Virologie et Immunologie Moléculaires

Vaccination is critical for the future of aquaculture, and nucleic acid vaccines have a major potential for fighting emerging fish infectious diseases, yet their mechanisms remain poorly understood. We compared B-cell responses induced by an mRNA, a DNA, and an attenuated vaccine, all encoding the same antigen against a fish rhabdovirus. Rainbow trout IgHμ repertoires were examined to investigate how vaccines reshape clonal composition and complexity of the B-cell repertoire. The attenuated virus drove protection through a small number of highly shared public clonotypes encoding neutralizing antibodies. The mRNA vaccine profoundly remodelled the repertoire in some individuals and induces low, but still protective, neutralising Ab titers without public expansions. The DNA vaccine induced high neutralizing Ab titers, providing full protection with minimal impact on B-cell repertoire. Clustering analysis revealed partial sharing of private responses between fish. These findings highlight profound divergences between fish B-cell responses to nucleic acid and attenuated vaccines whilst all of three vaccines induce protective responses.

Coronaviruses (CoVs) are emerging pathogens that have been extensively studied over the last twenty years and can cause acute respiratory diseases in humans, as exemplified by the SARS-CoV-2 pandemic. CoVs are also known for their importance in veterinary medicine and are responsible for severe pathologies in pets and livestock. These include feline infectious peritonitis virus (FIPV), which causes fatal disease in cats. In livestock, porcine CoVs such as transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhoea virus (PEDV) are the causative agents of acute enteric disease in piglets, which has a high mortality rate and a significant impact on the pork industry. In addition, animal CoVs may represent zoonotic reservoirs. Therefore, efficient antiviral strategies are needed to inhibit the replication of CoVs that infect various animal species. Here, we synthesized twenty small-molecule ligands that target cyclophilins, a family of cellular chaperones hijacked by several viruses, including CoVs. We screened their antiviral activity against feline and porcine α-CoVs and identified F83233 as a potent inhibitor of FIPV, TGEV and PEDV replication at micromolar concentrations that was effective in feline, porcine, and simian cells. As cyclophilins are highly conserved among mammals, F83233 could be a promising antiviral to treat different animal and zoonotic CoVs.

Members of the CD28 family are critical for the control of immune cell activation. While CD28 and CTLA4 were previously identified in teleost fish, most members of the CD28 family have been described only in tetrapods. Using a comparative genomics approach, we found (co)orthologs of all members of the CD28 family both in Chondrichthyes and basal Osteichthyes groups, but not in Agnathans. Four additional members of the family were identified, which were present in both Chondrichthyes and Osteichthyes, some even in the tetrapod lineage but all of them absent in human. Herein, we extend the composition of the jawed vertebrate CD28 family to nine members: CD28, CTLA4, ICOS, CD28H, CD28HL1, CD28HL2, CD28HL3, CD28X and PD-1. Each of these genes had a single extracellular IgSF V domain, and conserved motifs in the V and the cytoplasmic domain. While a genomic cluster of three consecutive genes like CD28/CTLA4/ICOS was conserved across jawed vertebrates except in teleosts, the other members of the CD28 family were located on multiple chromosomes. Our findings show that these co-stimulatory/co-inhibitory receptors likely arose in early jawed vertebrates, and diversified when the Ig/TCR/MHC-based adaptive immunity emerged, heralding the advent of complex regulatory networks controlling lymphocyte activation.

Abstract The use of synthetic microbial communities (SynComs) engineered to form positive biofilms that prevent the settlement of harmful bacteria is emerging as a promising strategy in biotechnology, particularly in reducing reliance on chemical antimicrobials. Despite this potential, the rationale for selecting specific strains in SynComs and the mechanisms underlying their antagonistic effects remains insufficiently understood. In this study, we present a bottom-up approach integrating live-cell imaging with high-throughput analysis of multi-strain biofilms across diverse scenarios. Through this method, we identified beneficial strains based on their superior ability to exclude undesirable bacteria and form mixed biofilms. Notably, our findings revealed that competitive strains against undesirable bacteria could also exclude other beneficial strains, emphasising the need for compatibility control in SynComs design. SynComs composed ofB. velezensisandPediococcusspp. demonstrated enhanced pathogen exclusion compared to single strains. Temporal analysis of biofilm interactions, supported by mathematical models, showed that pathogen exclusion was primarily driven by nutritional competition (Jameson effect) with additional specific interference mechanisms (prey-predator Lotka-Volterra model). Furthermore, pre-establishing SynComs to surfaces significantly increased pathogen inhibition, indicating a distinct biofilm-associated exclusion effect. These insights offer a framework for rational SynCom design and deepen our understanding of the mechanisms underpinning positive biofilm applications.Abstract Figure

