Adeno-associated virus (AAV) vector-based therapies can effectively correct some disease pathology in murine models with mucopolysaccharidoses. However, immunogenicity can limit therapeutic effect as immune responses target capsid proteins, transduced cells, and gene therapy products, ultimately resulting in loss of enzyme activity. Inherent differences in male versus female immune response can significantly impact AAV gene transfer. We aim to investigate sex differences in the immune response to AAV gene therapies in mice with mucopolysaccharidosis IVA (MPS IVA). MPS IVA mice, treated with different AAV vectors expressing human N-acetylgalactosamine 6-sulfate sulfatase (GALNS), demonstrated a more robust antibody response in female mice resulting in subsequent decreased GALNS enzyme activity and less therapeutic efficacy in tissue pathology relative to male mice. Under thyroxine-binding globulin promoter, neutralizing antibody titers in female mice were approximately 4.6-fold higher than in male mice, with GALNS enzyme activity levels approximately 6.8-fold lower. Overall, male mice treated with AAV-based gene therapy showed pathological improvement in the femur and tibial growth plates, ligaments, and articular cartilage as determined by contrasting differences in pathology scores compared to females. Cardiac histology revealed a failure to normalize vacuolation in females, in contrast, to complete correction in male mice. These findings promote the need for further determination of sex-based differences in response to AAV-mediated gene therapy related to developing treatments for MPS IVA.

Glycosaminoglycans (GAGs) are present in proteoglycans, which play critical physiological roles in various tissues. They are known to be elevated in mucopolysaccharidoses (MPS), a group of rare inherited metabolic diseases in which the lysosomal enzyme required to break down one or more GAG is deficient. In a previous study, we found elevation of GAGs in a subset of patients without MPS. In the current study, we aim to investigate serum GAG levels in patients with conditions beyond MPS. In our investigated samples, the largest group of patients had a clinical diagnosis of viral or non-viral encephalopathy. Clinical diagnoses and conditions also included epilepsy, fatty acid metabolism disorders, respiratory and renal disorders, liver disorders, hypoglycemia, developmental disorders, hyperCKemia, myopathy, acidosis, and vomiting disorders. While there was no conclusive evidence across all ages for any disease, serum GAG levels were elevated in patients with encephalopathy and some patients with other conditions. These preliminary findings suggest that serum GAGs are potential biomarkers in MPS and other disorders. In conclusion, we propose that GAGs elevated in blood can be used as biomarkers in the diagnosis and prognosis of various diseases in childhood; however, further designed experiments with larger sample sizes are required.