Antibodies are among the most sophisticated detection tools available
for fundamental and biotechnological purposes. These proteins are
produced by the immune system and are very efficient at binding
molecules specifically. This property makes them the tools of choice in
diagnostic tests, for passive immunity therapy, for therapeutic
neutralization and identification and localization of proteins in
biological samples. Alas, both antibodies and antigen-binding fragments
generated thereof are difficult and expensive to produce with current
procedures. These typically start with immunization of an animal with a
target antigen—and then they require a demanding follow up in the
laboratory.
In this context, we set out to design and implement an alternative
technology to produce antibodies in a fashion reminiscent of the immune
system but assembled with Synthetic Biology approaches. To this end, we
embarked in setting up an effective platform composed of parts recruited
from bacteria that behaves as an immune-system-like machine. This setup
permits generation of single-chain camel antibodies (nanobodies)
displayed on the surface of bacterial cells—thus enabling a large number
of uses in medical and industrial Biotechnology. The platform relies on
three main blocks: [i] autonomous functional modules assembled in the
genomic chassis of a streamlined /Escherichia coli/ strain that allows
the display of nanobody scaffolds on the surface of the bacterial cells,
[ii] a method of mutagenesis for conditional diversification of
target-binding sequences of the nanobody leading to affinity maturation.
This is then followed by clonal selection and proliferation of improved
binders that is based on their functionality.
The hereby described all-bacterial immune system-like platform executes
the major steps involved in the genesis of antibodies by recreating the
way animal lymphoid tissues react to antigens and drive cells through
the maturation of affinity and specificity towards desired molecular
targets. This approach is fast, simple and functions with minimal
external intervention.
