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Anabolic and catabolic signalling mediated via mTOR and AMPK have to be intrinsically coupled to mitochondrial functions for maintaining homeostasis and mitigate cellular/organismal stress. Although, glutamine is known to activate mTOR, if/how differential mitochondrial utilization of glutamine impinges on mTOR signalling is less explored. Mitochondrial SIRT4, which unlike other sirtuins is induced in a fed state, is known to inhibit catabolic signalling/pathways through AMPK-PGC1a/SIRT1-PPARa axis and negatively regulate glutamine metabolism via TCA cycle. However, physiological significance of SIRT4 functions during a fed state is still unknown. Here, we establish SIRT4 as key anabolic factor that activates TORC1 signalling and regulates lipogenesis, autophagy and cell proliferation. Mechanistically, we demonstrate that the ability of SIRT4 to inhibit anaplerotic conversion of glutamine to α-ketoglutarate potentiates TORC1. Interestingly, we also show that mitochondrial glutamine sparing or utilization is critical for differentially regulating TORC1 under fed and fasted conditions. Moreover, we conclusively show that differential expression of SIRT4 during fed and fasted states is vital for coupling mitochondrial energetics and glutamine utilization with anabolic pathways. These significant findings also illustrate that SIRT4 integrates nutrient inputs with mitochondrial retrograde signals to maintain a balance between anabolic and catabolic pathways.

Anabolic and catabolic signaling mediated via mTOR and AMPK (AMP-activated kinase) have to be intrinsically coupled to mitochondrial functions for maintaining homeostasis and mitigate cellular/organismal stress. Although glutamine is known to activate mTOR, whether and how differential mitochondrial utilization of glutamine impinges on mTOR signaling has been less explored. Mitochondrial SIRT4, which unlike other sirtuins is induced in a fed state, is known to inhibit catabolic signaling/pathways through the AMPK-PGC1α/SIRT1-peroxisome proliferator-activated receptor α (PPARα) axis and negatively regulate glutamine metabolism via the tricarboxylic acid cycle. However, physiological significance of SIRT4 functions during a fed state is still unknown. Here, we establish SIRT4 as key anabolic factor that activates TORC1 signaling and regulates lipogenesis, autophagy, and cell proliferation. Mechanistically, we demonstrate that the ability of SIRT4 to inhibit anaplerotic conversion of glutamine to α-ketoglutarate potentiates TORC1. Interestingly, we also show that mitochondrial glutamine sparing or utilization is critical for differentially regulating TORC1 under fed and fasted conditions. Moreover, we conclusively show that differential expression of SIRT4 during fed and fasted states is vital for coupling mitochondrial energetics and glutamine utilization with anabolic pathways. These significant findings also illustrate that SIRT4 integrates nutrient inputs with mitochondrial retrograde signals to maintain a balance between anabolic and catabolic pathways.

For the development of a therapeutic vaccine against human papillomavirus (HPV), viral epitopes bona fide presented on the surface of HPV-transformed cells need to be identified. The constitutively expressed HPV oncoproteins E6 and E7 represent ideal targets for immunotherapeutic vaccination approaches. However, viral epitopes are low abundant and human leukocyte antigen (HLA)-restricted, posing a challenge for developing peptide-based vaccines. For the identification of novel epitopes, in silico HLA-binding prediction was used to preselect HPV16 E6- and E7-derived peptides for 7 major HLA-types representing 5 HLA supertypes. Based on performance evaluation of predictors, new individual binding affinity thresholds were applied. HLA-binding of synthesized predicted binders was validated in vitro in competitive cellular binding assays. Interferon-γ ELISpot assays performed with blood samples from HLA-characterized healthy donors identified memory T cell responses against HLA-binding HPV peptides. T cells of responding donors were further characterized for epitope-specific mediation of specific target cell lysis by CD8+ CTLs using a flow cytometry based cytotoxicity assay. Complementary, an immunopeptidomics approach was used to determine the surface presentation of epitopes on HPV16-transformed cancer cells. Targeted liquid chromatography-mass spectrometry was capable of detecting epitopes predicted within the new individual affinity thresholds but missed by common thresholds. Completing the identification of bona fide target cell surface-presented E6- and E7-derived T cell epitopes will provide a map of targets for the development of a therapeutic vaccine to treat HPV16-induced malignancies.

For rational design of therapeutic vaccines, detailed knowledge about target epitopes that are endogenously processed and truly presented on infected or transformed cells is essential. Many potential target epitopes (viral or mutation-derived), are presented at low abundance. Therefore, direct detection of these peptides remains a challenge. This study presents a method for the isolation and LC-MS3-based targeted detection of low-abundant human leukocyte antigen (HLA) class-I-presented peptides from transformed cells. Human papillomavirus (HPV) was used as a model system, as the HPV oncoproteins E6 and E7 are attractive therapeutic vaccination targets and expressed in all transformed cells, but present at low abundance due to viral immune evasion mechanisms. The presented approach included preselection of target antigen-derived peptides by in silico predictions and in vitro binding assays. The peptide purification process was tailored to minimize contaminants after immunoprecipitation of HLA-peptide complexes, while keeping high isolation yields of low-abundant target peptides. The subsequent targeted LC-MS3 detection allowed for increased sensitivity, which resulted in successful detection of the known HLA-A2-restricted epitope E711–19 and ten additional E7-derived peptides on the surface of HPV16-transformed cells. T-cell reactivity was shown for all the 11 detected peptides in ELISpot assays, which shows that detection by our approach has high predictive value for immunogenicity. The presented strategy is suitable for validating even low-abundant candidate epitopes to be true immunotherapy targets.

