Profiling Of Secondary Progressive Multiple Sclerosis By Multicolor Flow Cytometry

Background: Opexa Therapeutics is conducting a placebo-controlled Phase 2B clinical trial (Abili-T) to investigate the efficacy and safety of Tcelna, an autologous attenuated myelin-reactive T-cell immunotherapy, in 180 subjects with Secondary Progressive Multiple Sclerosis (SPMS).  The study will include a comprehensive immune monitoring program to describe the immune status of subjects with SPMS, and the impact of Tcelna on the immune profile. As a prelude to the immune monitoring program, Opexa wished to further characterize the status of subjects entering the trial at baseline, and compare the data sets to those of healthy donors.

Objectives: To phenotype and characterize the functional status of T-cell, B-cell, monocyte and dendritic cell (DC) populations in the peripheral blood of SPMS subjects at baseline, compared to that of healthy donors.  Multi-color flow cytometry was used to identify phenotypes described in the literature such as T-reg, Tr1, Th1, Th2, Th17, in addition to monocyte subsets, B-cells and DC.  Finally, an empirical approach was undertaken using a bio-informatic analysis of all evaluable markers to determine if any additional atypical phenotypes can be distinguished that characterize immunity in subjects with SPMS.

Methods: PBMC from SPMS subjects, and healthy donors were subjected to multi-color flow cytometry employing sixteen, 6-color marker panels. 

Results: The analysis of data shows that subjects with SPMS have a reduced frequency of T-reg cells compared to healthy donors. However, the residual population expresses high levels of Foxp3 and CD39. SPMS subjects also display a reduced frequency of Tr1 cells as defined by the phenotype CD4+/CD49b+/CD18bright.  In addition, phenotyping of monocytes and B-cells showed that these populations express markers of chronic activation, such as CD80 and CD40 in subjects with SPMS.  A comprehensive analysis of multiple T-cell lineages will be presented employing chemokine receptor profiling and the induction of intracellular cytokine.

Conclusions: A comprehensive analysis of mononuclear cell populations in subjects with SPMS, when compared to healthy donors, confirms the presence of a chronically activated innate immune response on the backdrop of impaired T-regulation in subjects suffering from SPMS. The impact of Tcelna treatment will be studied over time, and compared to subjects receiving placebo, to determine the potential mechanism of action for the therapy.