Lack of PD-L1 Expression by iNKT Cells Improves the Course of Influenza A Infection

There is evidence indicating that invariant Natural Killer T (iNKT) cells play an important role in defense against influenza A virus (IAV). However, the effect of inhibitory receptor, programmed death-1 (PD-1), and its ligands, programmed death ligand (PD-L) 1 and 2 on iNKT cells in protection against IAV remains to be elucidated. Here we investigated the effects of these co-stimulatory molecules on iNKT cells in the response to influenza. We discovered that compare to the wild type, PD-L1 deficient mice show reduced sensitivity to IAV infection as evident by reduced weight loss, decreased pulmonary inflammation and cellular infiltration. In contrast, PD-L2 deficient mice showed augmented weight loss, pulmonary inflammation and cellular infiltration compare to the wild type mice after influenza infection. Adoptive transfer of iNKT cells from wild type, PD-L1 or PD-L2 deficient mice into iNKT cell deficient mice recapitulated these findings. Interestingly, in our transfer system PD-L1−/−-derived iNKT cells produced high levels of interferon-gamma whereas PD-L2−/−-derived iNKT cells produced high amounts of interleukin-4 and 13 suggesting a role for these cytokines in sensitivity to influenza. We identified that PD-L1 negatively regulates the frequency of iNKT cell subsets in the lungs of IAV infected mice. Altogether, these results demonstrate that lack of PD-L1 expression by iNKT cells reduces the sensitivity to IAV and that the presence of PD-L2 is important for dampening the deleterious inflammatory responses after IAV infection. Our findings potentially have clinical implications for developing new therapies for influenza

Inclusion of CD80 in HSV Targets the Recombinant Virus to PD-L1 on DCs and Allows Productive Infection and Robust Immune Responses

CD80 plays a critical role in stimulation of T cells and subsequent control of infection. To investigate the effect of CD80 on HSV-1 infection, we constructed a recombinant HSV-1 virus that expresses two copies of the CD80 gene in place of the latency associated transcript (LAT). This mutant virus (HSV-CD80) expressed high levels of CD80 and had similar virus replication kinetics as control viruses in rabbit skin cells. In contrast to parental virus, this CD80 expressing recombinant virus replicated efficiently in immature dendritic cells (DCs). Additionally, the susceptibility of immature DCs to HSV-CD80 infection was mediated by CD80 binding to PD-L1 on DCs. This interaction also contributed to a significant increase in T cell activation. Taken together, these results suggest that inclusion of CD80 as a vaccine adjuvant may promote increased vaccine efficacy by enhancing the immune response directly and also indirectly by targeting to DC

Immune regulation by allergen immunotherapy : lessons learned from experimental approaches

Veel allergische aandoeningen kunnen onderdrukt worden. Er zijn echter nauwelijks medicijnen die de oorzaak van de ziekte aanpakken en die langdurig werkzaam zijn. Dat is ook het geval bij allergische astma. Omdat er over de oorzaak van deze ziekte weinig bekend is, zijn er geen goede medicijnen beschikbaar. Hadi Maazi en Soheila Shirinbak gingen op zoek naar de cellulaire mechanismen die aan allergische astma ten grondslag liggen. De inzichten die dit onderzoek opleverde kunnen wellicht helpen bij de ontwikkeling van een medicijn tegen allergische astma. Maazi en Shirinbak ontdekten dat FoxP3-positieve regulatoire T-cellen belangrijk zijn voor onderdrukking van de luchtwegontsteking die bij allergische astma een rol spelen. B-cellen, plasmacytoide dendritische cellen en CD8-positieve T-cellen daarentegen zijn niet vereist voor de onderdrukking van luchtwegontsteking, luchtweghyperreactiviteit en allergeen-specifiek IgE responsen. Eerder hadden Maazi en Shirinbak al ontdekt dat ook het cytokine IL-10 een belangrijke rol speelt bij de behandeling van allergische astma. In dit proefschrift brengen ze de precieze rol van dit cytokine in kaart. Tenslotte laten ze zien dat CTLA4-Ig en TGFβ de efficiëntie van de SIT behandeling sterk vergroten. In this PhD thesis we aimed to unravel the mechanism of action of SIT at cellular level on the one hand and find ways to improve the efficacy of SIT in the other hand in a mouse model of allergic asthma. We found that while FOXP3+ regulatory T cells play a role in SIT-induced suppression of airway eosinophilia, CD8+ T cells, B cells and plasmacytoid dendritic cells play dispensable roles in SIT-induced suppression of airway hyperreactivity, airway eosinophilia and allergen-specific IgE levels in the serum.

