Adeno-associated virus (AAV) vectors have been successfully employed in patients with rare neurologicaldiseases. Recently, two AAV based gene therapy drugs have been approved by the FDA, Luxturna beenvalued at $850,000 with a one-time application for blindness and Zolgensma at $2,100,000 for spinal muscleatrophy. AAV vector mediated gene therapy has shown to be a potentially huge market. Although successful inclinical studies for neurological disorders, one of the major concerns for effective AAV brain application is highprevalence of neutralizing antibody (Nab) in humans. In the general human population, over 95 % ofindividuals are infected by AAV and, on average, 50 % of them develop Nabs. The inhibition effect of Nabs onAAV brain transduction has been well documented regardless of delivery routes (direct intra-brain injection orsystemic administration). Several approaches have been exploited to escape AAV Nabs, including chemicalmodification, use of different AAV vector serotypes, AAV capsid engineering, and biological depletion of Nabtiter (empty capsid utilization, B cell depletion, plasma-apheresis, and Ig proteases). Generally, theseapproaches have low efficiency, unwanted side effects, or AAV tropism change. Recently, Nabgen hasdeveloped a vector independent protein-based strategy to universally block Nabs using a unique mycoplasmaderived protein, termed Protein-M. Protein-M is able to interact with immunoglobulin from any species withoutantigen dependence by binding to variable regions on the antibody light and heavy chains. Using human IVIGand serum from AAV immunized mice, we have found that Protein-M reduced AAV vector neutralization over100 fold when compared to control group without Protein-M in vitro. Most importantly, we have observed thatProtein-M was able to retain AAV transduction over 1000 fold in mice with adoptive transfer of Nab positiveserum. So far, this is the most effective strategy to evade AAV Nabs. To explore the application of Protein-M inpatients with AAV brain targeted therapy, it is imperative to address the efficacy of Protein-M to protect AAVfrom Nabs for brain transduction in subjects with Nabs. In this proposal, we will first study the effect of Protein-M co-administered with AAV vectors on AAV Nab blockage via direct injection into the brain in mice with pre-immunization of AAV (Aim 1). Next, we will study the effect of Protein-M via systemic injection on braintransduction after direct delivery of AAV vectors (Aim 2). If successful, this novel and effective technology willextend the benefits of AAV targeted gene therapy to every patient with brain disorders and AAV Nabs.
Public Health Relevance Statement: Gene Therapy with adeno-associated virus (AAV) vector has shown promise in patients with central nervous
system (CNS) disorders in recent clinical trials, however, these trials are exclusively applied to the patients
without AAV neutralizing antibodies. We have demonstrated that protein M derived from mycoplasma was able
to potentially block AAV neutralizing antibody activity in vitro and in mice with adoptive transfer of AAV
immunized serum. This proposal will further study the effect of protein M on protection of AAV brain
transduction in pre-immunized mice.
Project Terms: 