Classification of individuals based on ex-vivo glatiramer acetate-induced interferon-γ and interleukin-4 response.

BACKGROUND: Glatiramer acetate (GA) in multiple sclerosis acts through the induction of GA-specific T-helper 2 cells. Nevertheless, the phenomenon is not universal in patients, explaining individual differences in clinical response. OBJECTIVE: The objective of this article was to categorize GA-treated patients. METHOD: An enhanced quantitative PCR assay was used for measuring ex-vivo GA-induced IFNγ and IL4 mRNA responses in mononuclear cells from 23 healthy donors, 27 untreated patients, 33 short-term (≤6 months) and 77 long-term (>6 months) GA-treated patients. Thresholds for IFNγ and IL4 transcriptional response were calculated by ROC analysis and long-term treated patients were compared in terms of prognostic stratification. RESULTS: Thresholds for IFNγ and IL4 transcriptional response were calculated at 5.36 and 1.41 relative expression (RE). Finally, 67% of long-term treated patients scored above both response thresholds. These patients had a higher proportion of relapse-free subjects (74% vs 40% when compare to patients who scored below both thresholds) and a significantly better relapse-free survival rate (p=0.006; CI 0.29-0.75). The negative predictive value to predict adverse clinical outcome was 79% (CI 0.63-0.90), meaning that by a positive response, there is a 79% chance that the patient will not experience a negative outcome at 3 years. CONCLUSIONS: Our enhanced quantitative PCR assay produced clinically significant results for GA-treated patients. As such, if patients have a positive response, it means they have less chance of a relapse, while patients with a negative response have a greater probability of a worse outcome.