The present invention provides compositions comprising peptides derived from amino acid sequences (or from combinations thereof) of fusion and other protein regions of various viruses, including but not limited to, severe acute respiratory syndrome coronavirus, herpesvirus saimiri, human herpesvirus 6, Lassa virus, lymphocytic choriomeningitis virus, Mopeia virus, Tacaribe virus, Friend murine leukemia virus; human T lymphotropic virus type 1; herpesvirus ateles; Marburg virus; Sudan Ebola virus; Zaire Ebola virus, and comprising L- and/or D-amino acids and combinations thereof, which affect T cells by acting on the T cell antigen receptor (TCR). More specifically, the peptides act on the TCRαβ-CD3δε-CD3γε-ζζ signaling complex. Yet more specifically, the peptides act on the TCRα/CD3δε/ζζ signaling module of TCR. The present invention further relates to the prevention and therapy of various T cell-related disease states involving the use of these compositions. Specifically, the compositions are useful in the treatment and/or prevention of a disease or condition where T cells are involved or recruited. The compositions of the present invention also are useful in the production of medical devices comprising peptide matrices (for example, medical implants and implantable devices).