H2A.Z overexpression suppresses senescence and chemosensitivity in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most intractable and devastating malignant tumors. Epigenetic modifications such as DNA methylation and histone modification regulate tumor initiation and progression. However, the contribution of histone variants in PDAC is unknown. Here, we demonstrated that the histone variant H2A.Z is highly expressed in PDAC cell lines and PDAC patients and that its overexpression correlates with poor prognosis. Moreover, all three H2A.Z isoforms (H2A.Z.1, H2A.Z.2.1, and H2A.Z.2.2) are highly expressed in PDAC cell lines and PDAC patients. Knockdown of these H2A.Z isoforms in PDAC cell lines induces a senescent phenotype, cell cycle arrest in phase G2/M, increased expression of cyclin-dependent kinase inhibitor CDKN2A/p16, SA-β-galactosidase activity and interleukin 8 production. Transcriptome analysis of H2A.Z-depleted PDAC cells showed altered gene expression in fatty acid biosynthesis pathways and those that regulate cell cycle and DNA damage repair. Importantly, depletion of H2A.Z isoforms reduces the tumor size in a mouse xenograft model in vivo and sensitizes PDAC cells to gemcitabine. Overexpression of H2A.Z.1 and H2A.Z.2.1 more than H2A.Z.2.2 partially restores the oncogenic phenotype. Therefore, our data suggest that overexpression of H2A.Z isoforms enables cells to overcome the oncoprotective barrier associated with senescence, favoring PDAC tumor grow and chemoresistance. These results make H2A.Z a potential candidate as a diagnostic biomarker and therapeutic target for PDAC.

The Role of Flaviviral Proteins in the Induction of Innate Immunity

Flaviviruses are positive, single-stranded, enveloped cytoplasmic sense RNA viruses that cause a variety of important diseases worldwide. Among them, Zika virus, West Nile virus, Japanese encephalitis virus, and Dengue virus have the potential to cause severe disease. Extensive studies have been performed to elucidate the structure and replication strategies of flaviviruses, and current studies are aiming to unravel the complex molecular interactions between the virus and host during the very early stages of infection. The outcomes of viral infection and rapid establishment of the antiviral state, depends on viral detection by pathogen recognition receptors and rapid initiation of signalling cascades to induce an effective innate immune response. Extracellular and intracellular pathogen recognition receptors play a crucial role in detecting flavivirus infection and inducing a robust antiviral response. One of the main hallmarks of flaviviral nonstructural proteins is their multiple strategies to antagonise the interferon system. In this chapter, we summarize the molecular characteristics of flaviviral proteins and discuss how viral proteins target different components of the interferon signalling pathway by blocking phosphorylation, enhancing degradation, and downregulating the expression of major components of the Janus kinase/signal transducer and activator of transcription pathway. We also discuss how the interactions of viral proteins with host proteins facilitate viral pathogenesis. Due to the lack of antivirals or prophylactic treatments for many flaviviral infections, it is necessary to fully elucidate how these viruses disrupt cellular processes to influence pathogenesis and disease outcomes.

Evaluation of the safety and adjuvant effect of a detoxified listeriolysin O mutant on the humoral response to dengue virus antigens

Listeriolysin O (LLO) has been proposed as a potential carrier or adjuvant molecule in the vaccination field. However, the cytotoxic and pro-apoptotic effects of LLO are the major limitations for this purpose. Here, we have performed a preclinical safety evaluation and characterized a new potential adjuvant application for a non-cytolytic LLO mutant (dtLLO) to enhance and modulate the immune response against the envelope (E) protein from dengue virus. In addition, we have studied the adjuvant effects of dtLLO on human immune cells and the role of membrane cholesterol for the binding and proinflammatory property of the toxoid. Our in-vivo results in the murine model confirmed that dtLLO is a safer molecule than wild-type LLO (wtLLO), with a significantly increased survival rate for mice challenged with dtLLO compared with mice challenged with wtLLO (P < 0·001). Histopathological analysis showed non-toxic effects in key target organs such as brain, heart, liver, spleen, kidney and lung after challenge with dtLLO. In vitro, dtLLO retained the capacity of binding to plasma membrane cholesterol on the surface of murine and human immune cells. Immunization of 6-8-week-old female BALB/c mice with a combination of dtLLO mixed with E protein elicited a robust specific humoral response with isotype diversification of immunoglobulin (Ig)G antibodies (IgG1 and IgG2a). Finally, we demonstrated that cholesterol and lipid raft integrity are required to induce a proinflammatory response by human cells. Taken together, these findings support a potential use of the dtLLO mutant as a safe and effective adjuvant molecule in vaccination.

