Choice of immunogen

Current efforts in vaccine development have predominantly utilized clade B isolates, which represent the subtype in North America and Western Europe. There is also an increased interest in the development of clade A and C vaccines for the expanding pandemic in Asia and sub-Saharan Africa. A concern in fhe clade-specific vaccine strategy is the potential inability to produce large amounts of vaccine specific for distinct clades. This leaves open the question of specific vs. cross-clade effectiveness. Choice of immunogen(s), adjuvant, dose, and mode of administration are also additional variables that must be addressed in candidate vaccine research. 

Excipients are additives that are included in a formulation, because they either impart or enhance the stability, delivery, and manufacturability of a drug product. Regardless of the reason for their inclusion, excipients are an integral component of a drug product and therefore need to be safe and well tolerated by patients. For protein drugs, the choice of excipients is particularly important because they can affect both efficacy and immunogenicity of the drug. Hence, protein formulations need to be developed with appropriate selection of excipients that afford suitable stability, safety, and marketability. 

It appears that fluorescence techniques are poised to receive more serious consideration for accelerated development efforts. Key obstacles remaining include stability of receptors and fluorophores, challenges that will possibly be met partially by results of the intense efforts of molecular biology, polymer science, and nanotechnology. Advances in nanomaterials such as quantum dots will likely enable improvements in optical stability and choice of excitation/emission wavelengths for various transduction methods. Stabilization of natural and artificial enzymes and rendering immunogenic protein receptors stealthy may also aid the pursuit. 

The choice of animal is mostly one of convenience rather than necessity. A notable exception is the production of anti-insulin antibodies for which guinea pigs should be used. Generally, rabbits, goats and sheep are used for polyclonal antisera and mice and rats for monoclonal antisera. As a rule of thumb, about 15 pg of immunogen or 5 X 10 cells per kg of body weight suffices. 

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