Background: The complex multi-chain architecture of antibodies has spurred
interest in smaller derivatives that retain specificity but can be more easily produced in bacteria.
Domain antibodies consisting of single variable domains are the smallest antibody
fragments and have been shown to possess enhanced ability to target epitopes that are difficult
to access using multidomain antibodies. However, in contrast to natural camelid antibody
domains, human variable domains typically suffer from low stability and high propensity
Methods: This review summarizes strategies to improve the biophysical properties of heavy
chain variable domains from human antibodies with an emphasis on aggregation resistance.
Several protein engineering approaches have targeted antibody frameworks and complementarity
determining regions to stabilize the native state and prevent aggregation of the denatured
Conclusion: Recent findings enable the construction of highly diverse libraries enriched in aggregation-resistant
variants that are expected to provide binders to diverse antigens. Engineered domain antibodies possess unique
advantages in expression, epitope preference and flexibility of formatting over conventional immunoreagents and
are a promising class of antibody fragments for biomedical development.