Materials and Reagents

Pipette tips
Inoculating loops (10 μl) (Copan Diagnostics, catalog number: 8177CS20H )
Aluminum foil
PVDF membrane (0.2 μm) (Merck, catalog number: ISEQ00010 )
H. pylori cells
Columbia blood agar (CBA) plates (Autobio Diagnostics, catalog number: M0109-2 )
Sodium chloride (NaCl) (Sigma-Aldrich, catalog number: 746398-500G )
Potassium chloride (KCl) (Sigma-Aldrich, catalog number: 746436-500G )
Sodium phosphate dibasic (Na₂HPO₄) (Sigma-Aldrich, catalog number: 795410-500G )
Potassium phosphate dibasic (K₂HPO₄) (Sigma-Aldrich, catalog number: 795496-500G )
NaOH (Sigma-Aldrich, catalog number: S5881-500G )
Proteinase K (Sigma-Aldrich, catalog number: P8044-1G )
Ethanol (Sigma-Aldrich, catalog number: 24102-5L-R )
SDS (Sigma-Aldrich, catalog number: L3771-1KG )
Glycerol (Sigma-Aldrich, catalog number: G9012-1L )
Tris base (Sigma-Aldrich, Roche Diagnostics, catalog number: 11814273001 )
Glycine (Sigma-Aldrich, catalog number: G8898-1KG )
Bromphenol blue (AMRESCO, catalog number: 0449-50G )
β-Mercaptoethanol (AMRESCO, catalog number: 0482-100ML )
Periodic acid (Sigma-Aldrich, catalog number: P7875 )
Acetic acid (BDH, catalog number: 100015N )
Ammonium persulfate (Sigma-Aldrich, catalog number: A3678 )
Ammonium hydroxide (Sigma-Aldrich, catalog number: 320145 )
Silver nitrate (Sigma-Aldrich, catalog number: 209139 )
Citric acid (Sigma-Aldrich, catalog number: C7129 )
Formalin (37% formaldehyde) (Sigma-Aldrich, catalog number: 252549 )
Freshly-made 15% SDS-PAGE gels
30% Acrylamide/Bis (Bio-Rad Laboratories, catalog number: 1610157 )
TEMED (Bio-Rad Laboratories, catalog number: 1610801 )
Methanol (Sigma-Aldrich, catalog number: 34860-4X4L-R )
Bovine serum albumin (BSA) (AMRESCO, catalog number: 0332-100G )
Tween-20 (Solarbio, catalog number: T8220-500 ml )
Mouse anti-Le^x (Santa Cruz Biotechnology, catalog number: sc-59471 )
Mouse anti-Le^y (Santa Cruz Biotechnology, catalog number: sc-59472 )
Mouse anti-Le^a (Santa Cruz Biotechnology, catalog number: sc-51512 )
Mouse anti-Le^b (Santa Cruz Biotechnology, catalog number: sc-51513 )
Secondary rabbit anti-mouse peroxidase-conjugated IgM antibody (Jackson ImmunoResearch Laboratories, catalog number: 315-035-049 )
Chemiluminescent peroxidase substrate-1 (Sigma-Aldrich, catalog number: CPS1120 )
PBS (pH 7.2) (10x) (see Recipes)
SDS-PAGE running buffer (10x, see Recipes)
0.1 N NaOH solution (see Recipes)
LPS lysis buffer (see Recipes)
Oxidation solution (see Recipes)
Silver staining solution (see Recipes)
Color developer solution (see Recipes)
Termination solution (see Recipes)
SDS-PAGE transfer buffer (10x, see Recipes)
TBS (10x, see Recipes)

Equipment

Pipettes (Eppendorf, catalog numbers: 4920000024 , 4920000059 , 4920000067 , 4920000083 )
Centrifuges (Eppendorf, catalog number: 5418 R )
Glass wares
Water bath
Rotary shaker
Cell electrophoresis tank (Bio-Rad Laboratories, catalog number: 1658001 )
Electrophoresis power supply (Bio-Rad Laboratories, catalog number: 1645070 )
Semi-dry electrophoretic transfer system (Bio-Rad Laboratories, catalog number: 1703940 )
pH meter
Spectrophotometer (Shimadzu, model: UV-1601 UV-Visible)
Digital camera
Luminescent Image Analyzer (Fujifilm, model: LAS-3000 )

