PD-L1/CD9 Exosome ELISA Kit (Human)

Cosmo Bio LTD

Catalog No: HAK-HELPDL109-1

This product is a sandwich ELISA kit that uses high-performance antibodies against CD9, an exosome marker, and PD-L1, an immune checkpoint-related molecule, to detect PD-L1 molecules expressed on the surface of exosomes secreted by cells in human blood and cell culture fluid.

Background

What is PD-L1?

Cancer cells express PD-L1 (programmed cell death ligand-1) on their surface, which is a receptor for the PD-1 receptor expressed on the surface of activated T cells, and suppress T cell activity through PD-1/PD-L1 binding, thereby evading immune surveillance.1 ^),2) In recent years, these immune surveillance mechanisms have been applied to cancer treatment, and anti-PD-1 and anti-PD-L1 antibodies have been developed to enhance T cell activation by inhibiting this binding, and their clinical efficacy and safety have been confirmed in various solid cancers.3 ^),4) The
most well-known predictor of the efficacy of these immune checkpoint inhibitors is the expression of PD-L1 on cancer cells, and the PD-L1 IHC test (immunohistochemical staining method), which has been incorporated into clinical trials, is currently being developed to measure the PD-L1 expression rate in cancer tissues and cells, and is being used as a companion diagnostic.
In general, IHC testing is highly invasive and places a large burden on subjects, so research is also underway into liquid biopsies using exosomes that can reduce this burden.
PD-L1 is also expressed on exosomes, and has the same topology as PD-L1 on the surface of cancer cells, with the extracellular domain exposed on the surface of exosomes, which binds to PD-1 on T cells in a concentration-dependent ^manner5) . In addition, a comparison of circulating exosomes in the blood of metastatic melanoma patients and healthy subjects suggests that PD-L1 levels are significantly higher in metastatic melanoma ^patients5) . However, this method requires the purification of exosomes by ultracentrifugation, and direct measurement cannot be performed quickly and easily.

Features

• Highly sensitive detection of human PD-L1-positive exosomes by ELISA (detection sensitivity: 0.05 ng/mL ^* )
• Direct quantification of PD-L1-positive exosomes in human blood samples, cell culture supernatants, etc.
• No special equipment is required; measurements can be performed with a standard plate reader.
• Stability and reproducibility are ensured by using PD-L1/CD9 fusion protein (standard protein) instead of exosomes themselves, which lack storage stability as a standard reagent.
• Relative quantification of each sample is possible by reading it against a standard curve using PD-L1/CD9 fusion protein (standard protein)
  *Calculated from the standard deviation of blank absorbance and the slope of the calibration curve6 ⁾

Kit Components

Contents	capacity	quantity
Anti-CD9 antibody immobilized plate	96 well (8-well x 12 strips)	1 sheet
Standard protein (PD-L1/CD9 fusion protein)	100 µL	1pc ^*
Assay Buffer	25 mL	1 bottle
Washing buffer (10x)	25 mL	1 bottle
HRP-labeled anti-PD-L1 antibody (500x)	20 µL	1 bottle
Substrate solution	12 mL	1 bottle
Stop solution ( 2N H2SO4 )	6 mL	1 bottle
Plate seal	-	2 sheets

*; n=2, two calibration curves

Specification

Cross-reactivity	Sample Type	Measurement range	sensitivity
Human	Serum, Plasma, Cell culture supernatant	0.156–10 ng/mL	0.05ng/mL

Example data

Figure 1. Standard curve