The RNA genome of respiratory syncytial virus (RSV) is constitutively encapsidated by the viral nucleoprotein N, thus forming a helical nucleocapsid. Polymerization of N along the genomic and antigenomic RNAs is concomitant to replication and requires the preservation of an unassembled monomeric nucleoprotein pool. To this end, and by analogy with Paramyxoviridae and Rhabdoviridae, it is expected that the viral phosphoprotein P acts as a chaperone protein, forming a soluble complex with the RNA-free form of N (N 0 -P complex). Here, we have engineered a mutant form of N that is monomeric, is unable to bind RNA, still interacts with P, and could thus mimic the N 0 monomer. We used this N mutant, designated N mono , as a substitute for N 0 in order to characterize the P regions involved in the N 0 -P complex formation. Using a series of P fragments, we determined by glutathione S-transferase (GST) pulldown assays that the N and C termini of P are able to interact with N mono . We analyzed the functional role of amino-terminal residues of P by site-directed mutagenesis, using an RSV polymerase activity assay based on a human RSV minireplicon, and found that several residues were critical for viral RNA synthesis. Using GST pulldown and surface plasmon resonance assays, we showed that these critical residues are involved in the interaction between P[1-40] peptide and N mono in vitro. Finally, we showed that overexpression of the peptide P[1-29] can inhibit the polymerase activity in the context of the RSV minireplicon, thus demonstrating that targeting the N 0 -P interaction could constitute a potential antiviral strategy. IMPORTANCERespiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants. Since no vaccine or efficient antiviral treatment is available against RSV, it is essential to better understand how the viral machinery functions in order to develop new antiviral strategies. RSV phosphoprotein P, the main RNA polymerase cofactor, is believed to function as a chaperon protein, maintaining N as a nonassembled, RNA-free protein (N 0 ) competent for RNA encapsidation. In this paper, we provide the first evidence, to our knowledge, that the N terminus of P contains a domain that binds specifically to this RNA-free form of N. We further show that overexpression of a small peptide spanning this region of P can inhibit viral RNA synthesis. These findings extend our understanding of the function of RSV RNA polymerase and point to a new target for the development of drugs against this virus. T he human respiratory syncytial virus (HRSV) is the leading cause of severe respiratory tract infections in newborn children worldwide (1). HRSV infects close to 100% of infants within the first 2 years of life and is the main cause of bronchiolitis. It is also recognized as a significant cause of severe respiratory infections in the elderly. The virus belongs to the Mononegavirales order and constitutes the prototype virus of the Pneumovirus genus of the Paramyxoviridae family. As f...

ObjectivePancreatic cancer is associated with an abundant stromal reaction leading to immune escape and tumour growth. This massive stroma drives the immune escape in the tumour. We aimed to study the impact of βig-h3 stromal protein in the modulation of the antitumoural immune response in pancreatic cancer.DesignWe performed studies with p48-Cre;KrasG12D, pdx1-Cre;KrasG12D;Ink4a/Arffl/fl, pdx1-Cre;KrasG12D; p53R172H mice and tumour tissues from patients with pancreatic ductal adenocarcinoma (PDA). Some transgenic mice were given injections of anti-βig-h3, anti-CD8, anti-PD1 depleting antibodies. Tumour growth as well as modifications in the activation of local immune cells were analysed by flow cytometry, immunohistochemistry and immunofluorescence. Tissue stiffness was measured by atomic force microscopy.ResultsWe identified βig-h3 stromal-derived protein as a key actor of the immune paracrine interaction mechanism that drives pancreatic cancer. We found that βig-h3 is highly produced by cancer-associated fibroblasts in the stroma of human and mouse. This protein acts directly on tumour-specific CD8+ T cells and F4/80 macrophages. Depleting βig-h3 in vivo reduced tumour growth by enhancing the number of activated CD8+ T cell within the tumour and subsequent apoptotic tumour cells. Furthermore, we found that targeting βig-h3 in established lesions released the tissue tension and functionally reprogrammed F4/80 macrophages in the tumour microenvironment.ConclusionsOur data indicate that targeting stromal extracellular matrix protein βig-h3 improves the antitumoural response and consequently reduces tumour weight. Our findings present βig-h3 as a novel immunological target in pancreatic cancer.