Human BDCA3+ dendritic cells (DCs) were suggested to be homologous to mouse CD8α+ DCs. We demonstrate that human BDCA3+ DCs are more efficient than their BDCA1+ counterparts or plasmacytoid DCs (pDCs) in cross-presenting antigen and activating CD8+ T cells, which is similar to mouse CD8α+ DCs as compared with CD11b+ DCs or pDCs, although with more moderate differences between human DC subsets. Yet, no specific marker was known to be shared between homologous DC subsets across species. We found that XC chemokine receptor 1 (XCR1) is specifically expressed and active in mouse CD8α+, human BDCA3+, and sheep CD26+ DCs and is conserved across species. The mRNA encoding the XCR1 ligand chemokine (C motif) ligand 1 (XCL1) is selectively expressed in natural killer (NK) and CD8+ T lymphocytes at steady-state and is enhanced upon activation. Moreover, the Xcl1 mRNA is selectively expressed at high levels in central memory compared with naive CD8+ T lymphocytes. Finally, XCR1−/− mice have decreased early CD8+ T cell responses to Listeria monocytogenes infection, which is associated with higher bacterial loads early in infection. Therefore, XCR1 constitutes the first conserved specific marker for cell subsets homologous to mouse CD8α+ DCs in higher vertebrates and promotes their ability to activate early CD8+ T cell defenses against an intracellular pathogenic bacteria.

Coronavirus disease 2019 (COVID-19) has rapidly become a global pandemic and no antiviral drug or vaccine is yet available for the treatment of this disease 1-3. Several clinical studies are ongoing to evaluate the efficacy of repurposed drugs that have demonstrated antiviral efficacy in vitro. Among these candidates, hydroxychloroquine (HCQ) has been given to thousands of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-the virus that causes COVID-19-worldwide but there is no definitive evidence that HCQ is effective for treating COVID-19 4-7. Here we evaluated the antiviral activity of HCQ both in vitro and in SARS-CoV-2-infected macaques. HCQ showed antiviral activity in African green monkey kidney cells (Vero E6) but not in a model of reconstituted human airway epithelium. In macaques, we tested different treatment strategies in comparison to a placebo treatment, before and after peak viral load, alone or in combination with azithromycin (AZTH). Neither HCQ nor the combination of HCQ and AZTH showed a significant effect on viral load in any of the analysed tissues. When the drug was used as a pre-exposure prophylaxis treatment, HCQ did not confer protection against infection with SARS-CoV-2. Our findings do not support the use of HCQ, either alone or in combination with AZTH, as an antiviral drug for the treatment of COVID-19 in humans. Infection with SARS-CoV-2 is characterized by initial mild disease associated with respiratory symptoms at the peak of viral replication 1,8. In some patients, a late severe immunological syndrome occurs 6-14 days after the onset of symptoms that may require intensive care and is responsible for most of the fatalities 1-3. HCQ has well-documented in vitro activity against various viruses 4 and has emerged as an active compound against SARS-CoV-2 in different screening programmes, including a library of 1,520 Food and Drug Administration (FDA)-approved compounds 5. In Vero E6 cells, HCQ has a 50% maximal effective concentration (EC 50) 5,9,10 that varies between 0.7 and 4 μM. It may inhibit viral transport in endosomes by alkalinizing the intra-organelle compartment 10,11 and affect glycosylation, as reported for other viruses 12. The drug may also act as an immunomodulatory agent 13,14. In patients with lupus, HCQ decreases the level of inflammatory cytokines 11,15,16 , which may be relevant for the treatment of COVID-19 2. Furthermore, it has been proposed that AZTH, which displays in vitro antiviral activity against SARS-COV-2 5,17 , could potentiate the efficacy of HCQ 6. On the basis of these properties, HCQ has been considered for the treatment of COVID-19, alone or in combination with AZTH 6,7. We and others have set up non-human primate (NHP) models of SARS-CoV-2 infection 18-20. Here we used cynomolgus macaques (Macaca fascicularis) to test different treatment strategies with HCQ, alone or in combination with AZTH, before or after the peak of viral replication. We also tested HCQ administration as pre-exposure prophylaxis treatment...

