IFNB1 and infection: The amount of latency in IFNβ-/- mice infected with 1 × 103, 1 × 104, 1 × 105, or 2 × 105 PFU/eye of LAT(+) and LAT(-) viruses was similar to 2 × 105 copy numbers per microgram of TG DNA (Fig. 4A; P > 0.05 for all four infection doses, Fisher's exact test).