First evidence of host range expansion in virophages and its potential impact on giant viruses and host cells

Said Mougari; Nisrine Chelkha; Dehia Sahmi-Bounsiar; Fabrizio Di Pinto; Philippe Colson; Jonatas Abrahao; Bernard La Scola

The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/780841 doi: bioRxiv preprint knowledge, such a study has never been conducted. A. castellanii cells were coinfected with Tupanvirus at an MOI of 100 and each virophage (Sputnik, Zamilon or mutant Guarani) at MOIs of 10. Moumouvirus, a lineage B mimivirus, was used as a control because it allows the replication of all virophages used in this study. First, at 9 h p.i., 5x10 5 cells were collected to check the impact of Guarani on ribosomal shutdown. We found that in contrast to the controls, irrespective of mutant Guarani infection, Tupanvirus was able to induce a severe shutdown in host ribosomal RNA abundance (Fig. 9a) . We then measured the replication of each virophage by qPCR and calculated their DNA amount increase using the delta Ct method considering times 0 and 48 p.i. All virophages were able to replicate with Moumouvirus at the MOI of 100 (Fig. 9b) . In contrast, all of the virophages, including Guarani, failed to infect Tupanvirus at high MOI (Fig. 9c) . These results suggest that the cytotoxic profile of Tupanvirus allowed it to escape virophage infection and, notably, the eradication that could be caused by Guarani.