-Bluetongue (BT) virus, an orbivirus of the Reoviridae family encompassing 24 known serotypes, is transmitted to ruminants via certain species of biting midges (Culicoides spp.) and causes thrombo-hemorrhagic fevers mainly in sheep. During the 20th century, BTV was endemic in sub-tropical regions but in the last ten years, new strains of BTV (serotypes 1, 2, 4, 8, 9, 16) have appeared in Europe leading to a devastating disease in naive sheep and bovine herds (serotype 8). BTV enters into insect cells via the viral inner core VP7 protein and in mammalian cells via the external capsid VP2 haemagglutinin, which is the major determinant of BTV serotype and neutralization. BTV replicates in mononuclear phagocytes and endothelial cells where it induces expression of inflammatory cytokines as well as apoptosis. BTV can remain as nonreplicating entities concealed in erythrocytes for up to five months. Homologous protection against one BTV serotype involves neutralizing antibodies and T cell responses directed to the external VP2 and VP5 proteins, whereas heterologous protection is supported by T cells directed to the NS1 non structural protein and inner core proteins.

Material

Highlights d Two-component protein nanoparticles display multiple copies of the SARS-CoV-2 spike d Spike protein nanoparticles enhance cognate B cell activation in vitro d Vaccination induces potent neutralization in mice, rabbits, and cynomolgus macaques d Vaccination protects macaques against a high-dose SARS-CoV-2 challenge

Bluetongue virus (BTV) is the etiological agent of bluetongue, a hemorrhagic disease of ruminants (particularly sheep), which causes important economic losses around the world. BTV is transmitted primarily via the bites of infected midges, which inject the virus into the ruminant's skin during blood feeding. The virus initially replicates in the draining lymph node and then disseminates to secondary organs where it induces edema, hemorrhages, and necrosis. In this study, we show that ovine conventional dendritic cells (cDCs) are the primary targets of BTV that contribute to the primary dissemination of BTV from the skin to draining lymph nodes. Lymph cDCs support BTV RNA and protein synthesis, as well as the production of infectious virus belonging to several different BTV serotypes, regardless of their level of attenuation. Afferent lymph cell subsets, other than cDCs, showed only marginal levels of BTV protein expression. BTV infection provoked a massive recruitment of cDCs to the sheep skin and afferent lymph, providing cellular targets for infection. Although BTV productively infects cDCs, no negative impact on their physiology was detected. Indeed, BTV infection and protein expression in cDCs enhanced their survival rate. Several serotypes of BTV stimulated the surface expression of the CD80 and CD86 costimulatory molecules on cDCs as well as the mRNA synthesis of cytokines involved in inflammation and immunity, i.e., interleukin-12 (IL-12), IL-1␤, and IL-6. BTV-infected cDCs stimulated antigen-specific CD4 and CD8 proliferation as well as gamma interferon production. BTV initially targets cDCs while preserving their functional properties, reflecting the optimal adaptation of the virus to its host cells for its first spread.

The current pandemic of coronavirus disease (COVID) 2019 constitutes a global public health issue. Regarding the emerging importance of the gut-lung axis in viral respiratory infections, analysis of the gut microbiota's composition and functional activity during a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection might be instrumental in understanding and controling COVID 19. We used a nonhuman primate model (the macaque), that recapitulates mild COVID-19 symptoms, to analyze the effects of a SARS-CoV-2 infection on dynamic changes of the gut microbiota. 16S rRNA gene profiling and analysis of β diversity indicated significant changes in the composition of the gut microbiota with a peak at 10-13 days post-infection (dpi). Analysis of bacterial abundance correlation networks confirmed disruption of the bacterial community at 10-13 dpi. Some alterations in microbiota persisted after the resolution of the infection until day 26. Some changes in the relative bacterial taxon abundance associated with infectious parameters. Interestingly, the relative abundance of Acinetobacter (Proteobacteria) and some genera of the Ruminococcaceae family (Firmicutes) was positively correlated with the presence of SARS-CoV-2 in the upper respiratory tract. Targeted quantitative metabolomics indicated a drop in short-chain fatty acids (SCFAs) and changes in several bile acids and tryptophan metabolites in infected animals. The relative abundance of several taxa known to be SCFA producers (mostly from the Ruminococcaceae family) was negatively correlated with systemic inflammatory markers while the opposite correlation was seen with several members of the genus Streptococcus. Collectively, SARS-CoV-2 infection in a nonhuman primate is associated with changes in the gut microbiota's composition and functional activity.

Highlights d Two-component protein nanoparticles display multiple copies of the SARS-CoV-2 spike d Spike protein nanoparticles enhance cognate B cell activation in vitro d Vaccination induces potent neutralization in mice, rabbits, and cynomolgus macaques d Vaccination protects macaques against a high-dose SARS-CoV-2 challenge