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.
