ONCHOCERCA-VOLVULUS - EXPRESSION AND PURIFICATION OF RECOMBINANT ANTIGEN RAL2 - STUDIES ON IMMUNOGENICITY AND PATHOGENICITY

Detailed studies on the immune response to defined Onchocerca volvulus antigens have been impaired by a paucity of parasite material. This p roblem has been overcome for an infective larvae-associated antigen RA L2 by expression in Escherichia coli as a fusion protein with the E. c oli maltose-binding protein. The fusion protein was purified by affini ty chromatography using amylose resin and digested with factor Xa to r elease RAL2 which was further purified to homogeneity by gel filtratio n using high performance liquid chromatography. Biochemically purified recombinant RAL2 elicited significant and sustained proliferation of lymphocytes in peripheral blood manonuclear cells from chimpanzees pre viously inoculated with live non-attenuated or radiation-attenuated O. volvulus larvae. Thus, a purified onchocercal protein is implicated i n immune recognition by chimpanzees experimentally immunized with irra diated or infected with non-irradiated O.volvulus third stage larvae. The purified recombinant antigen failed to produce any ocular patholog y in a murine model of onchocercal sclerosing keratitis. Availability of large quantities of RAL2 in a soluble form will permit investigatio n of the relationship between the structure of the antigen and the hos t immune response elicited by it.