Found this info from a totally unrelated forum (UV studies) most of this
went over my head, but I thought I'd share anyway.

Herpes simplex virus (HSV) normally causes vescular lesions on mucocutaneous
surfaces but can also cause encephalitis. The virus can reactivate from the
latent state in neurons to form recrudescent lesions. One common stimulus
for reactivation is exposure to sunlight. In the present study, the effects
of irradiating rats with suberythemal ultraviolet (UV) before or after
infecting them epidermally with HSV was investigated. Preexposure to UV
impaired HSV-specific cellular immune responses, as indicated by delayed
type hypersensitivity (DTH) and in vitro lymphoproliferation assays.
However, the number and severity of the skin lesions were not altered. In
contrast, exposure after infection did not affect cellular immunity but
resulted in a large increase in the severity and number of lesions. In a
second series of experiments, the effects of preirradiating with UV on HSV
infection was examined using a route of inoculation which was not
skin-associated, namely intranasal, allowing direct noninvasive access to
the nervous system. It was found that suppressed DTH resulted, together with
an increase in the incidence and severity of neurological symptoms and an
increased viral load in the brain. Therefore, unlike the situation in the
skin, irradiation of rats before intranasal inoculation led to a suppressed
immune response to HSV which correlated with increased viral load and
symptoms. These results indicate that the effects of UV may be dependent on
whether the animal is exposed before or after the infection, and whether the
infection is skin-associated or systemic.