About a year ago, Miss Pezaro thought she may have been exposed to HIV and her doctor prescribed emergency antiretroviral drugs.
"Three days after I took the drugs I walked up a flight of stairs," she said.
"That was an unbelievable, massive change."
Prof Julian Gold from the Prince of Wales Hospital in Sydney, saw a video of Miss Pezaro climbing the stairs and a clinical trial was set up to look at the impact of single or combination antiretroviral drugs on MS patients.
An earlier study led by Dr Gold conducted with Queen Mary University, London and the University of Oxford showed an association between HIV and MS.
They reported antiretroviral treatment may suppress other viruses such as those which may cause MS.
Dr Gold said: "The next stage of the investigation is to use a very similar combination [of HIV drugs] that Shana took. I think that might be quite optimistic."