Use of western blot to analyze the reactivity of sera from patients with Mediterranean spotted fever.

The reactivity of antigenic components of Rickettsia conorii with sequentially obtained sera from 20 adult Spanish patients with Mediterranean spotted fever was analyzed by Western blot. The major rickettsial antigens reacting with the serum samples corresponded to molecular weights of 135 and 115 kDa. These antigens constantly exhibited higher staining intensity than the other antigens, and reacted with 100% and 86.7%, respectively, of acute sera and with 100% of convalescent phase samples. Rickettsial lipopolysaccharide antigens reacted with 94.7% of sera collected in the fourth and fifth week after onset of symptoms. Other major antigens reactive in the blots had molecular sizes of 160, 100, 90 and 60 kDa, and a relatively frequent humoral immune response was also seen to antigens of 80, 73 and 55 kDa.