Software

Image reader LAS 3000 V2.2

Procedure

LPS sample preparation

Culture H. pylori strains on CBA plates, incubate at 37 °C for 24 h under microaerobic conditions.
Use a loop (10 μl) to harvest H. pylori cells grown on CBA plates (24 h growth) into 1 ml of cold 1x PBS (see Recipes) to a turbidity of 3.0 at OD₆₀₀.
Centrifuge the H. pylori cells at 5,000 x g for 5 min, discard supernatant.
Resuspend the pellet in 100 µl LPS lysis buffer (see Recipes) and heat the sample at 100 °C for 10 min, and allow to cool at room temperature.
Add 5 μl Proteinase K (20 mg/ml) to the cooled samples, and incubate in a 55 °C water bath overnight.
Load 10 μl of the above-obtained LPS sample per well to the 15% SDS-PAGE gel and electrophorese with 1x SDS-PAGE running buffer (see Recipes).
Once the gel electrophoresis is complete, remove the gel from the apparatus and trim away the stacking gel.

LPS silver staining

Rinse the gel 3 times with ddH₂O.
Transfer the gel to a separate ware with freshly-made oxidation solution (see Recipes), oxidize for 20 min on a rotary shaker (70 rpm/min) (all shaking in this protocol is done at room temperature).
Transfer the gel to a separate clean ware, rinse and wash with ddH₂O for 3 times, each time with 200 ml ddH₂O on a rotary shaker for 10 min.
Transfer the gel to a separate ware with freshly-made silver staining solution (see Recipes), stain for 10 min on a rotary shaker.
Note: The silver staining solution must be freshly-made, which can be made during the final wash of step B4. During the staining process, the ware should be wrapped in aluminum foil, but make sure the foil is not in contact with the solution.
Transfer the gel to a separate clean ware, rinse and wash for 3 times, each time with 200 ml ddH₂O on a rotary shaker for 10 min.
Transfer the gel to a separate ware with freshly-made color developer solution (see Recipes), develop for 2-10 min on a rotary shaker.
Note: The color developer solution must be freshly-made, which can be made during the final wash of step B6. The color will develop on the gel within to 2-10 min, the longer the developer solution remains in contact with the gel the darker the bands will become. Therefore, it is important to watch the gel develop. The operator must decide when the gel is sufficiently developed and transfer the gel to the termination solution (see Recipes).
Transfer the gels to a separate ware with freshly-made termination solution for 1 min. The gels are then rinsed and stored in ddH₂O.
Use a digital camera to take images of the silver-stained LPS gels.

Western blot for the detection of Lewis antigen expression
Proceed from step 7 of Procedure A.

Transfer LPS from the gel to PVDF membrane with 1x SDS-PAGE transfer buffer (see Recipes).
Once the transfer is complete, remove the membrane from the apparatus.
Rinse the membrane 3 times with ddH₂O.
Block the membrane with TBST (see Recipes) containing 3% BSA, on a rotary shaker for 2 h or overnight at 4 °C.
Pour off the blocking solution.
Probe with primary antibodies: mouse anti-Le^x/^y or anti-Le^a/^b (1:1,500) (Santa Cruz) in TBST containing 1% BSA, on a rotary shaker for 2 h or overnight at 4 °C.
Pour off the primary antibody solution.
Rinse and wash with TBST for 3 times, each time on a rotary shaker for 10 min.
Probe with secondary rabbit anti-mouse peroxidase-conjugated IgM antibody (1:10,000) (Jackson ImmunoResearch Laboratories) in TBST, on a rotary shaker for 1 h.
Pour off the secondary antibody solution.
Rinse and wash with TBST for 3 times, each time on a rotary shaker for 10 min.
Place the membrane on a flat sheet of plastic film.
Add approximately 5 ml of the chemiluminescent peroxidase substrate-1 working solution (Sigma-Aldrich) on the membrane.
Cover the membrane with a second flat sheet of plastic film.
Detect chemiluminescence using a LAS-3000 Intelligent DarkBox (Fujifilm) (software Image reader LAS 3000 V2.2).

Data analysis

Figure 1 below illustrates LPS prepared from H. pylori wild-type strains 26695, P1, B128 and J99 analyzed by silver staining and Western blot using anti-Lewis X (Le^x) and anti-Lewis Y (Le^y).

