Dr. Casella's primary focus is on medical education, where she is the course director of the multidisciplinary course Molecular Basis of Life Defense and Disease for year one medical students. She also teaches medical, dental, and graduate students and has been the recipient of two awards given by students. In 2017, she received the Gender Equity Award given by the American Medical Woman’s Association. In 2020, Dr. Casella received the Golden Apple from the medical class of 2022.

Although Dr. Casella no longer has an active research position, she has studied many aspects of the replication of retroviruses in both graduate school and post-doctoral work.  This includes studies detailing the requirement for HIV’s matrix protein in incorporating viral envelope glycoproteins and the role HIV proteins play in the apoptosis of infected cells. More recently, Dr. Casella’s research has involved the detoxified endotoxin vaccine adjuvant monophosphoryl lipid A and mimetics of lipid A structures, with an interest in the interactions of these adjuvants with the immune system.