Human papillomavirus type 16 (HPV16) is a causal factor of ~50% of cervical cancers, and of ~95% of extra-cervical (other anogenital and oropharyngeal) HPV-mediated cancers. The aim of our group is to develop a therapeutic vaccine against HPV16-induced malignancies. To find optimal vaccine antigens, it is important to assess the effect of the tumor microenvironment on viral antigen presentation. Hypoxia has been reported to regulate HLA class-I expression levels in the context of various tumors. Thus, the aim of the present study was to explore the effect of hypoxia on various components of the antigen processing machinery (APM) in HPV16-positive tumor cells and on the HPV16 E6- and E7-derived HLA class-I epitope repertoire. We are investigating the effect of hypoxia on cervical cancer cells transformed with HPV16 variant lineages (European, Asian-American and African) correlated with differences in oncogenic potential. This is achieved by comparing cells cultured under hypoxia (1.2% O2) or normoxia (21% O2). We investigate E6 protein levels by immunoblotting and HLA-A2 surface expression by flow cytometry. Subsequently, quantitative PCR and immunoblotting are used to assess whether components of the APM are affected by hypoxia. Cervical cancer cell lines transformed by sublineages of the HPV16 European variant (CaSki and SNU17) showed a decrease in E6 protein levels upon hypoxic treatment. HLA-A2 levels were increased in SNU17 cells (HPV16 European Asian prototype), but no change was observed in CaSki cells (European Prototype 2). First qPCR experiments of SNU17 cells showed changes in additional components of the APM at the mRNA level, which still have to be assessed at the protein level. Cell lines transformed by HPV16 variants other than European will be subjected to the same analysis. Potential changes in the HPV16 epitope repertoire will be investigated using a targeted mass spectrometry-based epitope detection strategy established in the lab. These investigations may yield novel insights into HPV16 immune evasion pathways. Furthermore, the identification of epitopes that are presented under both normoxic and hypoxic conditions will provide optimal candidates for therapeutic vaccine design against HPV-induced malignancies. Citation Format: Nitya Mohan, Maria Bonsack, Jonas Förster, Alina Steinbach, Renata Blatnik, Mogjiborahman Salek, Angelika B. Riemer. Investigation of the effect of hypoxia on presentation of HPV16-derived antigens - implications for therapeutic vaccine design [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 578.

For rational therapeutic vaccine design, detailed knowledge about target epitopes that are truly presented on cancer cells is essential. Many potential tumor-specific epitopes, such as viral epitopes or mutation-derived neoepitopes, are presented at low abundance. Thus, detection of these epitopes remains a challenge. We have developed a high-sensitivity targeted mass spectrometry (MS) approach for direct detection of low-abundant epitopes. We used human papillomavirus (HPV) as a model system, as high-risk HPVs cause over 600,000 cervical, anogenital and oropharyngeal cancer cases per year. Moreover, the HPV oncoproteins E6 and E7 are essential for the induction and maintenance of the malignant phenotype, and thus are ideal targets for immunotherapy. Potential HPV16 E6 and E7 target epitopes were predicted in silico and their HLA-binding verified in cellular binding assays. HLA-peptide complexes were immunoprecipitated from HPV16-positive cancer cells and the purified peptides were analyzed by MS. Identified HPV epitopes were assessed for immunogenicity in vitro with PBMC from healthy donors and in vivo in the MHC-humanized mouse model A2.DR1. The binding assays resulted in the identification of known and novel HPV16-derived HLA-binding peptides. Furthermore, we used this data to formulate rules on how to optimally use epitope prediction tools to increase the chances of predicting true HLA ligands. 14 HLA-A2-restricted HPV16 epitopes were detected on the surface of CaSki and 866 cervical cancer cells, 9 of which were novel. 13 out of the 14 MS-detected peptides were immunogenic in ELISpot assays. Vaccination of A2.DR1 mice with one selected epitope induced high numbers of specific cytotoxic T-cells, and caused anti-tumor effects in a newly developed HPV16 E6/E7-expressing A2.DR1-compatible tumor model. We conclude that our epitope detection and validation approach is suitable for validating even low-abundant candidate epitopes to be true immunotherapy targets. MS-detection of epitopes appears to be a good predictor of immunogenicity, which makes this approach an attractive platform for determining target epitopes for therapeutic cancer vaccines. Citation Format: Sebastian Kruse, Maria Bonsack, Sara Becker, Nitya Mohan, Alina Steinbach, Stephanie Hoppe, Renata Blatnik, Angelika B. Riemer. Development of a therapeutic HPV vaccine based on mass spectrometry-verified target epitopes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 721.

In the context of the targets for primary health identified by the MDGs this article evaluates the link between decentralisation and positive outcomes for women and children. Using India as a case study, the article traces the changes in health attainments as a result of decentralisation reforms. The evidence presented, drawn from the experiences of two states, speaks to the relevance of such a link. Despite the heterogeneity of contexts and in implementation, in general democratic decentralisation has enhanced health outcomes for women in the selected village Panchayats. However, the article unearths significant differences in the impacts of decentralisation between the two states. The variations in outcomes between the two states are found to be linked to the architecture of decentralisation design as well as to ‘non-statutory’ provisions that can create a process of path-dependency towards achieving MDGs. The article also flags key methodological complexities inherent in the current MDG framework with respect to the actualization of the goals of equity and access to primary health.