The following provides information on the use and containment of recombinant herpes viral vectors. Investigators should use these guidelines as part of their risk assessment when planning experiments with these vectors and preparing applications to the Institutional Biosafety Committee (IBC). Note the listed containment levels are the minimum that should be employed with these vectors: some experiments, such as the expression of toxins or oncogenes, may require higher levels of containment. The appropriateness of the containment should be considered as part of the investigator’s risk assessment and will be reviewed by the IBC.
NIH Risk Group
RG2
Herpesviruses are enveloped, icosahedral, doublestranded linear DNA viruses.
Biocontainment Level
BSL-2
Infectious to Humans/Animals
Yes
Route of Transmission
HSV-1 is typically transmitted by saliva or by the infection on hands of healthcare personnel. HSV-2 is typically transmitted through sexual contact. HSV can be transmitted by direct contact with epithelial or mucosal surfaces.
Laboratory Hazards
In the laboratory, HSV can be transmitted by ingestion, parenteral injection, droplet exposure of the mucous membranes (eyes, nose or mouth), and inhalation of aerosolized materials.
Disease
Depends on type:
- Oral Herpes
- Genital Warts
- Herpes esophagitis
- Herpes encephalitis or meningitis
Treatment/Prophylaxis
Antivirals may reduce shedding
Pathogenesis
After infection, the viruses are transported along sensory nerves to the nerve cell bodies, where they reside lifelong. Causes of recurrence may include: decreased immune function, stress, and sunlight exposure. The first episode is often more severe and may be associated with fever, muscle pains, swollen lymph nodes and headaches. Over time, episodes of active disease decrease in frequency and severity
Replication Competent
All versions of HSV vectors are prone to recombination. Additionally, approximately
50% - 90% of adults possess antibodies to HSV type 1; 20% - 30% of adults possess
antibodies to HSV type 2. This is a concern since reactivation from latency is not
well understood. Infection by HSV vectors into latently infected cells could potentially
reactivate the wild-type virus, or
spontaneous reactivation of a latent infection could produce an environment where
replication defective vectors could replicate.
RCV Testing
Viral preparations used for in vitro studies should be tested every 6 months for replication competent viruses by plaque assay. These assays should be tested at a sensitivity limit of 1 infectious unit per mL.
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 will be maintained at ABSL-2 for the duration of the study. Animals
must be injected in a Biological Safety Cabinet. All bedding, waste and animals infected
with HSV shall be treated as biohazardous. After all animals are removed from their
primary enclosure immediately autoclave or treat with chemical disinfectant. After
disinfection, dump the cage contents and begin cleaning the cage for re-use. All waste
must be decontaminated by autoclaving or chemical disinfection prior to disposal.
Animal carcasses must be placed in autoclave bags and be designated for infectious
waste disposal. All necropsies must be performed in a designated room using animal BSL-2 practices and procedures. - Animal cages must be labeled with a biohazard sign.
Sources
http://web.stanford.edu/dept/EHS/prod/researchlab/bio/docs/Working_with_Viral_Vectors.pdf
http://www.dartmouth.edu/~ehs/biological/biosafety_docs/110_1_ibc_viral_vector_policy.pdf