Adenovirus Titer Immunoassay Kit

Catalog No. ABIN2345180

Product Details

Reactivity: Adenovirus

Application: Immunoassay (IA), Quantification (Q)

Brand: QuickTiter™

Sample Type: Cell Extracts

Characteristics: QuickTiter™ Adenovirus Titer Immunoassay Kit provides a quick and complete system to functionally titer virus infectivity, it provides sufficient reagents for up to 100 titrations in 24-well plate. In contrast to the 10-day infection of a classical plaque assay, the kit only requires a 2-day infection. The kit antibody against hexon protein recognizes all 41 serotypes of adenovirus by immunocytochemistry and can be used with any adenovirus system as long as the virus is able to amplify in HEK 293 cells.

Components:

1. Anti-Hexon Antibody (1000X) : One tube - 30 μL.
2. Secondary Antibody, HRP Conjugate (1000X) : One tube - 50 μL.
3. DAB Substrate (25X) : One tube - 1.5 mL.
4. Diluent (10X) : Three tubes - 1.5 mL each.
5. Ad-β gal Positive Control : One tube - 50 μL at 1.0 x 109 ifu/mL. 3

Material not included:

1. Recombinant adenovirus of interest
2. HEK 293 cells and cell culture growth medium
3. Methanol
4. 1 % BSA/PBS
5. H2O2
6. Light Microscope
7. (optional) β-Galactosidase Staining Kit (Cat.# AKR-100)

Application Details

Application Notes: Optimal working dilution should be determined by the investigator.

Comment:

• More accurate adenoviral titer than traditional plaque-forming unit assays
• Faster results: 2.5 days vs. 10 days
• No agar overlay steps

Assay Time: 2.5 d

Reagent Preparation:

The table below is suggested for tests in a 24-well plate. Use twice the amount of reagents for samples in a 12-well plate.

• 1X Anti-Hexon antibody solution: Prepare a 1X anti-hexon antibody solution by diluting the provided 1000X Anti-Hexon antibody stock 1:1000 in 1 % BSA/PBS. Store the diluted solution on ice.
• 1X Secondary antibody solution: Prepare a 1X Secondary antibody solution by diluting the provided 1000X stock 1:1000 in 1 % BSA/PBS. Store the diluted solution on ice.
• 1X DAB working solution: Prior to use, FRESHLY prepare a 1X DAB working solution. First dilute the provided 10X Diluent to 1X with ddH2O, and add H2O2 to a final concentration of 0.01 %. Then dilute the 25X DAB stock to 1X with 1X Diluent/ H2O2 and use the 1X DAB working solution immediately. Note: When dilute 10X diluent, use ddH2O. Heavy metals in impure H2O will cause DAB precipitation. 24 tests (24-well 48 tests (24-well 96 tests (24-well Reagents plate) plate) plate) 1000X Anti-hexon Antibody 6 μL 12 μL 24 μL 1000X Secondary Antibody 6 μL 12 μL 24 μL 25X DAB 240 μL 480 μL 960 μL Final Volume (Each Reagent) 6 mL 12 mL 24 mL Table 1. Preparation of antibody and DAB solutions. 4

Sample Preparation:

1. Immediately before infection, create a 10-fold serial dilution of viral sample from 10-3 to 10-7. First, dilute original viral sample 1:100. For example, adding 10 μL of viral sample to a sterile tube containing 990 μL of culture medium.
2. Label six sterile tubes #1 to #6, and add 900 μL of culture medium to each tube. Add 100 μL of 1:100 diluted viral sample to tube #1, mix tube #1 well. Transfer 100 μL of the mixture (1:1000 dilution) to the next tube. Repeat the steps until tube #5 and use tube #6 as a blank. Note: An Ad-β gal Positive Control is provided as an assay control, you may include 1:104 and 1:105 dilutions of this stock in your assay. Ad-β gal expression can also be visualized by X-gal staining.

Assay Procedure:

The instructions below are suggested for assays performed in 24-well plate. Use twice as much the amount of cells and reagents for assays performed in 12-well plate.

I. Virus Infection

1. Harvest HEK 293 cells and resuspend cells in culture medium at 2.5 x 105 cells/mL. Seed 1 mL in each well of a 24-well plate and incubate at 37 °C, 5 % CO2 for 1 hr. Note: Adenovirus titer assay is critically dependent of the firm attachment of cells. If the cells look thin and easy to come off during immunostaining steps, you won't get consistent result. Only use low passage 293 cells with flattened morphology or 293AD (Cat.# AD-100), a selected 293 cell line for plasmid transfection, adenovirus amplification and tittering. To improve cell adhesion, you can also precoat plate with polylysine or extracellular matrix.
2. Prepare a 10-fold serial dilution of your viral sample in culture medium. Dropwise add 100 μL of diluted viral sample to each well of the 24-well assay plate (note: a negative control should be performed simultaneously). To ensure accuracy, perform each sample in duplicate.
3. Incubate infected cells at 37 °C, 5 % CO2 for 2 days.

