Pre-existing alveolar macrophages (live PAM or AMɸ) showed a strong negative correlation with lung viral load, whereas monocyte-derived cells (moMɸ, cDC1, and cDC2), T cells, and NK cells were positively correlated, indicating virus-induced destruction of PAMs and host-driven recruitment of immune cells into the lung as a response to infection. Here, MPPE1 is linked to infection.