20.109(F11):Ebola Virus Edgar Brook
Inducing apoptosis in lukemea and liver cancer cells using Ebola Virus (EBOV)
The Ebola Virus has been shown to induce apoptosis in lymphocytes and heptacytes without having to infect any cells. This behavior can be very useful in ridding undesirable cells, such as cancer cells, from the body. There are two pathways by which the virus induces apoptosis. We plan to test out both pathways by modifying the genome of EBOV to create a non virulent version of the virus that will have an affinity for causing apoptosis in cancer cells.
Inhibition of IRF Activation by VP35 is Critical for the High Level of Virulence of Ebola Virus The Ebola Virus (EBOV) uses three main mechanisms to inhibit the innate immune system. One important method is through the VP35 protein, which inhibits IRF-3 (transcription factor that induces antiviral proteins and chemokines), protein kinase R, and acts as an RNA-silencing suppressor (inhibit RNA interference). Modifying the VP35 protein by an amino acid substitution suppressed its ability to inhibit both IRF-3 and RNA-silencing, significantly decreasing virulence in mice. These results suggest the importance of VP35 for infecting cells, and that the innate immune system, if uninhibited, may be able to effectively combat EBOV. Referenced in Hartman A, et. al. (2008) Inhibition of IRF Activation by VP35 is Critical for the High Level of Virulence of Ebola Virus. Journal of Virology 82: 2699-2704
Single-Injection Vaccine Protects Nonhuman Primates against Infection with Marburg Virus and Three Species of Ebola Virus Currently, vesicular stomatitis virus (VSV), a virus in the same family as rabies, is being used to attempt to develop vaccines for filoviruses. VSV is modified to express a single filovirus glycoprotein (which is used by EBOV to enter cells). Macaques where injected with a single vaccine composed of VSV containing the glycoproteinfor the Sudan, Zaire, Cote d’Ivoire strains of EBOV and were then infected with each strain. All the macaques that received the vaccine survived the infection, demonstrating that the vaccine was successful in nonhuman human primates. Referenced in Geisbert A, et. al. (2009) Single-Injection Vaccine Protects Nonhuman Primates against Infection with Marburg Virus and Three Species of Ebola Virus. Journal of Virology, 83: 7296-7304
CD8+ Cellular Immunity mediates rAd5 Vaccine Protection Against Ebola Virus Infection of Nonhuman Primates Immunity to EBOV granted by vaccines elicits both an antigen-specific cellular and humoral immune responses, although the mechanism of protection is not known. Antibodies transferred from vaccinated virus immune macaque to unvaccinated macaque, but immunity was not transferred. Furthermore, it was noted that depletion of CD3 and CD8 T cells diminishes immunity to EBOV. Therefore, it is likely that humoral immunity has a limited role in EBOV inhibition, while T cells are crucial to prevent infection. Referenced in Sullivan N, et. al. (2011) CD8+ Cellular Immunity mediates rAd5 Vaccine Protection Against Ebola Virus Infection of Nonhuman Primates.Nature Medicine 17: 1128-1131
Mechanisms and Consequences of Ebolavirus-Induced Lymphocyte Apoptosis EBOV induces lymphocyte apoptosis, but the pathways by which it does so remains unknown. Lymphocyte apoptosis was examined in death domain (extrinsic apoptosis pathway) dominant negative transgenic miceand over expressing bcl-2 (regulates apoptosis). In both cases, the mice were resistant to EBOV induced lymphocyte apoptosis. These observations indicated that EBOV induces apoptosis via the death receptor and mitochondrial pathways. Also, inhibiting lymphocyte apoptosis did not improve animal survival, suggesting that they do not play a crucial role in EBOV immunity. Referenced in Sullivan N, et. al. (2010) Mechanisms and Consequences of Ebolavirus-Induced Lymphocyte Apoptosis.The Journal of Immunology 184: 327-335
Role of the GTPase Rab1b in Ebolavirus Particle Formation The VP40 matrix protein plays a key role in virion assembly and emergence. Rab1b activates GFB1, which stimulates. ARF1 then recuits coat protein to cellular membranes to assemble coat protein complex I (COPI) vesicles. Both COPI and COPII serve to help transport VP40 to the plasma membrane. Mutant dominant negative GTPase Rab1b interferes with the transport system, reducing the particle formation of the virus.
Referenced in Yamayoshi N, et. al. (2010) Role of the GTPase Rab1b in Ebolavirus Particle Formation. Journal of Virology 84: 4816-4820