DESCRIPTION

VISTA (V-domain Ig suppressor of T cell activation), also known as C10orf54, B7-H5, PD-1H and Dies1, is a member of the immune checkpoints of the B7 family that shares significant homology with PD-L1 and PD-L2. VISTA is predominantly expressed on haematopoietic cells, myeloid cells, and weakly expressed on T cells. It can act as a ligand expressed on antigen presenting cells (APCs), and also functions as an coinhibitory receptor for CD4+ T cells. VISTA exerts negative regulatory functions by suppressing the activation, proliferation, and cytokine secretion of T cells. VISTA plays an important role in tumor progression and immune escape and can be used as a predictor for diagnosis or immunotherapy of cancer.

PRINCIPLE OF THE ASSAY

Sandwich ELISA structure (Detection antibody labeled with HRP) A capture antibody is pre-coated onto the bottom of wells which binds to analyte of interest. A detection antibody labeled with HRP also binds to the analyte. TMB acts as the HRP substrate and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns solution yellow. The color intensity is proportional to the quantity of bound protein which is measurable at 450 nm with the correction wavelength set at 630 nm.

Intra-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	20	4.76	0.23	4.9
2	20	1.12	0.05	4.7
3	20	0.32	0.02	6.3

Inter-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	24	5.20	0.22	4.2
2	24	1.19	0.05	4.1
3	24	0.31	0.03	10.8

RECOVERY

The recovery of human VISTA/C10orf54 spiked to three different levels throughout the range of the assay in human serum was evaluated.

Sample Type		Average% of Expected	Range (%)
Human serum	1:4	97	86-106
	1:8	104	87-125

LINEARITY

To assess the linearity of the assay, human serum samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay.

		Human serum
1:2	Average% of Expected	100
	Range (%)	-
1:4	Average% of Expected	102
	Range (%)	94-113
1:8	Average% of Expected	99
	Range (%)	73-123
1:16	Average% of Expected	104
	Range (%)	76-130

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human VISTA/C10orf54 Sandwich ELISA Kit produced at Sunlong Medical™.