Hong Kong Guangdong Rheumatology Meeting

Sjögren’s syndrome is a chronic autoimmune disease that is estimated to affect 35 million people worldwide. Hallmarks of the disease are a loss of salivary and lacrimal gland function as well as lymphocytic infiltration, elevated proinflammatory cytokines, and circulating autoantibodies. The effective treatments are limited. However, new therapies targeting specific immune pathways associated with Sjögren’s syndrome are being developed. Gene transfer to the salivary glands has been considered a promising approach to treating the dysfunction. The application of this treatment on salivary gland injuries has been studied for decades, yet its clinical progress is delayed. This chapter provides a coup d’oeil into gene transfer methods and various gene/vector types for salivary glands. AAV2-LAMP3-treated mice developed an SS-like phenotype with progressive salivary hypofunction and autoantibody production. To confirm the role of TLR4 in the induction of BMP6 following stimulation, AAV2-LAMP3–treated mice with established salivary hypofunction were treated i.p. with the TLR4 antagonist TAK242 for 10 days, and the effect of the drug on salivary gland protein expression and function was tested. We observed that treatment with TAK242 significantly decreased BMP6 expression and increased AQP5 expression in the salivary gland tissues. In agreement with this observation, the saliva flow rate of AAV2-LAMP3–treated mice also increased compared with that in vehicle control–treated mice. Gene therapy using recombinant viruses as gene transfer vectors to deliver a water channel (aquaporin 1, AQP1) to restore membrane water permeability in the salivary gland was shown to be safe and resulted in some patients with radiation-induced xerostomia having a sustained increase in saliva flow. A clinical trial using AAV2 to transfer AQP1 to the salivary glands of radiation-induced xerostomia patients is ongoing (NCT02446249) and results from this study may support application of this treatment in Sjögren’s syndrome. Gene therapy could also be used to deliver immunomodulators locally to the salivary gland resulting in a higher local concentration within the gland that could deliver therapeutics levels of recombinant protein, while minimizing the side effects associated with the drugs. Another study investigated whether a neurturin-expressing adenovirus could be used for gene therapy in vivo to protect parasympathetic neurons and prevent gland hypofunction after irradiation. The results suggest that in vivo neurturin gene therapy prior to irradiation protects parasympathetic function and prevents irradiation-induced hypofunction.