1. Department of Microbiology and Molecular Genetics, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
2. Department of Microbiology and National Emerging Infectious Diseases Laboratories, Boston University School of Medicine, Boston, MA 02118, USA
3. Center for Vaccine Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15216, USA
4. School of Medicine, Dentistry and Biomedical Sciences, The Queen’s University of Belfast, Belfast, Northern Ireland, BT7 9BL, UK