Thursday, January 8, 2009
I have noticed a change in C6 antibody results. They are generally much lower than they were a year ago. The test measures an ELISA reaction to ViSE, a surface protein unique to Bb. The ability of the Lyme bacteria to alter this surface antigen has been well described. It is not surprising that reactivity would be variable. I would expect this to occur in individual patients; instead the change in reactivity covers a wide swath of patients, many of whom have not been treated. On the other hand, a subset of patients who have been treated extensively with antibiotics "seroconvert" with regard to this parameter. I have noted that the test measures an IgG antibody to a synthetic version of this antigen. Perhaps the test is failing because it fails to measure IgM responses which are more prominent in Lyme patients. Typically, in the past Western Blot positive Lyme patients had C6 peptide index levels, on average of 0.2 to 0.4. Recently I have seen WB positve patients with C6 indices approaching zero.