Evidence from the literature and our own data suggest that MMPs are responsible for AAT proteolysis, in particular MMP-7, MMP-9 and MMP-26 [38, 39] . Altered levels of MMP-9 have been reported to correlate with HIV-1 infection, and breakdown of extracellular matrix has been suggested to aid dissemination of the virus [40, 41] . Our in vitro experiments confirmed the known MMP-7 cleavage sites on the C-terminal part of AAT and also demonstrated that VIRIP can be generated despite presence of an additional cleavage site within the sequence of the peptide. This cleavage site between Pro 381 -Met 382 , directly neighbouring the active site Ser 383 , has been shown previously to be sensitive to the oxidation state of the Met 382 residue [42] , thereby protecting VIRIP from further degradation. In addition, our results support the notion that the biological function of cleavage of AAT by MMP-7 may not solely be inactivation of its serine protease function, but also to generate new proteolytic peptides that have additional activities in themselves.