Dot-immunobinding assay for the activity of egg yolk anibody
- VernacularTitle:斑点免疫结合法测定卵黄抗体的活性
- Author:
Guangping RUAN
;
Mei AN
;
Guihua WANG
;
Lei YE
;
Shufen DENG
- Publication Type:Journal Article
- From:
Chinese Journal of Tissue Engineering Research
2007;11(12):2397-2400
- CountryChina
- Language:Chinese
-
Abstract:
BACKGROUND: There are differences in physical and biological activity between the antibody from mammals and egg yolk antibody (IgY) from chicken. IgY is acid- and heat-resistant, and can prevent and cure the infectious diseases in animals and human being, which is also benefit to develop routine diagnostic immunoassays. Conventional ELISA assay for IgY takes much more time than dot-immunobinding assay.OBJECTIVE: To detect the IgY stability byusing dot-immunobinding assay.DESIGN: Open trail.SETTING: Department of Transfusion, Kunming General Hospital of Chinese PLA.MATERTALS: The experiment was completed in the Kunming General Hospital of Chengdu Military Area Command of Chinese PLA from January to June 2006. Two White Leghorn hens (30 weeks old) were selected. HLA-A*0201 α chain served as the antigen. The total protein concentration of the purified antigen was 0.04 g/L with the molecular mass of 32 000(self-prepared); nitrocellulose filter (NC, import and divided); nonfat dry milk (Anyi Corp. No. 20051220); DAB (Boshide Corp.);caprylic acid (made by Shanghai Xinghuo Chemical Factory); ammonium sulfate (Shantou Guanghua Chemical product).METHODS: ①HLA-A*0201 α chain with the total protein concentration of 0.04 g/L was purified with egg yolk antibody,and identified by SDS-PAGE. ②1 μL antigen was spotted into the center of NC membrane and dried in the incubator at 37 ℃. Then the NC membrane was blocked in 1 mL PBST and put in the incubator at 37℃ with shaking in 90 r per minute for 15 minutes. Then the liquid was exchanged with 1 mL PBST and added the primary antibody at a final concentration of 10 mg/L. After 30 minutes shaking in the incubator at 37 ℃, the NC membrane was washed in PBST for three times. The second antibody, mouse anti-chicken IgY conjugated to horseradish peroxidase (HRP) was added and after 30 minutes incubation, the NC membrane was washed three times in PBST. Binding was revealed by incubation with a DAB reagent. A positive reaction was represented by adeep brown spot,Irdlcating that IgY had better activity; if the spot became lighter IgY lost part activity, and when the spot disappeared, the IgY lost a the activty.According to intensity (gray degree)of the dot compared tothe standard, the remained percent of activity of the IgY was calculated. ③IgY was adjusted to three different protein concentrations with PBS: 1, 0.1, 0.01 g/L and stayed at room temperature for four months. 10 μg lgY was taken out from each concentration sample every month to detect the activity by dot-immunobinding assay. ④IgY was put into seven EP tubes with 100 μL per tube and numbered 1-7. Number 1 to 3 was adjusted pH to 5, 3 and 2, respectively with 1 mol/L HCI; Number 4 to 6 was to 9, 11 and 12, respectively with 1 mol/L NaOH. The pH of number 7 was neutral without adding acid or base. The samples were stayed in incubator at 37 ℃ for 3 hours. 10 μg IgY from each tube was taken every hour to detect the stability at different pH by dot-immunobinding assay. ⑤IgY was added to six EP tubes (10 μL per tube) and numbered 1-6. Number 1-6 was put into waterbath at 30, 40, 50, 60, 70 and 80 ℃ for 15 minutes. After cooled in refrigerator at 4 ℃, 10 mg samples from each tube and standard sample (untreated sample) taken to check the thermal stability by dot-immunobinding assay.MAIN OUTCOME MEASURES: ①SDS-PAGE of IgY. ②IgY stability at room temperature. ③IgY stability at different pH. ④ Detection of IgY thermal stability.RESULTS: ①Purified IgY after SDS-PAGE had two major binds, the molecular mass of the heavy chain was 66.000,and the light chain was 25 000. ②1, 0.1, 0.01 g/L IgY still had partial activity after staying at room temperature for four months. ③When pH ranged from 5 to 9, IgY still had partial activity after staying in 37 ℃ for 3 hours. If pH was lower than 5 or higher than 9, it lost the whole activity in above condition. ④Purified IgY was added to six EP tubes, the number 1-4 still had partial activity, but number 5 and 6 showed some white precipitate, which was caused by protein denaturation at higher temperature.CONCLUSION: IgY stability is higher than others. The dot-immunobinding assay described a rapid and simple method for the demonstration and characterization of functional activity of egg yolk antibody. With only small volume antigen and antibody, and specific dot, the dot-immunobinding assay method could process many samples at the same time.
