PubMed · 6347317
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M E Ward. 1983. Chlamydial classification, development and structure.. https://doi.org/10.1093/oxfordjournals.bmb.a071800
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Mycobacterium tuberculosis is an obligate human pathogen capable of persisting in individual hosts for decades. We sequenced the genomes of 21 strains representative of the global diversity and six major lineages of the M. tuberculosis complex (MTBC) at 40- to 90-fold coverage using Illumina next-generation DNA sequencing. We constructed a genome-wide phylogeny based on these genome sequences. Comparative analyses of the sequences showed, as expected, that essential genes in MTBC were more evolutionarily conserved than nonessential genes. Notably, however, most of the 491 experimentally confirmed human T cell epitopes showed little sequence variation and had a lower ratio of nonsynonymous to synonymous changes than seen in essential and nonessential genes. We confirmed these findings in an additional data set consisting of 16 antigens in 99 MTBC strains. These findings are consistent with strong purifying selection acting on these epitopes, implying that MTBC might benefit from recognition by human T cells.
Syphilis serodiagnosis relies on a combination of nonspecific screening tests (antilipoidal antibodies) and Treponema pallidum-specific tests (anti-T. pallidum antibodies). We studied a group of six recombinant T. pallidum antigens for their sensitivities and specificities with sera from individuals with syphilis (n = 43), relapsing fever (n = 8), Lyme disease (n = 8), and leptospirosis (n = 9) and from uninfected individuals (n = 15). Three recombinant proteins, Tp0155, Tp0483, and Tp0751, demonstrated sensitivity values that ranged from 28 to 42%. In contrast, three other recombinant proteins exhibited the following sensitivity and specificity values: Tp0453, 100% sensitivity and 100% specificity; Tp92 (Tp0326), 98% sensitivity and 97% specificity; and Gpd (Tp0257), 91% sensitivity and 93% specificity. Tp0453, Tp92, and Gpd also were recognized by sera from individuals with early primary syphilis that were nonreactive with the antilipoidal Venereal Disease Research Laboratory test. The reactivities of syphilis patient sera with Tp0453, Tp92, and Gpd were proportional to the titers of these sera with the treponemal test MHA-TP (microhemagglutination assay for T. pallidum). Thus, the recombinant T. pallidum antigens Tp0453, Tp92, and Gpd show promise as diagnostic antigens in the enzyme-linked immunosorbent assay-based assay.
Mammals mount a rapid inflammatory response to gram-negative bacteria by recognizing lipopolysaccharide (LPS, endotoxin). LPS binds to CD14, and the resulting LPS-CD14 complex induces synthesis of cytokines and up-regulation of adhesion molecules in a variety of cell types. Gram-positive bacteria provoke a very similar inflammatory response, but the molecules that provoke innate responses to these bacteria have not been defined. Here we show that protein-free, phenol extracts of Staphylococcus aureus contain a minor component that stimulates adhesion of neutrophils and cytokine production in monocytes and in the astrocytoma cell line, U373. Responses to this component do not absolutely require CD14, but addition of soluble CD14 enhances sensitivity of U373 cells by up to 100-fold, and blocking CD14 on monocytes decreases sensitivity nearly 1,000-fold. Deletion of residues 57-64 of CD14, which are required for responses to LPS, also eliminates CD14-dependent responses to S. aureus molecules. The stimulatory component of S. aureus binds CD14 and blocks binding of radioactive LPS. Unlike LPS, the activity of S. aureus molecules was neither enhanced by LPS binding protein nor inhibited by bactericidal/permeability increasing protein. The active factor in extracts of S. aureus is also structurally and functionally distinct from the abundant species known as lipoteichoic acid (LTA). Cell-stimulating activity fractionates differently from LTA on a reverse-phase column, pure LTA fails to stimulate cells, and LTA antagonizes the action of LPS in assays of IL-6 production. These studies suggest that mammals may use CD14 in innate responses to both gram-negative and gram-positive bacteria, and that gram-positive bacteria may contain an apparently unique, CD14-binding species that initiates cellular responses.