title: Use of a recombinant vaccinia virus expressing interferon gamma for post-exposure protection against vaccinia and ectromelia viruses.
abstract: Post-exposure vaccination with vaccinia virus (VACV) has been suggested to be effective in minimizing death if administered within four days of smallpox exposure. While there is anecdotal evidence for efficacy of post-exposure vaccination this has not been definitively studied in humans. In this study, we analyzed post-exposure prophylaxis using several attenuated recombinant VACV in a mouse model. A recombinant VACV expressing murine interferon gamma (IFN-γ) was most effective for post-exposure protection of mice infected with VACV and ectromelia virus (ECTV). Untreated animals infected with VACV exhibited severe weight loss and morbidity leading to 100% mortality by 8 to 10 days post-infection. Animals treated one day post-infection had milder symptoms, decreased weight loss and morbidity, and 100% survival. Treatment on days 2 or 3 post-infection resulted in 40% and 20% survival, respectively. Similar results were seen in ECTV-infected mice. Despite the differences in survival rates in the VACV model, the viral load was similar in both treated and untreated mice while treated mice displayed a high level of IFN-γ in the serum. These results suggest that protection provided by IFN-γ expressed by VACV may be mediated by its immunoregulatory activities rather than its antiviral effects. These results highlight the importance of IFN-γ as a modulator of the immune response for post-exposure prophylaxis and could be used potentially as another post-exposure prophylaxis tool to prevent morbidity following infection with smallpox and other orthopoxviruses.
authors.affiliation: Center for Infectious Diseases and Vaccinology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Holechek
authors.forename: Karen L
authors.initials: KL
authors.lastname: Denzler
authors.forename: Michael C
authors.initials: MC
authors.lastname: Heck
authors.forename: Jill
authors.initials: J
authors.lastname: Schriewer
authors.forename: R Mark
authors.initials: RM
authors.lastname: Buller
authors.forename: Fatema A
authors.initials: FA
authors.lastname: Legrand
authors.forename: Paulo H
authors.initials: PH
authors.lastname: Verardi
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Jones
authors.forename: Tilahun
authors.initials: T
authors.lastname: Yilma
authors.forename: Bertram L
authors.initials: BL
authors.lastname: Jacobs
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D004195:Disease Models, Animal; D004481:Ectromelia virus / Q000276:immunology*; D005260:Female; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D014615:Vaccinia / Q000276:immunology / Q000378:metabolism*; D014616:Vaccinia virus / Q000276:immunology / Q000378:metabolism*
chemical_list: D007371:Interferon-gamma