Team:Virginia/Applications

Polysialic Acid

The K1 strain of E. coli produces and encapsulates itself in α-2,8-linked polysialic acid (PSA), a polysaccharide that biochemically mimics the human glycoprotein Neural Cell Adhesion Molecule (NCAM). This similarity renders virulent K1 E. coli poorly immunogenic in humans because they aren’t seen as foreign and are therefore cloaked from antibody opsonization and complement-mediated killing. Clearly, equipping our minicells with such protection would be highly advantageous for improving their successful delivery rate and reducing harmful immune responses.

A significant amount of machinery (14 genes in total) is required to generate the PSA capsule in K1 E. coli and transferring this ability over to the comparatively docile K12 E. coli is quite the feat. Thankfully, we were able to find previous work by Dr. Eric Vimr that accomplished just that and obtain a single pSR23 plasmid that contains all the required genes. We are currently in the process of confirming the presence of PSA on our K12 E. coli via antibody-labeled fluorescence microscopy.

Targeting

Previous researchers who have worked on minicells have attached Protein A/G Fc receptors to an OmpA autotransporter located on the surface of minicells. This patented approach allowed them to add antibodies specific to their target host cell to purified minicells, thereby creating targeted minicells. Additionally, the antibody coating serves to protect the minicells from the host immune system and induce endocytosis when binding to certain target cell receptors. Such a modular targeting system is ideal for such a versatile vector. We hope to create a similar system that allows our minicells utilize the vast library of commercial antibodies available as highly specific receptors for a variety of applications.

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