Non-Conjugated Chitosan-Based Nanoparticles to Proteic Antigens Elicit Similar Humoral Immune Responses to Those Obtained with Alum

Biodegradables Chitosan-based Nanoparticles (CS NPs) have been extensively studied as delivery system for therapeutic molecules and as efficient carriers or adjuvants in experimental vaccination. Physicochemical association between CS NPs and antigens is a key step for the biological function as carrier devices. However, for the adjuvant CS NPs property, it is not well known if coupling with vaccine antigens is required or not to potentiate the immune response. To address this issue, in this work, we evaluated the potential adjuvant effect of CS NPs by simply mixing with two different antigens such as Bovine Serum Albumin (BSA) or E protein from Dengue Virus serotype 2 (E protein DENV2). Thus the CS NPs were prepared by ionic gelation with sodium tripolyphosphate, resulting particles among 68 and 188 nm of size. Immunization of 6–8 week old female BALB/c mice, were carried out by intraperitoneal route with a simple combination of CS NPs either with BSA (CS NPs-BSA) at 10 μg or with E protein DENV2 (CS NPs-Protein E) at 5 μg. Combinations with the above antigens with CS NPs elicited robust specific primary and secondary humoral responses comparable to alum, a well-known adjuvant. BSA-specific IgG titers were detectable by day 14 after priming with the CS NPs-BSA formulation, with titers that ranged from 102 to 103 EU ml-. After a second immunization, the anti-BSA titers ranged around 104 EU ml-. In contrast, in the group of mice immunized with the protein alone, BSA-specific serum IgG titers were undetectable at day 14 and 28. For the immunizations with the CS NPs-E protein formulation, we observed also a remarkable specific-antibody production in the primary response, with titers reaching 103 EU ml-. After the booster immunization the anti-E protein DENV2 antibodies titers reached peak values around 104 EU ml-. Interestingly, for both antigens, the combination with CS NPs polarized the immune response to a Th2-like profile, which is characterized mainly by the production of the IgG1 Isotype, confirming that CS NPs can enhance and modulate the humoral immune responses against different antigens independently of physicochemical conjugation. This could represent a simplification in the use of CS NPs as adjuvants in vaccination.

Analysis of antibody response in human dengue patients from the Mexican coast using recombinant antigens

This study was undertaken to evaluate the feasibility of using recombinant dengue proteins to discriminate between acute dengue infections versus uninfected dengue samples. Dengue virus proteins E, NS1, NS3, and NS4B were cloned as fusion proteins and expressed in Escherichia coli. Recombinant products were tested in 100 serum samples obtained from acute dengue fever cases collected from 3 states of Mexico where dengue is endemic. Sera from 75 healthy individuals living in nonendemic areas for dengue were used as a control group. In sera from the dengue patients group, antibody responses to E protein were demonstrated in 91% of cases and NS1 protein was recognized to various extents (99%) within the first 7 days of infection. The antibody responses to NS3 and NS4B were frequently of low magnitude. Consistent negative antibody responses to all proteins were found in sera from the control group. These data suggest that the glutathione-S-transferase (GST)-dengue fusion proteins may be feasible antigens for a sensitive and specific serological assay.

Production and characterization of a monoclonal antibody specific for NS3 protease and the ATPase region of Dengue-2 virus

Dengue is considered a reemerging disease of worldwide distribution. The Dengue virus non-structural protein 3 (NS3) is known to possess ATPase, helicase, and protease activities that are a constitutive part of the replication complex of Dengue virus. In this report, we discuss the cloning, expressing, and purifying of the Dengue-2 NS3 protein, to immunize mice and then generate monoclonal antibodies (MAbs). Our results show the production of MAbs specific to NS3 protein of Dengue-2 virus, which by immunofluorescence recognize the native protein in experimentally infected endothelial cells (HMEC). Likewise, C6/36-infected lisates were used in Western blots, and observed the specific characteristic band that defines the NS3 protein. We conclude that these antibodies may be a useful tool, not only to study the replicative process of Dengue virus, but also to generate specific diagnostic tools for Dengue infection.