Peter Tattersall

Our research efforts are directed at understanding the molecular mechanisms by which mammalian parvoviruses target particular cell types, express their genes, take over their host cells and replicate their own DNA. Eukaryotic and prokaryotic expression systems, coupled with directed mutagenesis, are currently being used to separate the various functions of the complex, multi-functional parvoviral gene products, in order to understand how the virus subverts the macromolecular metabolism of its target host cell to its own ends. We are currently applying this knowledge to the construction of vectors for transducing immunomodulatory genes into tumor cells as therapeutic strategy against cancer.

I wish to be contacted by interested students (medical, graduate or undergraduates) as a potential research mentor/thesis advisor.

How parvoviruses enter their host cell and traffic to the nucleus

Parvoviruses do not have a lipid envelope, and so cannot deliver their virions into the host cell by fusing with its plasma or endosomal membranes. These viruses have developed an alternative strategy to breach their host cell's outer membrane and gain entry into the cytoplasm. We have recently shown that the compact, icosahedral virion of the murine parvovirus Minute Virus of Mice, MVM deploys a lipolytic enzyme, phospholipase A2 (PLA2) that is expressed at the N-terminus of the minor coat protein, VP1. This region of VP1 is normally sequestered within the viral shell, but is extruded during the entry process as a capsid-tethered domain, via an 8Å pore that extends through the prominent 5-fold cylinder. [Figure] In addition to the PLA2 domain, the extruded VP1 N-terminus also displays a number of small protein interaction domains predicted to engage both ubiquitin ligases of the NEDD4 family, involved in endocytosis and vesicle trafficking, and nuclear transport proteins of the α-importin family. We are currently collaborating with Dr. Michael Hodsdon, in our Department, to determine the structure of this polypeptide domain by NMR spectroscopy, in order to understand how it unfolds and refolds during its transition through the 5-fold pore. The sequential conformational shifts within the particle that allow this transition to occur as the virion transits its entry pathway, exposing first its VP2 N-termini, then its VP1 N-termini and ultimately its DNA are being analyzed using X-ray crystallography and asymmetric cryo-electron microscopy, in a collaboration with Drs. Susan Hafenstein and Michael Rossmann at Purdue University. Finally, we are using reverse genetics combined with differential real-time PCR, sub-cellular fractionation and in situ imaging techniques, to explore the roles of the VP1 N-terminal domain in the trans-cytosolic trafficking and nuclear import of MVM virions.


Manipulating the oncoselectivity of parvoviruses in human tumor models

Many of the rodent parvoviruses will bind to and enter human cells with high efficiency, but fail to initiate gene expression, replicate their genomes, generate progeny or spread through the culture, unless the host cell is neoplastically transformed. As a consequence, these viruses are promising candidates as oncolytic agents for cancer therapy, particularly in situations where other treatments have proven ineffective. Our current efforts are directed toward understanding, at the molecular level, why cellular changes that accompany oncogenic transformation promote viral growth, and how we can use this knowledge to further improve the efficacy of the virus in tumor eradication. Since tumorigenesis normally involves loss of genomic integrity, tumor cells carry many mutations that are secondary to those causing the transformed phenotype. To avoid studying or selecting for viral traits that represent adaptations to such "collateral" transformed cell properties, we are using host cells that have been transformed in a stepwise fashion with activated oncogenes and/or tumor suppressor knock-downs. Currently we are exploring the contribution of the viral capsid and initiating promoter to the discrimination between normal and transformed cells, using stepwise transformed human fibroblasts and melanocytes, the latter being a model for malignant melanoma. These studies are directing strategies for selecting more oncotropic versions of these critical oncoselective elements, using gene shuffling and degenerate promoter library approaches.


Translational studies on a newly-discovered human bocavirus

Human bocavirus (HBoV) is a human parvovirus that was discovered in 2005 and shown to be present in a significant fraction of bronchioalveolar samples from children presenting in the clinic with respiratory tract infection. We have an ongoing collaboration with Dr. Jeffrey Kahn in Pediatric Infectious Diseases to develop tools that will allow us to study this virus in the clinic, and to explore its biology in the laboratory. Using baculovirus technology, we have derived HBoV virus-like particles with which we have developed diagnostic assays for HBoV-specific IgG and IgM antibodies. We have used these to show that infection with this virus is common in very young infants. Currently we are involved in developing prospective and retrospective seroepidemiological screens, in an attempt to identify potential clinical sequelae of infection with this ubiquitous agent. In addition, we are attempting to grow the virus in cell culture, in order to study its non-structural polypeptides, particularly the function of the unique bocaviral NP1 protein.

Development of methods for the detection and elimination of parvoviral contaminants in industrial processes and products.
Development of diagnostic tools for newly-discovered parvoviral infections in the human population.
Development of parvoviral vectors for the treatment of cancer.
Development of parvoviral vectors for vaccination against infectious disease, including HIV-1 and Lyme Disease.