Influenza A Virus Infection of Human Primary Dendritic Cells Impairs Their Ability to Cross-Present Antigen to CD8 T Cells

Influenza A virus (IAV) infection is normally controlled by adaptive immune responses initiated by dendritic cells (DCs). We investigated the consequences of IAV infection of human primary DCs on their ability to function as antigen-presenting cells. IAV was internalized by both myeloid DCs (mDCs) and plasmacytoid DCs but only mDCs supported viral replication. Although infected mDCs efficiently presented endogenous IAV antigens on MHC class II, this was not the case for presentation on MHC class I. Indeed, cross-presentation by uninfected cells of minute amounts of endocytosed, exogenous IAV was ∼300-fold more efficient than presentation of IAV antigens synthesized by infected cells and resulted in a statistically significant increase in expansion of IAV-specific CD8 T cells. Furthermore, IAV infection also impaired cross-presentation of other exogenous antigens, indicating that IAV infection broadly attenuates presentation on MHC class I molecules. Our results suggest that cross-presentation by uninfected mDCs is a preferred mechanism of antigen-presentation for the activation and expansion of CD8 T cells during IAV infection

Aquaporin-3 regulates endosome-to-cytosol transfer via lipid peroxidation for cross presentation.

Antigen cross presentation, whereby exogenous antigens are presented by MHC class I molecules to CD8+ T cells, is essential for generating adaptive immunity to pathogens and tumor cells. Following endocytosis, it is widely understood that protein antigens must be transferred from endosomes to the cytosol where they are subject to ubiquitination and proteasome degradation prior to being translocated into the endoplasmic reticulum (ER), or possibly endosomes, via the TAP1/TAP2 complex. Revealing how antigens egress from endocytic organelles (endosome-to-cytosol transfer, ECT), however, has proved vexing. Here, we used two independent screens to identify the hydrogen peroxide-transporting channel aquaporin-3 (AQP3) as a regulator of ECT. AQP3 overexpression increased ECT, whereas AQP3 knockout or knockdown decreased ECT. Mechanistically, AQP3 appears to be important for hydrogen peroxide entry into the endosomal lumen where it affects lipid peroxidation and subsequent antigen release. AQP3-mediated regulation of ECT was functionally significant, as AQP3 modulation had a direct impact on the efficiency of antigen cross presentation in vitro. Finally, AQP3-/- mice exhibited a reduced ability to mount an anti-viral response and cross present exogenous extended peptide. Together, these results indicate that the AQP3-mediated transport of hydrogen peroxide can regulate endosomal lipid peroxidation and suggest that compromised membrane integrity and coordinated release of endosomal cargo is a likely mechanism for ECT

Primary cilia membrane assembly is initiated by Rab11 and transport protein particle II (TRAPPII) complex-dependent trafficking of Rabin8 to the centrosome

Sensory and signaling pathways are exquisitely organized in primary cilia. Bardet-Biedl syndrome (BBS) patients have compromised cilia and signaling. BBS proteins form the BBSome, which binds Rabin8, a guanine nucleotide exchange factor (GEF) activating the Rab8 GTPase, required for ciliary assembly. We now describe serum-regulated upstream vesicular transport events leading to centrosomal Rab8 activation and ciliary membrane formation. Using live microscopy imaging, we show that upon serum withdrawal Rab8 is observed to assemble the ciliary membrane in ∼100 min. Rab8-dependent ciliary assembly is initiated by the relocalization of Rabin8 to Rab11-positive vesicles that are transported to the centrosome. After ciliogenesis, Rab8 ciliary transport is strongly reduced, and this reduction appears to be associated with decreased Rabin8 centrosomal accumulation. Rab11-GTP associates with the Rabin8 COOH-terminal region and is required for Rabin8 preciliary membrane trafficking to the centrosome and for ciliogenesis. Using zebrafish as a model organism, we show that Rabin8 and Rab11 are associated with the BBS pathway. Finally, using tandem affinity purification and mass spectrometry, we determined that the transport protein particle (TRAPP) II complex associates with the Rabin8 NH2-terminal domain and show that TRAPP II subunits colocalize with centrosomal Rabin8 and are required for Rabin8 preciliary targeting and ciliogenesis

