Human heavy chain antibodies
Drabek and coworkers
Group head: Dubravka Drabek
Group members: Sylvia Dekker (technician), Rick Janssens (technician).
Camelids contain, in addition to conventional antibodies, functional single chain antibodies (containing only heavy chains). These are coded for by a distinct set of VH segments referred to as VHH genes. Antigen binding for single chain antibodies is different from that seen with conventional antibodies, but high affinity is achieved the same way, i.e. through hypermutation of the variable region and selection of the cells expressing such high affinity antibodies (affinity maturation). Natural VHH containing antibodies are missing the entire CH1 domain of the constant region of the heavy chain due to the loss of a functional splice acceptor sequence at the 5'side of the CH1 exon. They also posses conserved hydrophilic amino acid substitutions in the region involved in hydrophobic interaction with the light chain in conventional antibodies. The simple structure of the variable domain of camelid heavy chain immunoglobulins turned out to overcome the folding and aggregation problems of conventional antibodies. Camelid VHHs have been shown to be superior to conventional antibodies in many different aspects. Since mouse is smaller, easier to keep than any of the camelids and more practical animal for immunization, we are working on generation of a transgenic mouse containing "lamelized" human heavy chain immunoglobulin locus, able to produce functional fully human heavy chain antibodies.
The transposable element Minos from Drosophila hydei, a member of the Tc1/mariner superfamily of transposons, has been shown to transpose in other insect species as well as in mammalian cells. Recently we tested the suitability of Minos as a vector for insertional mutagenesis in the mouse germ line. Minos transposase, expressed in growing oocytes, catalyses the excision of a modified, non autonomous Minos transposon and promotes its re-integration into new sites of the genome. The fact that exogenous DNA sequences can be inserted into the mouse genome using Minos-based transposons makes this element a potential vector for insertional mutagenesis, gene trapping and enhancer trapping experiments. Our research goal is establishment of an efficient system for forward mutagenesis based on transposition events.
Collaboration with Minos Biosystems (http://www.minosbiosystems.com)