Characterisation of a panel of recombinant antigens from Echinococcus granulosus and their role in the immunological follow up, after treatment, of cystic hydatid patients from Turkana, Kenya
Cystic echinococcosis is a serious zoonotic disease caused by the metacestodeof Echinoccoccus granulosus inflicting significant morbidity and mortality inmany parts of the world. Treatment of human hydatid cases involveschemotherapy with the drug Albendazole which has beneficial effects in somecases but not others. Disease progression can be monitored by ultrasoundusing the WHO classification system, but this only indicates large scalechanges in cyst morphology. Antibody responses to cyst fluid antigens havepreviously been used to provide further information on follow up after treatmentand the current project explores the usefulness of a panel of novel recombinantantigens in mapping antibody responses to cyst morphological changes.Positive clones pET19b-EgFABP1-C10, pET19b-EgHSP70-C10, pET19b-EgTPx-2Cb, pET19b-EgEF1-p/6-C9 and pET19b-EgAgB-C7 were selected andused to synthesise recombinant fatty acid binding protein 1 (EgFABPI), heatshock protein 70 (EgHSP70), thioredoxin peroxidase (EgfTPx) elongation factor1-beta/delta (EgEF1-(3/6) and antigen B (EgAgB) fusion proteins respectivelycarrying N-terminal His-tagged sequences. A panel of defined sequential seraof Turkana origin (Kenya), untreated (n =9) and treated (n =22) was probed inELISA with the recombinant parasite antigens. Results show that differentantigens react differently towards total IgG and lgG1 and lgG4 isotype subclassantibodies. Some antigens are associated with fluctuation in antibody levels ator during the time of transition from one cyst morphology to that of another type,whilst other antigens show little or no difference in reactivity. In some cases,fluctuating levels of antibody are correlated to pre and post treatment withalbendazole. Antibodies are rarely static and fluctuate up and down during andafter treatment, indicating a more varied release of extraneous antigenicmaterial supplementary to those antigens normally associated with hydatid cystfluid. In a number of cases particular antibody profiles could be linked toimportant changes in cyst structure and could have potential as markers of cystdevelopment. Throughout the current research, fluctuation in antibodyresponses in CE sequential sera towards recombinant AgB has shown consistency in line with other authors. A high level of total serum IgG andspecific IgG subclass antibodies in response to REgTPx antigen and REgFABP1has shown some association with active type cysts (CE1, CE2 and CE3).Furthermore, peaking levels in activity of serum IgG and specific lgG1antibodies in response towards REgEF1-p/8 antigen seem strongly correlated toCE3 cysts just prior to, during, or upon transition to inactive type cysts (CE4 andCE5). These serum antibody responses are also seen with REgHSP70 antigenwhen other active type cysts (CE1 and CE2) show signs of deterioration. Theresults therefore conclude that serological responses to each antigen may differin individual patients and that particular antibody reactivity may be useful inpredicting disease progression or regression. Recombinant EgFABPI andEgTPx antigens may be functional as indicators of early cyst fertility and viabilityrespectively; REgEF1-p/6 antigen might be valuable as a marker of diseaseregression and REgHSP70 antigen could be practical as an indicator of parasiteinstability.
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