METHOD OF CHARACTERIZING ANTIBODIES
A method of characterizing a population of antibodies to an antigen comprises contacting a sensor surface having the antigen immobilized thereto with a sample containing the antibody population to bind antibodies to the surface, and detecting dissociation of antibodies from the sensor surface during a dissociation phase when sample no longer contacts the surface. Based on the dissociation behaviour, the antibody population is characterized in terms of subpopulations of more and less stable antibodies, respectively. The method may be used to determine the immunogenicity of drug by monitoring the appearance of anti-drug antibodies in a patient over time, and determining any shift in proportions between more stable and less stable antibodies.
1 . A method of characterizing a population of antibodies to an antigen, which comprises providing a sensor surface having the antigen immobilized thereto, contacting the sensor surface with a sample containing the antibody population to bind antibodies to the surface, detecting dissociation of antibodies from the sensor surface during a dissociation phase when sample no longer contacts the surface, wherein the dissociation behaviour of the antibody population is characterized by analyzing a first subpopulation and a second subpopulation of said antibody population, and wherein antibodies in said first subpopulation form a more stable complex with the immobilized antigen than antibodies in said second subpopulation.
2 . The method of claim 1 , further comprising fitting dissociation phase detection data to a kinetic model which describes simultaneous dissociation from two independent monovalent sites, one with a faster dissociation phase, and one with a slower dissociation phase.
3 . The method of claim 2 , wherein the kinetic model is a two-component equation:
R=R 1 *e −k d1 (t−t 0 ) +R 2 *e −k d2 (t−t 0 )
where R is the detection response time at time t, R 1 and R 2 are the response contributions from the sites with the faster and slower dissociation phases, respectively, at the beginning of the dissociation at time t 0 , and k d1 and k d2 are the dissociation rate constants for the sites with the faster and slower dissociation phases, respectively.
4 . The method of claim 3 , wherein the dissociation rate constants determined by the fitting are converted to half-lives (t 1/2 ) by the equation:
t
1
2
=
ln
2
k
d
where t 1/2 is the time required for the amount of antibody-antigen complex to be reduced to 50% during dissociation.
5 . The method of claim 4 , wherein the results of the fitting are presented by four parameters: fraction fast, t 1/2 fast, fraction slow, t 1/2 slow.
6 . The method of claim 1 , further comprising contacting the sample with sensor surfaces or discrete areas of a sensor surface having different domains of the antigen immobilized thereto.
7 . The method of claim 1 , further comprising contacting the sample with sensor surfaces or discrete areas of a sensor surface having different densities of immobilized antigen or antigen domains.
8 . The method of claim 1 , wherein the antigen is a drug.
9 . The method of claim 1 , wherein the antigen is a vaccine.
10 . A method of determining the immunogenicity of drug, comprising monitoring the appearance of anti-drug antibodies in a patient over time by the method of claim 1 , and determining any shift in proportions between more stable and less stable antibodies.