FIG 3.

Systemic and intestinal humoral immune responses. Blood and stool samples were collected at 0, 7, 14, 21, and 28 days after infection or immunization. Serum IgG (A) and secretory IgA (B) levels were determined by ELISA using a polyclonal mouse anti-gerbil IgG and IgA developed in our laboratory (see Materials and Methods). Plates were sensitized with G. lamblia WB1267 soluble extract. Each point represents the mean value ± standard error of the mean of the results obtained in three independent experiments (n = 12). *, P < 0.01 compared to results in uninfected animals; **, P < 0.05 compared to results in uninfected animals; #, P < 0.01 for results in infected animals versus those in animals immunized with VSPs (Tukey's test between the groups). (C) Levels of specific serum IgG and fecal IgA anti-VSP1267 or anti-VSP9B10. Samples of blood and stool from 28 dpi or immunizations were tested. Plates were sensitized with immunopurified VSP1267 or VSP9B10, respectively. Values are the means ± standard errors of the means (n = 12). (D and E) Linear correlation between cyst numbers and either serum IgG or fecal IgA response. Data from 14, 21, and 28 dpi were included in the analysis.