B- and T-cell epitopes from Giardia proteins as candidates in the design of a multipeptide-based vaccine against giardiasis.

Giardia lamblia is a prevalent protozoan that colonizes the gut epithelium causing giardiasis. Several Giardia antigens have been described as immunogenic. To design an effective oral vaccine, Giardia proteins able to activate immune responses in the gut mucosa are required. Binding immunoglobulin protein (BIP) and α-1 giardin are candidates for Giardia vaccine. This work focuses on searching immunogenic regions of antigens recognized by the humoral and cellular immune response. C3H/HeJ mice were orally immunized with BIP and α-1 giardin recombinant antigens (50 µg/without adjuvant) weekly during 4 weeks. The specific-antibody response (IgG and IgA) was evaluated by ELISA. IL-2 levels were analyzed in the supernatant of Giardia protein-stimulated splenocytes for 96 h. To identify immunogenic regions from G. lamblia antigens we used Western Blotting and Mass spectrometry analysis. Additionally, we predicted B- and T- cell epitopes using bioinformatics. Only BIP antigen-induced secretory and systemic antibody response also showed an antigen-specific T-cell activation. BIP protein was an antigen able to break oral tolerance, showing its potential as a vaccine candidate. Nevertheless, both proteins have regions recognized by antibodies (BIP: 357-511 aa, α-1 giardin: 35-93 aa) and regions that could activate T cells (BIP: 396-410 aa, α-1 giardin: 173-187 aa). These antigen fragments could contribute to the rational design of an effective epitope-based vaccine against giardiasis.