Overview
This video demonstrates an in vitro technique to detect hepatitis B virus (HBV) infection via a recombinant HBV reporter system. Upon infecting host cells, the recombinant viral genome expresses the luciferase reporter enzyme, which produces bioluminescence upon oxidizing its substrate — helping detect viral infection.
Protocol
1. Production of Recombinant HBV Encoding the Reporter Protein
- Preparation of HepG2 cells
- Prepare cell culture medium (Dulbecco's modified Eagle's medium or DMEM) supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, 100 µg/ml streptomycin, and 100 U/ml nonessential amino acids).
- Plate 4 x 106 HepG2 cells in a 10-cm collagen-coated dish in 10 ml of culture medium the day before transfection. Incubate HepG2 cells at 37 °C in a humidified 5% CO2 incubator.
NOTE: When approximately 4 x 106 HepG2 cells are plated in a 10 cm collagen-coated dish in 10 ml of culture medium, they will be 70-90% confluent the next day.
- Transfection
- Transfect HepG2 cells with 5 µg of pUC1.2HBV (hepatitis B virus) delta epsilon and 5 µg of pUC1.2HBV/NL15 using a transfection reagent as per manufacturer's instructions.
- The next day, remove the culture medium and add 10 ml of fresh culture medium.
- One week after transfection, transfer the culture medium containing the recombinant HBV to a 50 ml tube and proceed to step 1.3.1. Add 10 ml of fresh culture medium to the plate containing the transfected cells.
NOTE: Production of the recombinant HBV is maintained for 4 weeks. The culture medium containing recombinant HBV can be stored at 4 °C for 1 month.
- Purification of recombinant HBV
- Remove cell debris from the culture medium containing recombinant HBV by centrifugation (2,300 x g for 5 min).
- Pass the supernatant through a 0.45 µm membrane filter.
- Add an equal volume of 26% PEG/1.5 M NaCl (polyethylene glycol 6000: 130 g, NaCl, 49 g, 1 ml of 0.5 M EDTA (ethylenediaminetetraacetic acid) pH 8.0 and 5 ml of 1 M HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (pH 7.6 in 500 ml) to the culture medium containing recombinant HBV and mix gently. Incubate overnight at 4 °C.
- Centrifuge at 2,300 x g for 20 min at 4 °C.
- Discard the supernatant and dissolve the pellet in 0.5 ml of TNE (10 mM Tris (tris(hydroxymethyl)aminomethane), 50 mM NaCl, 1 mM EDTA).
- Remove the debris by centrifugation at 2,300 x g for 5 min.
- Load 0.5 ml of TNE containing recombinant HBV onto 0.8 ml of 20% sucrose in TNE.
- Centrifuge at 100,000 × g for 3 hr at 15 °C.
- Discard as much of the supernatant as possible, and save the pellet. Resuspend it in 1 ml of serum-free DMEM per 40 ml of starting culture medium.
- Incubate overnight at 4 °C.
- Filter through a 0.45 µm filter. Prepare 0.5 ml aliquots and store at -80 °C.
NOTE: If reporter protein contamination of the original virus sample is observed, purify the virus by density gradient ultra-centrifugation of 5-30% sucrose in TNE at 100,000 x g for 2 hr, or CsCl density equilibrated centrifugation from 1.1-1.6 g/ml at 150,000 x g for 50 hr.
2. Infection of Recombinant HBV
- Culture HepG2 cells stably expressing NTCP (sodium taurocholate co-transporting polypeptide) (HepG2/NTCP) that are susceptible to HBV infection in DMEM supplemented with 10% FBS, 100 U/ml penicillin, 100 µg/ml streptomycin, 250 µg/ml G-418 (geneticin) and 100 U/ml nonessential amino acids at 37 °C in a humidified 5% CO2 incubator.
- One day before infection, plate approximately 5 x 104 HepG2/NTCP cells into a 96-well collagen-coated plate in 0.1 ml of culture medium.
- Thaw recombinant HBV in a 37 °C water bath until there is a small bit of ice remaining in the vial.
- Prepare the medium for infection by combining the following:10 µl of 40% PEG8000 in 1x phosphate-buffered saline (PBS), 2 µl of dimethyl sulfoxide (DMSO), 10 µl of recombinant HBV, and 78 µl of fresh culture medium per well of a 96-well plate.
- Add 100 µl of recombinant HBV solution to one well of the 96-well plate.
- One day after infection, wash the infected cells 3 times with 300 µl PBS per well to remove the contaminating reporter protein from the virus fraction.
- Incubate infected cells in 200 µl of culture medium containing 2% DMSO for one week or less.
3. Analysis
- One week after infection, wash the infected cells 3 times with PBS.
- Add 50 µl of lysis buffer to the infected cells.
- Rock the culture plate for 5 min, and then centrifuge at 2,000 x g for 5 min.
- Add 50 µl of the reporter substrate into the luminometer plate.
- Add 20 µl of cell lysate to a luminometer plate containing the reporter substrate. Mix by vortexing briefly.
- Place the plate in the luminometer and initiate the reading.
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Materials
Name | Company | Catalog Number | Comments |
Nano-Glo Luciferase Assay Regent | Promega | N1110 | |
Penicillin-Streptomycin Mixed Solution | Nacalai tesque | 09367-34 | |
MEM Non-Essential Amino Acids Solution | Thermo Fisher Scientific | 11140050 | |
DMEM | Thermo Fisher Scientific | 11995065 | |
Opti-MEM I Reduced Serum Medium | Thermo Fisher Scientific | 31985070 | |
100 mm/collagen-coated dish | Iwaki | 4020-010 | |
Lipofectamine 3000 Transfection Reagent | Thermo Fisher Scientific | L3000001 | |
Polyethylene glycol (PEG) 6000 | Sigma-Aldrich | 81255 | |
Polyethylene glycol (PEG) 8000 | Sigma-Aldrich | 89510 | |
NaCl | Nacalai tesque | 31319-45 | |
0.5 mol/l-EDTA Solution | Nacalai tesque | 06894-14 | |
Tris-HCl | Nacalai tesque | 35434-21 | |
Millex-HP, 0.45 μm, polyethethersulfone, filter | Merck Millipore | SLHP033RS | |
Dimethyl sulfoxide (DMSO) | Sigma-Aldrich | D2650 | |
Collagen coated 96-well plate | Corning | NO3585 | |
Passive Lysis 5xBuffer | Promega | E1941 | |
GloMax 96 Microplate Luminometer | Promega | E6501 | |
Sucrose | Nacalai tesque | 30403-55 | |
Luminometer plate | Greiner bio-one | 655075 | |
HepG2-NTCP1-myc-clone22 | - | - | Nishitsuji, H., et al. Cancer. Sci. (2015) |
pUC1.2HBV delta epsilon | - | - | Nishitsuji, H., et al. Cancer. Sci. (2015) |
pUC1.2HBV/NL | - | - | Nishitsuji, H., et al. Cancer. Sci. (2015) |
50 ml tube | Violamo | 1-3500-02 | |
Anti-Myc antibody | Sigma-Aldrich | C3956 | |
HBIG | Japan Blood Products Organization | - | |
IFN-β | Mochida Pharmaceutical | 1.49872E+13 | |
Heparin | Sigma-Aldrich | H3393 |