How It Works

VAST Details

Panosome’s technology is focused in the area of monoclonal antibodies (mABs). Our VAST technology develops antibody drugs that bind disease targets that are traditionally challenging for mAB technologies.

In medicine, antibodies are generated by a 3-step process:
(1) Generation of an immunogen of target of interest
(2) Immunization to elicit an antibody response
(3) Screening of thousands of antibodies in a cumbersome process to find those with high affinity to their target

Panosome’s VAST technology drastically improves antibody elicitation and selection:
(1) An innovative and extremely powerful immunization platform (the VAST)
(2) Adapted immunization processes
(3) A highly efficient digital antibody drug selection process (VAST Hyper Speed, see below)

The Trypanosome Coat

Trypanosomes are parasites living in the blood where they are constantly in direct contact with the immune system. The trypanosome surface is densely carpeted with 10 million copies of a single highly immunogenic protein: the Variant Surface Glycoprotein (VSG). The VSG-covered trypanosome surface is highly immunogenic as it quickly elicits extremely powerful antibodies against a specific VSG that kill all trypanosomes with that respective VSG.

Counterintuitively, Trypanosomes benefit from eliciting specific antibodies. This is due to their unique survival strategy of antigenic variation. While every trypanosome has 2000+ VSG variants encoded in its genome, every individual cell expresses only one VSG variant at a time. Upon infection with some trypanosomes of one VSG variant (denoted green in figure), the green trypanosomes multiply. A highly specific antibody response against the green VSG is elicited and kills all trypanosomes with the green VSG variant. Some trypanosomes switch off expression of the green VSG and switch on expression of the "blue" VSG variant that is not detected by the green-specific antibodies, rendering them ineffective and ensuring the trypanosome’s survival. During infection, this process repeats continuously. The highly-specific antibodies elicited to each VSG insures that switching to a new VSG will make those antibodies useless.

VAST redirects anti-VSG immune responses to molecules of choice

Over a decade ago, we investigated whether we could derivatize the VSG arrays that make up the surface layer of the African Trypanosome with molecules of interest in order to exploit the exceptional antigenicity of this coat. Initially, we genetically engineered VSGs to incorporate short peptides (e.g. FLAG) into solvent-exposed loops of the proteins with great success. To extend the system's applicability to other types of antigens, we then engineered VSGs to serve as substrates for the transpeptidation reaction catalyzed by the bacterial enzyme sortase (known as "sortagging").

By genetically engineering “sortagable” VSGs and chemically synthesizing sortagable antigens of interest, we have transformed the surface envelope of the African trypanosome into a molecular display platform. This allows us to display a very wide range of antigens against which antibodies can be produced. We have named this platform the VAST (VSG-immunogen Array by Sortase Tagging).

VAST Hyper Speed process allows fast digital selection of superior antibodies

In conjunction with the VAST, we have also developed a novel bioinformatic pipeline to streamline and accelerate the discovery of high-affinity antibodies, that we call Hyper Speed. The key breakthrough is the coupling of two techniques in a novel manner. The first is single, B-cell sorting of antigen-baited antibodies from immunization. The second is analyzing the entire transcriptome (expressed genes) of these cells and developing a set of markers to classify which are memory B-cells expressing the most potent antibodies. Coupled together, these elements allow us to identify powerful antibody sequences from a few memory cells rather than testing thousands of clones as is often required to find good candidate therapies.