Host-based processes as therapeutic targets for Rift Valley fever virus

In silico identification of novel pre-microRNA genes in Rift valley fever virus suggest new pathomechanisms for embryo-fetal dysgenesis

MicroRNAs (miRNAs) are small non-coding RNAs that regulate the post-transcriptional expression of target genes. Virus-encoded miRNAs play an important role in the replication of viruses, modulate gene expression in both the virus and host, and affect their persistence and immune evasion in hosts. This renders viral miRNAs as potential targets for therapeutic applications, especially against pathogenic viruses that infect humans and animals. Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic RNA virus that causes severe disease in both humans and livestock. High mortality among newborn lambs and abortion storms are key characteristics of an RVF outbreak. To date, limited information is available on RVFV-derived miRNAs. In this study, computational methods were used to analyse the RVFV genome for putative pre-miRNA genes, which were then analysed for the presence of mature miRNAs. We detected 19 RVFV-encoded miRNAs and identified their potential mRNAs targets in sheep (Ovis aries), the most susceptible host. The identification of significantly enriched O. aries genes in association with RVFV miRNAs will help elucidate the molecular mechanisms underlying RVFV pathogenesis and potentially uncover novel drug targets for RVFV.

An LIR motif in the Rift Valley fever virus NSs protein is critical for the interaction with LC3 family members and inhibition of autophagy

Rift Valley fever virus (RVFV) is a viral zoonosis that causes severe disease in ruminants and humans. The nonstructural small (NSs) protein is the primary virulence factor of RVFV that suppresses the host's antiviral innate immune response. Bioinformatic analysis and AlphaFold structural modeling identified four putative LC3-interacting regions (LIR) motifs (NSs 1-4) in the RVFV NSs protein, which suggest that NSs interacts with the host LC3-family proteins. Using, isothermal titration calorimetry, X-ray crystallography, co-immunoprecipitation, and co-localization experiments, the C-terminal LIR motif (NSs4) was confirmed to interact with all six human LC3 proteins. Phenylalanine at position 261 (F261) within NSs4 was found to be critical for the interaction of NSs with LC3, retention of LC3 in the nucleus, as well as the inhibition of autophagy in RVFV infected cells. These results provide mechanistic insights into the ability of RVFV to overcome antiviral autophagy through the interaction of NSs with LC3 proteins.

Use of Single-Domain Antibodies Against the NSm Protein for the Detection of Cells Infected by Rift Valley Fever Virus

Single-domain antibodies, referred to as VHH (variable heavy chains of heavy chain-only antibodies) or in their commercial name as nanobodies, are potent tools for the detection of target proteins in biological samples. They have the advantage of being highly stable, specific, and sensitive, with affinities reaching the nanomolar range. We utilized this tool to develop a rapid detection method that discriminates cells infected with Rift Valley fever virus (RVFV), based on the intracellular detection of the viral nonstructural NSm protein localized on the outer membrane of mitochondria. Here we describe how NSm-specific VHHs have been produced, cloned, and characterized, highlighting their value in RVFV research and diagnosis. This work may also raise interest in other potential applications such as antiviral therapy.

Exosome-Autophagy Crosstalk in Enveloped Virus Infection

Exosomes, which are extracellular vesicles (EVs) predominantly present in bodily fluids, participate in various physiological processes. Autophagy, an intracellular degradation mechanism, eliminates proteins and damaged organelles by forming double-membrane autophagosomes. These autophagosomes subsequently merge with lysosomes for target degradation. The interaction between autophagy and endosomal/exosomal pathways can occur at different stages, exerting significant influences on normal physiology and human diseases. The interplay between exosomes and the autophagy pathway is intricate. Exosomes exhibit a cytoprotective role by inducing intracellular autophagy, while autophagy modulates the biogenesis and degradation of exosomes. Research indicates that exosomes and autophagy contribute to the infection process of numerous enveloped viruses. Enveloped viruses, comprising viral nucleic acid, proteins, or virions, can be encapsulated within exosomes and transferred between cells via exosomal transport. Consequently, exosomes play a crucial role in the infection of certain viral diseases. This review presents recent findings on the interplay between exosomes and autophagy, as well as their implications in the infection of enveloped viruses, thereby offering valuable insights into the pathogenesis and vaccine research of enveloped virus infection.

A comprehensive review on the antiviral activities of chalcones

Some viral outbreaks have plagued the world since antiquity, including the most recent COVID-19 pandemic. The continuous spread and emergence of new viral diseases have urged the discovery of novel treatment options that can overcome the limitations of currently marketed antiviral drugs. Chalcones are natural open chain flavonoids that are found in various plants and can be synthesised in labs. Several studies have shown that these small organic molecules exert a number of pharmacological activities, including antiviral, anti-inflammatory, antimicrobial and anticancer. The purpose of this review is to provide a summary of the antiviral activities of chalcones and their derivatives on a set of human viral infections and their potential for targeting the most recent COVID-19 disease. Accordingly, we herein review chalcones activities on the following human viruses: Middle East respiratory syndrome coronavirus, severe acute respiratory syndrome coronavirus, human immunodeficiency, influenza, human rhinovirus, herpes simplex, dengue, human cytomegalovirus, hepatitis B and C, Rift Valley fever and Venezuelan equine encephalitis. We hope that this review will pave the way for the design and development of potentially potent and broad-spectrum chalcone based antiviral drugs.