APOBEC3F is the main source of editing identified during the 2022 outbreak of human monkeypox virus

On May 6, 2022, a powerful outbreak of monkeypox virus (MPXV) had been reported outside of Africa, with many continuing new cases being reported around the world. Analysis of mutations among the two different lineages present in the 2021 and 2022 outbreaks revealed the presence of G->A mutations occurring in the 5GpA context, indicative of APOBEC3 cytosine deaminase activity. By using a sensitive PCR (3D-PCR) method allowing differential amplification of AT-rich DNA, we demonstrate that G->A hypermutated MPXV genomes can be recovered experimentally from APOBEC3 transfection followed by MPXV infection. Here, among the 7 human APOBEC3 cytidine deaminases (A3A-A3C, A3DE, A3F-A3H), only APOBEC3F was capable of extensively deaminating cytidine residues in MPXV genomes. Hyperedited genomes were also recovered in ~42% of analyzed patients, indicating that editing is part of the natural cycle of MPXV infection. Moreover, we demonstrate that substantial repair of these mutations occurs. Upon selection, corrected G->A mutations escaping drift loss contribute to the MPXV evolution observed in the current epidemics. Thus, stochastic or transient overexpression of APOBEC3F gene exposes the MPXV genome to a broad spectrum of mutations that may be modeling the mutational landscape after multiple cycles of viral replication.