Generation of a polyclonal Fab phage display library to the protozoan parasite Cryptosporidium parvum

We had developed a technology for creation of recombinant polyclonal antibo dy libraries, standardized perpetual mixtures of polyclonal whole antibodie s for which the genes are available and can be altered as desired. We repor t here the first phase of generating a polyclonal antibody library to Crypt osporidium parvum, a protozoan parasite that causes severe disease in AIDS patients, for which there is no effective treatment. BALB/c mice, immunized by neonatal oral infection with oocysts followed by intraperitoneal immuni zation with a sporozoite/oocyst preparation of C. parvum, were used for con struction of a Fab phage display library in a specially-designed bidirectio nal vector. This library was selected for reactivity to an oocyst/sporozoit e preparation, and was shown to be antigen-specific and diverse. Following mass transfer of the selected variable region gene pairs to appropriate mam malian expression vectors, such anti-C. parvum Fab phage display libraries could be used to develop chimeric polyclonal antibody libraries, with mouse variable regions and human constant I regions, for passive immunotherapy o f C. parvum infection.