Western blot assay (WB) and cross adsorption studies of 2 patients with severe tick-borne rickettsioses in Nîmes, southern France, 2007.

WB procedures were performed as described elsewhere [47] using 20 µl of a 1 mg/ml suspension of rickettsial antigen per lane. The cross-adsorption assay using R. massiliae and R. conorii antigens followed by WB on the resulting supernatant was performed as previously described [47]. Columns Rc and Rm depict western blots using R. conorii and R. massiliae antigens, respectively. Molecular weights (MW) are indicated on the left (arrow = 135 kDa). Untreated sera is acute sera tested by WB. For patient 1, when adsorption is performed with R. massiliae antigens (columns AdM), it results in the disappearance of homologous and heterologous antibodies. In contrast, when absorption is performed with R. conorii antigens (columns AdC), only homologous antibodies disappear indicating that antibodies are specific for R. massiliae. For patient 2, when adsorption is performed with R. conorii antigens (columns AdC), it results in the disappearance of homologous and heterologous antibodies. However, when it is performed with R. massiliae antigens (columns AdM), only homologous antibodies disappear indicating that antibodies are specific for R. conorii.