ABSTRACT
Human serum samples from 25 acute schistosomiasis patients, 20 chronic cases and 15 normal healthy controls were analyzed by IgG avidity enzyme linked immunosorbent assay [ELISA] and IgG avidity immunoblotting assay. Using avidity ELISA, a pronounced overlap of avidity index values was observed between acute and chronic infections with a range of uncertainty [0.86-1], which was encountered in both groups. Using avidity immunoblotting assay, antigenic bands at >116, 84, 48, 40 and 34 kDa were exclusive for the acute phase. From these bands, 34 kDa was recognized mostly by low-avidity antibodies and showed a high sensitivity [96%] and specificity [100%], making it an optimal marker for the acute phase. 40 kDa band was recognized mostly by high-avidity antibodies, even during acute infection. Bands of 80, 70, 42, 36, 30 and 26 kDa were exclusive for the chronic phase. Only 70 kDa band was recognized by high-avidity antibodies, yet with low sensitivity [35%] that limits its use as an optimal marker for the chronic infection. Meanwhile, 70 and 40 kDa bands, recognized by high-avidity antibodies, are considered as potential vaccine antigen candidates