Could giant viruses be considered as a biotechnological tool for preventing and controlling Acanthamoeba infections?

AIM: The aim of the study was to evaluate the efficiency of mimivirus as a potential therapeutic and prophylactic tool against Acanthamoeba castellanii, the etiological agent of Acanthamoeba keratitis, a progressive corneal infection, that is commonly associated with the use of contact lenses and can lead to blindness if not properly treated. METHODS AND RESULTS: Mimivirus particles were tested in different multiplicity of infection, along with commercial multipurpose contact lenses' solutions, aiming to assess their ability to prevent encystment and excystment of A. castellanii. Solutions were evaluated for their amoebicidal potential and cytotoxicity in MDCK cells, as well as their effectiveness in preventing A. castellanii damage in Madin-Darby canine kidney (MDCK) cells. Results indicated that mimivirus was able to inhibit the formation of A. castellanii cysts, even in the presence of Neff encystment solution. Mimivirus also showed greater effectiveness in controlling A. castellanii excystment compared to commercial solutions. Additionally, mimivirus solution was more effective in preventing damage caused by A. castellanii, presented greater amoebicidal activity, and were less cytotoxic to MDCK cells than commercial MPS. CONCLUSIONS: Mimivirus demonstrates a greater ability to inhibit A. castellanii encystment and excystment compared to commercial multipurpose contact lens solutions. Additionally, mimivirus is less toxic to MDCK cells than those commercial solutions. New studies utilizing in vivo models will be crucial for confirming safety and efficacy parameters.

Bovine serum albumin nanoparticles containing Poly (I:C) can enhance the neutralizing antibody response induced by envelope protein of Orthoflavivirus zikaense.

Since the Orthoflavivirus zikaense (ZIKV) has been considered a risk for Zika congenital syndrome development, developing a safe and effective vaccine has become a high priority. Numerous research groups have developed strategies to prevent ZIKV infection and have identified the domain III of the ZIKV envelope protein (zEDIII) as a promising target. Subunit antigens are often poorly immunogenic, necessitating the use of adjuvants and/or delivery systems to induce optimal immune responses. The subject of nanotechnology has substantial expansion in recent years in terms of research and applications. Nanoparticles could be used as drug delivery systems and to increase the immunogenicity and stability of a given antigen. This work aims to characterize and validate the potential of a vaccine formulation composed of domain zEDIII and bovine serum albumin nanoparticles containing polyinosinic-polycytidylic acid (NPPI). NPPI were uptake in vitro by immature bone marrow dendritic cells and histological analysis of the skin of mice treated with NPPI showed an increase in cellularity. Immunization assay showed that mice immunized with zEDIII in the presence of NPPI produced neutralizing antibodies. Through the passive transfer of sera from immunized mice to ZIKV-infected neonatal mice, it was demonstrated that these antibodies provide protection, mitigating weight loss, clinical or neurological signs induced by infection, and significantly increased survival rates. Protection was further substantiated by the reduction in the number of viable infectious ZIKV, as well as a decrease in inflammatory cytokines and tissue alterations in the brains of infected mice. Taken together, data presented in this study shows that NPPI + zEDIII is a promising vaccine candidate for ZIKV.

Surface fibrils on the particles of nucleocytoviruses: A review.

The capsid has a central role in viruses' life cycle. Although one of its major functions is to protect the viral genome, the capsid may be composed of elements that, at some point, promote interaction with host cells and trigger infection. Considering the scenario of multiple origins of viruses along the viral evolution, a substantial number of capsid shapes, sizes, and symmetries have been described. In this context, capsids of giant viruses (GV) that infect protists have drawn the attention of the scientific community, especially in the last 20 years, specifically for having bacterial-like dimensions with hundreds of different proteins and exclusive features. For instance, the surface fibrils present on the mimivirus capsid are one of the most intriguing features of the known virosphere. They are 150-nm-long structures attached to a 450-nm capsid, resulting in a particle with a hairy appearance. Surface fibrils have also been described in the capsids of other nucleocytoviruses, although they may differ substantially among them. In this mini review for non-experts, we compile the most important available information on surface fibrils of nucleocytoviruses, discussing their putative functions, composition, length, organization, and origins.

