A recent study has found evidence that myalgic encephalomyelitis, better known as chronic fatigue syndrome (CFS), may be triggered by a variety of infections, such as infectious mononucleosis. Researchers discovered that the blood plasma of patients with CFS contained a distinct biomarker called interleukin-17A, a cytokine molecule known to be produced by the immune system as a faulty defense response to infection and inflammation. People who had suffered from CFS for longer than three years, however, had lower levels of interleukin-17A despite ongoing symptoms, such as persistent exhaustion and physical pain. This apparently is due to the exhaustion of the immune system itself, which has had to run on "high gear" for an extended period of time.
Which of the following would most need to be done before testing drugs that target interleukin-17A to see if they would be effective in treating CFS?