Mice constitute one of the most commonly used models for
influenza viral research. Because mice are small, inexpensive,
and require minimal husbandry requirements, the mouse is a
convenient model of influenza infection. In addition, the large
number of genetically mutant murine strains allows investigators
to design genetic and loss-of-function approaches to
causally link proteins and pathways with disease pathogenesis
and to determine the mechanism of action of proposed
therapies. Detailed methods to carefully phenotype the
severity of the infection in mice and the ability to precisely
vary the delivered viral inoculum allow for the detection of
small differences that might be important when applied across
large populations. Despite these advantages, the mouse is not
a natural host for influenza viruses and human IAV subtypes
must be adapted to mice for the virus to replicate efficiently
within the murine respiratory tract. It is also a poor model
of transmission of the virus (Figure 1).
The susceptibility of mice to the influenza virus is dependent
on both the strain of the mouse and the strain of the
influenza virus. Because the majority of human influenza
virus isolates cause only mild infection in mice, investigators
typically use one of a handful of murine-adapted strains.