LP-BM5-infected programmed death-1 (PD-1) knockout (KO) animals were resistant to herpes simplex virus (HSV) brain infection. PD-1 KO and C57BL/6 mice infected with LP-BM5 (8 w post-infection) were super-infected with HSV. At 7 d post-HSV infection animals were sacrificed and brain tissues were harvested. Data shown represent virus recovery from the brain stem and trigeminal ganglia. Data are expressed as percentage of positive tissues. Total RNA extracted from the trigeminal ganglia and brain stem of three to five mice/time point was reverse transcribed and examined for the expression of gD mRNA.