Do Accelerated Antibody Production Protocols Work?
Given the increasingly fast pace with which research is conducted, it’s natural that scientists want to obtain a custom antibody as quickly as possible. This is a pressure felt by companies that develop custom antibodies and has led to the introduction of accelerated protocols that promise ready-to-use antibodies in as little as 28 days. Sadly, these short protocols are simply marketing gimmicks and researchers are nearly certain to be disappointed with the antibodies that they receive with these protocols.
This quest to speed up the animal’s natural immune response leads to the use of harsh immunization protocols that require multiple site injections and often in locations that are painful to the animal (such as in the foot pads, which prevents the animal from being able to walk). Or, companies tout the use of exotic adjuvants that are somehow capable of tricking the animal’s immune system into overdrive. But, the reality (as confirmed in numerous studies) is that these techniques make virtually no difference in terms of the speed of the immune response and serve only to increase discomfort for the animal.
Regardless of the adjuvant or immunization technique used, it’s critical to understand that antibodies are produced as part of the adaptive immune response and so require time to undergo the genetic mutations (somatic hypermutation) required to develop novel antibodies that are specific to the epitopes presented on the antigen. By the 4th or 5th week after the initial immunization, very little IgG is present. Instead, the immune system initially produces IgM antibodies, which are large pentameric complexes of immunoglobulins that aren’t useful for research applications. More important, antibodies at this stage stil have low affinity (the strength with which they bind) to the antigen.
Between the 5th and 7th weeks of the production protocol, we begin to see the development of IgG (the singular antibody proteins used in research applications) against the antigen. In our own protocols, we take the first bleed at the 7th week since we feel that antibodies at this point have had sufficient time to develop affinity towards the antigen and also because antibody titers typically peak at this point (in rabbits).
However, the affinity maturation process has not completed even by the 7th week (there will be a mix of high and low affinity clones at this point) and in our studies, has not finished until between the 9th and 11th weeks. By the third production bleed (week 11) in our protocol, the affinity maturation process is typically complete and the population of antigen-specific antibodies present in the serum at this point will come from clones that have survived the affinity maturation process and so will bind with superior affinity to the antigen. It is for this reason that we typically run affinity purifications of the serum at this point.
Despite what companies may promise in terms of marketing gimmicks and accelerated protocols, it is impossible to escape the reality of the speed with which the affinity maturation process occurs. Yes, some antibody (mostly IgM) will technically be present in the serum by the 4th or 5th week. But, this antibody will have low affinity to the antigen and will not be desirable for research applications. For this reason, the development of a custom antibody still requires the use of a longer protocol for the best results.