Recombinant vaccinia viruses for the characterization of Plasmodium falciparum-specific cytotoxic T lymphocytes: recognition of processed antigen despite limited re-stimulation efficacy

Cytotoxic T lymphocytes (CTL) have been implicated in immunity toPlasmodium falciparum infection and disease. We have previously describedthe use of peptides to define malaria-specific CTL epitopes. To determinewhether these peptide epitopes are processed intracellularly from the wholeantigen we have developed recombinant vaccinia viruses (rVV) expressingthree malaria antigens: thrombospondin-related adhesive protein (TRAP),Pfs16 and the C- terminal half of liver-stage antigen (LSA)-1. Target cellsinfected with recombinant viruses were lysed by malaria-specific CTL fromsemi- immune African donors. We also tested the ability of cells infectedwith these recombinant vaccinia viruses to re-stimulate malaria- specificCTL in peripheral blood lymphocytes from malaria immune adults. Two otherpox virus recombinants, NYVAC, an attenuated vaccinia virus, and ALVAC, acanarypox virus, both expressing malaria antigens were also evaluated fortheir ability to stimulate malaria-specific CTL in contrast to peptide,none of these viruses successfully re- stimulated CTL from the peripheralblood lymphocytes of semi-immune donors. The ability of human CTL fromnaturally exposed individuals to recognize processed antigen supports therelevance of these cells in protective immunity to malaria.