Loop-mimetic vaccine targets misfolded SOD1 and slows ALS-like disease in mice

A new immunization strategy has shown promise in a mouse model of amyotrophic lateral sclerosis (ALS), according to a study published in Acta Neuropathologica Communications. Researchers developed an engineered antigen, called Ag2, designed to train the immune system to recognize a specific shape that appears on misfolded SOD1 protein — a molecule long implicated in ALS — while leaving the normal, healthy form of the protein untouched.

The team built Ag2 on a highly stable six-helix scaffold, a protein structure engineered to display the SOD1 β6/β7 loop, a neo-epitope that is exposed in pathogenic SOD1 conformers and has been implicated in their prion-like activity. The scaffold also carries helper T-cell epitopes arranged in alternating tandem repeats, an arrangement intended to boost the antibody response. In SOD1G93A mice, a widely used ALS model, this design induced an antibody response whose strength could be tuned by the adjuvant used, and generated high-titer conformational antibodies that recognized multiple ALS-linked SOD1 mutants but not wild-type SOD1.

A key observation concerned the specificity of these antibodies. Binding was not reproduced against wild-type SOD1 even under conditions that promote misfolding, indicating that exposure of the targeted epitope depends on more than conversion to a generic non-native state. Instead, the antibodies required a conformational context specifically associated with pathogenic SOD1 mutations, suggesting the epitope is a genuine disease-linked molecular signature rather than a byproduct of generic protein damage.

Vaccination with Ag2 produced measurable benefits in the mice: disease onset was delayed, and the treatment attenuated the accumulation of misfolded SOD1 in the spinal cord, the loss of motor neurons, and gliosis. According to the authors, these findings show that structural loop mimicry can focus humoral immunity on disease-relevant SOD1 conformations while sparing the native protein in vivo.

Misfolded Cu/Zn-superoxide dismutase (SOD1) contributes to ALS, but effective immunization depends on identifying a pathogenically relevant neo-epitope that is selectively exposed in the misfolded protein. By presenting only the disease-specific loop in a repeated, immunogenic format, Ag2 aims to sidestep that problem.

Beyond ALS, the researchers suggest their platform may have wider applications.

The study was published as an open-access research article on 27 October 2026, and the version shared early is subject to further edits before the final Version of Record appears.

Subject of Research: Immunization against a misfolded SOD1 neo-epitope in an ALS mouse model

Article Title: A loop-mimetic SOD1 antigen elicits antibodies to a mutant-associated conformational epitope and ameliorates disease in SOD1G93A mice

Article References: Dhandapani, R., Armoza, A., Bersudsky, M., Nemirovsky, A., Shlifer, A., Yehezkel, G., Tsitrina, A., Voronov, E., Barak, Z., Lichtenstein, R. G., Monsonego, A., & Engel, S. (2026). A loop-mimetic SOD1 antigen elicits antibodies to a mutant-associated conformational epitope and ameliorates disease in SOD1G93A mice. Acta Neuropathologica Communications. https://doi.org/10.1186/s40478-026-02457-x

Image Credits: AI Generated

DOI: 10.1186/s40478-026-02457-x

Keywords: ALS, SOD1, misfolded protein, vaccination, neo-epitope, six-helix scaffold, SOD1G93A mice, motor neuron loss, gliosis, proteopathy, immunotherapy, conformational antibodies