Dr Diefenbach is a Senior Research Fellow based at Macquarie University. As well he is an honorary principal research fellow at the University of Sydney. He completed a PhD in Biochemistry at the University of Queensland in 1992. He embarked on postdoctoral studies at the University of Toronto (1991-1994) working on the structural-functional relationships of complement C3. He then returned to Australia as a Research Fellow in the Biochemistry Department, University of Sydney (1995). He moved to the Centre for Virus Research, The Westmead Institute for Medical Research in 1996. His focus here was the protein-protein interactions which drive viral entry, assembly and egress with an emphasis on herpes simplex virus and HIV. More recently he has also initiated studies in oncolytic virotherapy and moved to Macquarie University in 2017 to work in the melanoma field on liquid biopsies.