Eur J Gastroenterol Hepatol

OBJECTIVES: HIV/hepatitis C virus (HCV) co-infection leads to major complications, and noninvasive markers developed to stage liver fibrosis could be used as prognostic markers. We aimed to compare the performances of liver stiffness (LS), fibrosis-4 (FIB-4), and aspartate aminotransferase to platelet ratio index (APRI) to predict liver-related events in HIV/HCV co-infected patients. PATIENTS AND METHODS: HIV/HCV co-infected patients from the ANRS CO13 HEPAVIH cohort were included if they had LS, FIB-4, and APRI measurements done in a window of 3 months. Primary outcome was the time between inclusion and occurrence of a liver-related event. Univariable and multivariable Fine and Gray models were performed. Predictive performances were compared by the area under the receiver operating characteristic (AUROC) differences after correction of optimistic by bootstrap samples. Best cutoffs to predict liver-related events were estimated by sensitivity and specificity maximization. RESULTS: A total of 998 patients were included. Overall, 70.7% were men. Their median age was 46.8 years. According to LS value, 204 (20.4%) patients had cirrhosis. Overall, 39 patients experienced at least one liver-related event. In univariable analysis, LS AUROC curve was significantly superior to FIB-4 and APRI AUROC curves, being 87.9, 78.2, and 75.0%, respectively. After adjustment on age, CD4 levels, and insulin resistance, no differences were observed. The best cutoffs to identify patients at low or high risk of liver-related events were below 8.5, 1.00, and 0.35 and above 16.5, 4.00, and 1.75 for LS, FIB-4, and APRI, respectively. CONCLUSION: To predict HCV-related events, APRI had lower performance than LS and FIB-4. FIB-4 is as good as LS to predict HCV-related events, suggesting that it can be used for the management of HIV/HCV co-infected patients and replace LS

FRET Reagent Reveals the Intracellular Processing of Peptide-Linked Antibody–Drug Conjugates

Despite the recent success of antibody–drug conjugates (ADCs) in cancer therapy, a detailed understanding of their entry, trafficking, and metabolism in cancer cells is limited. To gain further insight into the activation mechanism of ADCs, we incorporated fluorescence resonance energy transfer (FRET) reporter groups into the linker connecting the antibody to the drug and studied various aspects of intracellular ADC processing mechanisms. When comparing the trafficking of the antibody–FRET drug conjugates in various different model cells, we found that the cellular background plays an important role in how the antigen-mediated antibody is processed. Certain tumor cells showed limited cytosolic transport of the payload despite efficient linker cleavage. Our FRET assay provides a facile and robust assessment of intracellular ADC activation that may have significant implications for the future development of ADCs

Direct, indirect and total effect of HIV coinfection on the risk of non-liver-related cancer in hepatitis C virus-infected patients treated by direct-acting antivirals: a mediation analysis

OBJECTIVES: HIV-coinfected patients experience higher incidences of non-liver-related cancers than HCV-monoinfected patients. Chronic inflammation, immunosuppression, but also higher tobacco or alcohol consumption and metabolic dysregulation could explain this higher risk. We aimed to estimate the direct, indirect and total effects of HIV coinfection on the risk of non-liver-related cancers in HCV participants treated with direct-acting antivirals (DAAs). METHODS: Up to four HCV-monoinfected participants from the ANRS CO22 HEPATHER cohort were matched by age and sex to HIV/HCV-coinfected participants from the ANRS CO13 HEPAVIH cohort. Participants were followed from DAA initiation until the occurrence of a non-liver-related cancer. Counterfactual mediation analysis was carried out to estimate the direct (chronic inflammation and immunosuppression), indirect (tobacco and alcohol consumption and metabolic syndrome) and total effect of HIV coinfection on the risk of non-liver-related cancers. RESULTS: 548 HIV/HCV-coinfected and 2016 monoinfected participants were included. Overall, HIV coinfection was associated with a 3.7-fold [95% confidence interval (CI): 1.7-7.0] higher risk of non-liver-related cancers in HCV participants. This increased risk was explained by significant direct effect [hazard ratio (HR) = 3.4, 95% CI: 1.7-6.6] but not indirect effect (HR = 1.1, 95% CI: 0.8-1.5) of HIV coinfection. CONCLUSIONS: In HCV participants treated with DAAs, the direct effect of HIV coinfection, reflecting chronic inflammation and immunosuppression, was associated with a 3.7-fold higher risk of non-liver-related cancer. By contrast, the indirect effect of HIV coinfection, reflecting higher tobacco and alcohol consumption and metabolic dysregulation, was not significantly associated with the risk of non-liver-related cancers

FRET Reagent Reveals the Intracellular Processing of Peptide-Linked Antibody–Drug Conjugates

Despite the recent success of antibody–drug conjugates (ADCs) in cancer therapy, a detailed understanding of their entry, trafficking, and metabolism in cancer cells is limited. To gain further insight into the activation mechanism of ADCs, we incorporated fluorescence resonance energy transfer (FRET) reporter groups into the linker connecting the antibody to the drug and studied various aspects of intracellular ADC processing mechanisms. When comparing the trafficking of the antibody–FRET drug conjugates in various different model cells, we found that the cellular background plays an important role in how the antigen-mediated antibody is processed. Certain tumor cells showed limited cytosolic transport of the payload despite efficient linker cleavage. Our FRET assay provides a facile and robust assessment of intracellular ADC activation that may have significant implications for the future development of ADCs