1.Mycobacterium tuberculosis and the liver stage of Plasmodium falciparum are intracellular pathogens which are potentially susceptible to cytotoxic T-lymphocytes, a crucial component of the protective immune response to viral infections. Evidence from animal models points to a protective role for cytotoxic T-lymphocytes against M. tuberculosis and P. falciparum, but cytotoxic T-lymphocytes specific for these pathogens have been difficult to identify in man.

2.Using a reverse immunogenetic approach, candidate epitopes from selected antigens of P. falciparum and M. tuberculosis were used to detect peptide-specific cytotoxic T-lymphocyte responses in individuals exposed to these pathogens. Cytotoxic T-lymphocyte activity was detected by the 51Cr release cytotoxicity assay and a sensitive ELISPOT assay for single-cell interferon-γ release.

3.In naturally exposed, partially immune Africans in The Gambia, eight largely conserved cytotoxic T-lymphocyte epitopes in P. falciparum, restricted by several different HLA class I alleles, were identified. Several epitopes were also recognized in Tanzanians and cytotoxic T-lymphocytes recognized endogenously processed antigen.

4.In tuberculosis patients with HLA-B52, a CD8+ cytotoxic T-lymphocyte epitope was identified in ESAT-6, a secreted antigen specific for M. tuberculosis complex but absent in BCG. Cytotoxic T-lymphocytes exhibited HLA-B52-restricted peptide-specific interferon-γ release and lytic activity and recognized endogenously processed antigen.

5.These studies demonstrate that CD8+ cytotoxic T-lymphocytes specific for mycobacterial and protozoal antigens are induced during natural infections in humans. The identification of these T-cells endorses current strategies to develop cytotoxic T-lymphocyte-inducing vaccines against P. falciparum and M. tuberculosis and highlights candidate antigens for inclusion in subunit vaccines.

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Author notes

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This paper was awarded the Glaxo/MRS Young Investigator Prize at the MRS Meeting, Royal College of Physicians, London, 15 May 1997.