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Moss, B. Immunogenicity of a highly attenuated MVA smallpox vaccine and protection against monkeypox. Nature 2004, 428, 182 185. Stittelaar, K. J.; Kuiken, T.; de Swart, R. L.; van Amerongen, G.; Vos, H. W.; Niesters, H. G.; van Schalkwijk, P.; van der Kwast, T.; Wyatt, L. S.; Moss, B.; Osterhaus, A. D. Safety of modi ed vaccinia virus Ankara (MVA) in immune-suppressed macaques. Vaccine 2001, 19, 3700 3709. Tartaglia, J.; Cox, W. I.; Taylor. J.; Perkus. K.; Riviere, M.; Meignier, B.; Paoletti, E. Highly attenuated poxvirus vectors. AIDS Res. Hum. Retroviruses 1992, 8(8), 1445 1447. Danzig, R.; Berkowsky, P. B. Why should we be concerned about biological warfare JAMA 1997, 278, 431 432. Pearson, G. S. The complementary role of environmental and security biological control regimes in the 21st century. JAMA 1997, 278, 369 372. Inglesby, T. V.; Henderson, D. A.; Bartlett, J. G.; Ascher, M. S.; Eitzen, E.; Friedlander, A. M.; Hauer, J.; McDade, J.; Osterholm, M. T.; O Toole, T.; Parker, G.; Perl, T. M.; Russell, P. K.; Tonat, K. Anthrax as a biological weapon: medical and public health management. Working Group on Civilian Biodefense. JAMA 1999, 281, 1735 1745. Henderson, D. A. The looming threat of bioterrorism. Science 1999, 283, 1279 1282. Fenner, F.; Henderson, D. A.; Arita, I.; Jezek, Z.; Ladnyi, I. D. Smallpox and Its Eradication. World Health Organization, Geneva, 1988. Brandt, T. A; Jacobs, B. L. Both carboxy- and amino-terminal domains of the vaccinia virus interferon resistance gene, E3L, are required for pathogenesis in a mouse model. J. Virol. 2001, 75, 850 856. Saunders, L. R.; Barber, G. N. The dsRNA binding protein family: critical roles, diverse cellular functions. FASEB 2003, 17, 961 983.

Broad-Spectrum Antiviral Prophylaxis: Inhibition of Viral Infection by Polymer Grafting with Methoxypoly(ethylene glycol)

Canadian Blood Services and Department of Pathology and Laboratory Medicine, University of British Columbia

Previous bioterrorism research on viruses centered on agents characterized by rapid onset and high mortality.1,2 These agents typically included the smallpox, encephalitis, and hemorrhagic fever viruses.3 5 However, these speci c agents also pose signi cant, long-term risks to the individuals or nations utilizing them. Consequently, considerable interest has developed in easily transmissible viral agents that are characterized by rapid onset and signi cant, often immobilizing morbidity but that are of less long-term concern to the parties employing them.6 Nature itself has demonstrated signi cant versatility in designing such agents as evidenced by the annual cold and u epidemics and more recently by the severe acute respiratory syndrome (SARS) and avian u viruses.7 9 Indeed, analysis of the transmissibility traits of respiratory viruses (e.g., rhino, adeno, corona, and picornaviruses) clearly indicates that virulent and/or bioengineered strains could function as potent bioterrorism vectors without the serious long-term concerns of a smallpox-like agent. More importantly, these viruses are characterized by high mutation rates, making development of an antiviral cocktail dif cult. Indeed, current prophylactic options (versus disease treatment) to viral bioterrorism agents are almost exclusively focused on vaccine development.10,11 An inherent fallacy/ presumption of the vaccine approach is that it requires an informed guess as to the agent to be used, including any newly engineered genetic changes. As demonstrated

Antiviral Drug Discovery for Emerging Diseases and Bioterrorism Threats. Edited by Paul F. Torrence Copyright # 2005 John Wiley & Sons, Inc.

by the ef cacy of the annual u vaccine, this approach has been only partially effective.12 To this end, a broad-spectrum antiviral prophylactic agent would be of signi cant bene t. To date no such agent exists. Previous research from our laboratory has clearly demonstrated that the covalent grafting of methoxypoly(ethylene glycol) (mPEG) to cell surfaces sterically obscures membrane epitopes and obscures surface charge, leading to the immunocamou age of the modi ed cell.13 26 The resultant immunocamou age globally inhibits receptor ligand interactions, which result in decreased/absent red blood cell agglutination, loss of red cell sedimentation, attenuated allorecognition and T cell proliferation, and diminished antibody recognition of membrane surface antigens. Because of the importance of receptor ligand interactions to viral entry and infection, we hypothesized that the covalent grafting of mPEG to host cells and/or the virus particles would provide a potent, broad-spectrum antiviral effect.27 30 This hypothesis is diagrammatically shown in Figure 16.1 using the nasal passage epithelium as an example. In normal viral pathogenesis, the virus is introduced into the local environment, whereupon it recognizes cellular receptors (e.g., ICAM-1 for 80 90% of rhinoviruses) and is taken up by receptor-mediated endocytosis.31 The virus then uncoats and undergoes replication within the host cell and eventually packages and releases progeny virus into the nasal cavity, which infect naive epithelial cells. As proposed in Figure 16.1, covalent grafting of mPEG to either the virus (direct viral inactivation) or host cells (indirect viral inactivation) interferes with receptor ligand interactions, thereby preventing viral entry and disease induction. The same protective mechanism also functions with viruses whose entry is mediated by cell fusion.

FIGURE 16.1 Effects of immunocamou age on viral pathogenesis. (A) Virus recognizes, binds to cell receptor , is internalized  undergoes multiple rounds of replication , 1 2 3 progeny virus is packaged and shed  into the extracellular environment , whereupon it 4 5 infects new host cells . mPEG grafting to either the free virus (B) or host cells 1 (C) interrupts the disease cycle.