Multiplex Assay Detection of Immunoglobulin G Antibodies That RecognizeGiardia intestinalisandCryptosporidium parvumAntigens

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Abstract
Giardiasis and cryptosporidiosis are common enteric parasitic diseases that have similar routes of transmission. In this work, we have identified epitopes within theGiardiavariant-specific surface protein (VSP) sequences that are recognized by IgG antibodies from 13 of 14 (93%) sera from patients with stool-confirmed giardiasis. The conserved epitopes are shared among VSPs from both of the assemblages that commonly infect humans, and they are likely to be structural, as both sodium dodecyl sulfate treatment and dithiothreitol reduction decrease antibody recognition. In a multiplex bead assay (MBA), we used three VSP fragments from an assemblage AGiardiastrain, three VSP fragments from assemblage B strains, and the α-1 giardin structural antigen to detect IgG antibodies toGiardiaand used the recombinant 17- and 27-kDa antigens to simultaneously detect IgG antibodies toCryptosporidium. The MBA differentiated between sera fromGiardiaandCryptosporidiumoutbreaks and also identified a giardiasis outbreak that may have included cryptosporidiosis cases. Approximately 40% of cryptosporidiosis outbreak samples had high MBA responses for both the 27- and 17-kDa antigens, while Giardiaantigens, while ≤12% of nonoutbreak samples and samples from U.S. and British Columbia cryptosporidiosis outbreaks met our definition forGiardiaseropositivity. A MBA using multiple parasite antigens may prove useful in the epidemiologic analysis of future waterborne or food-borne outbreaks of diarrheal disease.

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