The breakthrough discovery that animals from the camel family (camelids include alpacas, camels, llamas, vicuñas and guanacos) produce antibodies with no light chains as part of their repertoire is possibly one of the lesser well known biological breakthroughs. This discovery demonstrated that a single-domain fragment had the ability to bind a target just as well as a full 4-chain antibody, such as IgG.
Smaller antibody fragments have received a lot of interest for their potential use as research tools and therapeutics, because classical IgG antibodies are too bulky to penetrate tissues effectively and are both costly and time-consuming to manufacture. Antigen-binding variable regions have been used in different combinations, such as Fab, diabody and scFv, all with some degree of success. Yet the N-terminal domain of the camelid antibody, the VHH domain (also termed a VHH antibody or nanobody), in comparison represents a naturally evolved fully functional target binding fragment with many advantages.
Apart from the camelid family the only other known species that produce these VHH antibodies are cartilaginous fish, such as the nurse shark. Evolutionary analysis of the small VHH antibodies in these different species has shown that they evolved independently, likely to allow the targeting of otherwise inaccessible epitopes, such as the catalytic centres of enzymes, where standard antibodies would be just too bulky.
The VHH domain is only 13-16kDa in size, so is more easily able to penetrate tissues than its 150kDa IgG counterpart. These camelid antibodies have also been shown to be able to withstand the harsh intracellular environment without unfolding and losing function, making them a preferable option for applications such as immunocytochemistry and live cell imaging or targeting specific cells for therapeutic applications in gene therapy. VHH domains can be linked to fluorescent protein markers or conjugated to HRP or other signal-generating moieties and their small size means that they can function in a highly specific manner in pull-down experiments, recognising antigens that are inaccessible to standard antibodies.
Unfortunately scientists lack an effective method of screening the VHH antibodies to identify the most specific binders, which has meant that generally no commercial service for the creation of custom camelid antibodies is available.
Fortunately though, Affimer technology is engineered to work in a similar manner to the VHH domain. Affimer molecules are small (just 15kDa), easily modifiable with different markers and tags, highly specific with greater affinities than standard antibodies and biologically inert and biochemically stable making them the perfect option for intracellular or pull-down studies. What’s more we can easily generate an Affimer to any target you wish, as unlike those camels our in vitro expression systems aren’t limited by the immune system, so toxicity or conserved proteins are simply not an issue. Our custom antibody alternative service takes just 7 weeks too, so you won’t have to wait around too long for your Affimer, allowing research to get underway much quicker.