PROJECT SUMMARY: Despite the widespread use of antiretroviral therapy (ART), the prevalence of neuro- inflammation remains high and is believed to involve >40% of HIV+ individuals. This inflammatory state likely causes cognitive dysfunction that impacts everyday functioning and increases morbidity and mortality among ART-suppressed HIV-infected individuals. However, the physiological processes underlying this neuro- inflammation remain poorly understood. This proposal builds on our ongoing investigation on whether glycomic alterations in circulating glycoproteins and exosomes play a role in the pathogenesis of HIV-associated neuro- inflammation and cognitive disorders. Our preliminary data demonstrate that higher levels of the pro- inflammatory hypo-sialylated glycans in plasma, plasma exosomes, and cerebrospinal fluid (CSF) strongly correlate with worse neurological impairment in HIV+ ART-suppressed individuals. However, whether glycomic alterations drive neuro-inflammation during HIV infection remains unknown. In this project we will test the central hypothesis that host glycomic dysregulation, in particular hypo-sialyation of circulating glycoproteins and exosomes, contributes to neuroinflammation and the pathogenesis of HIV-associated co- morbidities affecting the central nervous system (CNS). In Aim 1, we will identify the mechanism of the neuro-inflammatory effects of hypo-sialylated glycans during ART-suppressed HIV infection. We will use hyper-sialylated and hypo-sialylated glycoproteins and exosomes isolated from the plasma of HIV+ ART+ individuals with neurological impairments, in an ex-vivo model of monocyte activation/inflammation and migration, in the presence or absence of glycan signaling inhibitors. In Aim 2, we will test the hypothesis that manipulating the levels of circulating sialic acid impacts neuro- inflammation and cognitive behavior in a mouse model of HIV-associated neurological impairment. We will use the EcoHIV mouse model (using chimeric HIV capable of infecting mice) that was recently used as a successful model of HIV pathogenesis and neurological impairment. Using acutely and chronically EcoHIV-infected mice (with and without ART), that receive either a combination of sialic acid nanoparticles and sialidase inhibitors or nude nanoparticles as controls, we will evaluate: (1) levels of cognitive impairment; (2) brain markers of inflammation/immune activation [gene array and immunohistochemistry]; (3) EcoHIV expression in brain tissues [qPCR]; and (4) sialylation of brain tissues and brain-derived exosomes [lectin array and flow cytometry]. We will take advantage of recent advances in the emerging field of glycomics and an animal model of HIV-associated neurological impairment, to clarify the inter-related mechanisms between neuro-inflammation, cognitive dysfunction, and host immunity. Our work aims to create a new paradigm for discovering novel glycan- based interactions that can be targeted to prevent neuro-inflammation that persists in individuals living with HIV despite viral suppression.

PROJECT NARRATIVE Even in the era of ART, HIV+ individuals continue to suffer from neurocognitive disorders, likely arising from inflammatory processes in the brain. This study seeks to understand what causes this inflammation, with the hypothesis that the interactions between monocytes, an inflammatory type of white blood cell, and specific types of carbohydrate molecules (glycans) promote the development of cognitive impairment in HIV+ individuals who have achieved suppression of virus to undetectable levels. Understanding how these cell-free carbohydrates affect inflammation in the brain will be important for developing novel therapeutics to prevent, allow recovery from, or cure HIV-associated neurocognitive disorders.