VV_(Li)-iTyr-GusA is a recombinant vaccinia virus (VV) encoding the following additional transcription units: 1) the tet-repressor (tetR) cDNA under transcriptional control of the VV synthetic early late (pSEL) promoter, 2) the tet-operator sequence tetO followed by mouse tyrosinase (mTYR) cDNA under transcriptional control of the VV synthetic late (pSL) promoter, and 3) the β-glucuronidase (GusA) cDNA under transcriptional control of p11 promoter. These additional transcription units are inserted into, and disrupt the function of, the viral F14.5L, J2R (thymidine kinase), and A56R (hemagglutinin) genes, respectively. Expression of tyrosinase is under the control of an inducible promoter-system, whereby addition of doxycycline induces tyrosinase expression (see diagram below). The purchased virus is ready for use in cell-killing assays or can be amplified to create additional virus stocks.

The virus titer is functional infectious virus, not total virus particles, in clarified supernatant. The titer is determined using an end-point dilution assay that measures the amount of virus required to produce cytopathic effects in 50% of infected cells (tissue culture infective dose per mL).

Note: A USDA permit is required for shipping Vaccinia Virus. Click here to fill out Application Form VS 16-3 to obtain a USDA APHIS VS 16-6 or 16-6A permit.

This virus should be handled in a BSL2 facility  by trained personnel following proper biocontainment practices.

Basic protocol

(All volumes are given for a T75 flask; increase or decrease as needed.)
1. Seed producer cells (e.g. Vero) in complete medium at an appropriate density to achieve 80-90% confluency at the time of infection and incubate in an appropriate incubator.
2. Thaw the virus stock on ice.
3. In a microcentrifuge tube, prepare virus at a MOI of 0.1  in 3 mL total serum free media.
4. Remove culture medium from cells and replace with prepared virus. Return cells to incubator.
5. After 2-3 hours, remove virus innoculum and replace with 12 mL complete medium. Return cells to incubator.
6. Harvest supernatant at 48 hours post-infection.
7. Freeze-thaw or sonicate the supernatant and cells for 3 cycles.
8. Clarify the supernatant by low-speed centrifugation and purify through a  sucrose cushion.
9. Resuspend the viral pellet in 1mM TrisCl, pH 9. Determine virus titer using appropriate methods. Store at -80C.

Infectivity

A&B: Mock-infected A549 cells

C&D: VV_(Li)-iTyr-GusA infected A549 cells (MOI 0.1) at 48 h.p.i.

B&D: β-glucuronidase activity: Cells were incubated with media containing X-Gluc (5-bromo-4-chloro-3-indolyl-beta-glucuronide).

Tyrosinase Expression

A549 cells were mock-infected or infected with VV_(Li)-iTyr-GusA at an MOI of 0.1 in the presence (With DOX) or absence (No DOX) of 1µg/ml doxycycline (DOX). After 48 hours, cell lysates were harvested. To measure tyrosinase expression, 20 µg of cell lysates were incubated at 37ºC for 2h with 50 µL of 2mM L-DOPA. Absorbance was measured using a micro plate reader at 475nm.