Katherine Pak

The role of human endogenous retroviruses (HERVs) in disease pathogenesis is unclear. We show that HERV-K is activated in a subpopulation of patients with sporadic amyotrophic lateral sclerosis (ALS) and that its envelope (env) protein may contribute to neurodegeneration. The virus was expressed in cortical and spinal neurons of ALS patients, but not in neurons from control healthy individuals. Expression of HERV-K or its env protein in human neurons caused retraction and beading of neurites. Transgenic animals expressing the env gene developed progressive motor dysfunction accompanied by selective loss of volume of the motor cortex, decreased synaptic activity in pyramidal neurons, dendritic spine abnormalities, nucleolar dysfunction, and DNA damage. Injury to anterior horn cells in the spinal cord was manifested by muscle atrophy and pathological changes consistent with nerve fiber denervation and reinnervation. Expression of HERV-K was regulated by TAR (trans-activation responsive) DNA binding protein 43, which binds to the long terminal repeat region of the virus. Thus, HERV-K expression within neurons of patients with ALS may contribute to neurodegeneration and disease pathogenesis.

OBJECTIVE: Autoantibodies recognizing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) are found in patients with statin-associated immune-mediated necrotizing myopathy and, less commonly, in statin-unexposed patients with autoimmune myopathy. The main objective of this study was to define the association of anti-HMGCR antibody levels with disease activity. METHODS: Anti-HMGCR levels, creatine kinase (CK) levels, and strength were assessed in anti-HMGCR-positive patients. Associations of antibody level with CK level and strength at visit 1 were analyzed in 55 patients, 40 of whom were exposed to statins. In 12 statin-exposed and 5 statin-unexposed patients with serum from 5 serial visits, the evolution of antibody levels, CK levels, and strength was investigated. RESULTS: Antibody levels were associated with CK levels (P < 0.001), arm strength (P < 0.05), and leg strength (P < 0.05) at visit 1, but these associations were only significant among statin-exposed patients in stratified analyses. With immunosuppressive treatment over 26.2 ± 12.6 months (mean ± SD), antibody levels declined (P < 0.05) and arm abduction strength improved (P < 0.05) in the 17 patients followed up longitudinally. The separate analysis showed that statin-exposed patients developed decreased antibody levels (P < 0.01), decreased CK levels (P < 0.001), improved arm strength (P < 0.05), and improved hip flexion strength (P < 0.05) with treatment. Anti-HMGCR antibody levels did not normalize in any patient. CONCLUSION: In the entire cohort, initial anti-HMGCR levels correlated with indicators of disease activity; with immunosuppressive treatment, antibody levels declined and arm strength improved. Statin-exposed patients had significant improvements in CK levels and strength whereas statin-unexposed patients did not, suggesting a phenotypic difference between statin-exposed and statin-unexposed anti-HMGCR-positive patients.

<h3>Objective</h3> Activation of the type 1 interferon (IFN1) pathway is a prominent feature of dermatomyositis (DM) muscle and may play a role in the pathogenesis of this disease. However, the relevance of the IFN1 pathway in patients with other types of myositis such as the antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) is largely unknown. Moreover, the activation of the type 2 interferon (IFN2) pathway has not been comprehensively explored in myositis. In this cross-sectional study, our objective was to determine whether IFN1 and IFN2 pathways are differentially activated in different types of myositis by performing RNA sequencing on muscle biopsy samples from 119 patients with DM, IMNM, AS, or IBM and on 20 normal muscle biopsies. <h3>Methods</h3> The expression of IFN1- and IFN2-inducible genes was compared between the different groups. <h3>Results</h3> The expression of IFN1-inducible genes was high in DM, moderate in AS, and low in IMNM and IBM. In contrast, the expression of IFN2-inducible genes was high in DM, IBM, and AS but low in IMNM. The expression of IFN-inducible genes correlated with the expression of genes associated with inflammation and muscle regeneration. Of note, <i>ISG15</i> expression levels alone performed as well as composite scores relying on multiple genes to monitor activation of the IFN1 pathway in myositis muscle biopsies. <h3>Conclusions</h3> IFN1 and IFN2 pathways are differentially activated in different forms of myositis. This observation may have therapeutic implications because immunosuppressive medications may preferentially target each of these pathways.

OBJECTIVE: Statins, among the most commonly prescribed medications, are associated with a wide range of musculoskeletal side effects. These include a progressive autoimmune myopathy with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibodies that requires immunosuppression. However, it remains unknown whether these antibodies are found in statin users with and without self-limited musculoskeletal side effects; this limits their diagnostic utility. The current work assessed the prevalence of anti-HMGCR antibodies in these groups of statin users. METHODS: We determined the prevalence of anti-HMGCR antibodies in 1,966 participants (including 763 current statin users) in a substudy of the community-based Atherosclerosis Risk in Communities (ARIC) Study and 98 French Canadian subjects with familial hypercholesterolemia, including 51 with documented statin intolerance. RESULTS: No participant in the ARIC substudy, including those with past or current statin exposure at the time of sample collection, had anti-HMGCR antibodies. Similarly, none of 51 patients with self-limited statin intolerance or 47 statin-tolerant patients receiving maximal statin therapy were anti-HMGCR positive. CONCLUSION: The majority of patients with and without statin exposure, including those with self-limited statin intolerance, do not develop anti-HMGCR antibodies. Therefore, anti-HMGCR antibodies are highly specific for those with an autoimmune myopathy.