engleski

Teaching old bones new tricks ; molecular analysis of archaeological Mycobacterium leprae DNA

Background ; Leprosy is a chronic infection giving rise to characteristic lytic lesions that can be identified long after the death of an individual. The identification of M. leprae DNA in these skeletons provides conformation that leprosy caused these characteristic bone lesions and allows the M. leprae genome to be analysed in countries where leprosy no longer occurs. Methodology ; Bone powder was sampled from 82 human skeletons exhumed in the United Kingdom, Croatia, Denmark and Thailand and DNA extracts were prepared. These were subjected to a series of polymerase chain reactions (PCR) specific for regions on the Mycobacterium leprae genome. The repetitive element RLEP was used for confirmation of M. leprae DNA and then 5 microsatellite regions and 1 minisatellite region were identified in 15 aDNA extracts from 11 skeletons. Successfully amplified DNA was sequenced to determine the number of variable nucleotide tandem repeats (vntr) at these loci. In addition to the VNTR analysis, 3 single nucleotide polymorphisms (SNPs) were identified in 7 of the aDNA extractions from Denmark, Croatia and the UK. The findings were compared to SNP data from French biopsy samples, previously analysed by a different laboratory, using the same PCR assays. Conclusion ; This collection of skeletal material for molecular analysis is the first of its kind and contains skeletal samples ranging from 400 to over 2, 000 years old. VNTR analysis showed extensive diversity in all 15 of the aDNA extractions, suggesting that this type of molecular identification may not be suitable for tracking archaeological leprosy transmission. SNP analysis on the 7 aDNA extractions showed that for 2 PCR assays, an identical pattern of SNPs occurred for the aDNA extractions when compared to the French biopsy results, However, for one SNP assay, all of the aDNA extractions show a difference when compared to the previously identified French biopsy material. These findings suggest a difference in M. leprae strain type present in France in comparison to samples from Croatia, Denmark and the United Kingdom and may indicate that European leprosy originated from more than 1 source, in contrast to initial findings. The findings of this study influence the current understanding of leprosy transmission through Europe

molecular analysis; archaeology; Mycobacterium leprae DNA

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