1. Department of Medical Microbiology, Immunology, and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62794-9626, USA
2. Department of Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL 62702, USA
3. Present address: Duke Human Vaccine Institute, Duke University Medical Center, Durham, NC 27710, USA.
4. Cancer Virology Program, University of Pittsburgh Cancer Institute Hillman Cancer Center, Pittsburgh, PA 15232, USA
5. Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA 15213, USA
6. Simmons Cancer Institute, Southern Illinois University School of Medicine, Springfield, IL 62702, USA