An immunoglobulin G1 monoclonal antibody highly specific to the wall of Cryptosporidium oocysts

The detection of Cryptosporidium oocysts in drinking water is critically de pendent on the quality of immunofluorescent reagents. Experiments were perf ormed to develop a method for producing highly specific antibodies to Crypt osporidium oocysts that can be used for water testing. BALB/c mice were imm unized with six different antigen preparations and monitored for immunoglob ulin G (IgG) and IgM responses to the surface of Cryptosporidium oocysts. O ne group of mice received purified oocyst walls, a second group received a soluble protein preparation extracted from the outside of the oocyst wall, and the third group received whole inactivated oocysts. Three additional gr oups were immunized with sequentially prepared oocyst extracts to provide f or a comparison of the immune response. Mice injected with the soluble prot ein extract demonstrated an IgG response to oocysts surface that was not se en in the whole-oocyst group. Mice injected with whole oocysts showed an Ig M response only, while mice injected with purified oocyst walls showed litt le increase in IgM or IgG levels. Of the additional reported preparations o nly one, BME (2-mercaptoethanol treated), produced a weak IgM response to t he oocyst wall. A mouse from the soluble oocyst extract group yielding a hi gh IgG response was utilized to produce a highly specific IgG, monoclonal a ntibody (Cry104) specific to the oocyst surface. Comparative flow cytometri c analysis indicated that Cry104 has a higher avidity and specificity to oo cysts in water concentrates than other commercially available antibodies.