CD4 and infection: Further, IFNγ-secreting CD4+ T cells were detected on day 6, day 10 and day 14 post infection (p.i.)(Fig. 1c) using an enzyme linked immunospot assay (Elispot) under ex vivo stimulation with heat-inactivated HSV-1 (Heat-iHSV) for 24–48 hours.