Using Viruses to Deliver Cargo into Cells

Leo James, PhD

Challenge sponsored by:

The traditional view on immune response to viruses:Extracellular Antibody Immunity

Phagocytosis

Complement

Antibody recognition

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Entry neutralization

“antibodies patrol only the extracellular spaces so only recognise and targetfor destruction extracellular pathogens.” Male, D. et al.,

Immunology (7th Edition) 2006

ProliferationInfection

But does that make sense? If viruses are mainly active inside cells, shouldn’t the immune system fight them in there as well?

Antibodies actually travel with the virus into the cell – targeting the virus for degradation

1. Antibody recognition 2. Co-factor recruitment 3. Neutralisation

We found that antibodies don’t just travel into the cell, they activate an immune response by binding to an intracellular receptor: TRIM21. This binds the anitbody and targets the virus for destruction by the proteosome.

TRIM21 is a novel intracellular antibody receptor

Ultra-high affinity

0.6 nM

Cytosolic expression

James, LC, Proc Natl Acad Sci U S A. 2007 10;104(15):6200-5Keeble AH, Proc Natl Acad Sci USA. 2008 22;105(16):6045-50

Viruses as intracellular delivery vehicles

A Virus can deliver cargo bound to its surface into the cell via its normal infection pathway.

Ordinarily attach antibodies

Activates immune response, resulting in destruction of the virus

Can also use the antibodies to e.g. target proteins in the cell using this destruction pathway.

What else to attach & deliver?

Proteins Small moleculedrugs ?

Delivery of varied cargo to the cell interior

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Can attach different substances (proteins, small molecule drugs, …) to the viruses either directly or via an antibody for delivery to the cell.

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So, in summary what can we do with this information?

We have discovered that antibodies attached to non-enveloped viruses stays bound to the virus as it enters the cell. The antibody can activate a destruction pathway by binding to an intracellular receptor.• Could this be the base for new antiviral therapies?

We can add additional specificity to the bound antibodies, so they bind to certain components in the cell, in turn targeting them for destruction. We can essentially target antibody therapeutics to in-cell targets.• Could we use this to down-regulate certain activities of the cell? Kill

specific cells? Modify their behaviour in other ways? Deliver other cargo bound to the antibody?

We can attach other things to the virus, such as proteins or small molecule drugs• Could we base new therapies on this?• What else might this be useful for?

What new paths does all this knowledge make possible?