Impact of HIV on the human alveolar environment drivingthe early events of Mycobacterium tuberculosis infection - ABSTRACT Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb), reaches the lung alveoli where it is in contact with the alveolar mucosa. This mucosal surface is lined by alveolar epithelial cells (ATs) and composed of a monolayer formed by surfactant lipids and a hypophase, called alveolar lining fluid (or ALF), containing soluble innate components and enzymes. M.tb is exposed to ALF for an undetermined period of time before and during its engulfment by host cells, primarily alveolar macrophages (AMs) but also ATs, providing a shield for M.tb and portal for dissemination. M.tb infection drives inflammation, which eventually attracts neutrophils, monocytes, eosinophils and other innate cells entering the alveoli from the periphery. Following primary infection and dissemination, tissue granulomas begin to develop. This proposal is in response to the specific RFA, “Analyzing Early Events in TB and TB/HIV Infection for Interventional Targets”. These earliest interactions, i.e., how the lung environment, specifically ALF and alveolar host cells interact with M.tb, are poorly understood, yet critical to impacting eradication or progression of M.tb infection. Our research program is focused on these earliest events for M.tb in the alveoli. Our data support the finding that M.tb’s interaction with ALF from HIV-infected individuals (as well as elderly individuals), fundamentally remodels the bacterial surface and its metabolism thereby affecting host cell entry, trafficking and host response, culminating in enhanced host susceptibility to infection. Thus, our central hypothesis is that the first interactions of M.tb with soluble human ALF components shape its cell surface and metabolic status, impacting its subsequent interactions with AMs and ATs, the two major resident alveolar cell populations, and leading to control or spread of M.tb infection. To address our hypothesis, we will systematically integrate our unique in vitro and in vivo models starting with single cell interactions and moving to an innovative lung-on-chip infection model with time-lapse imaging to reveal the dynamics of host- M.tb interactions at the air-liquid interface with spatiotemporal resolution, and an in vivo experimental approach to assess early dynamic interactions in the alveoli using the rhesus macaque (RM) model. We will also delineate the effects of HIV infection on alveolar composition & function, addressing how HIV’s effects drive M.tb faster replication and dissemination within the alveoli. The specific aims are to: 1) Determine how M.tb exposure to people living with HIV ALF (HIV-ALF) vs. control ALF generates early-stage M.tb metabolic adaptations that lead to host cell immune dysregulation; 2) Determine how the combined effect of exposure of alveolar cells and M.tb to HIV-ALF (vs. control ALF) causes dysfunctional alveolar immunity that accelerates M.tb growth and dissemination using a lung-on-chip (LoC) model; and 3) Determine how infection of BAL-acquired AMs by HIV or control ALF-exposed M.tb instilled in the airways alters the alveolar cellular immune response using the NHP model. Results from this proposal will move science forward by guiding the scientific community on the development of effective immune-based early interventions, specifically for people living with HIV.
