title: The Use of CpG Oligodeoxynucleotides As Antiviral Treatments Against Orthopoxvirus Infection
Creators: name: Jackson, Matthew Christopher
Publisher: name: The Open University
Year: 2008

description: Complications with the current smallpox vaccine and the threat of a new smallpox epidemic have dramatically increased efforts to identify new antiviral compounds against orthopoxviruses. CpG oligodeoxynucleotides were investigated here for their ability to confer protection against vaccinia virus (VACV) in a model of orthopoxvirus infection in pre- and post-exposure settings. <br><br>Intranasal delivery of the B-class CpG 7909, prior to intranasal challenge with VACV, previously resulted in complete protection in a Balb/C mouse model of infection. Immunological analysis found that pre-stimulation with CpG resulted in the local release of pro-inflammatory cytokines such as IFN-α, IFN-γ, TNF-γ and IL-6 along with chemotactic messengers such as CCL2. In addition, activated innate effector cells such as macrophages, neutrophils, and dendritic cells were identified in high numbers in the lungs of CpG treated mice prior to infection. This heightened immune response persisted throughout early VACV infection in CpG-treated animals compared to that observed in un-stimulated control mice. Mice treated with CpG-B 7909 also initiated a second wave of immune activation late in infection indicative of a more rapidly formed adaptive response. Treatment and infection of B-cell Knock-out (KO) mice and neutrophil ablated mice suggested neither B-cells nor neutrophils alone were crucial in conferring CpG-mediated protection against VACV. <br><br>The success of CpG-B 7909 as a prophylactic against VACV led to its investigation as a post-exposure therapeutic. Intranasal treatment with CpG-B 7909, 24 hours after VACV challenge, boosted the pro-inflammatory response initiated after VACV infection in the lung. This response involved increased macrophage, neutrophil, dendritic cell and NK cell responses and increased levels of pro-inflammatory cytokines, interferons and chemokines. This enabled protection of 60% of VACV infected mice. Multiple dosing of CpG post-VACV exposure did not increase levels of protection. <br><br>The effectiveness of delivering CpG-B 7909 intranasally and identification of macrophages as a highly activated cell-type during CpG-mediated protection, led to the investigation of alveolar macrophages following CpG stimulation. Using <i>in vitro</i> macrophage cell-lines, A-class (CpG-A) and semi-soft C-class (CpG-sC) CpGs induced secretion of nitric oxide and expression of cytokines/chemokines more effectively than other classes of CpG in both alveolar (MH-S) and blood monocyte/macrophage (J774) cell-lines. In addition, MH-S macrophages were shown to secrete more nitric oxide but less IL-6 and TNF-γ than J774 macrophages after CpG stimulation. In an <i>in vitro</i> model of infection with VACV, pre-treatment of macrophages with CpG-B and CpG-sC significantly restricted viral replication independently of nitric oxide production. These antiviral properties led to the investigation of CpG-sC 10109 as a prophylactic against VACV <i>in vivo</i> where it conferred complete protection. <br><br>Collectively, these results suggest CpGs are highly immunostimulatory and can confer full protection against VACV when given pre-exposure. This protection correlates with the induction of a strong, local immune response prior to VACV challenge, without which, the host fails to control infection effectively.