II. Immunostaining

1. Slowly remove medium from the wells by tilting the plate and aspirating from the edge, then fix infected 293 cells by gently adding 0.5 mLof cold methanol down the side of each well of the 24-well assay plate, taking care not to dislodge the cells. Incubate 20 minutes at -20 °C.
2. Gently wash the fixed cells three times with 1X PBS, five minutes each wash.
3. Block for 1 hr with 1 % BSA in PBS at room temperature on an orbital shaker.
4. Add 0.25 mL of diluted 1X anti-Hexon antibody solution to each well and incubate for 1 hr at room temperature on an orbital shaker.
5. Gently wash the fixed cells three times with 1X PBS, five minutes each wash.
6. Add 0.25 mL of diluted 1X Secondary antibody solution (HRP-conjugated) to each well and incubate for 1 hr at room temperature on an orbital shaker.
7. Gently wash the fixed cells five times with 1X PBS, five minutes each wash. 5
8. Add 0.25 mL of freshly diluted 1X DAB working solution to each well and incubate for 10 minutes at room temperature on an orbital shaker. Note: Adenovirus infected cells should show dark brown staining within 5 minutes. During incubation, excess DAB starts to form light precipitates in solution, and this will not affect the staining results.
9. Aspirate DAB, wash twice with 1X PBS and add 1 mL of 1X PBS to each well.
10. Count positive stained cells (brown) for at least five separate fields per well using a light microscope and 10X objective.
11. Calculate the average number of positive cells per well and viral titer (infectious units/mL).

Calculation of Results:

1. Calculate the average number of positive cells per field. Ideally, choose a dilution with 5-50 positive cells/field and count at least five fields.
2. Determine the number of fields per well For most microscopes, a standard 10X objective lens with 10X eyepiece lens has a field diameter (D) of 1.8 mm, then: Area per field = 3.14 x (D/2)2 = 3.14 x 0.92 = 2.54 mm2 For 24-well plate, area of a well (standard 24-well plate) is 2.0 cm2, therefore, Fields/well = 2.0 cm2/2.54 mm2 = 2.0 cm2/2.54 x 10-2 cm2 = 79 For 12-well plate, area of a well (standard 12-well plate) is 3.8 cm2, therefore, Fields/well = 3.8 cm2/2.54 mm2 = 3.8 cm2/2.54 x 10-2 cm2 = 150 Note: If you are not sure about the field diameter of the 10X objective lens you are using or you are using objective lenses other than 10X, the field diameter can be determined by aligning with the grids of hemacytometer , or referring to Table
3. Figure
4. Hemacytometer Grid Dimensions. Objective Lenses Eyepiece Lenses (10X) Fields/Well Total Field Field Area 12-well 24-well Magnification Diameter (mm2) Plate Plate 4X 40X 5 mm 19.6 19 10 10X 100X 1.8 mm 2.54 150 79 20X 200X 0.9 mm 0.64 594 313 Table
5. Field sizes of objective lenses. 7
6. Calculate viral titer (Infectious Units or ifu/mL) Tests in 24-well: Viral Titer (ifu/mL) = (average positive cells/field) x (79 fields/well) x (dilution factor) (0.1 mL) Tests in 12-well: Viral Titer (ifu/mL) = (average positive cells/field) x (150 fields/well) x (dilution factor) (0.1 mL) Calculation Example: A serial of 10-fold dilutions of the provided Ad-β gal Positive Control was made and its titer was determined in a 24-well plate as described in assay instruction. Ten fields were counted and the average positive cells/field is 12 for 1/105 dilution under a standard 10X objective, therefore: Viral Titer (ifu/mL) = (average positive cells/field) x (79 fields/well) x (dilution factor) (0.1 mL) Viral Titer (ifu/mL) = (12/field) x (79 fields/well) x (105) = 0.95 x 109 (ifu/mL) (0.1 mL)

Restrictions: For Research Use only

Handling

Precaution of Use: Remember that you will be working with samples containing infectious virus. Follow the recommended NIH guidelines for all materials containing BSL-2 organims.

Storage: 4 °C/-80 °C

Storage Comment: Upon receipt, store the Ad-β-gal Positive Control at -80°C. Store all other kit components at 4°C until their expiration dates.

References

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Target Details

Background: Recombinant adenoviruses have tremendous potential in both research and therapeutic applications. There are numerous advantages they provide when introducing genetic material into host cells. The permissive host cell range is very wide. The virus has been used to infect many mammalian cell types (both replicative and non-replicative) for high expression of the recombinant protein. Recombinant adenoviruses are especially useful for gene transfer and protein expression in cell lines that have low transfection efficiency with liposome. After entering cells, the virus remains epichromosomal (i.e. does not integrate into the host chromosome so does not activate or inactivate host genes). Recently, recombinant adenoviruses have been used to deliver RNAi into cells. HEK 293 cells or their variants are used as host cells for viral amplification. Recombinant adenoviruses can be grown at high titer (1010 VP (viral particles)/mL, which can be concentrated up to 1013 VP/mL) and purified by ViraBind™ Adenoviral Purification Kit or traditional CsCl ultracentrifugation. A particular challenge in the delivery of a gene by a viral vector is the accurate measurement of virus titer. Traditionally, infectivity particles are measured in culture by a plaque-forming unit assay (PFU) that scores the number of viral plaques as a function of dilution. These methods are time-consuming (10 days), require a long infection period, and suffer from a high degree of inter-assay variability and are affected by virus-cell interactions. QuickTiter™ Adenovirus Titer Immunoassay Kit utilizes an antibody against adenovirus hexon proteins to visualize infected cells by immunocytochemistry staining. The hexon proteins are the largest and most abundant of the structural proteins in the adenovirus capsid, and they are distributed symmetrically to form capsid facets.