Expression of AXL receptor tyrosine kinase relates to monocyte dysfunction and severity of cirrhosis

Infectious complications in patients with cirrhosis frequently initiate episodes of decompensation and substantially contribute to the high mortality. Mechanisms of the underlying immuneparesis remain underexplored. TAM receptors (TYRO3/AXL/MERTK) are important inhibitors of innate immune responses. To understand the pathophysiology of immuneparesis in cirrhosis, we detailed TAM receptor expression in relation to monocyte function and disease severity prior to the onset of acute decompensation. TNF-α/IL-6 responses to lipopolysaccharide were attenuated in monocytes from patients with cirrhosis (n = 96) compared with controls (n = 27) and decreased in parallel with disease severity. Concurrently, an AXL-expressing (AXL+) monocyte population expanded. AXL+ cells (CD14+CD16highHLA-DRhigh) were characterised by attenuated TNF-α/IL-6 responses and T cell activation but enhanced efferocytosis and preserved phagocytosis of Escherichia coli. Their expansion correlated with disease severity, complications, infection, and 1-yr mortality. AXL+ monocytes were generated in response to microbial products and efferocytosis in vitro. AXL kinase inhibition and down-regulation reversed attenuated monocyte inflammatory responses in cirrhosis ex vivo. AXL may thus serve as prognostic marker and deserves evaluation as immunotherapeutic target in cirrhosis

Salmonella Typhi Porins OmpC and OmpF Are Potent Adjuvants for T-Dependent and T-Independent Antigens

Several microbial components, such as bacterial DNA and flagellin, have been used as experimental vaccine adjuvants because of their inherent capacity to efficiently activate innate immune responses. Likewise, our previous work has shown that the major Salmonella Typhi (S. Typhi) outer membrane proteins OmpC and OmpF (porins) are highly immunogenic protective antigens that efficiently stimulate innate and adaptive immune responses in the absence of exogenous adjuvants. Moreover, S. Typhi porins induce the expression of costimulatory molecules on antigen-presenting cells through toll-like receptor canonical signaling pathways. However, the potential of major S. Typhi porins to be used as vaccine adjuvants remains unknown. Here, we evaluated the adjuvant properties of S. Typhi porins against a range of experimental and clinically relevant antigens. Co-immunization of S. Typhi porins with ovalbumin (OVA), an otherwise poorly immunogenic antigen, enhanced anti-OVA IgG titers, antibody class switching, and affinity maturation. This adjuvant effect was dependent on CD4+ T-cell cooperation and was associated with an increase in IFN-γ, IL-17A, and IL-2 production by OVA-specific CD4+ T cells. Furthermore, co-immunization of S. Typhi porins with an inactivated H1N1 2009 pandemic influenza virus experimental vaccine elicited higher hemagglutinating anti-influenza IgG titers, antibody class switching, and affinity maturation. Unexpectedly, co-administration of S. Typhi porins with purified, unconjugated Vi capsular polysaccharide vaccine (Vi CPS)—a T-independent antigen—induced higher IgG antibody titers and class switching. Together, our results suggest that S. Typhi porins OmpC and OmpF are versatile vaccine adjuvants, which could be used to enhance T-cell immune responses toward a Th1/Th17 profile, while improving antibody responses to otherwise poorly immunogenic T-dependent and T-independent antigens

Dendritic cell-specific delivery of Flt3L by coronavirus vectors secures induction of therapeutic antitumor immunity

Efficacy of antitumor vaccination depends to a large extent on antigen targeting to dendritic cells (DCs). Here, we assessed antitumor immunity induced by attenuated coronavirus vectors which exclusively target DCs in vivo and express either lymphocyte- or DC-activating cytokines in combination with a GFP-tagged model antigen. Tracking of in vivo transduced DCs revealed that vectors encoding for Fms-like tyrosine kinase 3 ligand (Flt3L) exhibited a higher capacity to induce DC maturation compared to vectors delivering IL-2 or IL-15. Moreover, Flt3L vectors more efficiently induced tumor-specific CD8(+) T cells, expanded the epitope repertoire, and provided both prophylactic and therapeutic tumor immunity. In contrast, IL-2- or IL-15-encoding vectors showed a substantially lower efficacy in CD8(+) T cell priming and failed to protect the host once tumors had been established. Thus, specific in vivo targeting of DCs with coronavirus vectors in conjunction with appropriate conditioning of the microenvironment through Flt3L represents an efficient strategy for the generation of therapeutic antitumor immunity

Divergent memory responses driven by adenoviral vectors are impacted by epitope competition

Adenoviral vectors induce robust epitope-specific CD8+ T cell responses. Within the repertoire of responses generated both conventional memory evolution and the phenomenon of memory inflation are seen. The rules governing which epitopes inflate are not fully known, but may include a role for both antigen processing and competition. To investigate this we looked at memory generated from vectors targeting the Gp33-41 (KAVYNFATC/K9C) epitope from the glycoprotein of Lymphocytic Choriomeningitis Virus (LCMV) in mice. This well described epitope has both the Gp33-41 and Gp34-41 epitopes embedded within it. Vaccination with a full-length glycoprotein (Gp) or a minigene Ad-Gp33/K9C vector induced conventional memory responses against the immunodominant Gp33/K9C epitope but a strong inflationary response against the Gp34/A8C epitope. These responses showed sustained in vivo function, with complete protection against LCMV infectious challenge. Given the unexpected competition between epitopes seen in the minigene model we further tested epitope competition using the full-length Ad-LacZ (β-galactosidase) model. Generation of an Ad-LacZ vector with a single amino acid disruption of the inflationary β-gal96-103 /D8V epitope transformed the β-gal497-504 /I8V epitope from conventional to inflationary memory. This work collectively demonstrates the importance of epitope competition within adenoviral vector inserts and is of relevance to future studies using adenoviral vectored immunogens. This article is protected by copyright. All rights reserved

