IMMUNOGLOBULIN-G SUBCLASS RESPONSES IN HUMAN CYSTIC AND ALVEOLAR ECHINOCOCCOSIS

Immunoglobulin G (IgG) subclass-specific antibody responses were inves tigated in both human cystic echinococcosis (CE) and alveolar echinoco ccosis (AE) by enzyme-linked immunosorbent assay (ELISA) and Western b lotting. Sera were tested from 81 CE and 50 AE surgically confirmed ca ses using partially purified hydatid cyst fluid antigen B (EgB), and c rude hydatid cyst fluid (EgCF) from Echinococcus granulosus and a prot oscolex extract (EmP) prepared from E. multilocularis metacestodes. Ei ghty-nine percent of CE patients and 94% of AE patients were seroposit ive for total IgG antibodies. The dominant IgG antibody isotype in bot h CE and AE was IgG4, for which 73% of CE and 84% of AE cases were ser opositive in the ELISA. Anti-Echinococcus IgG1 antibodies were detecte d in 58% of CE and 84% of AE patients. Sensitivity for IgG2 and IgG3 w as significantly lower for both CE and AE patients. The IgG4 antibodie s in CE patients predominantly recognized the E. granulosus antigen B subunits, i.e., at 20, 16 and 12 kD, while IgG1 antibodies primarily b ound to the 38-kD subunit of antigen 5 from E. granulosus hydatid flui d. The possible functional significance of an IgG4 response and the po tential use of combined assessment of total IgG, IgG1, and IgG4 antibo dies in serologic diagnosis and follow-up for human echinococcosis are discussed.