THE IMMUNOPATHOLOGY OF HUMAN SCHISTOSOMIASIS .3. IMMUNOGLOBULIN ISOTYPE PROFILES AND RESPONSE TO PRAZIQUANTEL

Immunoglobulin (Ig) isotype (IgG, IgG(1), IgG(2), IgG(3), IgG(4), IgM, IgD and IgE) levels were investigated, both pre- and post-treatment w ith praziquantel (PZQ), in 43 adults and children chronically infected with Schistosoma mansoni, by means of a two-site, isotype-specific im munoenzymometric assay. The patients were classified as responders (R) or non-responders (NR) on the basis of their circumoval precipitin te st (COPT) results 12 months after treatment. In comparison with contro ls, pre-treatment R children showed significantly higher levels of IgG , IgG(1), IgG(4) (p < 0.001) and IgE (p < 0.01), and diminished IgG(2) (p < 0.05), while NR children showed significantly elevated levels on ly of IgE (p < 0.05). Twelve months after therapy, R children maintain ed significantly lower levels of IgG(2), but showed significantly decr eased levels of IgG, IgG(1), IgG(4), and IgE, while the Ig isotype pro file of NR children was unaltered. Adult R and NR showed similar isoty pe profiles before chemotherapy, with the exception of significantly e levated IgM levels in R. Twelve months after therapy, R adults showed significantly decreased levels of IgG, IgG(1), and IgG(4), while NR ad ults showed only diminished IgG(4) levels. These results reveal differ ent Ig isotype profiles in untreated adults and children chronically i nfected with S. mansoni. The results further show that the pre-treatme nt Ig isotype profile may be significantly modified after an effective R to chemotherapy, accounted for by down regulation of the IgG(1) iso type in association with negative seroconversion of the COPT in R pati ents. The COPT reaction has been associated with the highly specific e gg glycoprotein antigen omega(1), which shows a significant reduction in reactivity six months after treatment. IgG(1) may thus play a main role in the response against the ol antigen.