31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Influence of PAR flux and temperature on the flower bud abortion of rose (Rosa hybrida cv. Frisco) and the carbon balance of the shoot

The occurrence of flower bud abortion for rose, especially during winter, is attributed to a disequilibrium between the carbohydrate production in the sources and the demand for the assimilates in the sinks, caused by a low light intensity or a limitation of the translocation pattern. Manipulating the source and the sink strength by the light intensity and the translocation by temperature may lead to a reduction of flower abortion and an improved flower stem quality. An experiment was set up for roses (cv. Frisco) in 3 growth chambers of the Laboratory of Plant Ecology, including a control treatment (day/night temperature of 18116 degrees C and 300 mu mol-PAR), a low night temperature combined with high light intensity (18/12 degrees C; 300 mu mol PAR) and a low night temperature and low light intensity (18/12 degrees C; 100 mu mol-PAR). Measurements of the photosynthesis rate at shoot level (for a shoot length of 6 cm, 10 cm and 15 cm) and the carbohydrate content of several plant parts (also for different shoot lengths, corresponding with different developmental stages of the apex), as well as observations of the degree of abortion and the flower stem quality were performed. From the results, it was shown that the treatments influenced the rate of development of the shoot. The low night temperature, combined with the non-limiting light intensity enhanced the quality of the flower stem and decreased the abortion rate. Moreover, for a shoot length of ca. 10 cm (the critical stage of flower bud abortion), the quantum efficiency of the shoot and the carbohydrate content of the most mature leaf on the shoot were significantly higher than in the other treatments. The results support that a sufficient supply of carbohydrates during the critical stage for abortion, in combination with a high light intensity, which is known to enhance the sink strength, leads to a reduction of flower abortion and better flower stem quality

Optimising LAI in bent rose shoots

The arching technique for cut rose cultivation knew a great success due to a higher yield and a better quality of the flowering shoots. The success is generally attributed to a higher carbohydrate content supplied to the flowering stem by the bent photosynthesising leaves. However, the photosynthesis rate of shaded (and older) leaves diminishes. As a consequence the undermost bent stems might not contribute to the carbon gain, especially under low natural light intensities. In January, the photosynthetic photon flux density (PPFD) was measured above, in the middle of, and under the leaf mass of bent shoots of Rosa hybrida cv. Frisco. The measurements showed an exponential light extinction pattern. The leaf area index (LAI) of the bent shoots, simultaneously registered, varied from 1.5-2 in the middle leaf layer to 4-5 under the bent shoots. Photosynthesis rate was measured at different light intensities for leaves of the upper and the lower leaf level of the bent shoots. The saturated photosynthesis rate in the lower bent layer was reduced to ca. 15 % of the CO2 exchange measured for upper leaves of the bent shoots. The dark respiration rate diminished and the light compensation point increased in leaves of the lower bent layer. In light limited circumstances, the intensity in the lower layer can drop below the light compensation point. Hence, the carbon balance of the lower leaf layer can become negative. Mathematical upscaling of the leaf photosynthesis rate to bent canopy level revealed that the contribution of the lower bent layer to the total carbon gain of the bent shoots was negative. Hence, it might be better to restrict the LAI. Based on our results, an LAI ranging between 1 and 3.5 is advised for the bent rose shoots in order to optimise the amount of photosynthesising leaves on bent shoots

Developmental changes in carbohydrate content in young rose shoots (Rosa hybrida ‘Frisco’)

Changes of carbohydrate content of a developing rose shoot, submitted to different day-night temperature conditions were investigated. Two successive experiments were set up in four glasshouse compartments with young rose plants (Rosa hybrida 'Frisco'). The plants were submitted to four day/night temperature regimes (19.3/12 degreesC, 18/16 degreesC, 17.5/17.5 degreesC and 16/22 degreesC) maintaining a daily mean temperature of 17.5 degreesC. The plants were grown under a photoperiod of 18 hours. The experiment started at decapitation and ended when all shoots were harvested. The light integral was 148 MJ/m(2) for the first experiment and 307 MJ/m2 for the second experiment. Carbohydrate measurements (glucose, fructose, sucrose and starch) were performed on the entire uppermost shoots, source leaves and sink tissue. Four different developmental stages of the shoot bud were analysed: stage 1 - vegetative bud, stage 4 - petal differentiation, stage 5/6 - pistil and stamen differentiation and a harvestable flower stem. The results show that both developmental stages and light intensity have a strong impact on the carbohydrate level of the shoot and source leaf while temperature regime has no direct effect

Proteasome inhibition reduces superantigen-mediated T cell activation and the severity of psoriasis in a SCID-hu model

There is increasing evidence that bacterial superantigens contribute to inflammation and T cell responses in psoriasis. Psoriatic inflammation entails a complex series of inductive and effector processes that require the regulated expression of various proinflammatory genes, many of which require NF-κB for maximal trans-activation. PS-519 is a potent and selective proteasome inhibitor based upon the naturally occurring compound lactacystin, which inhibits NF-κB activation by blocking the degradation of its inhibitory protein IκB. We report that proteasome inhibition by PS-519 reduces superantigen-mediated T cell–activation in vitro and in vivo. Proliferation was inhibited along with the expression of very early (CD69), early (CD25), and late T cell (HLA-DR) activation molecules. Moreover, expression of E-selectin ligands relevant to dermal T cell homing was reduced, as was E-selectin binding in vitro. Finally, PS-519 proved to be therapeutically effective in a SCID-hu xenogeneic psoriasis transplantation model. We conclude that inhibition of the proteasome, e.g., by PS-519, is a promising means to treat T cell–mediated disorders such as psoriasis