From immunotherapies to intracellular delivery of antibodies:
The first uses of passive immunization carried out to cure certain diseases were reported in the late 1890’s. In 1897 Paul Ehrlich developed his famous side-chain theory: He suggested that the effects of toxins on cells were mediated through these side-chain proteins and that immunity was made possible thanks to their overproduction. These side chains are reminiscent of antibodies as we know them today.
At first antibodies were prepared by purification during the Second World War as treatments against several diseases, huge progress was made in the 1970’s. In the “magic bullet” concept, also developed by Ehrlich, if a compound can be created to selectively target a disease-causing organism, then a toxin could be delivered along with this compound to kill this organism. This was realized to some extent many years later in 1975, with Khöler and Mildstein‘s invention: monoclonal antibodies, which can provide a very specific binding affinity.
Two years later, Alan Williams showed that these monoclonal antibodies could be raised against biologically interesting molecules. Since then, antibodies have become a fantastic tool not only for immunotherapies but also as in vitro tools for diagnostic and research purposes.
Producing antibodies into the cell: intrabodies
If some antibodies were first developed for very specific immunotherapies, these therapeutic antibodies mainly target extracellular proteins since they cannot enter cells. However, it would be of great interest if therapeutic antibodies could also address intracellular proteins involved in human diseases. This could pave the way to knowledge on the functions of certain proteins. To this end, but due to the lack of efficient delivery systems at that time, intrabodies were used in the mid 90’s to modulate or interrupt specific cellular functions. Such intracellular antibodies were specifically designed to be directed against antigens localized in the cytosol, bypassing the exocytosis pathway and its secretion. Some studies have described their use in several pathologies such as infectious diseases, cancers or neurodegenerative disorders. Although the application has shown some results, this gene-engineered technology is highly challenging for designing, selecting and expressing efficient intrabodies inside cells. Even if several technologies have been developed to produce and select a large repertoire of gene-engineered antibodies on the surfaces of phage or yeast, it is still highly-costly and time-consuming.
Bringing antibodies into the cell from the extracellular environment
More recently, other approaches such as Protein Transduction Domains (PTD) have been developed, enabling the delivery of exogenous proteins inside cells. But the use of PTD requires chemical coupling between the PTD and the antibody, which can result in the loss of antibody function.
The latest approach that offers the same benefits, minus all the burdens, is liposomal formulation.
Liposomal formulations are able to interact with antibodies through hydrophobic and electrostatic interactions and can introduce them inside cells. This does not require reengineering and the selection of new antibodies.
• It enables the use of thousands of existing antibodies as drug discovery tools or as new drug entities. It really opens new fields of investigation for scientists who want to elucidate molecular mechanisms. Although therapeutic application still seems a long way off, this is a good way to make it happen more quickly.
Inhibiting protein-protein interactions
• siRNA intracellular delivery allows to shutdown the expression of a given protein and consequently all the functions associated with this protein. But as we know, most proteins have several different functions inside the cell. It is much more advisable and appropriate to inhibit only one of them by using a specific monoclonal antibody which could interfere with a protein-protein interaction for example. This new technique is actually the best way to inhibit protein-protein interactions and it is really specific to modulating intracellular protein functions.
During this last years, BCC has developed a very efficient and non-toxic antibody intracellular delivery systems based on a liposomal formulation. It can be used very simply with no need of reengineering the antibody of the market. Therapeuticantibody internalization offers huge potential by allowing to reach many new targets.
From delivery to discovery and from discovery to therapy, BioCellChallenge can be your partner for a comprehensive way to intracellular mechanisms.