text: Base editors used for prime editing require delivery of both a protein and RNA molecule into living cells. Introducing exogenous gene editing technologies into living organisms is a significant challenge. One potential way to introduce a base editor into animals and plants is to package the base editor into a viral capsid. The target organism can then be transduced by the virus to synthesize the base editor in vivo. Common laboratory vectors of transduction such as lentivirus cause immune responses in humans, so proposed human therapies often centered around adeno-associated virus (AAV) because AAV infections are largely asymptomatic. Unfortunately, the effective packaging capacity of AAV vectors is small, approximately 4.4kb not including inverted terminal repeats. As a comparison, an SpCas9-reverse transcriptase fusion protein is 6.3kb, which does not even account for the lengthened guide RNA necessary for targeting and priming the site of interest. However, successful delivery in mice has been achieved by splitting the editor into two AAV vectors or by using an adenovirus, which has a larger packaging capacity.