What is it about the UK and graves and dead people to identify or bacteria to sequence? First, there are Black Death graves, then Richard III under a car park and now a leprosy grave site. While we do know leprosy has been a scourge of human beings for centuries, tracking the different strains and origins of the disease is relatively new. Taylor et al. were interested in this grave site near Winchester, located in southern Britain, north of Southampton and southwest of London, because little is known about the disease organism Mycobacterium leprae during this early medieval period (late 11th to 12th century). What could they learn about the strains that caused leprosy and the possible spread of the disease?
The grave site of St. Mary Magdalen, a hospital established during Norman times for those suffering from leprosy, was excavated and skeletons assessed for the distinct degradation areas of bone that are osteological hallmarks of leprosy. Of the 23 skeletons available for analysis, nine showed signs of leprosy, while two skeletons that did not were selected for controls. As with all molecular analysis of ancient samples, precautions were taken during sampling to prevent cross-contamination, including wearing gloves that were changed regularly, sterile sampling equipment and, for DNA analysis, using two different sites to amplify DNA from the bone samples—one in the UK and the other in Switzerland. RLEP, a 37-copy repetitive element in the M. leprae genome, and a single copy gene for a 18kD antigen were amplified in real-time PCR to confirm that the skeletal remains did have leprosy. For all nine leprosy-identified skeletons (and none of the two control skeletal remains), the RLEP repetitive element was amplified; only five remains resulted in strong amplification of both RLEP and the 18kD antigen. These five individuals were used in subsequent M. leprae analysis to type the strain. Additional loci and short nucleotide polymorphisms (SNPs) showed three of the skeletons were diagnosed with 3I-1 strains of M. leprae. However the other two cases were characterized as type 2F, a strain not previously identified in Britain. This is interesting because type 2 is a rarer type and usually found in the Middle East. Taylor et al. suggested the presence of type 2 strain showed its westward spread during this time period. The two control skeletons were negative for M. leprae. The researchers also amplified the amelogenin locus on the Y chromosome and identified nine of 10 remains as male despite the morphological analysis identifying one set of these remains as possibly female.
Another method for assessing the presence of leprosy is extracting lipids and using HPLC analysis to look for the expected lipid profile. The extracted lipids were compared with profiles for Mycobacterium tuberculosis, another human pathogen that could be present, and M. leprae. The total mycolic acids matched that of M. leprae, but not M. tuberculosis.
Three male skeletal remains infected with M. leprae were also tested to identify strontium (Sr) isotopes in tooth enamel and carbon and nitrogen isotopes in bone collagen. These are important for identifying the origins of the remains and characterizing the diet consumed when alive. Sr levels are compared with the local flora, soils and fauna to determine if the remains were local or from another location. The carbon and nitrogen isotopes will register any major changes in diet in the last decade of life, for example, if moving from another locale to Britain. The Sr isotopic indicators showed the individuals are likely from the area near the grave site while the carbon and nitrogen isotopes were consistent with a northern C3 European diet. However, there was a change in the diet during the last few years of life, possibly due to the hospital diet.
This PLOS ONE article offered some insight into the history of leprosy and the strains that were circulating in medieval Europe. As more grave sites are examined for human pathogens, the origins of some microbial disease and their differences from modern strains can give us a more complete history. And yes, I surmise many more graves in the UK will yield more data.
Taylor G.M., Tucker K., Butler R., Pike A.W.G., Lewis J., Roffey S., Marter P., Lee O.Y.C., Wu H.H.T. and Minnikin D.E. (2013). Detection and Strain Typing of Ancient Mycobacterium leprae from a Medieval Leprosy Hospital., PLOS ONE, PMID: 23638071