Taxonomic update for giant viruses in the order Imitervirales (phylum Nucleocytoviricota).

Large DNA viruses in the phylum Nucleocytoviricota, sometimes referred to as "giant viruses" owing to their large genomes and virions, have been the subject of burgeoning interest over the last decade. Here, we describe recently adopted taxonomic updates for giant viruses within the order Imitervirales. The families Allomimiviridae, Mesomimiviridae, and Schizomimiviridae have been created to accommodate the increasing diversity of mimivirus relatives that have sometimes been referred to in the literature as "extended Mimiviridae". In addition, the subfamilies Aliimimivirinae, Megamimivirinae, and Klosneuvirinae have been established to refer to subgroups of the Mimiviridae. Binomial names have also been adopted for all recognized species in the order. For example, Acanthamoeba polyphaga mimivirus is now classified in the species Mimivirus bradfordmassiliense.

Diversity of Surface Fibril Patterns in Mimivirus Isolates.

Among the most intriguing structural features in the known virosphere are mimivirus surface fibrils, proteinaceous filaments approximately 150 nm long, covering the mimivirus capsid surface. Fibrils are important to promote particle adhesion to host cells, triggering phagocytosis and cell infection. However, although mimiviruses are one of the most abundant viral entities in a plethora of biomes worldwide, there has been no comparative analysis on fibril organization and abundance among distinct mimivirus isolates. Here, we describe the isolation and characterization of Megavirus caiporensis, a novel lineage C mimivirus with surface fibrils organized as "clumps." This intriguing feature led us to expand our analyses to other mimivirus isolates. By employing a combined approach including electron microscopy, image processing, genomic sequencing, and viral prospection, we obtained evidence of at least three main patterns of surface fibrils that can be found in mimiviruses: (i) isolates containing particles with abundant fibrils, distributed homogeneously on the capsid surface; (ii) isolates with particles almost fibrilless; and (iii) isolates with particles containing fibrils in abundance, but organized as clumps, as observed in Megavirus caiporensis. A total of 15 mimivirus isolates were analyzed by microscopy, and their DNA polymerase subunit B genes were sequenced for phylogenetic analysis. We observed a unique match between evolutionarily-related viruses and their fibril profiles. Biological assays suggested that patterns of fibrils can influence viral entry in host cells. Our data contribute to the knowledge of mimivirus fibril organization and abundance, as well as raising questions on the evolution of those intriguing structures. IMPORTANCE Mimivirus fibrils are intriguing structures that have drawn attention since their discovery. Although still under investigation, the function of fibrils may be related to host cell adhesion. In this work, we isolated and characterized a new mimivirus, called Megavirus caiporensis, and we showed that mimivirus isolates can exhibit at least three different patterns related to fibril organization and abundance. In our study, evolutionarily-related viruses presented similar fibril profiles, and such fibrils may affect how those viruses trigger phagocytosis in amoebas. These data shed light on aspects of mimivirus particle morphology, virus-host interactions, and their evolution.

Integrative transcriptome analysis of human cells treated with silver nanoparticles reveals a distinct cellular response and the importance of inorganic elements detoxification pathways.

The field of Nanotechnology has taken a great leap in recent decades, with several products currently researched in the industrial sector and even available in the market bringing nanostructured components. The pharmaceutical industry has explored this type of structure as targeted drug delivery, especially against cancer. Integrative transcriptome analysis (ITA) is considered a promising technique for understanding biological events by analyzing several transcriptomes deposited in public databases. This research recovered seven transcriptomes' studies of human cells treated with silver nanoparticles without association or conjugation with any other substance or material for the performance of ITA. This analysis consists of a bipartite network for determining shared differentially expressed genes (DEGs) between different datasets from human cells treated with silver nanoparticles (AgNPs) at both early (4 or 6 h) and late treatment time (24 h). Most of the few upregulated DEGs shared by five or more datasets belong to biological pathways related to mineral absorption, suggesting that these processes were upregulated in AgNPs-treated cells. In addition, Ferroptosis, protein processing in the endoplasmic reticulum, and mitogen-activated protein kinase (MAPK) signaling pathway were also upregulated. Thus, the ITA of human cells treated with AgNPs indicates that the expression profile induced by these nanoparticles is specific to each cell type. However, they share inorganic compounds and oxidative stress responses genes, triggering apoptosis. This work reinforces the need for the biological characterization of cellular response to silver nanoparticles for application in humans, thus ensuring the safety and optimization of the desired results.

