1. Biomarkers of neuroinflammation: Using positron emission tomography (PET), we have recently imaged macrophage activation in human and non-human primate models of neurological disease. Using a novel radioligand (PK11195) to assess activated microglia in brains of living HIV-infected human and SIV-infected primates, these studies demonstrated the feasibility, but limited sensitivity of PK11195 PET in monitoring central nervous system (CNS) inflammation (Venneti et al., 2008; Venneti et al., 2004; Venneti et al., 2009; Wiley et al., 2009). While performing these PET studies, we took advantage of the study's serial time points to discover biomarkers of neuroinflammation in serum and cerebrospinal fluid. Using unbiased proteomic analysis with SELDI-TOF mass spectrometry, we discovered a highly sensitive and reproducible biomarker of CNS inflammation, chitinase 3-like 1 protein (CHI3L1). We and other groups have since observed expression of CHI3L1 in a broad spectrum of CNS inflammatory diseases (Bonneh-Barkay et al., 2010).
2. Control of neuroinflammation: While of great utility as a biomarker, CHI3L1 is becoming even more important as a member of a new class of proteins mechanistically involved in the control of neuroinflammation. These novel proteins modulate the interaction between inflammatory cells and CNS extracellular matrix. Using transgenic mice where the mouse homolog of CHI3L1 was deleted by homologous recombination, we have examined the role of this protein in animal models of multiple sclerosis (EAE) and traumatic brain injury (Bonneh-Barkay et al., 2012). In both models, deletion of CHI3L1 led to worse clinical and pathological outcome. Current studies in our lab are aimed at elucidating the molecular mechanism by which CHI3L1 limits inflammation and how to mimic its action using small molecules. These studies hold the potential of developing novel therapies to decrease neuroinflammation, potentially supplementing or synergistically interacting with current anti-inflammatories.
3. Age-related neurodegeneration: While intuitively obvious, it warrants remembering that the single most important determinant of neurodegeneration is age. Through extensive collaborations with the Alzheimer's Disease Research Center, we clinically document the neuropathology of AD and related diseases. The beta amyloid hypothesis of AD proposes that toxic fragments or oligomers of beta amyloid mediate neurodegeneration. We and others have explored the capacity of active immunization to eliminate beta amyloid from the aging primate brain (Kofler et al., 2012). Current studies in the lab are examining how lentiviral infection and combined anti-retroviral therapy modulate age related neurological processes and gene expression associated with neurodegeneration.
4. Viral encephalitis: Collaborations with other University of Pittsburgh investigators have allowed us to expand our studies of the brain's susceptibility to viral infections. Our research team has discovered the heightened susceptibility of the brain to aerosol transmission of common viral pathogens. Arboviruses that normally infect through insect vectors cause limited systemic disease, but when delivered through aerosol route, they rapidly cause lethal encephalitis. How the brain's innate immune response and systemic adaptive immunity protect the CNS is a current focus of the lab. We have discovered that host exposure to seasonal influenza determines susceptibility to lethal avian influenza. Newly proposed studies will elucidate the role of innate and adaptive immunity in conferring this protection. Importantly, from a public health perspective, this team is also researching how immunization protects or predisposes to encephalitis.