AAV PHP.S-CMV-Cre

Adeno-associated viruses (AAVs) have become one of the tools of choice for neuroscience research. Due to their ease of use and efficient delivery of a variety of gene products, including fluorescent proteins, AAVs have greatly facilitated the mapping and manipulation of brain neural circuits. Depending on the serotype, AAVs are effective in different brain regions, have specific uptake into neuronal and/or glial populations, and selectively transport anterogradely or retrogradely in CNS neurons. Stereotaxic injections at target sites, combined with the use of virally delivered or transgenic expressed Cre and Flp recombinases, allow for the construction of detailed maps of projections of selected neuronal populations and their functional interactions. To date, AAV-dependent manipulation of the peripheral nervous system has been greatly limited, although many open questions about connectivity would benefit from this approach. One difficulty is that the somata of these neurons are contained within relatively inaccessible dorsal root, cranial, or autonomic ganglia. Many studies have reported AAV-mediated transduction of peripheral neurons using various delivery methods, such as sciatic nerve injection, direct intraganglionic injection, and intrathecal infusion. However, these approaches are invasive and inefficient because the viral particles lack broad tropism for peripheral neurons. Another approach to preferentially transduce peripheral sensory neurons is to inject the virus into the blood circulation, taking advantage of the difficulty of AAV in crossing the blood-brain barrier. This approach alone does not completely limit transduction to peripheral neurons. A major advance came with the development of a synthetic neurotropic serotype, AAV.PHP.S, which was generated by directed evolution. A variant of the Cap gene of AAV9 was introduced, followed by repeated phenotypic selection to transdural sensory neurons. The resulting pseudotyped AAV-PHP.S particles, when introduced into the circulation, infected mostly or only peripherally located neurons.