Peter M Small | Search PubMed

PubMed2010

Human T cell epitopes of Mycobacterium tuberculosis are evolutionarily hyperconserved.

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.

Antigens, Bacterial↗

PubMed2004

High-throughput method for detecting genomic-deletion polymorphisms.

DNA microarrays have been successfully used with different microorganisms, including Mycobacterium tuberculosis, to detect genomic deletions relative to a reference strain. However, the cost and complexity of the microarray system are obstacles to its widespread use in large-scale studies. In order to evaluate the extent and role of large sequence polymorphisms (LSPs) or insertion-deletion events in bacterial populations, we developed a technique, termed deligotyping, which hybridizes multiplex-PCR products to membrane-bound, highly specific oligonucleotide probes. The approach has the benefits of being low cost and capable of simultaneously interrogating more than 40 bacterial strains for the presence of 43 genomic regions. The deletions represented on the membrane were selected from previous comparative genomic studies and ongoing microarray experiments. Highly specific probes for these deletions were designed and attached to a membrane for hybridization with strain-derived targets. The targets were generated by multiplex PCR, allowing simultaneous amplifications of 43 different genomic loci in a single reaction. To validate our approach, 100 strains that had been analyzed with a high-density microarray were analyzed. The membrane accurately detected the deletions identified by the microarray approach, with a sensitivity of 99.9% and a specificity of 98.0%. The deligotyping technique allows the rapid and reliable screening of large numbers of M. tuberculosis isolates for LSPs. This technique can be used to provide insights into the epidemiology, genomic evolution, and population structure of M. tuberculosis and can be adapted for the study of other organisms.

DNA Probes↗