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Protective immunity to Mycobacterium tuberculosis is poorly understood, but mounting evidence, at least in animal models, implicates major histocompatibility complex class I-restricted [CD8.sup.+] T cells as an essential component. By using a highly sensitive assay for single cell interferon [Gamma] release, we screened an array of M. tuberculosis antigen-derived peptides congruent with HLA class I allele-specific motifs. We identified [CD8.sup.+] T cells specific for epitopes in the early secretory antigenic target 6 during active tuberculosis, after clinical recovery and in healthy contacts. Unrestimulated cells exhibited peptide-specific interferon [Gamma] secretion, whereas lines or clones recognized endogenously processed antigen and showed cytolytic activity. These results provide direct evidence for the involvement of [CD8.sup.+] cytotoxic T lymphocytes in host defense against M. tuberculosis in humans and support current attempts to generate protective cytotoxic T lymphocyte responses against M. tuberculosis by vaccination.

Provides evidence which supports major histocompatibility complex class I-restricted CD8+T cells as an essential component for protective immunity to Mycobacterium tuberculosis in animals. Identification of CD8+T cells for epitobes in the early secretory antigenic target 6 during active tubercolis.

Isolates of Pneumocystis jiroveci from sulfa-exposed and nonexposed patients from London, United Kingdom, and Harare, Zimbabwe, were genotyped. At the dihydropteroate synthase (DHPS) locus, there was evidence of selection pressure from sulfa drug exposure, and reversal of DHPS genotype ratios occurred when selection pressure was absent or was removed.