NIH Risk Group

RG2

Rabies virus is a member of the Rhabdoviridae family and is a common zoonotic infection from bats and other wild mammals.  Rabies is an enveloped, single-stranded, negative sense RNA virus.

Replication-deficient rabies vectors can be useful tools for investigation into neuronal trafficking or targeted expression in neurons. SAD∆G-mCherry/EnvASAD∆G is an example of a modified rabies virus. This modified version of the rabies virus forces neurons it infects to produce a red fluorescent protein called mCherry. mCherry makes the infected cells glow red so they are visible under a microscope. The benefit is the ability to trace a neural circuit on the cellular level as only connected/attached neurons are affected. Initial deletion: This modification deletes a gene which encodes the rabies virus envelope B19- glycoprotein (RG) and which is required for the production of competent or infectious viral particles from the virus genome in transduced cells. As a result, the mutant virus cannot spread to any other surrounding cells from the originally infected cells. If the B19-glycoprotein is over- expressed as a transgene in a defined group of infected cells, the virus can trans-synaptically transport to adjacent cells only  (single-step) and never go beyond.

The tropism of the viral vector may also be changed so that it cannot infect any mammalian cells except those that express a genetically-specified neuronal population transgene that encodes the envelope receptor. Examples of this include EnvA, VSV-g, avian sarcoma leucosis virus glycoprotein, or HIV env. EnvA pseudotyped virus can only infect cells expressing the complementary receptor TVA. Since mammalian neurons do not express TVA, the injected virus cannot infect wild-type human neurons. If the virus is able to infect a TVA-positive neuron (for example, in transgenic mice), it can replicate and strongly label the first-order (initially infected) neurons, but since its genome lacks the B19 glycoprotein, it cannot infect other neurons by itself. In short, the risk for infection is specified by transgene expression and retrograde transport is limited to a single synapse. Thus the resultant virus  becomes a “mono-synaptic” transneuronal tracer and significantly reduces the biohazardous risk because the virus has no potential to infect or trans-synaptically transport to any mammalian cells, including human and mice.

Biocontainment Level 

BSL-2

Infectious to Humans/Animals

Yes

Route of Transmission

Percutaneous injury, such as animal bites. Potential non-bite modes of transmission include contamination of a pre-existing wound, contact of mucous membrane or respiratory tract with the saliva of an infected animal, exposure to aerosolised rabies virus
in the laboratory (or from bats), or via organ transplantation from an infected donor, or inhalation of droplets 

Laboratory Hazards

Accidental needlestick is a mode of transmission within research laboratories. Accidental ingestion of viral contaminated materials and inhalation are other routs of transmission. If working with infectious animal models, then bite wounds could transmit rabies virus infection. 

Disease

Rabies virus can cause an acute infection, marked by progressive encephalomyelitis, and is usually fatal. The initial symptoms of rabies resemble those of other systemic viral infections, including fever, headache, malaise, and upper respiratory and gastrointestinal tract disorders. This prodromal phase typically lasts about 4 days, but can last as long as 10 days before specific symptoms develop. 

Treatment/Prophylaxis

Consultation is available to determine if vaccination is appropriate for personnel working with recombinant rabies vectors. Vaccination is not needed for working with SAD B19 vaccine strain.

Post-exposure rabies prophylaxis with vaccines together with the administration of rabies immunoglobulin (RIG) is highly effective but is a medical urgency. There is no established treatment for wild-type rabies once symptoms have begun, but supportive therapy may include intubation, sedation, mechanical ventilation, fluid and electrolyte management, and nutrition. 

Replication Competent

Usually no but depends on pseudotyping and expression of envelope protein

RCV Testing

No effective methods for RCV testing.

Disinfection 

Effective disinfectants require a minimum of 20 minutes contact time. Use one of the  following:

• RECOMMENDED: Sodium hypochlorite (0.5%: use 1:10 dilution of fresh bleach)
• 5% Phenol
• 70% Ethanol or Isopropanol

Animals

• ABSL-2. Animals must be injected in a Biological Safety Cabinet. Take precautions to avoid creating aerosols when emptying animal waste material. Soiled cages are disinfected prior to washing. Animal cages must be labeled with a biohazard sign.
• If the B19 glycoprotein is not expressed in the recombinant vector and in the animals, stepdown to ABSL1 may be considered. The animals will be transferred to a clean cage, and the ABSL-2 cage will stay in the ABSL-2 quarantine space for appropriate waste disposal and cleaning. Once animals have been transferred to ABSL-1, they can be handled as with other ABSL-1  animals. The PI must provide a clear risk assessment for the experiments and the IBC will determine whether stepdown is appropriate and the time post injection for the stepdown to occur.