Epitope-specific immunity against Staphylococcus aureus coproporphyrinogen III oxidase.

Staphylococcus aureus represents a serious infectious threat to global public health and a vaccine against S. aureus represents an unmet medical need. We here characterise two S. aureus vaccine candidates, coproporphyrinogen III oxidase (CgoX) and triose phosphate isomerase (TPI), which fulfil essential housekeeping functions in heme synthesis and glycolysis, respectively. Immunisation with rCgoX and rTPI elicited protective immunity against S. aureus bacteremia. Two monoclonal antibodies (mAb), CgoX-D3 and TPI-H8, raised against CgoX and TPI, efficiently provided protection against S. aureus infection. MAb-CgoX-D3 recognised a linear epitope spanning 12 amino acids (aa), whereas TPI-H8 recognised a larger discontinuous epitope. The CgoX-D3 epitope conjugated to BSA elicited a strong, protective immune response against S. aureus infection. The CgoX-D3 epitope is highly conserved in clinical S. aureus isolates, indicating its potential wide usability against S. aureus infection. These data suggest that immunofocusing through epitope-based immunisation constitutes a strategy for the development of a S. aureus vaccine with greater efficacy and better safety profile.

CHIP ubiquitylates NOXA and induces its lysosomal degradation in response to DNA damage.

The BH3-only protein NOXA is a regulator of mitochondrial apoptosis by specifically antagonizing the anti-apoptotic protein MCL-1. Here we show that the E3 ubiquitin ligase CHIP controls NOXA stability after DNA damage. Our findings reveal that CHIP and MCL-1 are binding partners of NOXA and differentially define the fate of NOXA. Whereas NOXA is initially targeted to mitochondria upon MCL-1-binding, CHIP mediates ubiquitylation of cytosolic NOXA and promotes lysosomal degradation of NOXA, which is not bound by MCL-1. Our data indicate that MCL-1 defines NOXA abundance and its pro-apoptotic activity. Increased NOXA levels beyond this threshold are effectively removed by lysosomal protein degradation triggered via CHIP-mediated ubiquitylation. Together, these results shed new light on regulatory circuits controlling DNA damage response and identified the E3 ligase CHIP as a new molecular guardian, which restricts the cytosolic accumulation of NOXA upon genotoxic stress.

Tumour-infiltrating neutrophils counteract anti-VEGF therapy in metastatic colorectal cancer.

BACKGROUND: Immune infiltration is implicated in the development of acquired resistance to anti-angiogenic cancer therapy. We therefore investigated the correlation between neutrophil infiltration in metastasis of colorectal cancer (CRC) patients and survival after treatment with bevacizumab. Our study identifies CD177+ tumour neutrophil infiltration as an adverse prognostic factor for bevacizumab treatment. We further demonstrate that a novel anti-VEGF/anti-Ang2 compound (BI-880) can overcome resistance to VEGF inhibition in experimental tumour models. METHODS: A total of 85 metastatic CRC patients were stratified into cohorts that had either received chemotherapy alone (n = 39) or combined with bevacizumab (n = 46). Tumour CD177+ neutrophil infiltration was correlated to clinical outcome. The impact of neutrophil infiltration on anti-VEGF or anti-VEGF/anti-Ang2 therapy was studied in both xenograft and syngeneic tumour models by immunohistochemistry. RESULTS: The survival of bevacizumab-treated CRC patients in the presence of CD177+ infiltrates was significantly reduced compared to patients harbouring CD177- metastases. BI-880 treatment reduced the development of hypoxia associated with bevacizumab treatment and improved vascular normalisation in xenografts. Furthermore, neutrophil depletion or BI-880 treatment restored treatment sensitivity in a syngeneic tumour model of anti-VEGF resistance. CONCLUSIONS: Our findings implicate CD177 as a biomarker for bevacizumab and suggest VEGF/Ang2 inhibition as a strategy to overcome neutrophil associated resistance to anti-angiogenic treatment.