The commercialization of Cloud-RAN, and Open-RAN in particular, is a key factor to enable 5G cell densification by providing lower cost and more agile deployment of small cells. In addition, the adoption of multi-access edge computing (MEC) is important to support the ultra-low latency and high reliability required by mission-critical applications, which constitute a milestone of the 5G and beyond vision of a fully connected society. However, connecting antenna site, C-RAN processing, and MEC at low cost is challenging, as it requires high-capacity, low-latency connectivity delivered through a highly inter-connected topology. While passive optical networks (PONs) are being considered as a solution for providing low-cost connectivity to C-RAN, they only allow data transmission from the endpoints (e.g., hosting the radio unit, RU, at the antenna site) toward a central node (e.g., the central office, hosting computing equipment), and thus cannot support traffic from RUs toward MEC end nodes that could host the distributed unit (DU) and possibly central unit (CU) and network core. This has led to research into the evolution of PON architectures with the ability to provide direct communications between endpoints, thus supporting mesh traffic patterns required by MEC installations. In this context, virtualization plays a key role in enabling efficient resource allocation (i.e., optical transmission capacity) to endpoints, according to their Communication patterns. In this article, we address the challenge of dynamic allocation of virtual PON slices over mesh-PON architectures to support C-RAN and MEC nodes. We make use of a mixed analytical-iterative model to compute optimal virtual PON slice allocation, with the objective of minimizing the use of MEC node resources, while meeting a target latency threshold (100 µs in our scenario). Our method is particularly effective in reducing computation time, enabling virtual PON slice allocation in timescales compatible with real-t...