Search Results (71)

Bean common mosaic virus (BCMV; Potyvirus phaseovulgaris) is one of the primary viruses that severely impacts the yield and quality of common beans (Phaseolus vulgaris L.) and has a worldwide distribution. Utilizing small RNA sequencing and RT-PCR validation, this study identified widespread co-infection by multiple viruses in field-collected common bean samples, with BCMV being the dominant viral species. A novel isolate, designated DY9, was obtained from these field samples. Pathotype characterization confirmed DY9 as pathotype PG-III, while previous studies reported all other PG-III members as Bean common mosaic necrosis virus (BCMNV). Whole-genome sequencing and phylogenetic analysis revealed that DY9 was genetically closer to BCMV and diverged significantly from known PG-III isolates. Based on these findings, we constructed an infectious clone of DY9. To address the genetic instability of Potyvirus in the Escherichia coli (E. coli) expression system, we discovered that inserting Intron 2 (derived from the NiR gene of P. vulgaris, GenBank: U10419.1) at position 2431 of the HC-Pro gene and targeting Intron 1 (derived from the ST LS1 gene of Solanum tuberosum, GenBank: X04753.1) at position 4240 of the CI gene significantly improved the stability of the cloning vector. The clone was verified to systemically infect common bean plants and induce typical mosaic symptoms. Infectivity was validated through RT-PCR, RT-qPCR, Western blotting, and transmission electron microscopy. This study represents the first successful construction of an infectious clone for pathotype PG-III BCMV, providing a critical reverse genetics tool for dissecting viral pathogenesis and identifying resistance genes. These findings not only expand the genetic diversity of BCMV but also offer a methodological reference for constructing infectious clones of Potyvirus species. Full article

Although Torque Teno Viruses (TTVs) were initially considered to be ubiquitous members of the mammalian virome, the finding that swine TTVs (TTSuV) can act as primary pathogens elevates the possible status of swine TTVs (TTSuVs) to an emerging swine pathogen. Since their discovery, the molecular mechanisms of TTV–host interactions remain largely unknown as robust in vitro culture systems and in vivo animal models have not been available. This study was undertaken to address some of these long-standing gaps. Recombinant TTSuV1 rescued from an infectious clone was used to infect C57BL/J6 mice. Infected mice seroconverted within 15 days post-infection and mounted virus neutralizing antibody responses. Viral DNA was detected in blood and lung tissue for the duration of the study. TTSuV1 isolated from the lung tissue of infected mice productively and serially infected PK-15 cells in vitro, indicating that the treatment produced viable, replicative viral particles in the host. TTSuV1 antigen was also detected by flow cytometry in lymphocytes, including the T and B lymphocyte subsets. Infected mice exhibited mild splenic hyperplasia and lymphopenia. The ability to respond to mitogenic stimuli was highly diminished in infected mice and a striking lack of virus-specific recall responses was observed for the 30-day duration of the study. Therefore, this study is the first to provide experimental evidence that recombinant TTSuV1 rescued from an infectious clone is infective and induces immune responses in laboratory mice. This model provides a critical tool for advancing research on TTV immunopathogenesis. Full article

Human parvovirus B19 (B19V) is a major human pathogen in which the ssDNA genome is replicated within the nucleus of infected human erythroid progenitor cells (EPCs) through a process involving both cellular and viral proteins, including the non-structural protein (NS)1. We previously characterized the interaction between NS1 classical nuclear localization signal (cNLS: GACHAKKPRIT-182) and host cell importin (IMP)α and proposed it as a potential target for antiviral drug development. Here, we further extend on such findings. First, we demonstrate that NS1 nuclear localization is required for viral production since introducing the K177T substitution in a cloned, infectious viral genome resulted in a non-viable virus. Secondly, we demonstrate that the antiparasitic drug ivermectin (IVM), known to inhibit the IMPα/β dependent nuclear import pathway, could impair the NS1-NLS:IMPα interaction and suppress viral replication in UT7/EpoS1 cells in a dose-dependent manner. We also show that a panel of structurally related avermectins (AVMs) can dissociate the NS1-NLS:IMPα complex with half-maximal inhibitory concentrations in the nanomolar range. Among them, Eprinomectin emerged as the most selective inhibitor of B19V replication, with a selectivity index of c. 5.0. However, when tested in EPCs generated from peripheral blood mononuclear cells, which constitute a cellular population close to the natural target cells in bone marrow, the inhibitory effect of IVM and Eprinomectin was demonstrated to a lesser extent, and both compounds exhibited high toxicity, thus highlighting the need for more specific inhibitors of the NS1-NLS:IMPα interaction. Full article

