Our current focus is the development of improved recognition elements for biothreat detection. We work on the development of single domain antibodies (sdAb) derived from llamas as well as conventional antibody fragments (scFv), and a variety of fusion constructs with an eye towards developing improved recognition and signal transduction elements. The sdAb are derived from the unique heavy-chain antibodies found in camelids, and consist of only a variable heavy domain (Figure 1). Although half the size of an scFv, the sdAb bind target with high affinity and specificity; the majority of sdAb refold and are able to bind antigen after heat denaturation (Figure 2). In contrast, scFv and conventional antibodies aggregate irreversibly after identical heat treatment. We continue to develop sdAb towards a wide range of targets and to work towards a better understanding of their unique properties. In addition we aim to develop methods to engineer scFv to have higher affinities and thermal stabilities. Starting with a given scFv, our goal is to improve its affinity constant by an order of magnitude, and to raise its melting temperature to over 70 degrees C. Ideally we will develop methods that can be applied to improve scFv specific for any target.

Cartoon showing a conventional antibody, a heavy-chain-only antibody and their derived binding fragments, the scFv and sdAb respectively. Constant domains are shaded light blue. Variable domains are colored red and blue for conventional variable heavy domain and light domains, and purple for the heavy-chain antibody's variable domain.
Above, circular dichroism showing the ability of sdAb C8 (left) and B4 (right) to refold after heat denaturation. Left shows the ability of both sdAb to bind target after heating cycles.