isolated polynucleotide, isolated or purified isolated or purified leishmania major secreted / secreted polypeptide, immunogenic composition, vaccine composition, antibody, cloning or expression vector, method for preventing and / or treating a patient, method for identifying an secreted / secreted polypeptide, use of a polynucleotide, use of a polypeptide, in vitro diagnostic methods, diagnostic kits, transformed or transfected cells, genetically modified leishmania strains, method for detecting the presence or absence of lymphocyte stimulation and uses of a composition