Iván Andreu, Rafael Sanjuán

This doctoral thesis, directed by Rafael Sanjuán Verdeguer, addresses the evolutionary implications of the formation of collective infectious units in viral pathogens. The results have been published in the journals Current Biology, mBio and Science Advances. The thesis was defended on April 29, 2022.

Viruses use various strategies to transmit multiple particles or viral genomes to the same cell. These collective transmission strategies promote sustained interaction between co-infected viruses, which enables the evolution of social interactions such as cooperation, but also conflict. Furthermore, in the absence of other sources of benefit, the association of multiple virions or viral genomes to form collective infectious units implies a dispersive cost, by limiting the total capacity of viruses to initiate new foci of infection. The thesis, titled "Evolutionary implications of collective virus transmission", analyzes whether collective transmission provides benefits derived from co-infection that offset its dispersive cost in the short term, but also whether it promotes the evolution of cooperation or conflict in the longer term. To do this, the cooperative dynamics of coinfection are studied by combining mathematical modeling with experiments. Furthermore, using viral aggregates of the vesicular stomatitis virus, the net and immediate impact of this mode of collective transmission on viral biological efficacy has been experimentally determined, discerning the main factors and mechanisms involved. Likewise, the non-immediate consequences of aggregation on the evolution of social interactions and viral diversity have been explored.

Iván Andreu's thesis has been carried out in the Experimental Virus Evolution group of the I2SysBio, and has been directed by Rafael Sanjuán (Senior Professor of the Department of Genetics, Universitat de València and Principal Investigator of the group). During the development of the thesis Iván Andreu has enjoyed a contract within the University Teacher Training Program (FPU, Ministry of Universities). The qualifying panel was made up of José Manuel Cuevas (Senior Professor of the Department of Genetics, UV and researcher at I2SysBio), Ester Lázaro (Scientific Researcher at the CSIC, Astrobiology Center CSIC-INTA) and Santiago F. Elena (Research Professor at the CSIC, I2SysBio), who have rated the thesis as outstanding.