Novel genes encoding homologous immunoreactive thio-disulfide oxidoreductases,or disulfide bond formation (Dsb) proteins fromEhrlichia chaffeensis andEhrlichia canis are disclosed. While the E. chaffeensis and E. canis Dsbproteins are at most only 31 % or less homologous to other known Dsb proteins,the Ehrlichia Dsbs contain a cysteine active site, Cys-Cly-Tyr-Cys, similar tothose in known Dsb proteins. As predicted by 15-amino acid identical N-terminal signal peptides, the proteins are primarily localized in theperiplasm of E. chaffeensis and E. canis, possibly playing a role inantigenicity and pathogenesis. The present invention provides the nucleotideand amino acid sequences and expression vectors for the E. chaffeensis andE.canis genes, antisera directed against the proteins, and kits to determinewhether an individual or animal is infected with a given species of Ehrlichia.
