Plague immunodetection in remains of religious exhumed from burial sites in central France

Abstract

The skeletons of four Benedictine nuns and two priests were exhumed from two burial sites in central France. The corpses were dated to the 16th– 18th centuries (archaeological dating). Thick layers of lime were associated with their burials. During the Second Plague Pandemic, lime was associated with plague burials. We hypothesize that Yersinia pestis infection might have been the cause of death of these religious. A rapid diagnostic test for plague (RDT), that detects Y. pestis F1 antigen, was applied to all six putative plague victims. Y. pestis F1 antigen was detected in all six skeletons (100%). The F1 antigen concentrations ranged from 2.5 to 0.625 ng/ml. The eight samples used as negative controls yielded negative results. Soils samples taken from archaeological sites related to both positive and negative samples tested negative for F1 antigen. In earlier reports we provided suggestive evidence that the RDT for plague might be diagnostic for the detection of Yersinia pestis in ancient human remains. This putative evidence was based on four French and one German reputed plague sites in which RDT for plague and PCR sequenced-based analyses were performed. Both tests gave results consistent with our interpretation that RDT is effective in identifying plague in skeletal remains. Several different European putative plague burial sites are currently under investigation. We hope to obtain additional material to allow statistical validation of our results obtained thus far. We now confirm that the detection threshold of the RDT for plague (0.5 ng/ml) is sufficient for a retrospective diagnosis of plague in ancient skeletal remains. This method supplements the historical record with independent biologic evidence. Thus, our hypothesis that the six religious were infected by Y. pestis during the plague outbreaks which occurred in the two sites, Poitiers and La Chaize-le-Vicomte, between 1587 and 1632, has independent biologic support.