The Discovery of a New Mimivirus Isolate in Association with Virophage-Transpoviron Elements in Brazil Highlights the Main Genomic and Evolutionary Features of This Tripartite System.

Mimiviruses are giant viruses of amoeba that can be found in association with virophages. These satellite-like viruses are dependent on the mimivirus viral factory to replicate. Mimiviruses can also be associated with linear DNA molecules called transpovirons. Transpovirons and virophages are important drivers of giant virus evolution although they are still poorly studied elements. Here, we describe the isolation and genomic characterization of a mimivirus/virophage/transpoviron tripartite system from Brazil. We analyzed transmission electron microscopy images and performed genome sequencing and assembly, gene annotation, and phylogenetic analysis. Our data confirm the isolation of a lineage A mimivirus (1.2 Mb/1012 ORFs), called mimivirus argentum, and a sputnik virophage (18,880 bp/20 ORFs). We also detected a third sequence corresponding to a transpoviron from clade A (6365 bp/6 ORFs) that presents small terminal inverted repeats (77 nt). The main genomic features of mimivirus argentum and of its virophage/transpoviron elements corroborates with what is described for other known elements. This highlights that this triple genomic and biological interaction may be ancient and well-conserved. The results expand the basic knowledge about unique and little-known elements and pave the way to future studies that might contribute to a better understanding of this tripartite relationship.

Incomplete tricarboxylic acid cycle and proton gradient in Pandoravirus massiliensis: is it still a virus?

The discovery of Acanthamoeba polyphaga Mimivirus, the first isolated giant virus of amoeba, challenged the historical hallmarks defining a virus. Giant virion sizes are known to reach up to 2.3 µm, making them visible by optical microscopy. Their large genome sizes of up to 2.5 Mb can encode proteins involved in the translation apparatus. We have investigated possible energy production in Pandoravirus massiliensis. Mitochondrial membrane markers allowed for the detection of a membrane potential in purified virions and this was enhanced by a regulator of the tricarboxylic acid cycle but abolished by the use of a depolarizing agent. Bioinformatics was employed to identify enzymes involved in virion proton gradient generation and this approach revealed that eight putative P. massiliensis proteins exhibited low sequence identities with known cellular enzymes involved in the universal tricarboxylic acid cycle. Further, all eight viral genes were transcribed during replication. The product of one of these genes, ORF132, was cloned and expressed in Escherichia coli, and shown to function as an isocitrate dehydrogenase, a key enzyme of the tricarboxylic acid cycle. Our findings show for the first time that a membrane potential can exist in Pandoraviruses, and this may be related to tricarboxylic acid cycle. The presence of a proton gradient in P. massiliensis makes this virus a form of life for which it is legitimate to ask the question "what is a virus?".

Pristimerin isolated from Salacia crassifolia (Mart. Ex. Schult.) G. Don. (Celastraceae) roots as a potential antibacterial agent against Staphylococcus aureus.