Viola philippica, a medicinal herbaceous plant documented in the Chinese Pharmacopoeia, is a promising candidate for research into plant-derived pharmaceuticals. However, the study of newly emerging viruses that threaten the cultivation of V. philippica remains limited. In this study, V. philippica plants exhibiting symptoms such as leaf yellowing, mottled leaves, and vein chlorosis were collected and subjected to RNA sequencing to identify potential viral pathogens. A novel polerovirus, named Viola Philippica Polerovirus (VPPV), was identified in V. philippica. VPPV possesses a linear, positive-sense, single-stranded RNA genome consisting of 5535 nucleotides (nt) and encodes seven highly overlapping open reading frames (ORFs). Two potential recombination events were identified within ORF2, ORF3a, and ORF3, providing insights into the genetic diversity and evolution history of this novel polerovirus. An infectious cDNA clone of VPPV was successfully constructed and shown to infect Nicotiana benthamiana. Using a PVX-based heterologous expression system, the VPPV P0 protein was shown to trigger a systemic hypersensitive response (HR)-like reaction in N. benthamiana, indicating that P0 functions as the main pathogenicity determinant. These findings contributed to the detection and understanding of pathogenic mechanisms and control strategies for VPPV in V. philippica. Full article

Due to the error-prone nature of viral RNA-dependent RNA polymerases, the replication of RNA viruses results in a diversity of viral genomes harboring point mutations, deletions, insertions, and genome rearrangements. Citrus tristeza virus (CTV), a causal agent of diseases of economically important citrus species, shows intrinsic genetic stability. While the virus appears to have some mechanism that limits the accumulation of single-nucleotide variants, the production of defective viral genomes (DVGs) during virus infection has been reported for certain variants of CTV. The intra-host diversity generated during plant infection with variant T36 (CTV-T36) remains unclear. To address this, we analyzed the RNA species accumulated in the initially infected and systemic leaves of Nicotiana benthamiana plants inoculated with an infectious cDNA clone of CTV-T36, which warranted that infection was initiated by a known, well-defined sequence variant of the virus. CTV-T36 limited the accumulation of single-nucleotide mutants during infection. With that, four types of DVGs—deletions, insertions, and copy- and snap-backs—were found in all the samples, with deletions and insertions being the most common types. Hot-spots across the genome for DVG recombination and short direct sequence repeats suggest that sequence complementarity could mediate DVG formation. In conclusion, our study illustrates the formation of diverse DVGs during CTV-T36 infection. To the best of our knowledge, this is the first study that has analyzed the genetic variability and recombination of a well-defined sequence variant of CTV in an herbaceous host. Full article

East Asian Passiflora virus (EAPV) causes passionfruit woodiness disease, a major threat limiting passionfruit production in eastern Asia, including Taiwan and Vietnam. In this study, an infectious cDNA clone of a Taiwanese severe isolate EAPV-TW was tagged with a green fluorescent protein (GFP) reporter to monitor the virus in plants. Nicotiana benthamiana and yellow passionfruit plants inoculated with the construct showed typical symptoms of EAPV-TW. Based on our previous studies on pathogenicity determinants of potyviral HC-Pros, a deletion of six amino acids (d6) alone and its association with a point mutation (F₈I, simplified as I₈) were conducted in the N-terminal region of the HC-Pro gene of EAPV-TW to generate mutants of EAPV-d6 and EAPV-d6I₈, respectively. The mutant EAPV-d6I₈ caused infection without conspicuous symptoms in N. benthamiana and yellow passionfruit plants, while EAPV-d6 still induced slight leaf mottling. EAPV-d6I₈ was stable after six passages under greenhouse conditions and displayed a zigzag pattern of virus accumulation, typical of a beneficial protective virus. The cross-protection effectiveness of EAPV-d6I₈ was evaluated in both N. benthamiana and yellow passionfruit plants under greenhouse conditions. EAPV-d6I₈ conferred complete cross-protection (100%) against the wild-type EAPV-TW-GFP in both N. benthamiana and yellow passionfruit plants, as verified by no severe symptoms, no fluorescent signals, and PCR-negative status for GFP. Furthermore, EAPV-d6I₈ also provided complete protection against Vietnam’s severe strain EAPV-GL1 in yellow passionfruit plants. Our results indicate that the attenuated mutant EAPV-d6I₈ has great potential to control EAPV in Taiwan and Vietnam via cross-protection. Full article

