Paula Cannon Associate Professor Molecular Microbiology & Immunology, Pediatrics, Biochemistry & Molecular Biology Keck School of Medicine

Education:
BSc 1984 Microbiology - University of Liverpool, UK
PhD 1989 Genetics - University of Liverpool, UK

Postdoctoral Research Fellowship:
1990 - 1992 Harvard Medical School, Boston, Massachusettes
1992 - 1996 University of Oxford, United Kingdom

Started at USC: 1996

Research Topics: HIV-1, Virology, Gene Therapy, Hematopoeitic stem cells

Research Description

Research in the Cannon lab is focused on understanding how enveloped RNA viruses enter and exit host cells. These are critical steps in viral life cycles and represent important targets for drug development. The viruses that we study include HIV-1, and pathogenic arenaviruses such as Junin virus, which causes Argentine Hemorrhagic Fever.

There are 3 major areas of research in the lab, each funded by NIH grants:

1. Zinc-finger nuclease editing of hematopoeitic stem cells - an anti-HIV therapy
ZFNs are are sequence specific proteins that can be used to generate a double-stranded break in DNA at a precise locus, and which is then converted into a gene-disrupting lesion by host repair processes. My group has developed the techniques to perform this genome editing with high efficiency in human hematopoeitic stem cells (HSC), and we are currently assessing this technology as an anti-HIV gene therapy by targeting the CCR5 gene. 
       CCR5 is the major entry co-receptor used by HIV-1 and CCR5 inhibitors are an important class of anti-viral drugs. In addition, the recent finding that HSC transplantation from a CCR5-negative donor to an HIV-infected patient resulted in long-term control of HIV-1 in the absence of antiretroviral drugs suggests the potential of gene/stem cell therapies targeting CCR5. We have developed protocols to knock-out high levels of the CCR5 gene in human HSC after a single application of CCR5-targeted ZFNs. We evaluate the function of such ZFN-treated HSC by transplantation in a mouse model of human hematopoiesis, the NOD/SCID/IL2γcnull  (NSG) mouse, where ZFN-modified HSC retain the ability to differentiate into multiple hematopoietic lineages and maintain high rates of CCR5 disruption. We also evaluate the ability of this ZFN engineering to protect against HIV-1 infection by challenging the transplanted or 'humanized' mice with HIV-1. We find that mice receiving ZFN-treated HSC demonstrate significantly lower viral loads and a profound protection of human cells compared to animals receiving unmodified HSC.
       Our observations suggest that transient ZFN treatment resulting in permanent disruption of CCR5 in a patient's own HSC could be a viable clinical approach to treating HIV-infected patients. Together with a team of scientists at City of Hope and Sangamo Biosceinces, we have been awarded a "Disease Team" grant from the California Institute for Regenerative Medicine (CIRM) to work towards the goal of getting such a stem cell therapy into patients in 4 years.

CIRM press release: http://www.cirm.ca.gov/PressRelease_102809
NPR news story: http://www.scpr.org/news/2009/10/28/ca-stem-cell-institute-hands-out-200m-research-gra/

2. HIV release from cells and tetherin restriction
The release of virions from the surface of infected cells is the final stage in the HIV-1 life cycle and could be targeted for intervention, since any means of reducing the viral load in patients could significantly slow progression to AIDS.  However, no drugs are currently available that block these events.  Mammalian cells are know to express a variety of 'restriction factors' that inhibit virus replication, and one recently identifed factor is the BST-2/tetherin protein, which acts to prevent the release of enveloped viruses from the surface of infected cells.  Successful viral pathogens often express factors that block the action of restriction factors, and tetherin is known to be inhibited by the HIV-1 Vpu protein, HIV-2 Env, SIV Nef, KSHV K5 protein and Ebola virus GP proteins.  The widespread and diverse nature of anti-tetherin factors suggests that the ability to overcome tetherin restriction is of high importance for the replication of enveloped viruses. 
       We hypothesize that blocking the action of anti-tetherin factors such as Vpu could represent a novel strategy to combat HIV-1 replication.  To this end, we are studying how different anti-tetherin factors work, and also developing high throughput screens to search for compounds that could block the activity of the viral anti-tetherin proteins.

3. New World arenaviruses
Junin virus causes a highly contagious and frequently fatal hemorrhagic fever spread by field rodents in parts of rural Argentina.  Interest in this group of viruses is growing because of the awareness that they could be developed as bioweapons, and Junin has been designated by the CDC as a Category A agent. 
       Clearly, this virus is too dangerous to work with under normal laboratory conditions.  However, by using molecular tricks to create 'mix and match' or pseudotyped viruses, we can keep the features of the virus that we wish to study (such as its entry pathway), while removing the rest of the virus genome.  In this way, we are  investigating how these highly pathogenic viruses bind to and enter cells, and are searching for inhibitors of their replication.