Levels of BCMA protein expression on B cells and use in methods of treating systemic lupus erythematosus

Abstract

The present invention provides a method of measuring the levels of BCMA in a biological sample, specifically upon the B cell surface. The diagnostic assays are useful in predicting an individual's likelihood of developing or currently suffering from an autoimmune disease, such as SLE, and for methods for treating an individual clinically diagnosed with an autoimmune disease. This diagnostic test serves to predict a patient's likelihood to respond to a specific drug treatment, in particular treatment with BLyS antagonists, either singly or in combination with other immune suppressive drugs.

That which is claimed: 
     
       1. A method of reducing the systemic lupus erythematosus (SLE) disease activity of an individual clinically diagnosed with SLE, said method comprising:
 analyzing peripheral blood B cells from an individual clinically diagnosed with SLE for the presence or absence of elevated BCMA protein expression levels on said peripheral blood B cells, said analyzing step comprising:
 (i) measuring a first level of BCMA protein expression on the surface of peripheral blood B cells from said individual clinically diagnosed with SLE; 
 (ii) comparing the first level to a second level of BCMA protein expression on the surface of peripheral blood B cells from a healthy individual; and 
 (iii) identifying an individual wherein the first level is elevated as compared to the second level; and 
 administering a BLyS antagonist to said individual clinically diagnosed with SLE and having elevated BCMA protein expression levels on said peripheral blood B cells, wherein the BLyS antagonist is a receptor extracellular domain/Fc domain fusion protein selected from the group consisting of TACI-Ig, BCMA-Ig, and BAFF-R-Ig, 
 
 wherein the SLE disease activity of said individual is reduced following said administration of the BLyS antagonist. 
 
     
     
       2. The method of  claim 1  wherein said BLyS antagonist is also an APRIL antagonist. 
     
     
       3. The method of  claim 1 , wherein said receptor-extracellular domain/Fc domain fusion protein is TACI-Ig. 
     
     
       4. The method of  claim 3 , wherein said TACI-Ig is atacicept. 
     
     
       5. The method of claim 1, wherein said first level of BCMA protein expression is measured by flow cytometry. 
     
     
       6. The method of claim 1, wherein said second level of BCMA protein expression is measured by flow cytometry.