Japanese encephalitis virus (JEV), a flavivirus transmitted by mosquitoes, has caused epidemics and severe neurological diseases in Asian countries. In this study, we developed a cDNA infectious clone, pBAC JYJEV3, of the JEV genotype 3 strain (EF571853.1) using a bacterial artificial chromosome (BAC) vector. The constructed infectious clone was transfected into Vero cells, where it exhibited infectivity and induced cytopathic effects akin to those of the parent virus. Confocal microscopy confirmed the expression of the JEV envelope protein. Comparative analysis of growth kinetics revealed similar replication dynamics between the parental and recombinant viruses, with peak titers observed 72 h post-infection (hpi). Furthermore, plaque assays demonstrated comparable plaque sizes and morphologies between the viruses. Cryo-electron microscopy confirmed the production of recombinant virus particles with a morphology identical to that of the parent virus. Immunization studies in mice using inactivated parental and recombinant viruses revealed robust IgG responses, with neutralizing antibody production increasing over time. These results showcase the successful generation and characterization of a recombinant JEV3 virus and provide a platform for further investigations into JEV pathogenesis and vaccine development. Full article

In virology, the term reverse genetics refers to a set of methodologies in which changes are introduced into the viral genome and their effects on the generation of infectious viral progeny and their phenotypic features are assessed. Reverse genetics emerged thanks to advances in recombinant DNA technology, which made the isolation, cloning, and modification of genes through mutagenesis possible. Most virus reverse genetics studies depend on our capacity to rescue an infectious wild-type virus progeny from cell cultures transfected with an “infectious clone”. This infectious clone generally consists of a circular DNA plasmid containing a functional copy of the full-length viral genome, under the control of an appropriate polymerase promoter. For most DNA viruses, reverse genetics systems are very straightforward since DNA virus genomes are relatively easy to handle and modify and are also (with few notable exceptions) infectious per se. This is not true for RNA viruses, whose genomes need to be reverse-transcribed into cDNA before any modification can be performed. Establishing reverse genetics systems for members of the Caliciviridae has proven exceptionally challenging due to the low number of members of this family that propagate in cell culture. Despite the early successful rescue of calicivirus from a genome-length cDNA more than two decades ago, reverse genetics methods are not routine procedures that can be easily extrapolated to other members of the family. Reports of calicivirus reverse genetics systems have been few and far between. In this review, we discuss the main pitfalls, failures, and delays behind the generation of several successful calicivirus infectious clones. Full article

Hepatitis E virus (HEV) can cause self-limiting acute and chronic hepatitis infections, particularly in immunocompromised individuals. In developing countries, HEV is mainly transmitted via drinking contaminated water, whereas zoonotic transmission dominates the route of infection in developed countries, including Japan. Pigs are an important reservoir for HEV infection. Wild boars, which share the same genus and species as domestic pigs, are also an HEV reservoir. During our nationwide study of HEV infection in wild boar populations in Japan, a genotype 6 (HEV-6) strain, wbJHG_23, was isolated in Hyogo Prefecture in 2023. The genomic length was 7244 nucleotides, excluding the poly(A) tract. The wbJHG_23 strain exhibited the highest nucleotide identity throughout its genome with two previously reported HEV-6 strains (80.3–80.9%). Conversely, it displayed lower similarity (73.3–78.1%) with the HEV-1–5, HEV-7, and HEV-8 strains, indicating that, although closely related, the wbJHG_23 strain differs significantly from the reported HEV-6 strains and might represent a novel subtype. The wbJHG_23 strain successfully infected the human-derived cancer cell lines, PLC/PRF/5 and A549 1-1H8 cells, suggesting that HEV-6 has the potential for zoonotic infection. An infectious cDNA clone was constructed using a reverse genetics system, and a cell culture system supporting the efficient propagation of the HEV-6 strain was established, providing important tools for further studies on this genotype. Using this cell culture system, we evaluated the sensitivity of the wbJHG_23 strain to ribavirin treatment. Its good response to this treatment suggested that it could be used to treat human infections caused by HEV-6. Full article

