Gene Therapy for Spinal Muscular Atrophy Triggers Unexpected Immune Inflammation

This groundbreaking study challenges the traditional view of spinal muscular atrophy (SMA) as purely a motor neuron disease by revealing profound immune system involvement. Researchers analyzed blood samples from 7 SMA infants using bulk RNA sequencing and 4 infants using single-cell RNA sequencing, comparing them to healthy controls before and after AAV9-delivered SMN1 gene therapy (Zolgensma).

The key discovery was that gene therapy, while improving survival, actually triggered significant inflammatory immune activation rather than resolving it. NF-κB-related inflammatory gene expression was markedly elevated post-treatment compared to both pretreatment levels and healthy controls. Specific genes like IL1B and RNF19B emerged as key inflammatory mediators following therapy.

The researchers identified NECTIN1 as a novel biomarker of disease progression and validated HSPA7 from previous studies. A critical finding was the identification of a 6-7 month inflection point where SMA infants transition from metabolic regulation to immune activation, suggesting this timeframe may be crucial for intervention.

Single-cell analysis revealed early dysfunction in CD4+ T-cells with G1-phase arrest and a switch to RELB-mediated noncanonical NF-κB signaling. In symptomatic infants, CD8+ T-cells showed higher proliferation and exhaustion markers, with co-upregulation of TBX21 and EOMES genes consistent with chronic immune stimulation.

These findings have major clinical implications, suggesting that immune dysfunction is not just a consequence but a core feature of SMA that may influence treatment response. The study supports developing adjunct immunomodulatory strategies alongside gene therapy to enhance efficacy and potentially reduce treatment-related complications in this vulnerable population.