RESUMEN
In the context of the virosphere, viral particles can compete for host cells. In this scenario, some viruses block the entry of exogenous virions upon infecting a cell, a phenomenon known as superinfection inhibition. The molecular mechanisms associated with superinfection inhibition vary depending on the viral species and the host, but generally, blocking superinfection ensures the genetic supremacy of the virus's progeny that first infects the cell. Giant amoeba-infecting viruses have attracted the scientific community's attention due to the complexity of their particles and genomes. However, there are no studies on the occurrence of superinfection and its inhibition induced by giant viruses. This study shows that mimivirus, moumouvirus, and megavirus, exhibit different strategies related to the infection of Acanthamoeba. For the first time, we have reported that mimivirus and moumouvirus induce superinfection inhibition in amoebas. Interestingly, megaviruses do not exhibit this ability, allowing continuous entry of exogenous virions into infected amoebas. Our investigation into the mechanisms behind superinfection blockage reveals that mimivirus and moumouvirus inhibit amoebic phagocytosis, leading to significant changes in the morphology and activity of the host cells. In contrast, megavirus-infected amoebas continue incorporating newly formed virions, negatively affecting the available viral progeny. This effect, however, is reversible with chemical inhibition of phagocytosis. This work contributes to the understanding of superinfection and its inhibition in mimivirus, moumouvirus, and megavirus, demonstrating that despite their evolutionary relatedness, these viruses exhibit profound differences in their interactions with their hosts.IMPORTANCESome viruses block the entry of new virions upon infecting a cell, a phenomenon known as superinfection inhibition. Superinfection inhibition in giant viruses has yet to be studied. This study reveals that even closely related viruses, such as mimivirus, moumouvirus, and megavirus, have different infection strategies for Acanthamoeba. For the first time, we have reported that mimivirus and moumouvirus induce superinfection inhibition in amoebas. In contrast, megaviruses do not exhibit this ability, allowing continuous entry of exogenous virions into infected amoebas. Our investigation shows that mimivirus and moumouvirus inhibit amoebic phagocytosis, causing significant changes in host cell morphology and activity. Megavirus-infected amoebas, however, continue incorporating newly formed viruses, affecting viral progeny. This research enhances our understanding of superinfection inhibition in these viruses, highlighting their differences in host interactions.
RESUMEN
Genomic studies on sequence composition employ various approaches, such as calculating the proportion of guanine and cytosine within a given sequence (GC% content), which can shed light on various aspects of the organism's biology. In this context, GC% can provide insights into virus-host relationships and evolution. Here, we present a comprehensive gene-by-gene analysis of 61 representatives belonging to the phylum Nucleocytoviricota, which comprises viruses with the largest genomes known in the virosphere. Parameters were evaluated not only based on the average GC% of a given viral species compared to the entire phylum but also considering gene position and phylogenetic history. Our results reveal that while some families exhibit similar GC% among their representatives (e.g., Marseilleviridae), others such as Poxviridae, Phycodnaviridae, and Mimiviridae have members with discrepant GC% values, likely reflecting adaptation to specific biological cycles and hosts. Interestingly, certain genes located at terminal regions or within specific genomic clusters show GC% values distinct from the average, suggesting recent acquisition or unique evolutionary pressures. Horizontal gene transfer and the presence of potential paralogs were also assessed in genes with the most discrepant GC% values, indicating multiple evolutionary histories. Taken together, to the best of our knowledge, this study represents the first global and gene-by-gene analysis of GC% distribution and profiles within genomes of Nucleocytoviricota members, highlighting their diversity and identifying potential new targets for future studies.