Using specific synthetic peptide (p176) derived AgB 8/1-kDa accompanied by modified patient’s sera: A novel hypothesis to follow-up of Cystic echinococcosis after surgery

Cystic echinococcosis (CE) is caused by the larval stage of the tapeworm Echinococcus granulosus. Until now, CE does not have an effective follow-up after surgery. To date, CE follow-up is conducted based on either antibody or antigen detection assays by double antibody sandwich ELISA. Unlike antigen detection, antibodies to imply exposure to an Echinococcus infection while their titration could remain for a longer period (1–10 years) after surgery. Likewise, antibody respond may be related to the location of a mature hydatid cyst. Antigen detection shows presence of CE infection, it is extremely important and necessary in follow-up of CE after surgery. The circulating antigen (CAg) titration decrease faster than circulating antibody (during 1–3 weeks) after operation. Location of hydatid cyst in detecting antigen is affected less than antibody also. Regarding this subject, antigen detection has several limitations that lead to be used less in CE follow-up. Although, AgB 8/1-kDa subunit is considered as a principle and immunogenic CAg but sensitivity of CAg detection compared to with antibody has variable range, between 33% and 85% which owing to formation of circulating immune complexes (CICs) in result of antigen – antibody complex. The another problem is non using specific CAg (AgB 8/1-kDa subunit) for production of specific paratopes (rabbit hyper immune antiserum) against AgB 8/1-kDa which is used as capture (primary) antibody in double antibody sandwich ELISA assay. The designation of synthetic peptides from conserved regions of AgB 8/1-kDa can help to this problem. These regions (motifs) should be selected for allelic, dominant, immunogenic and conserved without any genetic variation. The first part of this hypothesis suggests which patient’s sera should be treated with acidic buffers such as boric acid, acetic acid, glycine/HCl, polyethylene glycol (PEG) or combination of each of them accompanied by boiling patient’s sera which causes breaking Ag-Ab complexes and in result of releasing AgB 8/1. These modifications are effective to releasing CAg from CIC. To date, the synthetic peptides have been widely used in CE serodiagnosis based on circulating antibody detection only. In second part of this hypothesis suggests the using synthetic peptide of p176 derived AgB 8/1-kDa subunit containing conserved specific epitopes for preparation of specific paratopes (rabbit hyper immune antiserum) based on CAg detection. So, there is no need any native antigens for preparation of non-specific rabbit hyper immune antiserum. These novel improvements can help to decrease the cross-reactivity with other parasitic diseases (specificity). Increasing antigen detection could make a chance in sensitivity of patient’s sera and in result of the best and suitable tool for CE follow-up.