1306. Identification of the Bcl-2-Like Vaccinia Virus Immunomodulatory Protein C16: an Activator of Mitogen Activated Protein Kinases
Session: Poster Abstract Session: Viral Immunology and Pathogenesis
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Toll-like receptors (TLRs) are key pattern recognition receptors that initiate innate immune responses by detecting a wide variety of microbial pathogens. Poxviruses encode a family of bcl-2 like proteins that were previously thought to only inhibit innate immune responses, for example by inhibiting TLR signaling TLRs to NF-kB and IRF3, and thus inhibiting secretion of interferon and antiviral inflammatory cytokines.

Methods: Sequence analysis of all vaccinia virus Copenhagen reading frames, as well as of several poxvirus C16 orthologs, was performed followed by a fold-prediction analysis of all known poxviral bcl-2-like proteins. Induction of NF-kB and IRF3 transcription activity and c-Jun and p38 kinase activity was assessed in luciferase assays. Immunoblots were used to assess phosphorylation of MAPKs as well as co-immunoprecipitation of C16 with Transforming Growth Factor Beta Activating Kinase-1 (TAK1) or Tumor Necrosis Factor Associated Factor 6 (TRAF6). Finally in vitro translation followed by immunoprecipitation was used to assess TRAF6:C16 associations in cell-free binding assays.

Results: The C16 open reading frame encodes a previously uncharacterized member of this poxvirus family of immunomodulatory proteins whose predicted fold resembles that of cellular bcl-2. C16 is highly conserved in the variola virus strains that caused smallpox, but is encoded by only certain vaccinia viruses.   C16 was found to significantly increase phosphorylation of the mitogen activated protein kinases (MAPKs), p38 and JNK. Trans-reporter assays detected significant (p<0.02) C16-enhanced activation of signaling by the p38 and JNK. C16 co-immunoprecipitated with the  TAK1 MAP3K and with TRAF6. Finally, C16 directly associated with TRAF6 in cell-free binding assays, indicating that the interaction between C16 and TRAF6 was a direct one.

Conclusion: C16 is a newly identified poxviral bcl-2 family member that targets MAP kinase signaling. Modulation of MAPKs is important mechanism in the lifecycle of other viruses such as the herpesviruses and adenoviruses. Since MAP kinase activation is also known to be critical for vaccinia virus replication, C16 is likely to play a role in poxviral pathogenesis.

Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

Kayla Morlock, BA, University of Massachusetts Medical School, Worcester, MA


K. Morlock, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.