Figure 1. Generation of an H1N1pdm virus lethal for Balb/c mice.
A) % Body weight changes and B) % survival of Balb/c (n = 4) and DBA (n = 4) mice inoculated intranasally with 5.4×105 TCID50 of Ca/04. DBA-Balb/c corresponds to Balb/c mice infected with lung homogenates containing the first passage Ca/04 virus from DBA mice. C) Growth kinetics of Ca/04 and ma-Ca/04 in MDCK cells. Viruses were inoculated at a multiplicity of infection of 0.001. Supernatants were collected at the indicated time points and titrated in MDCK cells by TCID50. D) Balb/c mice inoculated intranasally with 1.2×104 TCID50 of ma-Ca/04 or Ca/04. Lungs from infected mice (n = 3/time point) were collected at 3 and 6 dpi, homogenized and virus titers measured in MDCK cells by TCID50. Results are expressed as log10 TCID50/gr of tissue. E, F, G) Balb/c mouse lungs were collected at 3 dpi as described in D and fixed in 10% formalin, embedded in paraffin and sectioned. Serial sections were stained with H&E and the images were captured at ×20 magnification. E) Mock infected lung, F), Ca/04-infected lung, G) ma-Ca/04-infected lung.