The BRAIN Viral Vector Service and Distribution Core will serve as a resource for the maintenance, propagation, and distribution of viral vectors that are used by neuroscientists for neural circuit identification and manipulation, as well as for preclinical translational studies. High-quality viral vectors are essential tools to mark and manipulate neuronal circuits in live animals and identify long- range synaptic connections. Moreover, adeno-associated virus (AAV) vectors are the de facto standard for gene therapies. Existing commercial viral vector sources do not offer end-to-end services, from assisting with viral vector design, rigorous manufacturing and quality controls, troubleshooting with clients to enhance vector performance in the brain, and a mission focused on neuroscience. The Core Director (Dr. Kim Ritola) will translate her ten years of providing viral tools to the Howard Hughes Medical Institute neuroscience community towards creating a BRAIN Viral Vector Service and Distribution Core capable of producing and distributing AAV, rabies, and lenti virus tools to neuroscientists. The Core will have two main purposes: 1) Produce and disseminate affordable, high-quality AAV, rabies, and lenti viral vectors to the neuroscience community including newly developed vectors, custom preps and curated stocks and 2) Collaborate with BRAIN researchers to optimize vector design and prep conditions for optimal performance and serve as an educational resource for viral vector production. This Core will provide investigators with an extensive choice of vector capsid or envelope, paired with custom viral construct, including those with traditionally difficult to package genomes, titers and volumes appropriate for experiment type, rigorous quality controls, and affordability.