Catherine,
VZV reactivation is entirely controlled by CMI specific to that virus and I don't think dependant on TLR at all.
He may have an idiopathic CD4 deficiency or CD8 for that matter (although VZV specific CD4 are the predominant cell in the sensory neural ganglia).
It might be interesting to see if he has ever had testing for EBV prior or if he had evidence for reactivation or acute infection of EBV. Given his age this could well be reactivation a la EBV lymphoprolif disease.
HHV4 (VZV)and EBV have a totally different lifestyle and immunology to HSV1 and 2 (and to HHV6 and 8 for that matter) so wouldn't lump all the herpseviruses together.
I don't think that helps much though.
Daman Langguth
Wasting too much time on immunology of varicella.