Multiplex flow assays with magnetic particles as solid phase
Heterogeneous assays for different analytes in a single biological sample are performed simultaneously in a multiplexed assay that combines flow cytometry with the use of magnetic particles as the solid phase and yields an individual result for each analyte. The particles are distinguishable from each other by characteristics that permit them to be differentiated into groups, each group carrying an assay reagent bonded to the particle surface that is distinct from the assay reagents of particles in other groups. The magnetic particles facilitate separation of the solid and liquid phases, permitting the assays to be performed by automated equipment. Assays are also disclosed for the simultaneous detection of antibodies of different classes and a common antigen specificity or of a common class and different antigen specificities. Each type is accomplished by immunological binding at the surfaces of two distinct solid phases in a sequential manner with dissociation of the binding and washing of the solid phase in between the binding steps.
1. A method for the analysis of a sample to simultaneously yet individually detect antibodies of different antigen specificities that are of a single common immunoglobulin class, said method comprising:
contacting said sample with a first solid phase coated with class-specific antibody having specific binding affinity for a single selected class of antibodies to cause antibodies in said sample of said single selected class to be immobilized to said first solid phase through immunological binding to said class-specific antibody coated thereon,
washing said first solid phase to isolate said first solid phase from unbound species;
contacting said first solid phase thus washed with a liquid medium and releasing said antibodies of said single selected class from said first solid phase by dissociating said immunological binding to form a supematant containing antibodies of a said selected class but of multiple antigen specificities;
isolating said supematant from said first solid phase and contacting said supematant with a second solid phase, said second solid phase comprising one or more portions each having coupled thereto an immunological binding member with specific binding affinity for antibodies of a single antigen specificity that is distinct from antigen specificities of other portions, and each portion being capable of differentiation from other such portions wherein the second solid phase comprises microparticles of magnetically responsive material, the sizes of said microparticles varying in size over a range that is an aggregate of a plurality of subranges, each subrange distinguishable from other subranges of said aggregate by flow cytometry and by the immunological binding member coupled thereto, said microparticles being suitable for use in a multiplex assay procedure that includes the use of flow cytometry; and
individually detecting the occurrence of immunological binding between said antibodies and said immunological binding members while differentiating between said portions.
2. A method in accordance with claim 1 in which said first solid phase is a plurality of particles.
3. A method in accordance with claim 1 in which said second solid phase is a plurality of particles.
4. A method in accordance with claim 1 in which said first and second solid phases are each a plurality of particles.
5. A method in accordance with claim 2 in which said microparticles are of magnetically responsive material, and said washing is facilitated by magnetically separating said microparticles from said sample.
6. A method in accordance with claim 2 in which said microparticles are of magnetically responsive material, and both said washing of said microparticles and said isolating of said supernatant from said microparticles are facilitated by magnetically separating said first group of microparticles from said sample.
7. A method in accordance with claim 3 in which said portions differ from each other by particle size, and differentiation between said portions is achieved by flow cytometry.
8. A method in accordance with claim 3 in which said individual detection of the occurrence of immunological binding is achieved by the use of fluorophore-labeled binding members.
9. A method in accordance with claim 8 in which said fluorophore-labeled binding members are phycoerythrin-labeled binding members.