ETHNOPHARMACOLOGICAL RELEVANCE: Pristimerin is a triterpenoid considered the main component of Salacia crassifolia extracts. This terpene has shown promising antitumor, anti-inflammatory, and antimicrobial effects. Likewise, S. crassifolia has been used in traditional medicine to treat cancer and as an antimicrobial and anti-inflammatory agent. AIM OF THE STUDY: This study aimed to evaluate the antibacterial activity of the hexane extract of Salacia crassifolia roots (HER) and its isolate, pristimerin, against pathogenic bacteria. MATERIALS AND METHODS: First, we evaluated the spectrum of action of HER and pristimerin by the determination of the minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC). Subsequently, we analyzed the time-kill curve of these plant-derived compounds against Staphylococcus aureus. Then, we examined their mode of action by three different assays: the crystal violet methodology, the release of intracellular material, and transmission electron microscopy methods (TEM). Finally, we evaluated the effect of HER and pristimerin on the pre-formed biofilm of S. aureus by the crystal violet assay, the synergistic effect by the checkerboard method, the cytotoxicity against Vero cells, and the in silico activity using the online software PASS. RESULTS: HER and pristimerin presented a narrow spectrum of action against Gram-positive bacteria (MIC 0.195-25 µg/mL), and their primary mode of action is the alteration of membrane permeability of S. aureus. Our results show that the compounds disrupted the pre-formed biofilm of S. aureus in a dose-dependent manner. Furthermore, HER and pristimerin presented a significant synergic effect after the combination with well-known antibiotics, which was associated with the ability of these phytomedicines to change membrane permeability. Regarding the cytotoxic effect, the selective index (SI) of HER ranged from 0.37 to 11.86, and the SI of pristimerin varied from 0.24 to 30.87, according to the bacteria tested. CONCLUSIONS: Overall, HER and pristimerin showed a promising antibacterial effect in vitro through the alteration of membrane permeability of S. aureus.

A virophage cross-species infection through mutant selection represses giant virus propagation, promoting host cell survival.

Virus adaptation to new hosts is a major cause of infectious disease emergence. This mechanism has been intensively studied in the context of zoonotic virus spillover, due to its impact on global health. However, it remains unclear for virophages, parasites of giant viruses and potential regulators of microbial communities. Here, we present, for the first time to our knowledge, evidence of cross-species infection of a virophage. We demonstrated that challenging the native population of Guarani virophage with two previously unidentified giant viruses, previously nonpermissive to this virophage, allows the selection of a mutant genotype able to infect these giant viruses. We were able to characterize the potential genetic determinant (deletion) carried by the virophage with the expanded-host range. Our study also highlights the relevant biological impact of this host adaptation by demonstrating that coinfection with the mixture containing the mutant virophage abolishes giant virus production and rescues the host cell population from lysis.

Translating the language of giants: translation-related genes as a major contribution of giant viruses to the virosphere.

Giant viruses of amoebas are a remarkable group of viruses. In addition to their large size and peculiar structures, the genetic content of these viruses is also special. Among the genetic features of these viruses that stand out is the presence of coding regions for elements involved in translation, a complex biological process that occurs in cellular organisms. No viral genome described so far has such a complex genetic arsenal as those of giant viruses, which code for several of these elements. Currently, tupanviruses have the most complete set of translation genes in the known virosphere. In this review, we have condensed what is currently known about translation genes in different groups of giant viruses and theorize about their biological importance, origin, and evolution, and what might possibly be found in the coming years.

Isolation and genomic characterization of a new mimivirus of lineage B from a Brazilian river.

Since its discovery, the first identified giant virus associated with amoebae, Acanthamoeba polyphaga mimivirus (APMV), has been rigorously studied to understand the structural and genomic complexity of this virus. In this work, we report the isolation and genomic characterization of a new mimivirus of lineage B, named "Borely moumouvirus". This new virus exhibits a structure and replicative cycle similar to those of other members of the family Mimiviridae. The genome of the new isolate is a linear double-strand DNA molecule of ~1.0 Mb, containing over 900 open reading frames. Genome annotation highlighted different translation system components encoded in the DNA of Borely moumouvirus, including aminoacyl-tRNA synthetases, translation factors, and tRNA molecules, in a distribution similar to that in other lineage B mimiviruses. Pan-genome analysis indicated an increase in the genetic arsenal of this group of viruses, showing that the family Mimiviridae is still expanding. Furthermore, phylogenetic analysis has shown that Borely moumouvirus is closely related to moumouvirus australiensis. This is the first mimivirus lineage B isolated from Brazilian territory to be characterized. Further prospecting studies are necessary for us to better understand the diversity of these viruses so a better classification system can be established.

