ABSTRACT The immune system contributes to amyotrophic lateral sclerosis (ALS) progression and survival, and therapies to target the immune system are of burgeoning interest. However, the changes in the immune system during the course of ALS and the sex-specific alterations in immune function warrant a more in depth analysis in order to develop personalized ALS therapies and biomarkers. The long-term goals are to harness the immune sys- tem’s potential to slow and stop the progression of ALS. The overall objective is to determine how peripheral immune profiles, sex, age, and sex hormones, link to neuronal damage, neuroinflammation, and ALS progres- sion and survival. The central hypothesis is that peripheral immune profiles are an important pathophysiologic agent of ALS progression and survival; that sex, age and sex hormone levels impact these profiles; and that insight into ALS patient-specific immune profiles will yield new drug targets and therapeutic windows. Our ra- tionale is that linking patient-specific immune cell profiles to ALS progression and survival will facilitate person- alized immunomodulatory therapeutic development for ALS and identify potential treatment windows. The cen- tral hypothesis will be pursued with three aims: 1) Identify specific immune profiles that associate with ALS pro- gression and survival rates.; 2) Evaluate the effects of sex hormones on ALS immune profiles, progression, and survival; and 3) Identify immune profiles and corresponding cellular pathways that are most toxic to neu- rons and that associate with central inflammation. In Aim 1 longitudinal immunophenotyping of peripheral blood samples from ALS subjects will generate composite immune profiles that will then be linked to ALS subject characteristics, progression, and survival. Aim 2 will determine if observed sex-dependent associations be- tween immune profiles and ALS progression and survival are mediated by sex hormones, as sex hormones can alter immune profiles. Aim 3 will enrich a cohort of ALS subjects by immune profile clusters; their periph- eral immune populations will be analyzed using 1) RNA-seq and 2) cell toxicity studies via co-cultures with iPSC-derived neurons; subjects will also have positron emission tomography (PET) imaging to quantify central neuroinflammation. Datasets will be synthesized to build prediction models and create deep neural networks capable of associating immune profiles with sex, age, disease severity, progression, and survival The research proposed is innovative, in the applicants’ opinion, because it rigorously examines the effects of sex, age, and sex hormone levels on immune cells and ALS progression and survival in a longitudinal study. It also accounts for the interactions between immune cells by forming immune profiles for individual subjects and assesses how specific profiles associate with dysregulated pathways, cytotoxicity, and neuroinflammation. The proposed re- search is significant because it will provide critical data on the distinct immune profiles and pathways associ- ated with ALS progression and survival in a sex-, age- and sex hormone- specific fashion.

PROJECT NARRATIVE The proposed research is relevant to public health because it focuses on identifying the alterations in the im- mune system that impact amyotrophic lateral sclerosis (ALS) and also focuses on identifying whether these altered immune profiles are influenced by sex- and age-specific factors. The development of such strategies will greatly advance the ability to develop personalized treatment approaches for persons with ALS based on immunomodulatory drugs. Thus, the proposed research is relevant to part of the NIH’s mission that pertains to developing the fundamental knowledge about the nervous system and using that knowledge to reduce the bur- den of neurological disease.