Identification of a 30 kDa antigen from Leishmania (L.) chagasi amastigotes implicated in protective cellular responses in a murine model

An antigen of apparent molecular mass of 30 kDa, termed p30, was purified f rom Leishmania (L.) chagasi amastigotes after separation of parasite extrac ts by sodium dodecyl sulfate-polyacrylamide eel eletroctrophoresis followed by electroelution. The use of the purified antigen in lymphocyte cultures from BALB/c mice previously immunised with L. (L.) chagasi amastigotes led to high levels of proliferation. Animal immunisation with p30 plus complete Freund's adjuvant either by subcutaneous or intraperitoneal route led to c omparable antigenic stimulation. Similar stimulation indices induced by p30 were also obtained when animals were immunised with Corynebacterium parvum as adjuvant by the intraperitoneal route. Detection of IL-2 and IFN-gamma in the supernatants from lymphocytes stimulated by p30 and inhibition of th e production of these lymphokines in the presence of anti-CD4, strongly ind icated the involvement of the Th1 subset in the responses elicited by p30 a ntigen. Immunisation of BALB/c mice with p30 provided partial protection ag ainst challenge with L. (L.) chagasi amastigotes, indicating a protective r ole for p30 and that Th1 can be related to accquired resistance to visceral leishmaniasis in a murine model. Further characterisation studies were per formed by the use of a monoclonal antibody directed to a cysteine proteinas e of 30 kDa from L. (L.) amazonensis amastigotes. Despite the cross-reactiv ity presented by p30 from both Leishmania species, the p30 from L. (L.) cha gasi amastigotes lacks proteolytic activity. (C) 2000 Published by Elsevier Science Ltd on behalf of the Australian Society for Parasitology Inc. All rights reserved.