Abstract An analysis that combined bioinformatics, comparative sequence/structural analysis, and experimental assays has been completed on respiratory syncytial virus (RSV). Both the genomic RNA and its reverse complement were studied using the novel bioinformatics pipeline ScanFold, which predicted 49 regions on RSV RNAs that appear to encode functional secondary structures (based on their unusually stable sequence order). Multiple motifs appear to be conserved between RSV and related virus strains, including one region within the F gene, which had a highly favorable overall prediction metric of a paired secondary structure. This motif was subjected to additional experimental analyses using SHAPE analysis to confirm ScanFold predicted secondary structure. In subsequent analysis, RSV F mRNA transcripts were made by in vitro transcription using T7 polymerase and transcripts which relaxed the predicted secondary structure yielded slightly higher mRNA transcripts and protein expression levels as wildtype F. However, using reverse genetics for comparison of viruses containing wildtype or relaxed F suggested that the predicted secondary structures may be critical for RSV replication in cells. To our knowledge, this is the first study to examine conserved RNA structures across multiple RSV strains and may help identify potential therapeutic targets to inhibit.

Conventional immunosuppressants are ineffective for the management of EGPA-related asthma. Tezepelumab is a human monoclonal antibody that inhibits thymic stromal lymphopoietin (TLSP) that has proven efficacy in several phase 3 studies for the treatment of asthma. We treated with off-label tezepelumab the first two patients with severe refractory EPGA-related asthma. These preliminary findings suggest that targeting upstream signaling of the T2 inflammatory pathway can improve symptoms, reduce BVAS and increase Asthma Control Test scores, even in patients with refractory asthma who have failed several previous lines of treatment. Nevertheless, by analogy with dupilumab-induced IL-4/13 blockade, the persistence of sputum eosinophilia (reported in both patients) raises questions as to whether TSLP inhibition could lead to a rebound of eosinophilia and potentially to eosinophil-related symptoms in patients with EGPA.

Equine influenza virus (EIV) remains a threat to horses, despite the availability of vaccines. Strategies to monitor the virus and prevent potential vaccine failure revolve around serological assays, RT-qPCR amplification, and sequencing the viral hemagglutinin (HA) and neuraminidase (NA) genes. These approaches overlook the contribution of other viral proteins in driving virulence. This study assesses the potential of long-read nanopore sequencing for fast and precise sequencing of circulating equine influenza viruses. Therefore, two French Florida Clade 1 strains, including the one circulating in winter 2018–2019 exhibiting more pronounced pathogenicity than usual, as well as the two currently OIE-recommended vaccine strains, were sequenced. Our results demonstrated the reliability of this sequencing method in generating accurate sequences. Sequence analysis of HA revealed a subtle antigenic drift in the French EIV strains, with specific substitutions, such as T163I in A/equine/Paris/1/2018 and the N188T mutation in post-2015 strains; both substitutions were in antigenic site B. Antigenic site E exhibited modifications in post-2018 strains, with the N63D substitution. Segment 2 sequencing also revealed that the A/equine/Paris/1/2018 strain encodes a longer variant of the PB1-F2 protein when compared to other Florida clade 1 strains (90 amino acids long versus 81 amino acids long). Further biological and biochemistry assays demonstrated that this PB1-F2 variant has enhanced abilities to abolish the mitochondrial membrane potential ΔΨm and permeabilize synthetic membranes. Altogether, our results highlight the interest in rapidly characterizing the complete genome of circulating strains with next-generation sequencing technologies to adapt vaccines and identify specific virulence markers of EIV.