In-depth analysis of the replication cycle of Orpheovirus.

BACKGROUND: After the isolation of Acanthamoeba polyphaga mimivirus (APMV), the study and search for new giant viruses has been intensified. Most giant viruses are associated with free-living amoebae of the genus Acanthamoeba; however other giant viruses have been isolated in Vermamoeba vermiformis, such as Faustovirus, Kaumoebavirus and Orpheovirus. These studies have considerably expanded our knowledge about the diversity, structure, genomics, and evolution of giant viruses. Until now, there has been only one Orpheovirus isolate, and many aspects of its life cycle remain to be elucidated. METHODS: In this study, we performed an in-depth characterization of the replication cycle and particles of Orpheovirus by transmission and scanning electron microscopy, optical microscopy and IF assays. RESULTS: We observed, through optical and IF microscopy, morphological changes in V. vermiformis cells during Orpheovirus infection, as well as increased motility at 12 h post infection (h.p.i.). The viral factory formation and viral particle morphogenesis were analysed by transmission electron microscopy, revealing mitochondria and membrane recruitment into and around the electron-lucent viral factories. Membrane traffic inhibitor (Brefeldin A) negatively impacted particle morphogenesis. The first structure observed during particle morphogenesis was crescent-shaped bodies, which extend and are filled by the internal content until the formation of multi-layered mature particles. We also observed the formation of defective particles with different shapes and sizes. Virological assays revealed that viruses are released from the host by exocytosis at 12 h.p.i., which is associated with an increase of particle counts in the supernatant. CONCLUSIONS: The results presented here contribute to a better understanding of the biology, structures and important steps in the replication cycle of Orpheovirus.

Human Infection with Orf Virus and Description of Its Whole Genome, France, 2017.

Zoonotic transmission of parapoxvirus from animals to humans has been reported; clinical manifestations are skin lesions on the fingers and hands after contact with infected animals. We report a human infection clinically suspected as being ecthyma contagiosum. The patient, a 65-year-old woman, had 3 nodules on her hands. She reported contact with a sheep during the Aïd-el-Fitr festival in France during 2017. We isolated the parapoxvirus orf virus from these nodules by using a nonconventional cell and sequenced the orf genome. We identified a novel orf virus genome and compared it with genomes of other orf viruses. More research is needed on the genus Parapoxvirus to understand worldwide distribution of and infection by orf virus, especially transmission between goats and sheep.

Giant virus vs amoeba: fight for supremacy.

Since the discovery of mimivirus, numerous giant viruses associated with free-living amoebae have been described. The genome of giant viruses can be more than 2.5 megabases, and virus particles can exceed the size of many bacteria. The unexpected characteristics of these viruses have made them intriguing research targets and, as a result, studies focusing on their interactions with their amoeba host have gained increased attention. Studies have shown that giant viruses can establish host-pathogen interactions, which have not been previously demonstrated, including the unprecedented interaction with a new group of small viruses, called virophages, that parasitize their viral factories. In this brief review, we present recent advances in virophage-giant virus-host interactions and highlight selected studies involving interactions between giant viruses and amoebae. These unprecedented interactions involve the giant viruses mimivirus, marseillevirus, tupanviruses and faustovirus, all of which modulate the amoeba environment, affecting both their replication and their spread to new hosts.

Discovery and Further Studies on Giant Viruses at the IHU Mediterranee Infection That Modified the Perception of the Virosphere.

The history of giant viruses began in 2003 with the identification of Acanthamoeba polyphaga mimivirus. Since then, giant viruses of amoeba enlightened an unknown part of the viral world, and every discovery and characterization of a new giant virus modifies our perception of the virosphere. This notably includes their exceptional virion sizes from 200 nm to 2 µm and their genomic complexity with length, number of genes, and functions such as translational components never seen before. Even more surprising, Mimivirus possesses a unique mobilome composed of virophages, transpovirons, and a defense system against virophages named Mimivirus virophage resistance element (MIMIVIRE). From the discovery and isolation of new giant viruses to their possible roles in humans, this review shows the active contribution of the University Hospital Institute (IHU) Mediterranee Infection to the growing knowledge of the giant viruses' field.

