A novel cypovirus found in a betabaculovirus co-infection context contains a poxvirus immune nuclease (poxin)-related gene

Abstract

<jats:p>The cassava hornworm <jats:italic>Erinnyis ello ello</jats:italic> (Lepidoptera: Sphingidae) is an important pest in Brazil. This insect feeds on host plants of several species, especially <jats:italic>Manihot esculenta</jats:italic> (cassava) and <jats:italic>Hevia brasiliensis</jats:italic> (rubber tree). Cassava hornworm outbreaks are quite common in Brazil and can cause great impact over crop production. Granulare and polyhedral-shaped occlusion bodies (OBs) were observed in extracts of dead <jats:italic>E. ello</jats:italic> larvae from rubber-tree plantations by light and scanning electron microscopy (SEM), suggesting a mixed infection. The polyhedral-shaped OB surface revealed indentations that resemble those found in cypovirus polyhedra. After OB nucleic acid extraction followed by cDNA production and Illumina deep-sequencing analysis, the results confirmed for the presence of a putative novel cypovirus that carries ten segments and also a betabaculovirus (Erinnyis ello granulovirus, ErelGV). Phylogenetic analysis of the predicted segment 1-enconded RdRP showed that the new cypovirus isolate is closely related to a member of species <jats:italic>Cypovirus 2</jats:italic>, which was isolated from <jats:italic>Inachis io</jats:italic> (Lepidoptera: Nymphalidae). Therefore, we named this new isolate Erinnyis ello cypovirus 2 (ErelCPV-2). Genome <jats:italic>in silico</jats:italic> analyses showed that ErelCPV-2 segment 8 (S8) has a predicted amino acid identity of 35.82 % to a hypothetical protein of betabaculoviruses. This putative protein has a cGAMP-specific nuclease domain related to the poxvirus immune nucleases (poxins) from the 2′,3′-cGAMP-degrading enzyme family.</jats:p>

Structures of diverse poxin cGAMP nucleases reveal a widespread role for cGAS-STING evasion in host–pathogen conflict

“…Lepidopteran poxin enzymes cluster within Group 3, and have been shown to be highly upregulated after infection with various pathogens, including alphabaculoviruses and bacteria, providing evidence for a role in immunity or immune regulation (Shrestha et al, 2019;Woon Shin et al, 1998). Group 4 is formed by poxin proteins from the genomes of several additional lepidopteran viruses: betabaculoviruses (also called granuloviruses), cypoviruses (doublestranded RNA viruses in the family Reoviridae), and betaentomopoxviruses ( Figure 1B) (Silva et al, 2020). The vast evolutionary distance between these DNA and RNA viral families suggests related poxin genes may have been transferred between viruses within coinfected cells (Silva et al, 2020;Thézé et al, 2015).…”

“…Group 4 is formed by poxin proteins from the genomes of several additional lepidopteran viruses: betabaculoviruses (also called granuloviruses), cypoviruses (doublestranded RNA viruses in the family Reoviridae), and betaentomopoxviruses ( Figure 1B) (Silva et al, 2020). The vast evolutionary distance between these DNA and RNA viral families suggests related poxin genes may have been transferred between viruses within coinfected cells (Silva et al, 2020;Thézé et al, 2015). Notably, the enormous diversity of poxin enzymes in insect pathogens and moth and butterfly genomes confirms a broad role for 2′3′-cGAMP degradation, and strongly suggests these genomes served as a source for emergence of poxins in mammalian poxviruses.…”

Improving poxvirus-mediated antitumor immune responses by deleting viral cGAMP-specific nuclease

“…Since then, increasing evidence for the central role played by these cGAMP-specific nucleases in pathogen evasion has been published. In addition to poxviruses, different classes of pathogens have been described to encode proteins with similar functions, including baculovirus [ 13 ], cypovirus [ 14 ], ribovirus [ 15 ], and parasitoid wasps [ 15 ].…”