Endogenous retroviruses (ERVs) are sequences in animal genomes that originated from ancient retrovirus infections; they provide genetic novelty in hosts by being coopted as functional genes or elements during evolution. Recently, we demonstrated that endogenous elements from not only from retroviruses but also nonretroviral RNA viruses are a possible source of functional genes in host animals. The remnants of ancient bornavirus infections, called endogenous bornavirus-like elements (EBLs), are present in the genomes of a wide variety of vertebrate species, and some express functional products in host cells. Previous studies have predicted that the human EBL locus derived from bornavirus nucleoprotein, termed hsEBLN-2, expresses mRNA encoding a protein, suggesting that hsEBLN-2 has acquired a cellular function during evolution. However, the detailed function of the hsEBLN-2-derived product remains to be elucidated. In this study, we show that the hsEBLN-2-derived protein E2 acts as a mitochondrial protein thatnot been determined. In this study, we found that the E2 protein, an expression product of hsEBLN-2, interacts with apoptosis-related host proteins as a mitochondrial protein and affects cell viability. This study suggests that nonretroviral RNA viral EVEs have been coopted by hosts with more diverse functions than previously thought, showing a pivotal role for RNA virus infection in evolution.RNA helicase A/DHX9 is required for diverse RNA-related essential cellular functions and antiviral responses and is hijacked by RNA viruses to support their replication. Here, we show that during the late replication stage in human cancer cells of myxoma virus (MYXV), a member of the double-stranded DNA (dsDNA) poxvirus family that is being developed as an oncolytic virus, DHX9, forms unique granular cytoplasmic structures, which we named "DHX9 antiviral granules." These DHX9 antiviral granules are not formed if MYXV DNA replication and/or late protein synthesis is blocked. When formed, DHX9 antiviral granules significantly reduced nascent protein synthesis in the MYXV-infected cancer cells. MYXV late gene transcription and translation were also significantly compromised, particularly in nonpermissive or semipermissive human cancer cells where MYXV replication is partly or completely restricted. Directed knockdown of DHX9 significantly enhanced viral late protein synthesis and progeny virus formation in normaes sequester viral proteins and reduce viral late protein synthesis and thus regulate MYXV, and other poxviruses, that replicate in the cytoplasm. In addition, we show that in the absence of DHX9, the formation of DHX9 antiviral granules can be inhibited, which significantly enhanced oncolytic MYXV replication in human cancer cell lines where the virus is normally restricted. Our results also show that DHX9 antiviral granules are formed after viral infection but not by common nonviral cellular stress inducers. Thus, our study suggests that DHX9 has antiviral activity in human cancer cells, and this pathway can be targeted for enhanced activity of oncolytic poxviruses against even restrictive cancer cells.Live-attenuated virus vaccines are highly effective in preventing viral disease but carry intrinsic risks of residual virulence and reversion to pathogenicity. The classically derived Candid#1 virus protects seasonal field workers in Argentina against zoonotic infection by Junín virus (JUNV) but is not approved in the United States, in part due to the potential for reversion at the attenuating locus, a phenylalanine-to-isoleucine substitution at position 427 in the GP2 subunit of the GPC envelope glycoprotein. Previously, we demonstrated facile reversion of recombinant Candid#1 (rCan) in cell culture and identified an epistatic interaction between the attenuating I427 and a secondary K33S mutation in the stable signal peptide (SSP) subunit of GPC that imposes an evolutionary barrier to reversion. The magnitude of this genetic barrier is manifest in our repeated failures to rescue the hypothetical revertant virus. In this study, we show that K33S rCan is safe and attenuated in guinea pigs and capable of elicitattenuation, and a single nucleotide change may regenerate the pathogenic virus. Here, we take advantage of a unique genetic interaction between GPC subunits to design a mutant Candid#1 virus that establishes an evolutionary barrier to reversion. The mutant virus (K33S rCan) is fully attenuated and protects immunized guinea pigs against lethal JUNV infection. We find no instances of reversion in mice inoculated with K33S rCan. This work supports the further development of K33S rCan as a second-generation JUNV vaccine.Parvovirus B19 (B19V) infection causes diseases in humans ranging from the mild erythema infectiosum to severe hematological disorders. The unique region of the minor structural protein VP1 (VP1u) of 227 amino acids harbors strong neutralizing epitopes which elicit dominant immune responses in patients. Recent studies have shown that the VP1u selectively binds to and enters B19V permissive cells through an unknown cellular proteinaceous receptor. In the present study, we demonstrated that purified recombinant VP1u effectively inhibits B19V infection of ex vivo expanded primary human erythroid progenitors. Furthermore, we identified the amino acid sequence 5-68 of the VP1 (VP1u5-68aa) is sufficient to confer the inhibition of B19V infection at a level similar to that of the full-length VP1u. In silico structure prediction suggests that the VP1u5-68aa contains three α-helices. Importantly, we found that the inhibition capability of the minimal domain VP1u5-68aa is independent of its dimerization but is likely ded recombinant 5-68aa of the VP1 has a high efficiency in inhibition of parvovirus B19 infection of human erythroid progenitors, which has a half maximal effective concentration (EC50) of 67 nM and a low cytotoxicity. selleck inhibitor The N-terminal 5-68 amino acids holds the potential as an effective antiviral of parvovirus B19 caused hematological disorders, as well as a carrier to deliver proteins to human erythroid progenitors.