The field of proteomics has rapidly expanded due to the completion of the human genome sequence. This thesis validates affinity-purified monospecific antibodies of polyclonal origin, for protein profiling in a broad spectrum of normal tissues and cells. Validation of antibodies is crucial for development of reliable binders for target proteins and this thesis evaluates the generation and application of large sets of msAbs in different settings. MsAbs were generated towards recombinant Protein Epitope Signature Tag (PrEST) antigens using a stringent affinity-purification strategy, presented in the first study. The specificity of msAbs was studied using reverse phase protein arrays and immunohistochemistry (IHC), and results presented over 90% success rate in the protein array analysis. In IHC, 81% of the msAbs displayed apparent specific staining in normal tissues. MsAbs were also compared with commercial analogs (cAbs) using IHC and Western blot. Results presented similar outcome between msAbs and cAbs in both applications, although interpretation suggested more extensive IHC staining patterns with msAbs than with monoclonal analogs. For antibody validation, an approach called paired antibodies was presented and involved the generation of two msAbs towards non-overlapping epitopes on the same protein. Similarities in protein detection between paired antibodies were studied using three different antibody-based methods. Similar results were observed in several applications, indicating that this strategy can be a useful tool for studying known and unknown proteins. Given the reliability of msAbs, they were also applied in a study investigating the impact of tissue fixatives on protein detection. The study showed that different fixation mechanisms appeared to affect protein recognition by indicating that aldehyde-based fixation, e.g. induced by neutral buffered formalin, was preferred for tissues used in IHC and non-aldehyde based fixation was applicable for tissues used in protein extraction analysis and Western blotting. Conclusively, validation results suggest that msAbs are reliable affinity binders that can be used as valuable tools for proteome-wide protein profiling in tissues and cells.

As many genome sequencing efforts today are completed, we are now provided with the genetic maps for several organisms, including man. With these maps at hand, the scientific focus is now shifting towards investigations of the functionality of proteins. This task is even more challenging than the genomic field since proteins, in contrast to DNA, do not allow themselves to be specifically probed or amplified by easy and generic methods. However, to achieve knowledge regarding protein function, useful information includes where, when and how much certain proteins are expressed in an organism. Such information can be obtained if protein-specific binding molecules are available as tools. One such class of target specific binders are the antibody molecules, traditionally employed in a broad variety of biotechnical applications, including protein localization studies on both cellular and sub cellular levels. In a first serie of studies, new methodology for recombinant production and purification of antigens for generation of antibodies via immunization routes were investigated. Parallel affinity gene fusion-based expression systems were used for evaluation of different concepts for production of antigen and post-immunization antibody purification. Carefully designed protein antigens from different organisms were produced and used to raise antisera which were affinity purified on their respective antigens to obtain highly specific polyclonal antibodies (monospecific antibodies). One of the constructed expression systems includes an affinity handle, ZSPA-1, previously selected from a combinatorial protein library for its capacity to selectively bind protein A. This allows for convenient, non IgG-dependent, affinity purification of proteins on conventional protein A resins. A strategy where highly target specific antibody preparations could be affinity purified in a more streamlined setup is also presented. By this strategy it was possible to fractionate antibodies showing reactivity to different parts of the antigen into separate fractions. This resulted in affinity purified antibodies showing monospecific but still multi-epitope reactivity. Purified monospecific antibodies were used in different studies including Western blot immunofluorescence and recovery applications. For affinity purification of endogenous target from its native surrounding a selective elution strategy where the recombinant antigen was used to competitively elute the captured target was developed. / QC 20100824

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