Secretory immune response to membrane antigens during Giardia lamblia infection in humans

Abstract

The secretory immune response in humans infected with Giardia lamblia was studied by using saliva samples and a membrane-rich protein fraction. The membrane fraction, studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, showed 24 antigen bands, ranging from 170 to 14 kDa. Saliva samples from giardiasis patients showed a heterogeneous response against the membrane fraction when they were assayed by immunoblotting. Among the antigens recognized by patient saliva samples, those of 170, 105, 92, 66, 32, 29, and 14 kDa stood out. These antigens were not recognized by saliva samples from healthy individuals. They may be of importance in future studies of protection from or diagnosis of G. lamblia infections.

FIG. 1

Presence of anti-G. lamblia sIgA in saliva samples from patients with giardiasis (•) or healthy control individuals (▵) with MRPF as the antigen, as determined by ELISA. The horizontal line at 0.106 represents the mean optical density + 3 standard deviations for saliva samples from healthy individuals.

FIG. 2

SDS-PAGE of Giardia antigens under nonreducing conditions. (A) MRPF antigen; (B) total Giardia antigens. To the right of the lanes is shown the densitogram of the SDS-PAGE gels for MRPF (dotted line) and total (solid line) antigens. Molecular mass standards are also indicated.

FIG. 3

Immunoblot analysis of the Giardia MRPF antigen with saliva samples from patients with giardiasis. Molecular mass standards (in kilodaltons) are shown on the left.

FIG. 4

Immunoblot analysis of the Giardia MRPF antigen with saliva samples from healthy control individuals. Note that the intensity and number of bands in each blot are lower than those observed with saliva samples from giardiasis patients (Fig. 3). Molecular mass standards (in kilodaltons) are shown on the left.

FIG. 5

Immunoplot of simple frequencies of the populations studied patients with acute giardiasis (x axis) versus healthy controls (y axis). The numbers in the immunoplot represent the molecular mass (in kilodaltons) of each Giardia antigen. The 170-, 105-, 92-, 66-, 32-, 29-, and 14-kDa antigens were recognized solely by patient saliva samples (specific bands) and therefore fall on the x axis. Antigens which reacted with saliva samples from both patients and controls (cross-reacting bands) fall between the two axes.