HSV-1 infections are very frequent in the U.S. and are a major cause of viral-induced blindness. The corneal damage induced by HSV-1 appears to be mediated primarily by immune responses. We found that macrophages form early and predominant infiltrates in the corneas of mice ocularly infected with HSV-1. We have also shown that preferential expansion of the M2 macrophage subpopulation by injection of colony stimulating factor-1 (CSF- 1) reduced ocular virus replication and latency-reactivation, whereas activation of the M1 subpopulation was pro- inflammatory and exacerbated eye disease. Analyses of the natural history of very early infiltrates in ocularly infected mice suggest a dichotomy in the patterns of corneal infiltration by M1 and M2 macrophages that is temporally associated with subsequent involvement of other immune responses, clearance of the virus from the cornea, and establishment of latency. These results provide a framework for differentiating immune response- mediated exacerbation vs. immune-mediated control of acute and latent HSV-1 infections. Based on our published and preliminary data, our main hypothesis is that the natural variation in the activation of macrophages towards the M1 or M2 disease-relevant phenotype plays a key role in determining induction of inflammation, eye disease, and virus replication. Therefore, manipulation of M1 and M2 macrophage compartments can be used to safeguard the integrity of the anterior segment of the eye including the cornea in response to infection. Specifically, we will test whether manipulation of autophagy in the macrophage subsets can be used to control ocular HSV-1 infection. The feasibility of the proposed studies is rooted in our strategy that utilizes conditional knockout mice that we have generated to directly evaluate the M1 and M2 functions in vivo with regards to virus replication in the eye, eye disease and establishment of latency-reactivation in ocularly infected mice. We will: (1) Test if altering the phenotype of macrophage activation towards M2 in the cornea of ocularly infected mice will lead to a reduction in primary infection, inflammatory responses and eye disease, and a reduction in latency- reactivation; and (2) Test if inhibition of autophagy in M2 macrophages enhances eye disease and latency- reactivation, while its inhibition in M1 macrophages decreases inflammation, eye disease and latency- reactivation. We will determine the impact of blocking autophagy in transgenic mice expressing the anti- autophagy gene of HSV-1 (i.e., ?34.5) under the M1 (NOS2) or the M2 (Arg1) promoters following infection with WT HSV-1 strain McKrae or a ?34.5 deletion mutant of HSV-1 strain McKrae. In both Aims, we will further test the mechanisms associated with amelioration of the disease process in terms of quantification of antiviral responses, phagocytosis and/or autophagy in the macrophages and the impact on other immune infiltrates and cytokine release.
Herpes simplex virus (HSV-1) infection damages the cornea and is the leading cause of corneal blindness due to infections in the USA. Our recent novel findings indicate that a specific subset of macrophages (M2 cells) plays a crucial role in very early inhibition of both the infection and inflammatory responses thereby blocking the pathways that lead to irreversible corneal damage. We will test this hypothesis and potential therapeutic strategies that favor this response through in vivo analysis using a unique set of clinically relevant mouse models and reagents.
