Trapping the Enemy: Vermamoeba vermiformis Circumvents Faustovirus Mariensis Dissemination by Enclosing Viral Progeny inside Cysts

Abstract

Viruses depend on cells to replicate and can cause considerable damage to their hosts. However, hosts have developed a plethora of antiviral mechanisms to counterattack or prevent viral replication and to maintain homeostasis. Advantageous features are constantly being selected, affecting host-virus interactions and constituting a harsh race for supremacy in nature. Here, we describe a new antiviral mechanism unveiled by the interaction between a giant virus and its amoebal host. Faustovirus mariensis infects Vermamoeba vermiformis, a free-living amoeba, and induces cell lysis to disseminate into the environment. Once infected, the cells release a soluble factor that triggers the encystment of neighbor cells, preventing their infection. Remarkably, infected cells stimulated by the factor encyst and trap the viruses and viral factories inside cyst walls, which are no longer viable and cannot excyst. This unprecedented mechanism illustrates that a plethora of antiviral strategies remains to be discovered in nature. IMPORTANCE Understanding how viruses of microbes interact with its hosts is not only important from a basic scientific point of view but also for a better comprehension of the evolution of life. Studies involving large and giant viruses have revealed original and outstanding mechanisms concerning virus-host relationships. Here, we report a mechanism developed by Vermamoeba vermiformis, a free-living amoeba, to reduce Faustovirus mariensis dissemination. Once infected, V. vermiformis cells release a factor that induces the encystment of neighbor cells, preventing infection of further cells and/or trapping the viruses and viral factories inside the cyst walls. This phenomenon reinforces the need for more studies regarding large/giant viruses and their hosts.

In-depth analysis of the replication cycle of Orpheovirus

“…2). The CPE triggered by Orpheovirus is different from others previously described for Faustovirus, which revealed the formation of plaque forming units, and Tupanvirus, which was characterized by amoebae aggregates called bunches, as well as rounding and lysis in V. vermiformis [9, 10]. Furthermore, we observed that Orpheovirus infection induces an increase in the motility of V. vermiformis cells, especially those with a fusiform shape.…”

“…6a), which obtained more information about the morphogenesis of new particles. The morphogenesis of Orpheovirus starts with the formation of electron-dense semicircular structures named crescents, as observed for other giant viruses, such as Faustovirus and Cedratvirus [9, 12]. These structures extend and are filled by the internal content until the formation of a mature particle (Fig.…”

“…This study presents an in-depth description of the stages of the Orpheovirus life cycle, providing information about the entry, morphogenesis, release, structural characteristics and CPE triggered by this virus in its host cells. Other giant viruses are capable of inducing morphological changes in V. vermiformis , triggering amoebae aggregates called bunches, as described for Tupanvirus [10], and formation of plaque forming units evidenced for Faustovirus [9], as well as rounding and cell lysis. The morphological changes triggered by the Orpheovirus are different from those previously described, presenting cells with fusiform shapes and some branched cells.…”

Kinetic Analysis of the Motility of Giant Virus-Infected Amoebae Using Phase-Contrast Microscopic Images

“…It suggests that the amoebae formed "bunches" not because of normal movement but to assemble in response to some unknown signals, which caused the direction bias. This phenomenon may be an antiviral strategy of the host, similar to Faustovirus-infected amoeba releasing a factor that triggers the encystment of neighbor cells (Borges et al, 2019). Or it may be a viral spreading strategy, similar to the efficient spread of HIV-1 through contact and fusion of host cells (Bracq et al, 2017).…”

Vírus Gigantes - Faustovírus: Revisão Bibliografica

“…O vírus Mariensis (presentes no gênero Faustovírus) apresenta-se uma estrutura grande, código genético dsDNA, na qual infecta amebas de vida livre relacionada ao ambiente humano especificamente a Vermamoeba vermiformis. Ainda não há estudos que fundamentem sua patogenicidade ao organismo humano, entretanto existem algumas cepas patogênicas a outros organismos, levando em conta que, todos os organismos celulares estão sendo parasitados por um vírus, podem ou não ser do gênero Faustovirus 19 .…”