Abstract Enhancement of the immunogenicity of Mycobacteyium leprae peptides by means of polymerization

Alexei F. Licea ^1,4, Maria C. Gutierrez ^2,4, Jose Esparza³, Sergio Estrada Parra³, Iris Estrada G3,
Fausto Quesada Pascual3 and Lourival D. Possani4*

¹Facultad de Ciencias Quimicas, Universidad Autonoma de Baja California. Calzada Tecnologico s/n Mesa de Otay.
Tijuana B. C. 22390, Mexico; ²Centro de Biotecnologia, Universidad Autonoma de Morelos, Av. Universidad s/n
Cuernavaca, Mor 62210 Mexico; ³Departamento de Inmunologia, Escuela Nacional de Ciencias Biologicas, Instituto
Politecnico Nacional, Prolongacion de Carpio y Plan de Ayala, Mexico RE 11340 Mexico; ⁴Departamento de
Reconorimiento Molecular y Bioestructura, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico
Apartado Postal 510 3, Cuernavaca, Mor 622 71 Mexico.

(Received 10 March 1998 / Accepted 19 October 1998)

Abstract.
Several proteins from Mycobacterium leprae have been identified as potent antigens. Segments corresponding to the primary stucture of these proteins were synthesized and used for the development of a skin test for leprosy (Gutierrez et al., 1994). Here we describe the synthesis of dimers and a multiple antigenic peptide (MAP) prepared by polymerization of single peptides, and we study the potential enhancement of immunogenicity of such polymerized peptides from various M.Leprae proteins: 65 kDa (P2, P15), 28 kDa (P5) and 18 kDa (P7). For the synthesis of the dimers, an extra cysteine was added either at the amino or carboxyl termini of peptides P2 and P7, whereas for P15 an extra cysteine was added only at the C terminus. Since P5 already had a cysteine at position 2 of the amino terminus no modification was needed. For dimer formation these peptides were air oxidized. Four different dimers were obtained for P2 and P7, and one dimer for each of P5 and P15. A MAP was prepared by combination of Pc2 and P15. From the seven peptides synthesized, only the Pc2 dimer was able to stimulate T cell proliferation in a specific manner. None of the other dimers nor the MAP per se were capable of inducing any type ofproliferation. All peptides synthesized, except the MAP, were also tested in a delayed type hypersensitivity (DTH) assay in M. leprae immunized guinea pigs. Only P7 dimers, Pc7 and P7c, showed an increased reactivity measured by means of DTH, when compared with the parent peptide (P7). Possible interpretations of these data are discussed.

Keywords: leprosy, multiple antigenic peptide (MAP), Mycobacterium leprae, synthetic peptide, T cell activation, mouse