“Polyclonal antibody” refers to an immunoglobulin produced form more than a single clone of plasma cells (e.g., B lymphocytes). Although each B-cellclone produces an antibody which is specific for one particular epitope of an antigen, the serum antibodies produced in response to a complex antigen contain a mixture of antibodies because the multiple epitopes on an antigen will induce proliferation and differentiation of a variety of B cell clones. Each one of these cell clones produce antibodies which are specific for one of the various epitopes on the antigen. This polyclonal response is advantageous for the immune system because is helps localization, phagocytosis, and complementmediated lysis of the antigen.

Advantages of therapeutic polyclonal antibodies and antibody coctails

Evidence has accumulated supporting the idea that mixtures of antibodies binding multiple non-overlapping epitopes combine the benefits of an engineered monoclonal antibody, with the broad spectrum activity of a polyclonal therapeutic. Antibody cocktails for the treatment of infectious diseases for example are in development. Merck Medarex has recently shown that biolclonal therapeutic targeting C. difficile toxins A and B was able to lower the incidence of recurrence in patients when adminsitered in combination with vancomycin or metronidazole. Crucell is also pursing a biclonal coctail against SARS coronavirus. Excelimmune employed a set of five human antibodies recognizing S. aureus, cinluding methicillin-resistance S. Aureus (MRSA) strains. (Maynard, Current Opinion in Chemical Engineering, 2013, 2, 405-415).

Design of Antibodies targeting more than one Epitope (ie.., polyclonal antibodies).

Factors to consider in Design

A number of factors should be evaluated when designing target specific recombinant polyclonal antiboides includeing the impact of the natural antibody response in vivo by analyzing the antibody repertoires from individuals recovering from effects related to the relevant target, the neutralizing potential of antibodies raised against individual epitopes so as to avoid antiboides against epitopes with little impact, utilizing a broad antibody repertoire so as to use as broad a range of neutralizing epitopes as possible, while miaintaining an antibody composition resembling the neutralizing host immune response as closely as possible. Using polyclonal antiboides with desirable effector functions relfecting those relevant in the natural antibody mediated elimination should aslo be considered. Using different expression systems which could be cells of acterial, plant or eukaryotic origin can also be used for modulating the glycosylation pattern of antiboides and hence their effector function (Haurum, US 2008/0206236).

Design of Antibody Coctails and Bispecific antibodies

While a traditional IVIG product contains a large number of antibodies binding a variety of antigens, only a fraction bind the antigen of interest and of those, only a fraction are clinically relevant protective antibodies. IVIG thus typically requires large doses for efficacy. Multi-specific antibodies on the other hand yield a single molecular entity able to bind two distinct epitopes, thereby combining the ease of monoclonal antibody manufacturing with broader antigen specificity. Oligoclonal antibody cocktails are a combination of several monoclonal antibodies, each grown, purified and characterized in parallel before combining. Oligoclonal antibody cocktails ahve already been approved for use in human to treat cancer. For example, twoo approved anti-EGFR monocloanl antibodies (Cetuximab and Panitumumab) binding EGFR domain III, blocking ligand receptor activation and downstream signaling. Studies have shown that combinations of antibodies binding non-overlapping eptiopes are more effective than a single antibody at inhibiting tumor growth by triggering EGFR internalization and degradation. A recently approved biclonal combination onsisting of the monocloanl antibodies Trastuzumab and Pertuzumab, which target different epitopes on the HER-2 grwoth factor receptor, was effective in reducing progression rates in breast cancer than treatment with Trastuzumab alone. In addition, a bispecific antibody that binds both VEGF and HER@ with high affinity has been accomplished. (Maynard, Current Opinion in Chemical Engineering, 2013, 2, 405-415).

Cell Culture Systems and Vectors used for the Production of Polyclonal Antiboides

Haurum (WO2004/061104) discloses a method for manufacturing a recombinant polyclonal protein composition such as a recombinant polyclonal antibody composition by collecting cells transfected with a library of variant nucleic acid sequences wherein each cell in the collection is transfected with and capable of expressing one member of the library which encodes a distinct member of a polyclonal protein that binds a particular antigen (e.g., different antibody clones differing only in the variable region) and which is located at the same single site in the genome of each individual cells in the collection. The nucelic acid sequence is introduced into cells by transfection with a library of fectors for site specific integration (e.g., using a recombinase). See vector design under “biotechnology”). 

Nielsen discloses a method for manufacturing a recombinant polyclonal protein composition such as a polyclonal antibody (composition of different antibody molecules which are capable of binding to several different specific antigenic detemrinants on the same or on different antigens) by collecting cells transfected with a distinct member of the protein which is randomly integrated into the genome of the host cells. The individual cell clones each of which produce an individual member of the polyclonal protein are then mixed in  order to generate a polyclonal manufacturing cell line for the production of a polyclonal protein.  

Rasmussen (WO2006/007850) teaches a method for manufacturing an anti-RhD recombinant polyclonal antibody by transfecting a library of cells with anti-RhD anntibody expression vectors wehrein each cell line is then capable of expressing from a VH and VL comprising nucleic acid segment, one member of the library. Rasmussen (US2008/0131882) also teaches analytic techniques that can be used to obtain information with respect to the relative proportion of individual members in the samples such as restriction fragment lenght polymorphism (RFLP) analysis, microarray analysis, PCR and nucleic acid sequencing.