Antigen assay

Non-endoscopic testing methods include the urea breath test, serologic testing, and the stool antigen assay. Compared to endoscopic procedures, these tests are more comfortable, less expensive, and do not require a special procedure. The urea breath test is usually the first-line test to detect active... 

Office-based serologic testing provides a quick assessment (within 15 minutes) of an exposure to HP, but patients can remain seropositive for up to 1 year after eradication, making the clinical utility of this test limited. Stool antigen assays can be useful for the initial diagnosis or to confirm HP eradication, and unlike the urea breath test, are less affected by concomitant medication use.9... 

Diamandis, E. P., Yu, H., Melegos, D. N. Ultrasensitive prostate-specific antigen assays and their clinical application. Clin. Chem. 42,853-864 (1996). 

Stamey, T. A. Lower limits of detection, biological detection limits, functional sensitivity, or residual cancer detection limit/sensitivity reports on prostate-specific antigen assays mislead clinicians. Clin. Chem. 42, 849-850 (1996). 

Flood,J., et al. (1997). Diagnosis of cytomegalovirus (CMV) polyradiculopathy and documentation of in vivo anti-CMV activity in cerebrospinal fluid by using branched DNA signal amplification and antigen assays. J. Infect. Dis. 176,348-352. 

Sections in slide rack should be rapidly removed from the freezer and placed in a staining dish with the ethanol/acetic acid fixative solution for 2-10 min depending on tissue and antigen assayed (see Note 7). 

Calculate the number of cells needed for the antigen assay Each compound is tested at 4 concentrations in replicates of three three untreated samples (for each solvent) are needed for the standard curve. Each sample contains 3 x 10s C8166 cells. Twenty percent extra cells are used to allow for pipeting and for monitoring growth in a flask. The number of samples is calculated as 12/V+3.S. Thc total number of cells required is... 

Spin down the total number of cells required for the antigen assay and resuspend in 1 mL of media in a plastic universal. Carry out steps 5-13 in a Category 3 level containment laboratory. 

Carry out the antigen assay according to the manufacturer s instructions. 

Mix the PBMCs gently and remove a volume containing the required number of cells for the antigen assay. With PBMCs the concentration of cells needed is 2 x 105/200 pL growth medium. Spin down and resuspend the PMBC in 1 of medium and incubate with 100 TCID50 HIVIIIB for 1.5 h at 37°C (see Note 7). 

After 72 or 96 h the plates are examined and scored for cytopathic effect (CPE). Carefully remove 200 pL from each well or 50 pL from each replicate of four for testing to evaluate levels of HIV p24 antigen production in the wells. Testing in this laboratory was with the Coulter UK P24 antigen assay. 

For testing the function of the synthesized RNA template, run Amp-RT reactions with 10 ng of RNA template and 10-fold dilutions of rHIV-1 RT from 10-6 to 10-11 units. Alternatively, HIV-1 virions can be used as a source of RT at concentrations equivalent to 0.2-0.00002 pg of p24 antigen (measured by the Coulter HIV-1 p24 antigen assay). The dilutions should be made in IX RT buffer C (50 mM Tris-HCl, pH 8.3, 50 mM KC1, 10 mM MgCl2). 

Boni, J., Opravil, M Tomasik, Z., Rothen, M., Bisset, L., Grab, P. J., Liithy, R., and Schupbach, J. (1997) Simple monitoring of antiretroviral therapy with a signal-amplification-boosted human immunodeficiency virus type 1 p24 antigen assay with heat-denatured plasma. AIDS 11, F47-F52. 

Chemiluminescent labels may be employed in sandwich or competitive antigen assays. In sandwich assays, a solid support holds a primary antibody, and incubation with ligand yields a species that is detectable following a second incubation step with a labeled second antibody. Luminol has been tested as an immunoassay label it may be coupled to proteins through its primary amino group. Luminol reacts with hydrogen peroxide and hydroxide in a microperoxidase-catalyzed reaction, which yields light at 430 nm (Eq. 6.8) ... 

Diamandis EP. Clinical application of ultrasensitive prostate-specific antigen assays. J Natl Cancer Inst 1997 89 1077-78. 

Bilardi C, Biagini R, Dulbecco P, et al. Stool antigen assay (HpSA) is less reliable than urea breath test for post-treatment diagnosis of Helicobacter pylori infection. Aliment Pharmacol Ther 2002 16 1733-1738. 

Fig. 125. Chemically modified semiconductor electrode with covalently bound antibody for antigen assay. (Redrawn from Yamamoto et al., 1983).

Since VEGF plays an important role in other parts of the body, especially the cardiovascular system, systemic exposure was evaluated in preclinical studies. In monkey experiments, systemic exposure to ranibizumab was low, with plasma concentrations of the Fab antibody remaining below the limit of quantitation (<7.8 ng/mL) (10). Levels of plasma ranibizumab are highest on day one after injection and decrease rapidly by day seven (13). The ranibizumab antigen assay showed that the average detectable drug level in the vitreous was 32 ng/mL after the first injection and increased with subsequent injections (13). Thus, intravitreal injection of ranibizumab does not appear to lead to significant systemic levels. 

ELISA (Dako antibodies). Antithrombin level in the rhAT concentrate was assayed against the 8th British Blood Coagulation Factors Standard to compare the stated dose with the assayed dose per vial. Heparin binding was also assessed by two-dimensional electrophoresis with or without heparin in the first dimension, and by heparin-Sepharose gel filtration. The concentration of rhAT in the vial was 89% of the stated value by this thrombin-based assay, 85% by Xa-based assay, and 119% by the antigen assay. 

Fig. 2. ABBOTT PRISM HCV core Antigen Assay Format...

Lorenzo J, Castro A, Aguilera A, et al. Total HCV core antigen assay. A new marker of HCV viremia and its application during treatment of chronic hepatitis C. J Virol Methods 2004 120 173-7. 

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