Baculovirus and Baculoviral Vectors

Baculoviruses are lytic viruses, primarily pathogenic for insects.  Baculovirus vector systems are often used to obtain a high level of expression of a desired protein in insect cells (Sf9 cells).  In the natural environment, wild-type baculovirus can pose a threat to certain insect species; however, commonly used baculovirus based vectors have been modified to reduce the pathogenicity to insects.

Potential Health Hazards

Generally, non-genetically modified wild type baculoviruses are not capable of infecting vertebrate cells and thus do not pose any inherent hazards to laboratory workers.  However, more recent studies with the use of mammalian specific promoters have achieved expression of foreign genes in a wide variety of mammalian cell lines and primary cell cultures.

Modes of Transmission

Transmission of baculovirus is through direct contact with the infective virus/vector.  Baculovirus is highly sensitive to human complement and therefore, should an exposure occur, rapid inactivation of the virus is anticipated. 
The budded form of the virus routinely used in research is noninfectious for the insect host, decreasing the risk of recombinant viral release into the environment. 

Laboratory Acquired Infections

None reported.

Host Range

Baculovirus is mainly infective for insect cells; however, as noted above, some recombinant baculoviral vectors can infect mammalian cells.

Survival

Polyhedrin negative baculovirus expression system is susceptible to desiccation and UV light; survival time is limited to hours.
Wild-type and AcNPV baculovirus with normal polyhedron genes can survive for days or weeks in the environment.

Laboratory Practices

Biosafety level 1 practices and facilities are appropriate for activities involving baculovirus/viral vectors in insect cells, as determined by the Institutional Biosafety Committee (IBC, rDNA Committee).

  • Procedures are performed to minimize the creation of splashes or aerosols.
  • Persons wash hands after they handle viable material, after removing gloves, and prior to leaving the laboratory.
  • Work surfaces are decontaminated at least once a day and after any spill of viable material.

Biosafety level 2 practices and facilities must be used for activities involving modified baculoviral vectors in mammalian cell lines, as determined by the Institutional Biosafety Committee (IBC, rDNA Committee).

  • Biohazard signs and labels must be displayed in areas and on equipment where baculovirus is used and stored.  This includes, but is not limited to, laboratory entrance doors, biological safety cabinets, incubators, refrigerators, and freezers.
  • Use a biological safety cabinet (BSC) (a.k.a. tissue culture hood) for manipulations that can generate aerosols, such as pipetting, harvesting, infecting cells, filling tubes/containers, and opening sealed centrifuge canisters.  If a procedure cannot be done in a BSC and only on an open bench, use a plastic shield to prevent exposure through inhalation or splashing.
  • Use aerosol containment devices when centrifuging.  These include sealed canisters that fit in the centrifuge bucket, covers for the centrifuge bucket, heat sealed tubes, or sealed centrifuge rotors.  Rotors should be removed and opened inside a BSC.  Centrifuge tubes should be filled and opened in a BSC.
  • Vacuum lines must be protected with liquid disinfectant traps and micron filters.

Personal Protective Equipment.

Personal protective equipment (PPE) includes, but is not limited to:

  • Disposable gloves (nitrile, latex, etc.).
  • Lab coat when working in the area.  Remove when leaving the laboratory.
  • Goggles for splash protection.

Precautions When Using Animals

The use of insect cells does not fall under the responsibilities of the Institutional Animal Care and Use Committee (IACUC).  However, if work with animals will be proposed, requests are made to the IACUC by submitting an Animal Care and Use Form (ACURF).

Recombinant Baculoviral Research

Protocols involving recombinant baculoviral vectors must be approved by the Institutional Biosafety Committee (IBC); complete an online “rDNA Registration Document” available through UIRIS. 

Employee Exposure

  • Eye Exposure – Rinse eyes in an eyewash for at least 15 minutes.
  • Skin Exposure – Rinse skin with soap and water.
  • Accidental Needlestick Injury – Scrub contaminated skin with soap and water.
  • Report Incidents – Report actual or suspected exposure incidents to your supervisor.
  • Immunizations and Prophylaxis – none available.
  • Incubation Period – no symptoms apparent.

Spill and Disposal Procedures

For spills outside a biological safety cabinet, leave the area while holding your breath.  Once outside the area, wash hands and face with soap and water.  Do not allow anyone inside the area or room where the spill occurred.  Allow 30 minutes for the aerosols to settle.  Enter the room wearing required protective clothing, gently cover the spill with paper towels, and apply disinfectant starting at the perimeter and working towards the center.  Allow the disinfectant to remain on the spill for at least 20 minutes before initiating spill clean up.  After initial clean up, disinfect the area a second time.
For spills inside a biological safety cabinet, cover the spill with paper towels or wipes.  Gently pour disinfectant over the spill area.  Let the disinfectant soak for 20 minutes before cleaning up the spill.  After initial clean up, disinfect the area a second time.

Contaminated materials must be disposed of as biohazardous waste.

Decontaminate adjacent surfaces with a bleach or alcohol solution.

Disinfectants

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

  • Sodium hypochlorite (1-10% dilution of fresh bleach).
  • 70% Ethanol

Decontamination

Autoclave cultures for 30 minutes at 121° C or 250° F (15lbs per square inch of steam pressure).

Disinfect work surfaces using an effective germicide (see above).  This may be followed by an alcohol wipe to lessen the corrosive nature of the germicide.

Transport Requirements 

Materials must be appropriately contained and labeled for transport within the University.  Shipping infectious substances, diagnostic specimens, and/or shipping with dry ice off-campus require training and certification.  See EHS’s fact sheet “Transporting and Shipping Infectious Substances”.  

The use of baculovirus and baculoviral vectors may be subject to shipping regulations through the Animal and Plant Health Inspection Services (APHIS).  Please consult with an APHIS representative if you are shipping baculovirus/baculoviral vectors for any regulations that must be met.

If you have questions please contact EHS’s Biological Safety Section at 5-8501.

Information and References

Health and Safety Executive, United Kingdom. 2000. Advisory Committee on Genetic Modification. Guidance on commonly used vectors. Part 2B-Annex III.

Kost, T.A. and J.P. Condreay.  2002.  Innovations – Biotechnology: Baculovirus vectors as gene transfer vactors for mammalian cells: Biosafety considerations.  Applied Biosafety. 7:167-9.

U.S. Department of Health and Human Services Centers for Disease control and Prevention and National Institutes of Health. (2007 February)  Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition.  Section IV. Laboratory Biosafety Level Criteria. Biosafety level 2 requirements. Retrieved December 2008.