This proposal examines the role of herpes simplex virus type 1 (HSV-1) glycoproteins E and I (gE, gl) in immune evasion, and the contributions of gE, gl and Us9 to virus spread in neurons. We have three specific aims: i) to characterize mechanisms of gE-and gl-mediated immune evasion; ii) to define mechanisms of gE- and gl-mediated anterograde spread (from cell body to axon terminus); and iii) to evaluate gE-mediated retrograde spread (from axon terminus to cell body) and the role of Us9 in virus spread. We present mass spectrometry (MALDI-TOF) results that identify several cellular proteins that interact with gE or gl.
In Aim 1 we examine whether gE or gl inhibits inflammation and immunity induced by these cellular proteins. We use the mouse retina infection model and rat superior cervical ganglion (SCO) neuron cultures to demonstrate that HSV-1 gE null virus fails to transport virion proteins from the cell body to the axon initial segment (anterograde spread defect).
In Aim 2 we evaluate three hypotheses to explain this defect in anterograde spread: one examines whether gE is required for the assembly of virions in the neuron cell body; the second postulates that gE overcomes a physical barrier imposed by the dense cytoskeletal network at the axon initial segment; and the third determines whether gE links the virion to kinesin motors for rapid axonal transport. We demonstrate in the mouse retina infection model that HSV-1 gE null virus is also impaired in retrograde spread. This defect distinguishes HSV-1 gE from pseudorabies virus (PRV) gE, since PRV gE is not required for retrograde spread.
In Aim 3 we use SCG neuron cultures to evaluate the site of the retrograde spread defect for HSV-1 gE mutants. One HSV-1 gE mutant virus with a different spread phenotype than wild-type or gE null virus has an abnormal interaction with Us9. This result led to studies described in Aim 3 that evaluate the spread phenotype of HSV-1 Us9 null mutants to determine whether HSV-1 gE, gl and Us9 mediate anterograde spread by different mechanisms. HSV-1 causes significant morbidity and mortality, in part because it establishes latency in neurons and produces recurrent infections in immune individuals. This proposal addresses fundamental properties of HSV-1 gE, gl and Us9 related to infection of neurons and immune evasion. Understanding these activites may lead to novel therapies and better vaccines. ? ? ? ?
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