Immune System Signatures Proposed for Disease Diagnostics

National Institutes of Health

Researchers at Arizona State University in Tempe have developed a technique for harnessing the body’s immune system to give early indicators of disease. Student Brian Chase, postdoctoral fellow Barten Legutki, and faculty member Stephen Johnston at Arizona State’s Biodesign Institute published their findings in last month’s issue of the journal Clinical and Vaccine Immunology (paid subscription required).

The new methods, called immunosignaturing, use easy-to-collect samples of body fluids such as serum, plasma, saliva, and dried blood that can be analyzed for indicators of pre-symptomatic illness. The results also appear to yield reliable and highly stable diagnostic results under a variety of conditions.

Immunosignaturing uses random sequence arrays of peptides — short polymer amino acids — to test for antibodies to disease. Previous research indicates it is possible to test for the body’s full collection of antibodies with 10,000 of these sequences, each with 20 amino acids, on one glass slide.

The antibodies contained in a blood sample selectively bind to the peptides with varying degrees of affinity. Removing the blood, say the researchers, leaves the immunosignature: a machine-readable image of immune activity that can indicate the pre-symptomatic presence of diseases including infectious and chronic diseases, and some forms of cancer. The resulting immune fingerprint shows thousands of spots fluorescing at different levels, corresponding to antibody activity.

Unlike other diagnostic tools designed to indicate specific disorders, immunosignatures offer a general diagnostic screening technique for multiple disease factors from a single sample. Earlier research showed immunosignaturing can deliver useful diagnostics for influenza, Alzheimer’s disease, pancreatic diseases, and lupus.

The current study tested the stability and reliability of immunosignatures, when drawn from different types of fluid samples and under different environmental conditions. The researchers found immunosignatures
derived from both serum and plasma from the same donor, correlated with each other. Also, two sequential blood draws collected into either a serum separator tube or a plasma separator tube — to evaluate the influence of clotting factors — show that plasma and serum produce equivalent immunosignatures. This finding suggests immunosignatures from previous samples, collected using either blood source, could be used for disease diagnosis.

In a separate test, the researchers examined dried blood spots and recovered serum antibodies to produce an immunosignature. The team found as well a correlation of antibody activity between the dried blood and fresh serum samples. Rates of protein recovery from dried blood, which include functioning antibodies,  range from 78 to 100 percent, in both mouse and human samples. The team reports that immunosignatures from fresh serum samples show higher fluorescence intensities, but the effect is uniform across the array.

The Arizona State team evaluated the ability to immunosignatures to hold up over time and when exposed to heat or microorganisms, as a way of testing the impact of environmental factors if samples had to mailed or shipped over long distances. Samples of dried blood were stored at 25 degrees C (77 F) or 37.8 degrees C (100 F). The researchers found immunosignatures remain stable after two weeks at 25 C, but at 37.8 C samples retain stability only overnight, and then decline in stability after two weeks.

To test for the effect of microbes, the team tested two sets of mice for a characteristic immunosignature, one set with mice infected with influenza and a second group with no infection. The researchers found the presence of the characteristic immunosignature in both sets of mice.

The published research included a test of saliva as a non-invasive alternative to blood samples for immunosignatures. The team found immunosignatures for immunoglobulin A (IgA) antibodies in the saliva samples correlate with dried blood, but they also found low quantities of immunoglobulin G (IgG) antibodies.

Johnston says the the new data advance the use of immunosignaturing as a sensitive, low-cost, universal system for assessing health status. “Our ultimate goal is to monitor the health of healthy people,” says Johnston, “so it is crucial we have a technique that is cheap, simple and, as we demonstrate here, robust.”

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