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

Using genomics to examine the persistence of Streptococcus pneumoniae serotype 19A in Ireland and the emergence of a sub-clade associated with vaccine failures

Background Streptococcus pneumoniae serotype 19A remains a significant cause of invasive pneumococcal disease (IPD) in Ireland despite the successful introduction of a 13-valent pneumococcal conjugate vaccine (PCV13) in 2010 which reduced the overall incidence of IPD in children. Methods Invasive Streptococcus pneumoniae serotype 19A isolates from the Irish reference laboratory between 2007–08 and 2017–18 were analysed using whole genome sequencing (WGS) to investigate the persistence of this vaccine-preventable serotype. We compared the entire national 19A collection to other international collections using a standardised nomenclature of Global Pneumococcal Sequencing Clusters (GPSC). Results Expansion of GPSCs and clonal complexes (CCs) may have been associated with vaccine introduction and antimicrobial prescribing policies. A sub-clade of GPSC1-CC320 (n = 25) unique to Ireland, included five of the ten vaccine failures/breakthrough cases identified (p = 0.0086). This sub-clade was not observed in a global GPSC1-CC320 collection. All isolates within the sub-clade (n = 25) contained a galE gene variant rarely observed in a global pneumococcal collection (n = 37/13454, p < 0.001) nor within GPSC1-CC320 (n = 19/227) (p < 0.001). The sub-clade was estimated to have emerged at the start of the PCV-vaccine era (ancestral origin 2000, range 1995–2004) and expanded in Ireland, with most isolated after PCV13 introduction (n = 24/25). Conclusions The identification of a sub-clade/variant of serotype 19A highlights the benefit of using WGS to analyse genotypes associated with persistence of a preventable serotype of S. pneumoniae. Particularly as this sub-clade identified was more likely to be associated with IPD in vaccinated children than other 19A genotypes. It is possible that changes to the galE gene, which is involved in capsule production but outside of the capsular polysaccharide biosynthesis locus, may affect bacterial persistence within the population. Discrete changes associated with vaccine-serotype persistence should be further investigated and may inform vaccine strategies

International links between Streptococcus pneumoniae vaccine serotype 4 sequence type (ST) 801 in Northern European shipyard outbreaks of invasive pneumococcal disease

Background: Pneumococcal disease outbreaks of vaccine preventable serotype 4 sequence type (ST)801 in shipyards have been reported in several countries. We aimed to use genomics to establish any international links between them. Methods: Sequence data from ST801-related outbreak isolates from Norway (n = 17), Finland (n = 11) and Northern Ireland (n = 2) were combined with invasive pneumococcal disease surveillance from the respective countries, and ST801-related genomes from an international collection (n = 41 of > 40,000), totalling 106 genomes. Raw data were mapped and recombination excluded before phylogenetic dating. Results: Outbreak isolates were relatively diverse, with up to 100 SNPs (single nucleotide polymorphisms) and a common ancestor estimated around the year 2000. However, 19 Norwegian and Finnish isolates were nearly indistinguishable (0-2 SNPs) with the common ancestor dated around 2017. Conclusion: The total diversity of ST801 within the outbreaks could not be explained by recent transmission alone, suggesting that harsh environmental and associated living conditions reported in the shipyards may facilitate invasion of colonising pneumococci. However, near identical strains in the Norwegian and Finnish outbreaks does suggest that transmission between international shipyards also contributed to those outbreaks. This indicates the need for improved preventative measures in this working population including pneumococcal vaccination