Herpesviridae, Alphavirinae, genus Simplexvirus; double-stranded linear DNA virus, icosahedral, lipid envelope, 110 – 200 nm diameter, HSV types 1 and 2 can be differentiated immunologically. Vectors derived from Herpes simplex virus (HSV) have some unique features. The vectors have a wide host range and cell tropism, infecting almost every cell type in most vertebrates that have been examined. In addition, the natural property of the virus to infect and establish latent infection indefinitely in post-mitotic neurons has generated substantial interest in using it to deliver therapeutic genes to the nervous system.
What are the hazards?
Classic presentation of primary HSV-1 is herpes gingivostomatitis – oral mucosa, HSV 1 – primary infection is usually mild (10% of cases can be severe) and in early childhood; reactivation of latent infection results in fever blisters or cold sores, usually on the face and lips which crust and heal within a few days, may be CNS involvement (meningoencephalitis), 70% mortality rate if left untreated; causes about 2% of acute pharyngotonsillitis; Classic presentation of a primary HSV-2 infection is herpes genitalis, HSV 2 – genital herpes, sexually transmitted, associated with aseptic meningitis, vaginal delivery can cause risk to newborn, encephalitis and death; either HSV-1 and HSV-2 may infect the genital tract or oral mucosa.
Epidemiology
Type 1 – contact with saliva of carriers, infection of hands of health care personnel; Type 2 – usually by sexual contact; infected secretions from symptomatic or asymptomatic individuals. Virus may be secreted in saliva for up to 7 weeks after recovery and from genital lesions for 7-12 days: asymptomatic oral and genital infections, with transient viral shedding, are common; reactivation can be precipitated by over-exposure to sunlight, febrile, physical or emotional stress or foods and drugs, especially chemotherapy; HSV may be shed intermittently from mucosal sites for years, possibly lifelong.
HSV is spread by direct contact with epithelial or mucosal surfaces. 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 as 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.
Laboratory Hazards
Ingestion; accidental parenteral injection; droplet exposure of the mucous membranes of the eyes, nose, or mouth; inhalation of concentrated aerosolized materials.
| Laboratory hazards | ppe |
|---|---|
| Exposure of mucus membrane (eyes, nose, mouth) | Use of safety goggles or full face shields. Use of appropriate face mask |
| Injection | Use of safety needles; NEVER re-cap needle or remove needle from syringe |
| Aerosol inhalation | Use of appropriate respiratory protection |
| Direct contact with skin | Gloves, lab coat, closed shoes |
The above PPE are often required IN ADDITION to working in a certified Biosafety Cabinet.
Susceptibility to disinfectants: Susceptible to common disinfectants – 1% sodium hypochlorite, iodine solutions containing ethanol, 70% ethanol, glutaraldehyde, formaldehyde
Use in Lab: BSL-2
Use with Animals: ABSL-2 housing. Amplicon-only is ABSL-1.
Treatment
Anti-viral drug therapy for symptoms.