Programmed cell death ligand 2 regulates TH9 differentiation and induction of chronic airway hyperreactivity.

Our findings suggest that PD-L2 plays a pivotal role in the regulation of TH9 cell development in chronic AHR, providing novel strategies for modulating adaptive immunity during chronic allergic responses

Airway responsiveness, lung cells infiltration and OVA-specific IgE serum levels.

<p>Mice (n = 8) were sensitized with OVA/Alum and received a first series of 3 OVA inhalation challenges, during which TLR-2 agonist (20 µg per mouse in PBS) or PBS was administered intranasally 1 hour before challenge. After 3 weeks, mice received a second series of 3 inhalation challenges (OVA or PBS). Asthma manifestations were measured one day after the last challenge. A: Airway responsiveness to increasing doses of methacholine was measured by whole-body plethysmography and is expressed as enhanced pause (PenH) (gray symbols: PBS-challenged groups, white symbols: OVA-challenged groups, squares: Pam3Cys-treated groups, triangles: PBS-treated groups). B: total cell counts in the BAL of PBS and OVA-challenged mice as indicated. C: differential cell counts in the BAL of OVA-challenged mice only. D: OVA-specific IgE levels in pre-challenge and post-challenge sera of OVA-challenged mice. (E) Lung tissue cytokines measured in lung homogenates of PBS or Pam3Cys (P3C) treated mice after OVA challenge at timepoint 1 (left-hand panel) or at timepoint 2 (right-hand panel) as indicated. All values in panels A–D are displayed as average ± SEM, panel E displays individual values (dots)+mean (bar). Significance is indicated (*) when p<0.05.</p

Time schedule of the experimental procedures.

<p>Days of sensitization, OVA/PBS challenges, Pam3Cys/PBS treatments and lung function measurements/section are indicated for both the short protocol (A) and the long-term protocol (B).</p

Airway responsiveness, BAL cell counts and composition, and OVA-specific IgE serum levels.

<p>Mice (n = 8) were sensitized with OVA/Alum and received 4 OVA or PBS inhalation challenges. TLR-2 agonist (20 µg per mouse in PBS) or PBS was administered intranasally 1 hour before the 2 first challenges. Asthma manifestations were measured one day after the last challenge. A: Airway responsiveness to increasing doses of methacholine was measured by whole-body plethysmography and is expressed as enhanced pause (PenH) (gray symbols: PBS-challenged groups, white symbols: OVA-challenged groups, squares: Pam3Cys-treated groups, triangles: PBS-treated groups). B, C: total (B) and differential (C) cell counts in the BAL of PBS and OVA-challenged mice as indicated. D: OVA-specific IgE levels in the serum of PBS and OVA-challenged mice as indicated. All values are displayed as average ± SEM.</p

Airway responsiveness, lung cell infiltration and OVA-specific IgE serum levels.

