Giardia duodenalis: analysis of humoral immune response in experimentally infected gerbils (Meriones unguiculatus).

In this work, we have analyzed the humoral immune response in Mongolian gerbils infected with Giardia duodenalis trophozoites of strains P-1 and WB. The course of infection in the animals was assessed by monitoring cyst shedding in feces, and serum samples were collected at weekly intervals to measure antibody levels by ELISA. Parallel studies were carried out to determine the patterns of total and surface antigens of the parasite recognized by antibodies using Western blot and radioimmunoprecipitation (RIP) assays with the use of homospecific enzyme conjugates. Typical patterns of cyst shedding were observed in the infected animals and cyst numbers per gram of feces were consistently higher in gerbils infected with WB strain. Antibody levels to G. duodenalis antigens were observed by week 2 post-infection and were still detectable 4 months after infection. G. duodenalis antigens showed a complex but quantitatively and qualitatively different recognition pattern by infection-induced antibodies in Western blot assays which related to infecting strain. However, RIP assays showed a more restricted and common pattern of recognition of surface antigens from either strain. Taken together, the data obtained in this study provides further information regarding direct comparisons among infecting strain, patterns of infectivity, and host immune response toward G. duodenalis antigens in the gerbil model.