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Fully human antigen-specific polyclonal antibody responses induced in cloned human artificial chromosome transchromosomic cattle
Methods for engineering mice to express polyclonal repertoires of human antibodies are well established and their use to produce human monoclonal antibodies of predefined specificity has been widely demonstrated (Ishida, et al., 2002; Lonberg, et al., 1994; Mendez, et al., 1997; Nicholson, et al., 1999). Although such engineered mice do expresses diverse repertoires of human antibodies and are immunophysiologically similar to humans; due to their small size, they are not suitable for the production of significant quantities of human polyclonal antibodies (hPAbs). Currently, hPAbs are in wide clinical use for prophylaxis and therapy in immunocompetent and immunodeficient patients [Keller, et al., 2000). Because these antibodies are obtained from human sources their supply is limited and their titers are often low because immunization protocols to raise pathogen-specific antibodies in donors are optimized for safety rather than for magnitude and duration of antibody response. Given these limitations, a technology for the production of antigen-specific hPAbs in large nonhuman hosts is novel and has significant biomedical and biodefense interest. Considering the differences in the mechanisms and strategies used by bovines and humans to diversify their antibody repertoires (Butler, 1998; Flajnik, 2002; Reynaud, et al., 1991; Meyer, et al. , 1997), questions arise about the capacity of HACs to sponsor the generation of functional human Ig repertoires. This prompted the following critical questions to be addressed: Can a large and viable population of human Ig-producing cloned HAC-Tc cattle be produced? Does human Ig synthesis persist as the animals mature? Is any portion of the human Ig assembled as fully human antibodies free of bovine heavy or light chains? Do rearranged human heavy chain loci undergo class switching in bovine cells? Does the HAC construct encode a broad diversity of human immunoglobulins in cattle? Most importantly, does immunization induce any fully human, antigen-specific polyclonal antibodies in cloned, HAC-Tc cattle, and effect protective functions? Resolving these questions is necessary to determine if the immunological divergence of bovines and humans prevent the use of HAC-bovines as suitable bioreactors for production of human antibodies for therapy. The availability of cloned HAC-Tc cattle that are imrnunologically mature has enabled the conduct of studies to address these questions, and the following results have been obtained. Biochemical and serological studies determine that fully human Ig isolated from HAC-Tc cattle is polyclonal and is comprised of both human μ and γ isotypes, demonstrating that the HAC-borne human IgH locus undergoes class switching within bovine cells. (Abstract shortened by UMI.)
Immunology|Molecular biology|Veterinary services|Livestock|Genetics
Choi, Yoon Jong, "Fully human antigen-specific polyclonal antibody responses induced in cloned human artificial chromosome transchromosomic cattle" (2005). Doctoral Dissertations Available from Proquest. AAI3179866.