The overall goal of our proposed study is to establish the predictive correlation between neuroimaging markers of NeuroAIDS and the neuropathogenetic processes that occur as a result of the infection of the Central Nervous System (CNS) by the Human Immunodeficiency Virus (HIV-1). We propose the postmortem examination of brain specimens donated by HIV+ individuals who have been well-characterized radiologically, clinically, and behaviorally using different neuroimaging modalities at multiple levels of resolution. The correlation between imaging and neuropathological whole-brain data will be computed topographically and via the registration of complementary data sets relative to the same subject;in vivo and ex vivo. High-resolution MRI protocols, applied postmortem, will be used to localize and classify White Matter (WM) signal abnormalities and to measure morphometric parameters relative to cortical and subcortical Grey Matter (GM). Secondly, DTI-based Fractional Anisotropy (FA) and Mean Diffusivity (MD) maps, reflecting WM integrity will be registered to MRI volumetric data in order to highlight any discrepancy in the detection of macroscopic WM changes by different neuroimaging modalities. These maps will also be registered to newly-established DTI-based atlases of connectivity, identifying major fiber tracts that are compromised by the lesions, and thus tracing specific functional networks affected by WM pathology. We shall characterize for each case the relative contribution of GM and WM HIV-related changes to explain neurobehavioral profiles observed in the donor. Subsequent whole-brain histopathological protocols, using computer-aided, large-field microscopy and stereology, will produce quantitative maps of HIVE markers (i.e. viral burden, inflammation, axonal integrity, and cortical degeneration) directly comparable to neuroimaging data. For each brain specimen, the topographic registration of neuropathological and imaging data will be done using 2-dimensional (2D) and 3- dimensional (3D) routines combined for the optimal correlation between different modalities. This project establishes a unique context of analysis to compare specific neuropathological and neuroimaging markers. These are, for each subject, ultimately related to the characteristics of corresponding scans acquired in vivo. This `postmortem to in vivo'translation is the key to understanding the pathological basis of the imaging evidence that is clinically indispensable for the neurological diagnosis and the prognosis of the disease.
We will conduct, in a well characterized sample, a multi-parametric examination of neuropathogenetic phenomena that are induced by HIV infection, correlating markers of the disease revealed by different imaging modalities (in vivo and ex vivo) with those localized by specific histological methods. The study will improve our understanding of HIV neuropathogenesis towards the earliest detection by non-invasive means of neurological signs and response to treatment.
