Abstract Macrophages are mononuclear phagocytes that play an important role in tissue homeostasis and resolution of inflammation and are crucial players in mounting potent antiviral immune responses. Previously in wild-type (WT) mice, we found that a balance of M1 and M2 macrophages is important for virus replication in the eye, eye disease, and latency-reactivation. During the current funding period, we showed that M1 macrophages play an important role in virus replication, eye disease, survival, phagocytosis, and autophagy in ocularly infected mice. Our progress during the current funding period has provided novel insights into potential mechanisms by which induction of macrophage memory may define the extent of primary infection and eye disease but not latency-reactivation. Building on our published and preliminary studies, we hypothesize that acquisition of macrophage memory phenotype plays a key role in determining virus replication, eye disease, and survival. Memory macrophages express IRGM1 (immunity-related GTPase family M protein) and in macrophages from latently infected mice, IRGM1 is upregulated in M1 but not M2 macrophages. Thus, the corollary of this hypothesis is that generation of memory M1 macrophage can be used to safeguard the integrity of the anterior segment of the eye including the cornea in response to viral infection. These observations also suggest mechanisms that may provide innovative potential therapeutic targets to prevent ocular HSV-1 infection and HSV-1-induced eye disease. Feasibility of the proposed studies is rooted in an experimental strategy that combines in vitro and in vivo studies with conditional knockout and IRGM1-/- mice to directly evaluate the contribution of IRGM1 to M1, and not M2, macrophage memory functions that affect virus replication in the eye, eye disease, and survival in ocularly infected mice. Our preliminary studies led to our overall hypothesis that macrophages adapt to HSV-1 infection, a property termed “trained immunity” or as originally reported for CD8 T cells, “memory immunity”. Understanding the properties of trained immunity in macrophages and in the earliest ocular infiltrates after HSV-1 infection, will improve our understanding of host defense mechanisms and the pathogenesis of innate-mediated diseases. We will test this model by: (1) Determining whether macrophages have memory to HSV-1 that helps to reduce ocular virus replication, inflammation, and eye disease; and (2) Determining whether M1 rather than M2 macrophages contribute to memory. CLINICAL SIGNIFICANCE: Because the extent and duration of initial virus replication are key determinants of subsequent pathologic inflammatory responses, accumulation of immune cell populations early in infection provides an important target for prevention. Results of the proposed studies will determine whether manipulating macrophage responses by regulating trained immunity can be used to reduce ocular viral load and accelerate ocular viral ...