Identificacion y caracterizacion de determinantes t helper para la induccion de respuestas antitumorales

Resumo

IDENTIFICACIÓN Y CARACTERIZACIÓN DE DETERMINANTES T HELPER PARA LA INDUCCIÓN DE RESPUESTAS ANTITUMORALES RESUMEN: We have identified promiscuous T-helper cell determinants (THd) from tumor antigens carcinoembryonic antigen (cea) and alpha-fetoprotein (afp), (endogenous ThD) and designed de novo THd not related to tumor antigens (exogenous THd). Both types of THd were identified with the purpose of inducing anti-tumoral immune responses for cáncer therapy. Potential promiscuous THd from cea and afp were predicted using available computer algorithms. Predicted peptides were synthesized and tested in binding experiments to different HLA-dr molecules. Binder peptides were then used to prime T-cell responses both in vitro and in vivo. Twenty 15-mer peptides from cea were predicted to bind to different HLA-dr molecules. The promiscuous character of these peptides was demonstrated in binding experiments. Among these peptides, it was found that CEA(625-639) and CEA(653-667) could be recognized by T-cells in vitro after processing of recombinant CEA. CEA(625-639) was found to be presented by HLA-DR4 and HLA-DR53 whereas CEA(653-667) was effective in inducing in vitro T helper responses in the context of hla-DR4, hla-DR7, and hla-DR9 alíeles. Moreover, immunization of hla-DR4 transgenic mi ce with CEA (625-639) in conjunction with class I epitope OVA (257-264), induced a CTL response specific of OVA(257-264). Similar experiments allowed us to identify several promiscuos peptides from AFP. In another group of experiments we designed de novo promiscuous exogenous THd capable of binding to several hla-dr molecules. Some of these exogenous THd were able to bind to all seven hla-DR tested and were immunogenic in vivo in hla-DR4 transgenic mice. Among them, peptides p37, p42 and p45 elicited Thl cytokine profiles in vivo, providing help for the induction of potent CTL responses. Finally, in vitro stimulation assays carried out in humans, showed that these peptides could induce T cell responses in individuals with a broad spectrum of hla-DR molecules. in conclusion, these results suggest that endogenous THd peptides CEA(625-639) and CEA(653-667) as well as exogenous THd p37, p42 and p45 might be relevant promiscuous THd peptides for cancer therapy