RanDeL-Seq: a High-Throughput Method to Map Viral cis- and trans-Acting Elements

Defective viral genomes: advances in understanding their generation, function, and impact on infection outcomes

Defective viral genomes (DVGs) are truncated derivatives of their parental viral genomes generated during an aberrant round of viral genomic replication. Distinct classes of DVGs have been identified in most families of both positive- and negative-sense RNA viruses. Importantly, DVGs have been detected in clinical samples from virally infected individuals and an emerging body of association studies implicates DVGs in shaping the severity of disease caused by viral infections in humans. Consequently, there is growing interest in understanding the molecular mechanisms of de novo DVG generation, how DVGs interact with the innate immune system, and harnessing DVGs as novel therapeutics and vaccine adjuvants to attenuate viral pathogenesis. This minireview focuses on single-stranded RNA viruses (excluding retroviridae), and summarizes the current knowledge of DVG generation, the functions and diversity of DVG species, the roles DVGs play in influencing disease progression, and their application as antivirals and vaccine adjuvants.

Molecular evolution of methylesterase family genes and the BnMES34 is a positive regulator of Plasmodiophora brassicae stress response in Arabidopsis

Methylesterases (MES) are involved in hydrolysis of carboxylic esters, which have substantial roles in plant metabolic activities and defense mechanisms. This study aimed to comprehensively investigate Brassica napus BnMESs and characterize their role in response to Plasmodiophora brassicae stress. Forty-four BnMES members were identified and categorized into three groups based on their phylogenetic relationships and structural similarities. Through functional predictions in the promoter regions and analysis of RNA-Seq data, BnMES emerged as pivotal in growth, development, and stress responses to B. napus, particularly BnMES34, was strongly induced in response to P. brassicae infection. Gene Ontology analyses highlighted BnMES34's role in regulation of plant disease resistance responses. Furthermore, overexpression of BnMES34 in A. thaliana exhibited milder clubroot symptoms, and reduced disease indices, suggesting positive regulatory role of BnMES34 in plant's response to P. brassicae stress. Molecular docking and enzyme activity verification indicated that BnMES34 has the ability to generate salicylic acid via methyl salicylate, and further experimentally validated in vivo. This discovery indicates that the overexpression of BnMES34 in Arabidopsis confers resistance against clubroot disease. Overall, our research suggests that BnMES34 has a beneficial regulatory role in enhancing stress resistance to P. brassicae in B. napus.

Library-based analysis reveals segment and length dependent characteristics of defective influenza genomes

Found in a diverse set of viral populations, defective interfering particles are parasitic variants that are unable to replicate on their own yet rise to relatively high frequencies. Their presence is associated with a loss of population fitness, both through the depletion of key cellular resources and the stimulation of innate immunity. For influenza A virus, these particles contain large internal deletions in the genomic segments which encode components of the heterotrimeric polymerase. Using a library-based approach, we comprehensively profile the growth and replication of defective influenza species, demonstrating that they possess an advantage during genome replication, and that exclusion during population expansion reshapes population composition in a manner consistent with their final, observed, distribution in natural populations. We find that an innate immune response is not linked to the size of a deletion; however, replication of defective segments can enhance their immunostimulatory properties. Overall, our results address several key questions in defective influenza A virus biology, and the methods we have developed to answer those questions may be broadly applied to other defective viruses.

Identification of a therapeutic interfering particle-A single-dose SARS-CoV-2 antiviral intervention with a high barrier to resistance

Viral-deletion mutants that conditionally replicate and inhibit the wild-type virus (i.e., defective interfering particles, DIPs) have long been proposed as single-administration interventions with high genetic barriers to resistance. However, theories predict that robust, therapeutic DIPs (i.e., therapeutic interfering particles, TIPs) must conditionally spread between cells with R0 >1. Here, we report engineering of TIPs that conditionally replicate with SARS-CoV-2, exhibit R0 >1, and inhibit viral replication 10- to 100-fold. Inhibition occurs via competition for viral replication machinery, and a single administration of TIP RNA inhibits SARS-CoV-2 sustainably in continuous cultures. Strikingly, TIPs maintain efficacy against neutralization-resistant variants (e.g., B.1.351). In hamsters, both prophylactic and therapeutic intranasal administration of lipid-nanoparticle TIPs durably suppressed SARS-CoV-2 by 100-fold in the lungs, reduced pro-inflammatory cytokine expression, and prevented severe pulmonary edema. These data provide proof of concept for a class of single-administration antivirals that may circumvent current requirements to continually update medical countermeasures against new variants.