In this Study canine parvovirus, CPV, was found to induce disorder in DPPC:cholesterol membranes in acidic conditions. This acidicity-induced fluidizing effect is Suggested to originate from the N-terminus of the viral capsid protein VP1. In accordance with the model membrane Studies, a fluidizing effect was seen also in the endosomal membranes during CPV infection implying an important functional role of the fluidization in the endocytic entry of the virus. (C) 2008 Elsevier Inc. All rights reserved.