Microscopic Analysis of the Tupanvirus Cycle in Vermamoeba vermiformis.

Since Acanthamoeba polyphaga mimivirus (APMV) was identified in 2003, several other giant viruses of amoebae have been isolated, highlighting the uniqueness of this group. In this context, the tupanviruses were recently isolated from extreme environments in Brazil, presenting virions with an outstanding tailed structure and genomes containing the most complete set of translation genes of the virosphere. Unlike other giant viruses of amoebae, tupanviruses present a broad host range, being able to replicate not only in Acanthamoeba sp. but also in other amoebae, such as Vermamoeba vermiformis, a widespread, free-living organism. Although the Tupanvirus cycle in A. castellanii has been analyzed, there are no studies concerning the replication of tupanviruses in other host cells. Here, we present an in-depth microscopic study of the replication cycle of Tupanvirus in V. vermiformis. Our results reveal that Tupanvirus can enter V. vermiformis and generate new particles with similar morphology to when infecting A. castellanii cells. Tupanvirus establishes a well-delimited electron-dense viral factory in V. vermiformis, surrounded by lamellar structures, which appears different when compared with different A. castellanii cells. Moreover, viral morphogenesis occurs entirely in the host cytoplasm within the viral factory, from where complete particles, including the capsid and tail, are sprouted. Some of these particles have larger tails, which we named "supertupans." Finally, we observed the formation of defective particles, presenting abnormalities of the tail and/or capsid. Taken together, the data presented here contribute to a better understanding of the biology of tupanviruses in previously unexplored host cells.

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

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.

The Complex Nature of Tupanviruses.

The discovery of giant viruses revealed a new level of complexity in the virosphere, raising important questions about the diversity, ecology, and evolution of these viruses. The family Mimiviridae was the first group of amoebal giant viruses to be discovered (by Bernard La Scola and Didier Raoult team), containing viruses with structural and genetic features that challenged many concepts of classic virology. The tupanviruses are among the newest members of this family and exhibit structural, biological, and genetic features never previously observed in other giant viruses. The complexity of these viruses has put us one step forward toward the comprehension of giant virus biology and evolution, but also has raised important questions that still need to be addressed. In this chapter, we tell the history behind the discovery of one of the most complex viruses isolated to date, highlighting the unique features exhibited by tupanviruses, and discuss how these giant viruses have contributed to redefining limits for the virosphere.

"Tupanvirus", a new genus in the family Mimiviridae.

The genus "Tupanvirus" is a new proposed taxon to be included in the family Mimiviridae. The two known tupanvirus isolates were isolated from soda lake and oceanic sediments samples collected in Brazil and were named "tupanvirus soda lake" and "tupanvirus deep ocean", respectively. These viruses exhibit similarities to amoeba-infecting mimiviruses, but there are also several differences that place them in a separate group within the family Mimiviridae. Their virions have a mean size of 1.2 µm, which include a mimivirus-like capsid and a large cylindrical tail, both covered by fibrils. The linear double-stranded DNA genomes of up to 1,516,267 base pairs encode over 1,200 genes, among which ~ 30% have no homologs in any database, including in other mimivirus genomes. Compared to other mimiviruses, tupanviruses exhibit a broader host range and cause a cytotoxic effect in host and non-host organisms, a phenotype that is not observed for other mimiviruses. Remarkably, these viruses possess the most complete gene set related to the protein synthesis process, including 20 aminoacyl-tRNA synthetases, 67-70 tRNAs, many translation factors, and genes involved in maturation and modification of tRNA and mRNA, among others. Moreover, diverse phylogenomic analyses put tupanviruses in a distinct group within the family Mimiviridae. In light of the set of different features observed for these giant viruses, we propose establishment of a new genus to allow proper classification of two known tupanviruses and possibly many more similar viruses yet to be characterized.