Perforin pathway is essential for protection of mice against lethal ocular HSV-1 challenge but not corneal scarring

Perforin (cytolysin; pore-forming protein) is expressed in both CD8+ cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, and is a major factor responsible for the cytolytic activities of these cells. Both CD8+ T-cells and NK cells are important in eliminating cells infected with certain viruses. We examined the role of perforin in a mouse model of HSV-1 infection using perforin-deficient mice. Naïve perforin knockout (perforin0/0) mice were more susceptible to lethal HSV-1 ocular challenge (60% survival), than naïve parental C57BL/6 (100% survival). In contrast, both C57BL/6 and perforin0/0 mice had similar levels of HSV-1 induced corneal scarring. Vaccination of perforin0/0 mice induced a significantly higher HSV-1 neutralizing antibody titer than vaccination of C57BL/6 mice, and the mice were completely protected against lethal ocular challenge. These results suggest that in naïve mice ocularly challenged with HSV-1, the perforin pathway was involved in protection against death, but not in protection against corneal scarring.