The role of alveolar macrophages in Influenza A infection

Macrophages are innate immune cells that function as the first line defense against microorganisms. My project aims to generate transgenic models by which I can ablate macrophages in vivo in order to study their contribution in different experimental situations. In particular, I am harnessing Influenza A mouse model to better elucidate the roles of specific immune cell subsets. I am exploiting bacterial artificial chromosome transgenesis approach to incorporate the gene coding for human diphtheria toxin receptor (DTR) under the control of specific myeloid subset marker. The construct was then electroporated into BALB/c embryonic stem cells, from which transgenic mice were derived. Diphtheria toxin injection into the transgenic mice will deplete specific subsets where the myeloid marker of interest is expressed. I selected CD169 (also known as Siglec1 or Sialoadhesin) as the targeted marker due to its macrophage-specific expression patterns. CD169 is a sialic acid binding Iglike lectin which mediates macrophage adhesive function. This molecule is strongly expressed by specific populations of tissue macrophages in the spleen and lymph node; namely by marginal zone metallophilic macrophages and subcapsular sinus macrophages, respectively. Recent data highlights the importance of CD169 macrophages in concentrating pathogens to prevent systemic spread, eliciting Interferon-I responses upon viral infection, and even presentation of antigen to B cells in the lymph nodes. Hence, CD169-DTR mouse is an attractive tool to study role of tissue macrophage subsets in numerous settings.Currently, I have tested and characterized CD169-DTR mice generated in our laboratory. Intra-peritoneal administration of DT ablates tissue macrophages in different lymphoid and peripheral organs such as spleen, lymph nodes, bone marrow, and lungs. Lung and broncho-alveolar lavage analysis reveals >90% depletion of alveolar macrophages (CD11c+CD11bloF4/80+ cells) upon DT injection in CD169-DTR+/- mice. I then infected control and DT-treated CD169-DTR mice with mild dose of mouse-adapted Influenza A strain PR8. Collectively, my results suggest that alveolar macrophages play an essential role in executing antiviral immune responses in the pulmonary environment. Future research will be conducted to understand how the alveolar macrophages control different components of antiviral immunity. Knowledge provided by studying the roles of alveolar macrophage using CD169-DTR mice will further our understanding in influenza immunity and benefit translational research.DOCTOR OF PHILOSOPHY (SBS