Thursday, 14 March 2013

Research: JC virus assay

#MSBlog: Did STRATIFY JCV save natalizumab? Should we be congratulating Biogen-Idec and Elan?


BACKGROUND: JC virus (JCV) infection is a prerequisite for development of progressive multifocal leukoencephalopathy (PML). The development and validation of a two-step enzyme-linked immunosorbent assay (ELISA) that detects JCV antibodies in human serum or plasma and its clinical utility for stratification of PML risk have been described.

OBJECTIVE: To develop a second-generation JCV antibody ELISA kit with improved assay performance characteristics.

STUDY DESIGN: The assay design was optimized by pre-coating the JC virus-like particles (VLP) on microtiter plates. Assay cut-points were statistically established using sera from >1300 MSers from natalizumab clinical studies. The assay was analytically validated and then used to determine the presence of JCV antibodies in both treatment-naïve and natalizumab-treated MS patients, as well as in natalizumab-treated PML patients.

RESULTS: An improved assay for detection of JCV antibodies in human serum and plasma was developed. Key enhancements included improved delineation and reproducibility of low JCV antibody responses and assay ease of use. The assay was validated, demonstrating good agreement with the original two-step JCV antibody ELISA, and similar seroprevalence of 50%-60%. Samples from 63 natalizumab-treated PML MSers collected 6-180 months prior to PML diagnosis tested JCV antibody positive. One patient tested JCV antibody negative 15 months prior to PML diagnosis but JCV antibody positive 2 months prior to PML diagnosis.

CONCLUSIONS: The validated second-generation JCV antibody ELISA offers improved assay design as a kit and enhanced performance characteristics that advance routine clinical use of the assay as a PML risk stratification tool.


"This is the assay that most neurologists now use to measure whether or not you have previoulsy been exposed to JCV or not. It performs well. There have been teething problems with quite a few switchers here were negative in the first assay that became positive in the second assay.  The majority of these were at low titre or at the bottom end of the assay suggesting they were false negative with the first assay. Most neurologists are satisfied with the assay. You may be aware that natalizumab is now a bock-buster drug; i.e. with sales of over $1Billion. There are two reasons for  this; firstly, the drug is very effective and secondly the Statify JCV assay. Well done to Biogen-Idec and Elan for investing in science and salvaging a drug for MSers that at one stage looked doomed."

CoI: multiple

1 comment:

  1. Wow great JC virus assay blog, I was looking for something else on ask but found your site on page 1 so thought I would pay a visit and now have bookmarked. Pretty good post. I just stumbled upon your blog and wanted to say that I have really enjoyed reading your blog posts. Any way Ill be subscribing to your feed and I hope you post again soon

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