Assay for disease related conformation of a protein

An assay method, comprising:

• providing a sample suspected of containing a PrP protein which assumes a first conformation and a second, disease related conformation;
• treating the sample in a manner which causes an PrP protein in the second, disease related conformation to change its conformation to a different conformation having a higher binding affinity to a labelled antibody than the level of binding of said labelled antibody to said second, disease related conformation;
• contacting the treated sample with said labelled antibody which binds to the PrP protein in its first conformation and different conformation with a higher degree of affinity than it binds to the PrP protein in its second, disease related conformation;
• determining the level of binding of labelled antibody to PrP protein in the sample;
• comparing the level of labelled antibody binding in the sample to a previously established standard level of binding to a treated standard, which treated standard prior to treatment contains a known amount of the PrP protein in (i) the first conformation and (ii) in the second, disease related conformation, and;
• determining the probablilty of the sample containing PrP protein in the second, disease related conformation based on the comparison.

An assay method, comprising:

• providing a sample suspected of containing a PrP protein which assumes a first conformation and a second, disease related conformation;
• dividing the sample into a first portion and a second portion;
• contacting the first portion with a labelled antibody which binds to the PrP protein in its first conformation with a higher degree of affinity than it binds to the PrP protein in its second, disease related conformation;
• treating the second portion in a manner which causes any PrP protein in the second, disease related conformation to assume a different conformation which conformation has a higher degree of affinity for the labelled antibody as compared to the affinity for the PrP protein in the second disease related conformation;
• contacting the second portion with the labelled antibody;
• determining the levels of binding of labelled antibody to PrP protein in the first portion;
• determining the level of binding of labelled antibody to PrP protein in the second portion;
• adjusting the determined level of binding of labelled antibody to PrP protein in the second portion to compensate for increasing the affinity of the PrP protein in the first conformation for the antibody resulting from the treating;
• subtracting the level of binding of labelled antibody protein in the first portion from the adjusted level of binding of labelled antibody in the second portion to obtain a differential;
• and
• applying the differential to the formulae below wherein the differential is represented by the symbol .DELTA.
• ›PrP!.about..DELTA.F.sub..beta..fwdarw.d =F.sub.d -(F.sub.n *f.sub..alpha.n.fwdarw.d)
• wherein each of the above variables is provided below:
• F--any detectable signal;
• F.sub.n --signal of protein in native conformation;
• F.sub.n.alpha. and F.sub.n.beta. --signals of native non-disease and disease conformations, respectively;
• F.sub.d --signal of treated protein;
• F.sub.d.alpha. and F.sub.d.beta. --are the signals of treated non-disease and disease conformations;
• .DELTA.F.sub.n.fwdarw.d --increase of signal in the transition from native to treated state;
• .DELTA.F.sub..alpha.n.fwdarw.d --increase in the signal of non-disease conformation in the transition from native to treated state;
• .DELTA.F.sub..beta.n.fwdarw.d --increase in the signal of disease conformation in the transition from native to treated state;
• f.sub..alpha.n.fwdarw.d --correlation factor for the transition from native to treated state of non-disease conformation;
• ›PrP.sub..beta. !--concentration of protein in disease conformation;
• .about.--is proportional to;
• *--is multiply by.