VACCINATION OF VERVET MONKEYS AGAINST CUTANEOUS LEISHMANIASIS USING RECOMBINANT LEISHMANIA-MAJOR SURFACE GLYCOPROTEIN (GP63)

Vervet monkeys (Cercopithicus aethiops) were shown to give a positive delayed-type hypersensitivity (DTH) reaction to gp63, a major surface glycoprotein of Leishmania parasites, and also produce antibodies to t he molecule following a triple vaccination with a total dose of 150 mu g of recombinant gp63 mixed with Bacille Calmette Guerin (BCG). Howev er, peripheral blood leucocytes (PBL) from these animals neither proli ferated nor produced any interferon-gamma (IFN-gamma) following in vit ro stimulation with the antigen. Analysis of lymphocyte subsets follow ing vaccination did not reveal any striking phenotypic alteration of c ellular sub-populations in PBL. When vaccinated animals were rechallen ged, via the needle, with virulent Leishmania major promastigotes cont aining salivary gland extracts from vector sandflies, only partial pro tection was achieved. We concluded from these studies that rgp63 produ ced in Escherichia coli is a safe vaccine molecule which gives only pa rtial protection following vaccination in the vervet monkey host. The molecule requires further improvement for vaccine and/or immunodiagnos is application.