Paslahepevirus balayani and Rocahepevirus ratti are genetically diverse species of hepatitis E virus [HEV]. Previously, only members of the Paslahepevirus genus were known to infect humans but recently some Rocahepevirus members have been found to be infectious to both immunocompromised and immunocompetent humans. Paslahepevirus balayani genotypes (gt) 1, 2, and 4 are known for their detrimental effects during pregnancy, causing pregnancy-related disorders. Recent findings have demonstrated the ability of Paslahepevirus balayani gt3 to replicate within placental cell lines, suggesting a direct effect on the placenta and fetus. To study whether zoonotic rat HEV strains possess a similar human-host placental tropism, we utilized JEG-3 cells to understand the replicative ability of an infectious clone of a recently reported strain of Rocahepevirus ratti, the LCK-3110 strain. Infectious cDNA clones of Pasla-, Avi-, and Rocahepevirus were transcribed and then, transduced into JEG-3 cells. Cells were harvested, and cell lysates were used for testing infectivity. Five days post-transfection or after inoculation onto naive HepG2/C3A cells, the cells were analyzed for infection. Replication in transduced JEG-3 cells and the infection potential in HepG2/C3A cells were assessed via an indirect immunofluorescence assay and a flow-cytometry assay. We found that the Rocahepevirus ratti LCK-3110 strain did not have efficient replication in JEG-3 cell cultures. Full article

Virus infections cause devastative economic losses for various plant species, and early diagnosis and prevention are the most effective strategies to avoid the losses. Exploring virus genomic evolution and constructing virus infectious cDNA clones is essential to achieve a deeper understanding of the interaction between host plant and virus. Therefore, this work aims to guide people to better prevent, control, and utilize the youcai mosaic virus (YoMV). Here, the YoMV was found to infect the Solanum nigrum under natural conditions. Then, an infectious cDNA clone of YoMV was successfully constructed using triple-shuttling vector-based yeast recombination. Furthermore, we established phylogenetic trees based on the complete genomic sequences, the replicase gene, movement protein gene, and coat protein gene using the corresponding deposited sequences in NCBI. Simultaneously, the evolutionary relationship of the YoMV discovered on S. nigrum to others was determined and analyzed. Moreover, the constructed cDNA infectious clone of YoMV from S. nigrum could systematically infect the Nicotiana benthamiana and S. nigrum by agrobacterium-mediated infiltration. Our investigation supplied a reverse genetic tool for YoMV study, which will also contribute to in-depth study and profound understanding of the interaction between YoMV and host plant. Full article

Tomato black ring virus (TBRV) is a member of the Nepovirus genus in the Secoviridae family, which infects a wide range of important crop species worldwide. In this work, we constructed four cDNA infectious clones of the TBRV tagged with the green fluorescent protein (TBRV-GFP), which varied in (i) the length of the sequences flanking the GFP insert, (ii) the position of the GFP insert within the RNA2 polyprotein, and (iii) the addition of a self-cutting 2A protein. The presence of the GFP coding sequence in infected plants was verified by RT-PCR, while the infectivity and stability of the constructs were verified by mechanical inoculation of the host plants. The systemic spread of TBRV-GFP within plants was observed under UV light at a macroscopic level, monitoring GFP-derived fluorescence in leaves, and at a microscopic level using confocal microscopy. The obtained clones are a valuable tool for future studies of TBRV-host interactions, virus biology, and the long-term monitoring of its distribution in infected plants. Full article

