Antibody and cytokine responses to Giardia excretory/secretory proteins in Giardia intestinalis-infected BALB/c mice.

The humoral and cellular responses against excretory/secretory proteins and soluble extracts of Giardia intestinalis were evaluated in the course of experimental G. intestinalis infection in BALB/c mice. Production of IgG1, IgG2a, IgA, and IgE antibodies against excreted/secreted proteins and soluble extract was detected after infection by G. intestinalis. Specific IgA antibody against E/S proteins and soluble extract form intestinal fluids in infected mice was detected by ELISA. The Western blotting identified proteins of 30, 58, 63, and 83 kDa for IgA and IgG, respectively. High proliferation rate in vitro of spleen cell and secretion of interleukin-4 (IL-4) at 21 days p.i. after stimulation with excreted/secreted proteins and low proliferative response in the presence of soluble extract in infected BALB/c mice was observed. High production of interferon gamma (IFN-γ) and interleukin-5 (IL-5) at the time of decreasing cyst output (14-21 days p.i.) in infected mice was recorded, suggesting the important role of these cytokines in the control of the infection. Interestingly, progressive and gradual increase of the interleukin-10 after stimulation with both preparations was recorded from 7 days until 28 days after infection, indicating the possible regulatory effect of these antigens on the immune response during Giardia infection. Therefore, the infection by Giardia duodenalis stimulates a mixed response Th1 and Th2, mainly stimulated by excretory/secretory antigens. The immunogenicity of these antigens may be a suitable for identification of the proteins related with the effective immune response in the course of infection by G. duodenalsis.