Giardia lamblia infection induces different secretory and systemic antibody responses in mice

The adult mouse model of Giardia lamblia infection serves as an excellent animal model to understand the immunological mechanisms involved in the control and clearance of Giardia infection. Little is known about the G. lamblia-specific antigens that stimulate the humoral immune response in this model of giardiasis. We analysed the secretory and systemic antibody responses to G. lamblia during primary and secondary infection in C3H/HeJ adult mice. Faecal IgA and Serum IgG anti-G. lamblia antibodies were observed at week 2 post-infection. Serum IgG responses remained constant over the next several weeks, whereas faecal IgA titres continued to rise from weeks 2-6 post-infection. Western blot analysis revealed that intestinal IgA and serum IgG antibody responses were directed toward several distinct proteins of G. lamblia. Certain proteins appeared to be recognized by both faecal IgA and serum IgG, whereas other antigens were specific for either the secretory or systemic antibody responses. G. lamblia primary and secondary infections were associated with differences in the antibody recognition pattern. The biochemical and immunological characterization of these antigens will help us to better understand the immunobiology of the G. lamblia-host interaction.