Central Nervous System Stromal Cells Control Local CD8(+) T Cell Responses during Virus-Induced Neuroinflammation

Stromal cells generate a complex cellular scaffold that provides specialized microenvironments for lymphocyte activation in secondary lymphoid organs. Here, we assessed whether local activation of stromal cells in the central nervous system (CNS) is mandatory to transfer immune recognition from secondary lymphoid organs into the infected tissue. We report that neurotropic virus infection in mice triggered the establishment of such stromal cell niches in the CNS. CNS stromal cell activation was dominated by a rapid and vigorous production of CC-motif chemokine receptor (CCR) 7 ligands CCL19 and CCL21 by vascular endothelial cells and adjacent fibroblastic reticular cell (FRC)-like cells in the perivascular space. Moreover, CCR7 ligands produced by CNS stromal cells were crucial to support recruitment and local re-activation of antiviral CD8+ T cells and to protect the host from lethal neuroinflammatory disease, indicating that CNS stromal cells generate confined microenvironments that control protective T cell immunity

Evolution of <i>Salmonella Typhi</i> outer membrane protein-specific T and B cell responses in humans following oral Ty21a vaccination: A randomized clinical trial

<div><p>Vaccination against complex pathogens such as typhoidal and non-typhoidal <i>Salmonella</i> requires the concerted action of different immune effector mechanisms. Outer membrane proteins (Omps) of <i>Salmonella</i> Typhi are potent immunogens, which elicit long-lasting and protective immunity. Here, we followed the evolution of <i>S</i>. Typhi OmpC and F-specific T and B cell responses in healthy volunteers after vaccination with the vaccine strain Ty21a. To follow humoral and cellular immune responses, pre- and post-vaccination samples (PBMC, serum and stool) collected from 15 vaccinated and 5 non-vaccinated individuals. Immunoglobulin levels were assessed in peripheral blood by enzyme-linked immunosorbent assay. B cell and T cell activation were analyzed by flow cytometry. We observed a significant increase of circulating antibody-secreting cells and maximal Omp-specific serum IgG titers at day 25 post vaccination, while IgA titers in stool peaked at day 60. Likewise, Omp-specific CD4⁺ T cells in peripheral blood showed the highest expansion at day 60 post vaccination, concomitant with a significant increase in IFN-γ and TNFα production. These results indicate that <i>S</i>. Typhi Omp-specific B cell responses and polyfunctional CD4⁺ T cell responses evolve over a period of at least two months after application of the live attenuated vaccine. Moreover, these findings underscore the potential of <i>S</i>. Typhi Omps as subunit vaccine components.</p><p><b>Trial registration:</b><a href="https://clinicaltrials.gov/ct2/show/ISRCTN18360696" target="_blank">ISRCTN18360696</a></p></div

Identification of activated B cells and antibody secreting cells in peripheral blood following Ty21a vaccination.

<p>PBMCs were collected from vaccinated or control (Ctrl) subjects at the indicated time points and analysis of different B cell populations was performed by flow cytometry. (A) Gating strategy for FACS analysis of activated B cells (ABC, blue) or antibody secreting cells (ASC, red). (B) Representative dot plots showing the proportions of ABC (CD20^hi CD71⁺) and ASC (CD20^- CD71⁺) in vaccinated and Ctrl individuals at the indicated time points. (C and D). Proportions of ABC and ASC in vaccinated and Ctrl individuals at the indicated time points. Dots represent individual values; bars indicate mean ± SEM. Statistical analysis was performed using one way ANOVA with Dunnett’s multiple comparison test for comparisons between individuals of the same group at different time points (pre- versus post-vaccination) (*, P< 0.05; **, P< 0.01).</p

Induction of anti-OmpC/F-specific porin antibodies in serum and stool after Ty21a vaccination.

<p>(A) IgM and (B) IgG, OmpC/F-specific antibody titers in serum samples from vaccinated subjects were analyzed by ELISA at the indicated time points after vaccination; participant numbers assigned according to increasing IgG reactivity. (C and D) Kinetics of anti-OmpC/F IgM (C) and IgG (D) antibody titers in vaccinated or control (Ctrl) individuals. Dots represent individual values; bars indicate mean ± SEM. (E) <i>S</i>. Typhi OmpC/F-specific IgA was determined from stool samples from vaccinated or Ctrl subjects by ELISA. Dots represent individual values; bars represent mean ± SEM. Statistical analysis was performed using one way ANOVA with Dunnett’s multiple comparison test for comparisons between individuals of the same group at different time points (pre- versus post-vaccination) (*, P< 0.05; **, P< 0.01 ***, P<0.001).</p