Saturday, June 19, 2021
6/19/2021
ABSTRACT The goal of this renewal application is to determine if blocking the mechanisms involved in intracellular HSV-1 gK processing and trafficking to the cell surface reduces virus replication and infectivity and thereby corneal scarring (CS). It is well established that CS is the result of virus-induced immune responses although the identity of the pathogenic responses is controversial. Similarly, the HSV-1 gene(s) involved in eye disease is not yet known although several lines of evidence indicate that gK plays a crucial role in replication and infectivity as exemplified by the inability of HSV-1 gK mutants to grow in cells lacking gK as they fail to acquire a cytoplasmic envelope efficiently and are unable to infect and establish latency in neurons. Our progress during the current funding period has provided novel insights into potential mechanisms of regulating gK expression in conjunction with its binding to UL20 and suggest that SPP may define the extent of primary infections, latency-reactivation, and CS. We have now shown that: (1) Binding of gK to SPP and UL20 to GODZ is required for HSV-1-induced CS; and (2) Amino acids 31-46 of gK are involved in binding to SPP, aa 280-295 of gK bind to UL20, and aa 51-65 of UL20 bind to GODZ (preliminary studies). These observations suggest mechanisms that may reveal innovative potential therapeutic targets to prevent ocular HSV-1 infection and CS. Based on our data, we suggest a hypothetical model of the mechanisms underlying the pathogenic effects of gK. In this model, the pathogenic effects of gK during primary ocular infection are mediated by two different, but interrelated, mechanisms in which (i) gK binds to SPP in the endoplasmic reticulum (ER) and UL20 in the Golgi, leading to increased virus replication and cell surface expression of gK that is necessary for gK-induced CS and increased eye disease; and (ii) UL20 also binds to GODZ in the Golgi, which is required for cell surface expression of gK. Thus, potential therapies might include blocking of gK-SPP, gK-UL20, UL20- GODZ interactions, or a combination of these strategies. We will test a hypothetical model in which the pathogenic effects of gK during primary ocular infection is mediated by three inter-related mechanisms: (i) gK binds to SPP leading to higher levels of virus replication; (ii) gK binds to UL20, which is required for the cell surface expression of gK; and (iii) UL20 binds to GODZ, which is required for UL20 palmitoylation and thus its proper binding to gK. We will: (1) Test the hypothesis that complete absence of SPP in peripheral nerves or eyes will reduce primary HSV-1 infection, latency-reactivation, and eye disease in ocularly infected mice compared with tamoxifen-inducible SPP depleted mice; and (2) Identifying effective therapeutic targets to reduce HSV-1 primary infection, latency-reactivation, and thus HSV-1-induced CS. CLINICAL SIGNIFICANCE: HSV-1-induced CS can lead to blindness and is the leading cause of infectious blindness in developed countries but there is no FDA approved drug for its treatment. The proposed studies represent an entirely novel approach to the development of effective strategies for the prevention and treatment of this disease.
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