Diagnostic laboratories have been developing new assays to help assess both immunological responses and pathogen detection at the same time using a capture bead system developed by Luminex. This new technology is still in the development phase though many labs have the Luminex assays for foreign animal disease, the immune assays have been developed for pigs and are being developed for cattle.
Chris Chase, DVM, PhD, South Dakota State University, says each of the beads has its own colored "address" so up to 100 different antigens, antibodies, viruses and/or bacteria can be detected at the same time. "For example in a feedlot, specific antibodies for foreign animal diseases, immune cytokines, antibodies for viruses used in a 4-way vaccine and BVDV, IBR viruses could all be tested for at the same time," he explains.
Unlike using polymerase chain reaction (PCR) tests that can only detect RNA or DNA and enzyme-linked immunosorbent assay (ELISA) that detect either antibody or antigen, the Luminex system can measure all of these different types of biological molecules at the same time. Each special "addressed bead" can then have an antibody, an antigen or nucleotide attached to detect the specific analyte (immune cytokine, antibody, virus or bacteria) that is being tested.
"Almost any sample can be used including plasma, serum, lysates or other biological samples although blood is probably the most popular," notes Chase. The detection system uses a laser to emit fluorescence that is used to both detect the bead "address" and the amount of the target (immune cytokine, antibody, virus or bacteria). The unique fluorescent emission for a given microsphere enables the Luminex to identify discrete measurements of multiple microsphere based reactions from a single sample
This assay provides an opportunity for quickly measuring many different immune responses at a lower cost per immune cytokine. Some of the applications in the future would be to assess whether animals should be vaccinated (is their immune system "normal" or stressed), measuring the response after vaccination and/or using in "sick" animals to determine best therapy.
The Luminex technology was discussed in a diagnostic roundtable sponsored by Intervet/Schering-Plough.