The cotton rat (Sigmodon hispidus) is a commonly used model of influenza virus infection in humans because:
- Cotton rats can be infected by non-adapted human influenza viruses. Both influenza A and B strains replicate in the upper and the lower respiratory tract of cotton rats. Cotton rats can be infected with and replicate avian influenza H3N2 and H9N2 viruses.
- Virus infection results in histopathological lesions in the lungs that are similar to those seen during natural infection of humans.
- Virus replication in the lung coincides with the induction of cytokines characteristic of the innate immune response, a potentially important factor in understanding early antiviral mechanisms.
- Hetero-subtypic (or cross-protective) immunity has been observed in cotton rats as a result of influenza virus infection making the model a valuable tool for the development of broadly active influenza vaccines.
Viral titers in nasal tissue homogenates reached more than 105 PFU/g of tissue at Day 1 post infection and then declined to about 103 PFU/g of tissue by Day 4 post infection. See figure above.
Viral titers in lung homogenates reached more than 106PFU/g of tissue at Day 1 post infection and then declined to about 102 PFU/g of tissue by Day 4 post infection. See figure above.