The cotton rat (Sigmodon hispidus) is susceptible to non-adapted human RSV (respiratory syncytial virus) and displays many features of human pathology when infected with RSV thus making it the model of choice for preclinical development of RSV vaccines and therapeutic agents.The predictive quality of the model is so high that treatments for severe disease advanced to clinical trials based on the results of efficacy and safety studies using cotton rats without the need for testing in primates. The cotton rat model has been successfully used to test RSV vaccine and therapeutic candidates.


  • Determine the efficacy of vaccine or therapeutic agents against RSV infection as shown in the figure below

  • Test adenoviral vector-based gene therapies 

  • Study infectious disease pathogenesis


To demonstrate the use of the model for testing the efficacy of anti-viral agents, four animals were dosed with an anti-RSV antibody and then challenged with RSV at 4 x 104 PFU.  Because the efficacy of test therapeutics and vaccines is best measured at the peak of infection, the animals were euthanized on day 5 and viral titers determined.  Animals which received the anti-RSV monoclonal antibody showed a significant reduction in viral burden in the lungs compared to control animals. 


Kinetic studies demonstrate the increase in viral titers in the first 2-5 days post infection followed by a decline. Viral load is dependent on the titer of the viral challenge dose.  See figure above.


Animals are infected intranasally with RSV strain A2.  The time course of the infection is followed by determining viral titers in lung homogenates or broncho­alveolar lavage fluids (BALF). 

The efficacy of test agents in animals challenged with the virus is determined at peak viral titers.

Viral titers are determined via plaque assay or qPCR.  H&E stained sections of lung tissue can be prepared for evaluation of tissue histology.  


  • Drug Administration Route:  Intranasal, intravenous, intramuscular, continuous infusion 

  • Reference Substance & Control: Anti-RSV monoclonal antibody or other reference; vehicle

  • Length/Endpoint: Five to seven days post infection 

  • Assays & Measurements:  Viral load in nasal tissue, viral load in bronchoalveolar fluid (BALF), viral load in lung homogenate, immunohistochemistry, tissue pathology


Proven Expertise

We have experience with a variety of mammalian species used for vaccine and drug development. Our studies range from single digit to hundreds of animals.

Our scientists, with over 15 years of GLP experience, provide all aspects of the GLP process from design to regulatory support of your IND, IDE or PMA FDA submission.