[Antigenic Characterization of Immunodominant Epitopes of Alpha-8 giardin in Giardia lamblia].

Objective: To identify the dominant epitopes of α-8 giardin in Giardia lamblia, and analyze their immunoreactivity.

Methods: Three dominant epitopes G1（7-17 aa）, G2（30-40 aa） and G3（296-306 aa） were predicted for α-8 giardin by bioinformatic analysis using DNAstar, Biosun and CLUSTAL W softwares. Each epitope was conjugated to keyhole limpethemocyanin (KLH) and then used to immunize female Chinchilla rabbits via multi-point（8-10 points） subcutaneous injections on the back（0.5 mg conjugate/rabbit, 100 μl at each point）. Then the rabbits were boosted（0.2 mg conjugate/rabbit） on days 14, 21 and 28 after the first immunization. Blood was collected prior to each immunization, and carotid artery blood（50 ml） was collected on day 7 after the last immunization. The antibody titer for anti-KLH-G1, anti-KLH-G2 and anti-KLH-G3 sera was determined with indirect ELISA. The reactivity of the three anti-sera with recominant giardin (rGiardin) was analyzed with Western blotting.

Results: The concentration of the purified conjugates KLH-G1, KLH-G2, and KLH-G3 was 0.66, 0.95 and 0.25 mg/ml， respectively. ELISA showed that the antibody titer for anti-KLH-G1, anti-KLH-G2 and anti-KLH-G3 sera was 1∶12800, 1∶51200, 1∶51200, respectively. SDS-PAGE revealed a specific band at M(r) 36 000 for the three anti-sera. Western blotting showed that the three anti-sera all specifically recognized rGiardin.

Conclusion: Immunization with the KLH-G1, KLH-G2, and KLH-G3 conjugates induced production of specific IgG antibody in rabbits, which can recognize rGiardin.