Serodiagnosis of human plague by an anti-F1 capsular antigen specific IgG/IgM ELISA and immunoblot.

Plague is a re-emerging disease endemic in at least 24 countries. Non-endemic countries should be able to confirm plague to prevent outbreaks due to imported cases. We established a combination of a IgG/IgM screening ELISA and a confirmation immunoblot employing F1 capsular antigen (CA) for the serodiagnosis of plague in countries where yersiniosis is present. The ELISA and the immunoblot assay showed a specificity of 96.1% and 100% among sera from healthy German blood donors. This group had a seroprevalence of 39% of anti-yersinia outer protein (YOP) antibodies obviously caused by previous Y. enterocolitica infection. The ELISA detected anti-F1 CA antibodies in 22 and the immunoblot in 20 out of 26 sera of plague vaccinees. Five control sera from bacteriologically confirmed plague cases from Madagascar reacted positively. It can be concluded that anti-YOP antibodies do not affect assays based on purified F1 CA.