Two new umbravirus-like associated RNAs (ulaRNAs) discovered in maize and johnsongrass from Ecuador.

Two new umbravirus-like associated RNAs (ulaRNAs) were found, respectively, in maize and Johnsongrass samples from Ecuador. The complete sequences consist of 3,053 and 3,025 nucleotides, respectively, and contain four open reading frames (ORFs). Their genome sequences were 58% identical to each other and 28 to 60% identical to the most closely related viruses. Phylogenetic analysis using full genome sequences and amino acid sequence of the RNA-dependent-RNA polymerase (RdRp) placed both sequences in a clade sharing the most recent common ancestor with ulaRNAs from sugarcane and maize, suggesting that they belong to a monophyletic grass-infecting lineage. Their terminal regions exhibit features common to umbraviruses and ulaRNAs.

An umbra-related virus found in babaco (Vasconcellea × heilbornii).

The complete sequence of a new viral RNA from babaco (Vasconcellea × heilbornii) was determined. The genome consisted of 4,584 nucleotides, containing two open reading frames (ORFs 1 and 2), a 9-nt-long noncoding region (NCR) at the 5' terminus, and an unusually long (1,843 nt) NCR at the 3' terminus. The presence of a potential heptameric slippery signal located 12 nt upstream the stop codon of ORF 1 suggests a -1 ribosomal frameshift mechanism for the translation of ORF 2. Sequence comparisons of ORF 2 revealed similarity to the RNA-dependent RNA polymerase (RdRp) of several umbra- and umbra-like viruses. Phylogenetic analysis of the RdRp placed the new virus in a well-supported and cohesive clade that includes umbra-like viruses reported in papaya, citrus, opuntia, maize, and sugarcane hosts. Viruses of this clade share a most recent ancestor with the umbraviruses but have different genomic features. The creation of a new genus within the family Tombusviridae is proposed for the classification of these novel viruses.

A Heterologous Viral Protein Scaffold for Chimeric Antigen Design: An Example PCV2 Virus Vaccine Candidate.

Recombinant vaccines have low-cost manufacturing, regulatory requirements, and reduced side effects compared to attenuated or inactivated vaccines. In the porcine industry, post-weaning multisystemic disease syndrome generates economic losses, characterized by progressive weight loss and weakness in piglets, and it is caused by porcine circovirus type 2 (PCV2). We designed a chimeric antigen (Qm1) to assemble the main exposed epitopes of the Cap-PCV2 protein on the capsid protein of the tobacco necrosis virus (TNV). This design was based on the Cap-N-terminal of an isolated PCV2 virus obtained in Chile. The virus was characterized, and the sequence was clustered within the PCV2 genotype b clade. This chimeric protein was expressed as inclusion bodies in both monomeric and multimeric forms, suggesting a high-molecular-weight aggregate formation. Pigs immunized with Qm1 elicited a strong and specific antibody response, which reduced the viral loads after the PCV2 challenge. In conclusion, the implemented design allowed for the generation of an effective vaccine candidate. Our proposal could be used to express the domains or fragments of antigenic proteins, whose structural complexity does not allow for low-cost production in Escherichia coli. Hence, other antigen domains could be integrated into the TNV backbone for suitable antigenicity and immunogenicity. This work represents new biotechnological strategies, with a reduction in the costs associated with vaccine development.

Maize Lethal Necrosis: An Emerging, Synergistic Viral Disease.

Maize lethal necrosis (MLN) is a disease of maize caused by coinfection of maize with maize chlorotic mottle virus (MCMV) and one of several viruses from the Potyviridae, such as sugarcane mosaic virus, maize dwarf mosaic virus, Johnsongrass mosaic virus or wheat streak mosaic virus. The coinfecting viruses act synergistically to result in frequent plant death or severely reduce or negligible yield. Over the past eight years, MLN has emerged in sub-Saharan East Africa, Southeast Asia, and South America, with large impacts on smallholder farmers. Factors associated with MLN emergence include multiple maize crops per year, the presence of maize thrips ( Frankliniella williamsi), and highly susceptible maize crops. Soil and seed transmission of MCMV may also play significant roles in development and perpetuation of MLN epidemics. Containment and control of MLN will likely require a multipronged approach, and more research is needed to identify and develop the best measures.

Positive selection, molecular recombination structure and phylogenetic reconstruction of members of the family Tombusviridae: implication in virus taxonomy

A detailed study of putative recombination events and their evolution frequency in the whole genome of the currently known members of the family Tombusviridae, comprising 79 accessions retrieved from the international databases, was carried out by using the RECCO and RDP version 3.31β algorithms. The first program allowed the detection of potential recombination sites in seven out of eight virus genera (Aureusvirus, Avenavirus, Carmovirus, Dianthovirus, Necrovirus, Panicovirus, and Tombusvirus), the second program provided the same results except for genus Dianthovirus. On the other hand, both methods failed to detect recombination breakpoints in the genome of members of genus Machlomovirus. Furthermore, based on Fisher's Exact Test of Neutrality, positive selection exerted on protein-coding genes was detected in 17 accession pairs involving 15 different lineages. Except genera Machlomovirus, and Panicovirus along with unclassified Tombusviridae, all the other taxonomical genera and the unassigned Tombusviridae encompassed representatives under positive selection. The evolutionary history of all members of the Tombusviridae family showed that they segregated into eight distinct groups corresponding to the eight genera which constitute this family. The inferred phylogeny reshuffled the classification currently adopted by the International Committee on Taxonomy of Viruses. A reclassification was proposed.