Cell-based assays for detection of antibodies or other factors that neutralize uptake of lysosomal enzymes

1. A method for detecting lysosomal enzyme (LE)-specific neutralizing factors in a sample comprising the steps of:

(a) contacting a body fluid sample with a lysosomal enzyme conjugated to a detection moiety to detect LE-specific neutralizing factors in the body fluid sample, wherein the LE-specific neutralizing factor and lysosomal enzyme detection moiety form a complex;

(b) contacting the LE-specific factor/lysosomal enzyme complex from step (a) with cells comprising a cation independent mannose-6-phosphate receptor (CI-MPR), wherein the sample is contacted with the cells for at least three hours at approximately 37° C.; and

(c) detecting the presence of LE-specific neutralizing factor from the body fluid sample by detecting the presence of the lysosomal enzyme labeled with the detection moiety inside the cell or on the surface of the cell, wherein the limit of detection is less than about 500 ng/mL.

2. The method of claim 1 , wherein the body fluid sample is from a subject.

3. The method of claim 2 , wherein the subject is undergoing enzyme replacement therapy.

4. A method for determining the presence of lysosomal enzyme (LE)-specific neutralizing factors in a subject comprising the steps of:

(a) contacting a body fluid sample from the subject with a lysosomal enzyme conjugated to a detection moiety to detect LE-specific neutralizing factors in the body fluid sample, wherein the LE-specific neutralizing factor and lysosomal enzyme detection moiety form a complex;

(b) contacting the LE-specific neutralizing factor/lysosomal enzyme complex from step (a) with cells comprising a cation independent mannose-6-phosphate receptor (CI-MPR), wherein the sample is contacted with the cells for at least three hours at approximately 37° C., and

(c) detecting the presence of LE-specific neutralizing factor from the body fluid sample by detecting the lysosomal enzyme labeled with the detection moiety inside the cell or on the surface of the cell, wherein a low amount of detectable LE-detection moiety conjugate is indicative of the presence of LE-specific neutralizing factors in the sample, wherein the limit of detection is less than about 500 ng/mL.

5. The method of claim 1 , wherein the body fluid and lysosomal enzyme-detection moiety conjugate are contacted together in the same solution prior to contacting with cells.

6. A method for determining the percent inhibition of lysosomal enzyme activity by lysosomal enzyme (LE)-specific neutralizing factors in a subject comprising the steps of:

(a) contacting a body fluid sample from the subject with LE-conjugated magnetic beads;

(b) contacting the LE-specific neutralizing factor/LE-beads from step (a) with a composition comprising the lysosomal enzyme conjugated to a detection moiety to detect LE-specific neutralizing factors, wherein the sample is contacted with the cells for at least three hours at approximately 37° C.;

(c) contacting the combination of (a) and (b) with cells comprising a cation independent mannose-6-phosphate receptor (CI-MPR),

(d) detecting the presence of LE-specific neutralizing factor from the combination of (a), (b) and (c) and comparing the levels of captured LE-specific neutralizing factor to a control sample with a known amount of LE-specific neutralizing antibody in order to determine the percent inhibition of LE activity by neutralizing factors in the body fluid sample, wherein the limit of detection is less than about 500 ng/mL.

7. The method of claim 6 , wherein the levels of LE-specific neutralizing factor in the body fluid sample are determined by detecting the presence of the lysosomal enzyme labeled with the detection moiety inside the cell or on the surface of the cell.

8. The method of claim 6 , wherein a reduced level of detection in the presence of the body fluid sample compared to control indicates that the body fluid sample contains a neutralizing factor that inhibits LE uptake.

9. The method of claim 6 , wherein the body fluid, lysosomal enzyme-bead conjugate and lysosomal enzyme-detection moiety conjugate are all contacted together in the same solution prior to contacting with cells.

10. The method of claim 6 , wherein the body fluid, lysosomal enzyme-bead conjugate and lysosomal enzyme-detection moiety conjugate are contacted together for at least about 6 hours prior to contacting with cells.

11. The method of claim 6 , wherein the molar concentration of the lysosomal enzyme-detection moiety conjugate is about the same or less than the molar concentration of the lysosomal enzyme-bead conjugate.

12. The method of claim 6 , wherein the lysosomal enzyme-bead conjugate and lysosomal enzyme-detection moiety conjugate are used in about equimolar ratios.

13. The method of claim 1 wherein the detecting is by flow cytometry.

14. The method of claim 1 wherein the cells are T cells.

15. The method of claim 1 wherein the sample is contacted with the LE-detection moiety conjugate for at least about six hours.

16. The method of claim 15 wherein the samples sit with the LE-detection moiety conjugate at least six hours at approximately 4° C.

17. The method of claim 1 wherein the sample is contacted with the cells for about three hours.

18. The method of claim 1 , wherein LE-specific antibodies in a subject can be detected from a species selected from the group consisting of human, cynomolgus monkey, feline, canine, rabbit, goat, rat and mouse.

19. The method of claim 1 , wherein the body fluid is serum.

20. The method of claim 1 , wherein the lysosomal enzyme is selected from the group consisting of N-acetylgalactosamine 6-sulfatase (rhGALNS), N-acetyl-glucosaminidase (Naglu), tripeptidyl peptidase 1 (TPP1) and acid alpha glucosidase (GAA).

21. The method of claim 1 wherein the detection moiety is a fluorophore.

22. The method of claim 1 wherein the neutralizing factor is a neutralizing antibody.

23. The method of claim 1 , wherein a first washing step is performed after step (a) and a second washing step is performed after step (b).