chantal

Chantal Abergel

Information Génomique & Structurale, Université Aix-Marseille, France

Title: Twenty years of research on giant viruses

Bio Sketch

Chantal Abergel is CNRS Research Director and Director of the Information Génomique et Structurale (IGS) laboratory in Marseille, France. She received a Ph.D. in Materials Science before moving into structural biology during a five-year postdoctoral fellowship at the U.S. National Institutes of Health (NIH). In 1995, she joined the CNRS, where she co-founded the IGS laboratory with Jean-Michel Claverie. IGS was the first French laboratory to integrate computational biology with experimentalstructural biology and biochemistry, an interdisciplinary approach that remains at the core of its research.
Originally trained as a structural biologist, her research took a decisive turn following the discovery of Mimivirus, the first recognized giant virus. Since then, she has played a leading role in establishing giant virus biology as a new field of research at the interface of virology, evolutionary biology, and environmental microbiology. Her work has contributed to the discovery and characterization of several new families of giant viruses, including viruses revived from more than 30,000-year-old Siberian permafrost, providing unique insights into viral evolution and long-term environmental persistence. By combining structural biology, cell biology, genomics, and evolutionary analyses, her research has revealed the remarkable complexity of giant viruses and fundamentally expanded our understanding of the diversity and evolution of the virosphere. Her work has helped redefine the place of viruses in the living world and established giant viruses as a major model for investigating the origins, evolution, and diversification of biological complexity.

Abstract

The discovery of mimivirus in 2003 broadened the frontier of virology by revealing the existence of giant viruses with particle sizes and gene contents akin to those of cellular microbes1. Sampling expeditions revealed that mimivirus relatives were abundant in the environments where they infect unicellular eukaryotes and are active players in all ecosystems. I will present the infectious cycle of mimivirus and highlight the distinctive features of its virion. Members of additional families were isolated using the same sampling strategies, including the Marseilleviridae2, and I will present some surprises they revealed. As we thought we had reached the limit of viral complexity, members of the Pandoraviridae were discovered with virions exceeding 1 µm in length, containing genomes of up to 2.8 Mb, which encode a vast majority of family ORFan proteins3. Finally, sampling >30,000-year-old permafrost samples led to the reactivation of an ancient pithovirus and mollivirus sibericum on modern amoeba4,5.The new Pithoviridae family rapidly expanded, dividing the family into 3 clades. There are only two additional modern mollivirus isolated so far. To conclude, I will briefly present recent findings on the Mimivirus infectious cycle, which raise questions about the origin and evolution of DNA viruses and their possible link to the emergence of eukaryotes6.
chantal picture
Colorized electron microscopy images of ultrathin sections of Megavirus chilensis (Ø 0,7 µm, 1.2 Mb), Pandoravirus salinus (1x0,5 µm, up to 2.8 Mb), Pithovirus sibericum (1,2x0,5 µm, 610 kb) and Mollivirus sibericum (Ø 0.6 µm, 650 kb).
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  1. Raoult, D. et al. The 1.2-megabase genome sequence of Mimivirus. Science 306, 1344–1350 (2004).
  2. Boyer, M. et al. Giant Marseillevirus highlights the role of amoebae as a melting pot in emergence of chimeric microorganisms. Proc. Natl. Acad. Sci. U. S. A. 106, 21848–21853 (2009).
  3. Philippe, N. et al. Pandoraviruses: amoeba viruses with genomes up to 2.5 Mb reaching that of parasitic eukaryotes. Science 341, 281–286 (2013).
  4. Legendre, M. et al. Thirty-thousand-year-old distant relative of giant icosahedral DNA viruses with a pandoravirus morphology. Proc. Natl. Acad. Sci. U. S. A. 111, 4274–4279 (2014).
  5. Legendre, M. et al. In-depth study of ‘Mollivirus sibericum’, a new 30,000-y-old giant virus infecting Acanthamoeba. Proc. Natl. Acad. Sci. 112, E5327–E5335 (2015).
  6. Rigou, S. et al. Evolutionarily conserved grammar rules viral factories of amoeba-infecting members of the hyperdiverse Nucleocytoviricota phylum. Proc. Natl. Acad. Sci. 122, e2515074122 (2025).

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