<p>Mice (n = 8) were sensitized with OVA/Alum and received 3 OVA or PBS inhalation challenges. TLR-2 agonist (20 µg per mouse in PBS) or PBS was administered intranasally 1 hour before each challenge. Asthma manifestations were measured one day after the last challenge. A: Airway responsiveness to increasing doses of methacholine was measured by whole-body plethysmography and is expressed as enhanced pause (PenH) (gray symbols: PBS-challenged groups, white symbols: OVA-challenged groups, squares: Pam3Cys-treated groups, triangles: PBS-treated groups). B, C: total (B) and differential (C) cell counts in the BAL of OVA-challenged mice. D: OVA-specific IgE levels in the serum of OVA-challenged mice. (E) Lung tissue cytokines measured in lung homogenates of PBS or Pam3Cys (P3C) treated mice as indicated. All values are displayed as average ± SEM (panels A–D) or individual values (dots)+mean (bar) (panel E). Significance is indicated (*) when p<0.05.</p

Suppression of Th2-driven airway inflammation by allergen immunotherapy is independent of B cell and Ig responses in mice

Allergen-specific immunotherapy (IT) uniquely renders long-term relief from allergic symptoms and is associated with elevated serum levels of allergen-specific IgG and IgA. The allergen-specific IgG response induced by IT treatment was shown to be critical for suppression of the immediate phase of the allergic response in mice, and this suppression was partially dependent on signaling through Fc gamma RIIB. To investigate the relevance of the allergen-specific IgG responses for suppression of the Th2-driven late-phase allergic response, we performed IT in a mouse model of allergic asthma in the absence of FcgRIIB or Fc gamma RI/Fc gamma RIII signaling. We found that suppression of Th2 cell activity, allergic inflammation, and allergen-specific IgE responses is independent of Fc gamma RIIB and Fc gamma RI/Fc gamma RIII signaling. Moreover, we show that the IT-induced allergen-specific systemic IgG or IgA responses and B cell function are dispensable for suppression of the late-phase allergic response by IT treatment. Finally, we found that the secretory mucosal IgA response also is not required for suppression of the Th2-driven allergic inflammation by IT. These data are in contrast to the suppression of the immediate phase of the allergic response, which is critically dependent on the induced allergen-specific serum IgG response. Hence, IT-induced suppression of the immediate and late phases of the allergic response is governed by divergent and independent mechanisms. Our data show that the IT-induced suppression of the Th2 cell-dependent late-phase allergic response is independent of the allergen-specific IgG and IgA responses that are associated with IT treatment

A GWAS approach identifies Dapp1 as a determinant of air pollution-induced airway hyperreactivity.

Asthma is a chronic inflammatory disease of the airways with contributions from genes, environmental exposures, and their interactions. While genome-wide association studies (GWAS) in humans have identified ~200 susceptibility loci, the genetic factors that modulate risk of asthma through gene-environment (GxE) interactions remain poorly understood. Using the Hybrid Mouse Diversity Panel (HMDP), we sought to identify the genetic determinants of airway hyperreactivity (AHR) in response to diesel exhaust particles (DEP), a model traffic-related air pollutant. As measured by invasive plethysmography, AHR under control and DEP-exposed conditions varied 3-4-fold in over 100 inbred strains from the HMDP. A GWAS with linear mixed models mapped two loci significantly associated with lung resistance under control exposure to chromosomes 2 (p = 3.0x10-6) and 19 (p = 5.6x10-7). The chromosome 19 locus harbors Il33 and is syntenic to asthma association signals observed at the IL33 locus in humans. A GxE GWAS for post-DEP exposure lung resistance identified a significantly associated locus on chromosome 3 (p = 2.5x10-6). Among the genes at this locus is Dapp1, an adaptor molecule expressed in immune-related and mucosal tissues, including the lung. Dapp1-deficient mice exhibited significantly lower AHR than control mice but only after DEP exposure, thus functionally validating Dapp1 as one of the genes underlying the GxE association at this locus. In summary, our results indicate that some of the genetic determinants for asthma-related phenotypes may be shared between mice and humans, as well as the existence of GxE interactions in mice that modulate lung function in response to air pollution exposures relevant to humans