TDK conference 2017

Rabies is caused by a negative single stranded RNA virus belonging to the Rhabdoviridae family, Lyssavirus genus. This neurotropic virus causes inflammation of the brain and spinal cord that almost inevitably leads to death. By zoonotic spread the virus is responsible for the death of 60,000 people worldwide, annually. After the onset of clinical sings there is no effective treatment for the disease.

The aim of this research was to prove the efficiency of antiviral and anti-inflammatory compounds (suggested by previous in vitro results) against rabies infection in a mouse model. Six weeks old, female C57Bl/6JOlaHsd mice were used in the experiments. The candidate therapeutic compounds were antivirals: type-I mouse interferons (IFN -α és -β), ribavirin, favipiravir (T-705); and anti-inflammatory agents: Ac-YVAD-cmk (Caspase-1 inhibitor), infliximab (TNF-alfa inhibitor) and sorafenib,(MAP-kinase inhibitor).

The combinations were studied in two different experiments. In the first, all components were administered together and mannitol was also added to open the blood-brain-barrier. Mice were infected with rabies strain SHBRV-18 (silver-haired bat rabies virus), at a dose equivalent to LD100 by inoculating to left hind leg. The treatment could not increase survival time, tough the treated mice’s brains contained less viral RNA than those of the virus control group. This combination was toxic for mice: some of the treated animals showed clinical sings aspecific for rabies and eventually died.

In the second experiment virus dose was lowered to LD50. The combination contained sorafenib, infliximab and Ac-YVAD-cmk. By decreasing the amount of the challenge virus we could observe the clinical course of the disease for a longer time., Three different therapeutic groups were introduced with pre- and post-exposure administration of the compounds. The treatment increased the survival rate of the treated groups significantly compared to the virus control group (mostly in that group where treatment was initiated 96 hours after infection), while the combination had no toxic effect. We could detect virus multiplication in the brain and spinal cord samples of some of the mice that did not show any clinical signs, by using immunohistochemistry, histology and qRT-PCR methods. We proved the seroconversion of all infected mice with virus neutralisation test (FAVN).

Based on these results we can conclude that the used anti-inflammatory compounds increase the survival rate of rabies infected mice, which can be useful for a possible future human treatment, but further in vivo research is needed.