Abstract
Purpose:To compare the anti-viral efficacy of type I interferon (IFN) plasmid cassettes against ocular herpes simplex virus type 1 (HSV-1) infection.
Methods:Plasmid constructs containing type I IFN transgenes (575-626 base pairs) including (IFN-a1, -a4, -a5, -a6, -a9, or -b) were expressed under the control of a human CMV immediate-early enhancer/promotor. The plasmids (100 ug/eye) were topically applied to mouse corneas 24 h prior to infection with HSV-1 (McKrae strain, 240 pfu/eye). Mice were assessed for cumulative survival. In a separate experiment, mouse cornea was transfected with either the IFN-a6 or IFN-b transgene and assessed for STAT-1, IFN-inducible gene (OAS and PKR), and viral gene expression by Western blot analysis and real time PCR 24 h following in situ transfection or 24 h post infection.
Results:Recipients of the murine IFN-b or IFN-a1 transgene showed the greatest degree of protection against HSV-1-mediated mortality compared to recipients of other type I IFN transgenes and significantly (p<.05) above the null vector and IFN-a5 and IFN-a6 transgene-treated mice. Interestingly, the IFN-a6 transgene induced similar levels of STAT1 and IFN-inducible gene expression in the cornea as recipients of the IFN-b transgene prior to and 24 h following infection with HSV-1. However, cornea transfected with the IFN-b transgene but not the IFN-a6 showed a significant (3-10 fold) reduction in HSV-1 immediate early (ICP27) and early (TK) gene expression in the cornea 24 h post infection.
Conclusion:The IFN-b transgene topically applied to the cornea of mice 24 h prior to HSV-1 infection protect against viral-mediated mortality by antagonizing HSV-1 immediate early and early gene expression through PKR and OAS independent pathways that may or may not involve STAT-1 expression.