Insights from molecular evidence of Mycobacterium leprae from 15th century Normandy, France

International audienceLeprosy was widespread in Mediaeval Europe but molecular evidence indicates geographical differences in the Mycobacterium leprae genotypes found at different times and locations. M. leprae requires a living host, and different human populations are associated with different lineages. Data are available from the UK and Scandinavia, Central, Southern and Eastern Europe, but little is known of the molecular characteristics of leprosy from Northern France. The paleopathology of leprosy is distinctive, so enables recognition of the disease in established cases. Therefore, nasal scrapings, and samples from ribs, femurs and toes, were taken from 15 individuals with typical paleopathology at the leprosarium of Saint Thomas d’Aizier (1350-1450 CE). After grinding to a powder, samples were demineralised in EDTA/Proteinase K at 56oC, mixed on a bead beater then split into 2 aliquots. One was treated with 0.1M PTB to break any covalent cross-links then both aliquots were incubated in lysis buffer containing guanidium thiocyanate. DNA was captured by silica or precipitated from the silica supernatants. Real-time PCR was used, with primers and probes for the M. leprae repetitive sequences RLEP (37 copies/cell) and RepLep (15 copies/cell). Eleven individuals were strongly positive for M. leprae DNA, two were weakly positive and two were negative. The stronger positive samples were genotyped. Unlike M. leprae ancient DNA from central and southern Europe, these Norman strains were of genotype 3I. However, in two individuals a variant M. leprae 3I-1 type was also found that has only once been reported previously, from 800-900 years earlier. This was in a skeleton from Great Chesterfield, East Anglia, UK, dated to 600 CE. This variant appears to be intermediate between sub-type 2F and 3I