Viral Mercenaries to The Rescue
By Baltazar Gomez —
On May 29, 2007, Oncolytics Biotech Inc. of Calgary, Canada announced the grant of U.S. Patent No. 7,223,585, the biotech company’s twenty-first U.S. patent. The ‘585 patent, entitled "Viral Purification Methods," covers the production and purification of viruses, specifically human reovirus (Respiratory Enteric Orphan virus; see below). In particular, the patent covers methods for isolating virus from suspended mammalian cells using detergents to rupture the cells and a series of filtration, ion exchange, and size exclusion chromatography.
According to Oncolytics, the patent represents another piece of intellectual property that complements the company’s core technology directed to the formulation of viruses that seek and destroy cancerous cells. Such viral mercenaries may prove valuable in the treatment of at least a third of human cancers. Oncolytics is developing a REOLYSIN® therapy that utilizes a reovirus to treat a variety of advanced cancers. REOLYSIN® represents an ingenious way to treat tumor cells and other cellular proliferative disorders by taking advantage of tumor-specific cellular pathways – an activated Ras pathway is the key by which the reovirus infects a tumor cell where the virus can replicate eventually killing the cancerous cell. The reovirus cannot kill normal cells because normal cells do not have an activated Ras pathway and use an anti-viral response mediated by the host cellular protein PKR to stop reovirus from killing normal cells. Tumor cells with an activated Ras pathway are unable to activate the PKR-mediated anti-viral response so that tumor cells become susceptible to reovirus replication. But also important is that progeny reovirus released from killed tumor cells infect surrounding tumor cells, eventually eliminating all cancerous cells.
Oncolytics is presently conducting a number of Phase I and II clinical trials that have shown promising results and hold much hope for the treatment of advanced and metastatic cancers. Oncolytics’ technologies are based on discoveries from research conducted at the University of Calgary by Dr. Matt Coffey.
The ‘585 patent issued from U.S. Application No. 10/424,985 and claims the benefit of U.S. Provisional Application Nos. 60/377,273, filed April 30, 2002, and 60/443,176, filed January 29, 2003. Representative independent claims 1 and 14 of the ‘585 patent recite:
1. A method of producing virus from a culture of cells, comprising the steps of:
(a) providing a culture of mammalian cells in suspension which has been infected by the virus in culture;
(b) extracting the virus from the cells by adding a detergent to the culture of mammalian cells in suspension and incubating for a period of time to result in a cell lysate;
(c) separating cell debris from the virus in the cell lysate by step-wise filtration comprising:
(i) filtering through a prefilter having a pore size of 5 µM or 8 µM, and
(ii) filtering after step (i) through a combination filter having pore sizes of 3 µM and 0.8 µM;
(d) purifying the virus by a combination of ion exchange and size exclusion chromatography; and
(e) collecting the virus,
provided that after infection by the virus and before extraction of the virus, the mammalian cells are not pelleted or resuspended.14. A method of producing infectious reovirus, comprising:
(a) providing a culture of HEK 293 cells in suspension which has been infected by reovirus in culture;
(b) extracting the reovirus from the HEK 293 cells by adding octoxynol-9 to 10 to the culture of HEK 293 cells in suspension and incubating at about 25o C. to about 37o C.;
(c) treating the mixture from step (b) with a DNA-cleaving enzyme;
(d) separating cell debris from the reovirus in the mixture from step (c) by step-wise filtration comprising:
(i) filtering through a prefilter having a pore size of 5 µM or 8 µM, and
(ii) filtering after step (i) through a combination filter having pore sizes of 3 µM and 0.8 µM;
(e) concentrating the filtrate by ultrafiltration or diafiltration;
(f) purifying the reovirus by a combination of ion exchange and size exclusion chromatography; and
(g) collecting the reovirus,
provided that after infection by the reovirus and before extraction of the reovirus, the HEK 293 cells are not pelleted or resuspended.For additional information regarding Oncolytics’ REOLYSIN® technology, please see:
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