IN-VITRO EVALUATION OF PYRULARIA THIONIN - ANTI-CD5 IMMUNOTOXIN

The membrane-active peptide, Pyrularia thionin, purified from Pyrulari a pubera, was covalently conjugated to an anti-CDS monoclonal antibody . The membrane-active properties of thionin were not affected by the c onjugation. The immunotoxin killed CD5(+) lymphocytes in vitro at a co ncentration of 0.1 nmol/10(7) cells after 2 h of incubation. The immun otoxin also inhibited the proliferation of T cells in vitro, stimulate d either by mitogens or in the mixed lymphocyte reaction. It was shown by electron paramagnetic resonance of spin probes and differential sc anning calorimetry that the ability of the immunotoxin to perturb the lipid phase of membranes is close to that of unconjugated thionin. The results obtained suggest that Pyrularia-thionin-anti-CD5 conjugate ma y be useful for graft-versus-host disease therapy and potentially in t he treatment of CD5(+) leukemia and lymphomas.