Microplate ELISAs for soluble VCAM-1 and ICAM-1

Soluble vascular cell adhesion molecule (sVCAM-1) and soluble intercellular adhesion molecule (sICAM-1) are adhesion molecules that are detectable in the serum of patients with cancer, cardiovascular diseases (CVD), and type 2 diabetes. This report describes enzyme-linked immunosorbent assays (ELISAs) on microplates for sVCAM-1 and sICAM-1. The ELISAs have the sandwich test format; polyclonal antibodies are coated on microwells and a one-step procedure is used in which the serum specimen and detecting antibody are added simultaneously to an antibody-coated well. These assays both use HRP-conjugated sheep anti-mouse-IgG to generate the color for quantification. Sensitivities for detecting sVCAM-1 and sICAM-1 are 49 and 40 ng/ml, respectively. Coefficients of variation for within-day and day-to-day replicate analyses are <10%. Results by these in-house ELISAs for serum sVCAM-1 and sICAM-1 compared well with those obtained with commercial kits from R&D Systems, Inc. (correlation coefficients = 0.98 and 0.99 for sVCAM-1 and sICAM-1, respectively). Reference values for serum sVCAM-1 and sICAM-1 levels were measured in 369 apparently healthy Chinese adults, age 30 to 79 yr. There was no significant effect of gender on the reference values for sVCAM-1 or sICAM-1. Serum sVCAM-1 levels (mean +/- SD) were higher in subjects 60 yr old (625 +/- 126 ng/ml), compared to those <60 yr old (525 +/- 110 ng/ml) (p <0.001). Age did not significantly affect the reference values for serum sICAM-1 levels (mean +/- SD, 249 +/- 86 ng/ml). The authors believe that these simple, inexpensive ELISAs will be useful for assessing the risks for development of cancer, CVD, and type 2 diabetes.