Silver staining: the fast migration bands stained black represent molecules comprising lipid A and core-oligosaccharide (Lipid A-core); the slower migration bands represent O-antigen. It is obvious that LPS preparations from the four H. pylori strains show a different staining pattern, indicating the strains carrying different LPS structures (Figure 1A).
Western blot: LPS from H. pylori strains 26695, P1 and J99 were detected expressing both Le^x and Le^y antigens (Figure 1B, Lanes 1, 2 and 4), whereas LPS prepared from strain B128 was not detected expressing Le^x/^y(Figure 1B, Lane 3).

Figure 1. Crude preparation of LPS from H. pylori strains for silver staining and Western blot

Recipes

Note: ddH₂O is used for preparing all the solutions unless otherwise indicated.

PBS (pH 7.2) (10x) (1 L)
80 g NaCl
2 g KCl
14.4 g Na₂HPO₄
2.4 g KH₂PO₄
Add 900 ml H₂O to dissolve all the reagents and adjust the pH to 7.2, then add H₂O to make the total volume up to 1 L. The buffer is sterilized by autoclaving and stored at room temperature. The 1x working solution is prepared by mixing 100 ml 10x PBS buffer with 900 ml H₂O
0.1 N NaOH (1 L)
4 g NaOH
The total volume is made up to 1 L with H₂O. The buffer was sterilized by autoclaving and stored at room temperature
LPS lysis buffer (20 ml)
2 ml 20% SDS
800 μl β-mercaptoethanol
200 μl bromophenol blue
2 ml glycerol
15 ml 1 M Tris-HCl (pH 6.8)
Oxidation solution (100 ml)
0.7 g periodic acid
40 ml EtOH
5 ml acetic acid
55 ml H₂O
Silver staining solution (150 ml)
28 ml 0.1 N NaOH
2 ml ammonium hydroxide (29.4%)
115 ml H₂O
5 ml 20% silver nitrate (w/v)
Note: This solution is mixed in the following order by adding 28 ml 0.1 N NaOH, 2 ml concentrated ammonium hydroxide (29.4%), and 115 ml H₂O in a dedicated ware, then transfer the ware on the rotary shaker (50 rpm/min). Finally, add the 5 ml 20% silver nitrate dropwise to the solution, waiting for the brown precipitate to dissolve before adding more of silver nitrate solution. If the brown precipitate fails to dissolve, discard the solution and remake the solution by adding the 20% silver nitrate more slowly.
Color developer solution (200 ml)
Dissolve 1 g citric acid into 20 ml H₂O, resulting into 5% citric acid:
200 μl 5% citric acid
100 μl 37% formaldehyde
200 ml H₂O
Termination solution (100 ml)
10 ml acetic acid
90 ml ddH₂O
SDS-PAGE running buffer (10x) (1 L)
30.3 g Tris base
144 g glycine
10 g SDS
The total volume is made up to 1 L with H₂O. The buffer was sterilized by autoclaving and stored at room temperature. The 1x working solution is prepared by mixing 100 ml 10x running buffer with 900 ml H₂O
SDS-PAGE transfer buffer (10x) (1 L)
30.3 g Tris base
144 g glycine
The total volume is made up to 1 L with H₂O. The buffer was sterilized by autoclaving and stored at room temperature. The 1x working solution is prepared by mixing 100 ml 10x transfer buffer with 700 ml H₂O and 200 ml methanol
TBS (10x) (1 L)
80 g NaCl
2 g KCl
30 g Tris base
Add 900 ml H₂O to dissolve all the reagents and adjust the pH to be 7.4, then add H₂O to make the total volume up to 1 L. The stocking buffer is sterilized by autoclaving and stored at room temperature. TBST is 1x TBS containing 0.1% Tween-20 (v/v)

Acknowledgments

This protocol described here and in Li et al. (2017) was adapted from protocols described in Apicella et al. (2008) and in Tsai et al. (1982). This work was supported by a grant from West China Hospital, Sichuan University entitled ‘1.3.5 project for disciplines of excellence, West China Hospital, Sichuan University’ (ZY2016201).

References

Apicella, M. A. (2008). Isolation and characterization of lipopolysaccharides. Methods Mol Biol 431: 3-13.
Tsai, C. M. and Frasch, C. E. (1982). A sensitive silver stain for detecting lipopolysaccharides in polyacrylamide gels. Anal Biochem 119(1): 115-119.