Alkaline phosphatase from Echinococcus granulosus metacestodes for immunodiagnosis of human cystic echinococcosis.

The work examined the use of Echinococcus granulosus alkaline phosphatase (EgAP) (extracted from hydatid cyst membranes) as an antigen for immunodiagnosis of human cystic echinococcosis (CE). It was assessed by enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting (IB) for detection of serum anti-EgAP immunoglobulin (Ig)G antibody and was compared with hydatid cyst fluid (HCF). The EgAP and HCF were of sheep liver cysts origin. Sera from 30 patients with surgically confirmed CE (G. I), 30 patients with other parasitic infections (G. II), and 20 healthy controls (G. II) were examined. The mean optical density of each of anti-EgAP IgG and anti-HCF IgG antibodies in G. I was significantly higher (P < 0.01) than in each of G. II and III. The use of EgAP in ELISA showed 100% sensitivity and specificity recording significantly higher sensitivity (P < 0.05) and specificity (P < 0.01) than when using HCF in ELISA which showed 86.7% sensitivity and 84% specificity. SDS-PAGE resolution, under reducing conditions, of EgAP revealed a molecular weight of 56 KDa, while that of HCF revealed a number of antigenic bands ranged from 12 to 130 KDa. IB analysis showed that sera from CE patients recognized the EgAP 56 KDa and also one or more of HCF antigenic bands of molecular weights at 116, 63, 44, 39, 24, 20, 16 and 12 KDa. The use of EgAP in IB showed 100% sensitivity and specificity recording an insignificant difference (P > 0.05) in sensitivity and a significantly (P < 0.05) higher specificity than when using HCF in IB which showed 100% sensitivity and 90% specificity. Cross reactivity with HCF in ELISA and IB was seen with schistosomiasis mansoni, fascioliasis, hymenolepiasis nana and ascariasis. Using EgAP, there was an insignificant difference (P > 0.05) in each of the sensitivity and specificity between ELISA and IB. Using HCF, there was a significantly (P < 0.05) higher sensitivity and an insignificantly (P > 0.05) higher specificity by IB than ELISA. The implications of these results are discussed.