Dynamic changes of circulating miRNAs induced by the Ebola virus vaccine VSV-EBOV.

VSV-EBOV is a replication-competent Ebola virus (EBOV) vaccine, which was tested in clinical trials as response to the Ebola virus disease (EVD) outbreak 2013-2016. It is the most advanced EBOV candidate currently in the licensure process. The experimental vaccine was again administered as response to outbreaks in the Democratic Republic of Congo. However, underlying molecular mechanisms that convey protection remain incompletely understood. MicroRNAs (miRNAs) are known key regulators that influence gene expression on a post-transcriptional level. The miRNA-mediated control has emerged as a critical regulatory principle in the immune system, which strongly influences the balance of innate and adaptive immune responses by modulation of signaling pathways critical for differentiation of immune cells. We investigated expression levels of circulating miRNAs (c-miRNAs) in plasma from healthy vaccinees, as they may reflect cellular dynamics following VSV-EBOV immunization and additionally may serve as potential biomarkers for vaccine efficacy. As part of the WHO-led VEBCON consortium, we investigated safety and immunogenicity of VSV-EBOV in a phase I trial. A comprehensive analysis of expression levels on c-miRNAs from plasma samples following VSV-EBOV immunization (day 0, 1, 3 post vaccination) was conducted using RT-qPCR assays. Potential biological relevance was assessed using in silico analyses. Additionally, we correlated dynamics of miRNA expressions with our previously reported data on vaccine-induced antibody and cytokine responses and finally evaluated the prognostic power by generating ROC curves. We identified four promising miRNAs (hsa-miR-146a, hsa-miR-126, hsa-miR-199a, hsa-miR-484), showing a strong association with adaptive immune responses, exhibited favourable prognostic performance and are implicated in immunology-related functions. Our results provide evidence that miRNAs may serve as useful biomarkers for prediction of vaccine-induced immunogenicity. Furthermore, our unique data set provides insight into molecular mechanisms that underlie VSV-EBOV-mediated protective immune responses, which may help to decipher VSV-EBOV immune signature and accelerate strategic vaccine design or personalized approaches.

Kinetics of HIV-1 Latency Reversal Quantified on the Single-Cell Level Using a Novel Flow-Based Technique.

UNLABELLED: HIV-1 establishes a pool of latently infected cells early following infection. New therapeutic approaches aiming at diminishing this persisting reservoir by reactivation of latently infected cells are currently being developed and tested. However, the reactivation kinetics of viral mRNA and viral protein production, and their respective consequences for phenotypical changes in infected cells that might enable immune recognition, remain poorly understood. We adapted a novel approach to assess the dynamics of HIV-1 mRNA and protein expression in latently and newly infected cells on the single-cell level by flow cytometry. This technique allowed the simultaneous detection of gagpol mRNA, intracellular p24 Gag protein, and cell surface markers. Following stimulation of latently HIV-1-infected J89 cells with human tumor necrosis factor alpha (hTNF-α)/romidepsin (RMD) or HIV-1 infection of primary CD4(+) T cells, four cell populations were detected according to their expression levels of viral mRNA and protein. gagpol mRNA in J89 cells was quantifiable for the first time 3 h after stimulation with hTNF-α and 12 h after stimulation with RMD, while p24 Gag protein was detected for the first time after 18 h poststimulation. HIV-1-infected primary CD4(+) T cells downregulated CD4, BST-2, and HLA class I expression at early stages of infection, proceeding Gag protein detection. In conclusion, here we describe a novel approach allowing quantification of the kinetics of HIV-1 mRNA and protein synthesis on the single-cell level and phenotypic characterization of HIV-1-infected cells at different stages of the viral life cycle. IMPORTANCE: Early after infection, HIV-1 establishes a pool of latently infected cells, which hide from the immune system. Latency reversal and immune-mediated elimination of these latently infected cells are some of the goals of current HIV-1 cure approaches; however, little is known about the HIV-1 reactivation kinetics following stimulation with latency-reversing agents. Here we describe a novel approach allowing for the first time quantification of the kinetics of HIV-1 mRNA and protein synthesis after latency reactivation or de novo infection on the single-cell level using flow cytometry. This new technique furthermore enabled the phenotypic characterization of latently infected and de novo-infected cells dependent on the presence of viral RNA or protein.