Identification of Novel TAT-I24-Related Peptides with Antiviral Activities.

To identify novel peptides with potential antiviral activities, a database search was performed based on the primary sequence of the peptide I24 (CLAFYACFC), the effective part of the antiviral peptide TAT-I24 consisting of peptide I24 and the cell penetrating TAT-peptide (amino-acids 48-60; GRKKRRQRRRPPQ). A Protein BLAST search identified several sequences with high similarity to I24 in diverse proteins, some of which are known to be involved in the interaction with nucleic acids. Selected sequences and newly designed variants of I24 were synthesized as TAT fusion peptides and tested for antiviral activity in two well-established models: baculovirus transduction of HEK293 cells and mouse cytomegalovirus (MCMV) infection of NIH/3T3 cells. Several of the TAT-fusion peptides exhibited antiviral activities with a potency comparable to TAT-I24. The ability of these peptides to bind double-stranded DNA suggested the same mode of action. Several peptides caused swelling of red blood cells (RBC) but with only one peptide clearly inducing haemolysis. With two exceptions, RBC swelling was observed with antivirally active peptides but not with less active peptides, indicating that antiviral activities are linked to an effect on membrane integrity of target cells. Structural prediction of the TAT-fusion peptides indicated formation of two α-helical elements, with several of these peptides showing remarkable similarity when subjected to structural alignment.