Stage-Specific Immune Responses to AgB T-Peptides in Patients with Cystic Echinococcosis

<b>Background:</b> The identification of parasite- and stage-specific antigens is crucial for the development of new diagnostic tests for cystic echinococcosis (CE). We previously analysed the interleukin (IL)-4 response to T-specific peptides corresponding to the immunogenic regions of the five antigen B (AgB) subunits, demonstrating that AgB1 is the most immunogenic protein and that the response to all AgB peptides is associated with viable cysts. However, the response in patients with CE3a (WHO-IWGE) cystic stage was not evaluated and no other immunological factors besides IL-4 were included in the analysis. <b>Methods:</b> Four study groups were defined: "CE3a group" (transitional cysts), "CE3b group" (active cysts), "CE4/CE5 group" (inactive cysts), and "NO CE-group" encompassing patients with non-CE cysts (controls). Whole blood was stimulated in vitro with the five different T-specific peptide pools corresponding to the five AgB subunits and with a pool containing all five peptides' pools (total pool). IL-4 and other immunological markers were evaluated by ELISA and a multiplex assay, respectively. <b>Results:</b> Twenty-four patients with CE (CE3a-group n = 3; CE3b-group n = 6; CE4/CE5-group n = 15) and 14 subjects with non-CE cysts were enrolled. IL-4 levels in response to AgB1 and AgB3 pools were significantly increased in CE compared to NO CE groups (<i>p</i> = 0.0201, <i>p</i> = 0.0041). Within the CE patients, the highest IL-4 median level was observed in response to the AgB total pool, the AgB3 and AgB4 pools, followed by the AgB1 pool. Moreover, the IL-4 levels in response to the AgB1 pool were found to be significantly higher in the CE3b group compared to the CE4/CE5 group (<i>p</i> = 0.0070), while no differences were found for the CE3a group. As for other cytokines, we found higher IL-7 levels in response to the AgB4 pool in the CE4/CE5 group compared to the CE3b group (<i>p</i> = 0.0012), higher IL-2 levels in response to the AgB1 pool and AgB total pool in CE3b patients compared to controls (<i>p</i> = 0.0016), and higher IL-13 levels in response to the AgB total pool in patients with CE3b and CE4/CE5 cysts compared to NO CE (<i>p</i> = 0.0016; <i>p</i> = 0.0009). <b>Conclusions:</b> These results contribute to a better knowledge of the immune interplay in the presence of CE and may be useful for further exploring the use of recombinant proteins/peptides in cytokine release assays for the diagnosis and follow-up of CE.