TC Bovine� Technology
Sanford Applied Biosciences' technology produces unique human antibodies for research and development, both as therapeutics as well as diagnostics. To this end, we have established the siversitAb™ system that produces large quantities of fully human IgG antibodies. Tc BovineTM are generated by transferring a Human Artificial Chromosome (HAC) vector carrying the entire human IgH and IgL loci into bovine cells where bovine Ig genes are knocked out by the sequential gene targeting, followed by chromatin transfer. The diversitAbTM system can be divided into two parts, upstream and downstream (figure 6).
After immunization of a Tc bovine with an antigen (Ag) of interest, once Ag-specific human IgG titer is observed in serum of Tc bovine, a large amount of Ag-specific human polyclonal IgG antibodies are purified from plasma and used for quick proof-of-concept (POC) testing. Because they are fully human IgG antibodies, they are preferable for human translational researches. This is one of several unique characteristics of the Tc bovine system because it is difficult to obtain human polyclonal antibodies in large quantities for POC testing from small animal species such as mice, rats or rabbits that have been modified to produce human antibody. Once activity/efficacy is confirmed with human polyclonal antibodies, then we proceed to the downstream processes to convert them to a recombinant human IgG format. In order to evaluate the capability of Tc bovines to generate unique human IgG response, four "difficult-to-generate" antigens were immunized in Tc bovines (figure 7).
Our preliminary data indicate that Tc bovines show Ag-specific humoral immune responses with human IgG against "difficult-to-generate" antigens that are superior to rodents, rabbits or chickens. For instance, when whole Methicillin-resistant Staphylococcus aureus (MRSA) cells were immunized, Tc bovines showed human IgG titers against capsular polysaccharide (CP) antigens on MRSA cells in a serotype-specific manner (CP5 or CP8) whereas wild type mice did not.
We have developed downstream technology to convert such unique/distinct human IgG immune response in Tc bovines, compared to rodents, to recombinant human IgG format. Our specially optimized hybridoma system allows for generation of diversified, multiple fully human IgG antibodies at a time. It succeeded in establishment of several unique human IgG antibodies that specifically recognize a certain set of human cancer cells, exerting antibody-dependent cellular cytotoxicity (ADCC), with minimal binding to normal human cells, while such antibodies have never been obtained from rodents. In order to complement the hybridoma system, we have been also developing another system that can directly convert plasma-derived human polyclonal antibodies to recombinant format.