Endothelial cell tropism is a determinant of H5N1 pathogenesis in mammalian species
Fig 4
H5N1 infection of endothelial cells increases vascular leakage and causes pronounced damage in the lungs.
(A) Evaluation of vascular leakage in H5N1 infected lungs. C57BL/6J mice (n = 5) were intranasally infected with 25 PFU of the H5N1 viruses. On day 7 pi, Evans Blue dye was injected into mice via retro-orbital route. After 1h, mice were euthanized and the levels of Evans Blue dye in the BALF were measured. Each data point represents the concentration of Evans Blue dye in the BALF of individual mice (mean ± SEM). (B) Evaluation of infection of various cell populations in vivo. C57BL/6J mice (n = 3) were infected with 25 PFU of the H5N1 viruses. On day 3 pi, lungs were harvested and analyzed for H5N1 infection of the various cell compartments by flow cytometry. Cell surface markers CD45 and CD31 were used to distinguish endothelial cells (CD45-, CD31+), hematopoietic cells (CD45+) and non-hematopoietic cells (CD45-), and surface expression of viral HA was used to define infected cells (HA+). Data is represented as the mean (± SEM). Asterisk denotes statistical significance determined by one-way ANOVA and the values are denoted as *p<0.05, **p<0.01, ***p<0.001 and ns–non significant. Data presented here is a representative of at least two independent experiments. (C) Histopathological analysis of murine lungs by hematoxylin and eosin staining. C57BL/6J mice (n = 5) were intranasally infected with 25 PFU of the H5N1 viruses and on day 5 post-infection, the lungs were isolated and analyzed by H&E staining. The areas of infection and inflammation are indicated and outlined in black. B-bronchiole, V-blood vessel.