Human Interleukin-3/Granulocyte Macrophage-Colony Stimulating Factor Knock-In Mice Support Human Myeloid Cell Reconstitution and Human Immune Responses In the Lung.

Abstract 3789

Humanized mice, i.e. mice with a functional human immune system, have great potential to study human immunology in vivo and to allow vaccine testing. To this end, mice need to fully support engraftment with human immune cells, allow infection with human pathogens, and mount effective human immune responses to pathogens. A major limitation of current humanized mice is the poor development and function of human myeloid cells. Here we report a novel strategy to overcome this limitation by generating human interleukin-3/granulocyte macrophage colony stimulating factor knock-in (hIL-3/GM-CSF KI) mice to create a better environment for human myeloid cells. These mice faithfully expressed human GM-CSF and IL-3 and developed pulmonary alveolar proteinosis (PAP) due to elimination of mouse GM-CSF. We demonstrate that hIL-3/GM-CSF KI mice engrafted with human CD34+ hematopoietic cells had improved human myeloid cell reconstitution in the lung. In particular, hIL-3/GM-CSF KI mice supported the development of human alveolar macrophages that partially rescued the PAP syndrome. In addition, these mice showed an enhanced systemic inflammatory response to LPS. Finally, humanization of IL-3 and GM-CSF lead to a stronger innate immune response against influenza virus infection. In summary, hIL-3/GM-CSF KI mice represent a new mouse model to study human immune responses in the lung and against pathogens such as influenza.