase of infection and in determining the mortality, neuroinvasion, loss of sensory neurons, size of zosteriform, lesions and levels of latency. In particular, both are crucial determinants of clinical outcome, providing protection equivalent to a 1-log dose of virus. These NKT cells can be expected to provide protection at doses of virus that might be encountered naturally.