In mammals, the role of interleukin-18 (IL-18) in the immune response is to drive inflammatory and, normally therefore, anti-viral responses. IL-18 also shows promise as a vaccine adjuvant in mammals. Chicken IL-18 (chIL-18) has been cloned. The aim of this study was to investigate the potential of chIL-18 to act as a vaccine adjuvant in the context of a live recombinant Fowlpox virus vaccine (fpIBD1) against Infectious bursal disease virus (IBDV). fpIBD1 protects against mortality, but not against damage to the bursa of Fabricius caused by IBDV infection. The Fowlpox virus genome itself contains several candidate immunomodulatory genes, including potential IL-18 binding proteins (IL-18bp). We knocked out (Δ) the potential IL-18bp genes in fpIBD1 and inserted (::) the cDNA encoding chIL-18 into fpIBD1 in the non-essential ORF030, generating five new viral constructs –fpIBD1::chIL-18, fpIBD1ΔORF073, fpIBD1ΔORF073::chIL-18, fpIBD1ΔORF214, and fpIBD1ΔORF214::chIL-18. The subsequent protection from challenge with virulent IBDV, as measured by viral load and bursal damage, given by these altered fpIBD1 strains, was compared to that given by the original fpIBD1. Complete protection was provided following challenge with IBDV in chicken groups vaccinated with either fpIBDIΔ073::IL-18 or fpIBD1Δ214::IL-18, as no bursal damage nor IBDV was detected in the bursae of the birds. The results show that chIL-18 can act as an effective vaccine adjuvant by improving the fpIBD1 vaccine and providing complete protection against IBDV challenge. Full article

Porcine reproductive and respiratory syndrome (PRRS) has been a persistent challenge for the swine industry for over three decades due to the lack of effective treatments and vaccines. Reverse genetics systems have been extensively employed to build rapid drug screening platforms and develop genetically engineered vaccines. Herein, we rescued recombinant PRRS virus (rPRRSV) WUH3 using an infectious cDNA clone of PRRSV WUH3 acquired through a BstXI-based one-step-assembly approach. The rPRRSV WUH3 and its parental PRRSV WUH3 share similar plaque sizes and multiple-step growth curves. Previously, gene-editing of viral genomes depends on appropriate restrictive endonucleases, which are arduous to select in some specific viral genes. Thus, we developed a restrictive endonucleases-free method based on CRISPR/Cas9 to edit the PRRSV genome. Using this method, we successfully inserted the exogenous gene (EGFP gene as an example) into the interval between ORF1b and ORF2a of the PRRSV genome to generate rPRRSV WUH3-EGFP, or precisely mutated the lysine (K) at position 150 of PRRSV nsp1α to glutamine (Q) to acquire rPRRSV WUH3 nsp1α-K150Q. Taken together, our study provides a rapid and convenient method for the development of genetically engineered vaccines against PRRSV and the study on the functions of PRRSV genes. Full article

Classical swine fever (CSF) and porcine epidemic diarrhea (PED) are highly contagious viral diseases that pose a significant threat to piglets and cause substantial economic losses in the global swine industry. Therefore, the development of a bivalent vaccine capable of targeting both CSF and PED simultaneously is crucial. In this study, we genetically engineered a recombinant classical swine fever virus (rCSFV) expressing the antigenic domains of the porcine epidemic diarrhea virus (PEDV) based on the modified infectious cDNA clone of the vaccine strain C-strain. The S1N and COE domains of PEDV were inserted into C-strain cDNA clone harboring the mutated 136th residue of N^pro and substituted 3′UTR to generate the recombinant chimeric virus vC/SM3′UTR_N-S1NCOE. To improve the efficacy of the vaccine, we introduced the tissue plasminogen activator signal (tPAs) and CARD domain of the signaling molecule VISA into vC/SM3′UTR_N-S1NCOE to obtain vC/SM3′UTR_N-tPAsS1NCOE and vC/SM3′UTR_N-CARD/tPAsS1NCOE, respectively. We characterized three vaccine candidates in vitro and investigated their immune responses in rabbits and pigs. The N^pro_D136N mutant exhibited normal autoprotease activity and mitigated the inhibition of IFN-β induction. The introduction of tPAs and the CARD domain led to the secretory expression of the S1NCOE protein and upregulated IFN-β induction in infected cells. Immunization with recombinant CSFVs expressing secretory S1NCOE resulted in a significantly increased in PEDV-specific antibody production, and coexpression of the CARD domain of VISA upregulated the PEDV-specific IFN-γ level in the serum of vaccinated animals. Notably, vaccination with vC/SM3′UTR_N-CARD/tPAsS1NCOE conferred protection against virulent CSFV and PEDV challenge in pigs. Collectively, these findings demonstrate that the engineered vC/SM3′UTR_N-CARD/tPAsS1NCOE is a promising bivalent vaccine candidate against both CSFV and PEDV infections. Full article