Targeting Immune Checkpoint Molecules to Eliminate Latent HIV

The advent of antiretroviral therapy (ART) has seen a dramatic decrease in the morbidity and mortality of individuals infected with human immunodeficiency virus (HIV). However, ART is not curative and HIV persists in treated individuals within a pool of infected CD4+ memory T cells. The targeting and elimination of these cells, termed the latent HIV reservoir, may be essential in establishing a cure for HIV. Current HIV reservoir research is focused on identifying cells that harbor latent, replication-competent, HIV provirus using specific cell surface markers. Recently, studies have turned to immune checkpoint (IC) molecules, such as programmed cell death protein 1 (PD-1). IC molecules are regulators of the immune system and have previously been linked to HIV infection. Furthermore, cells isolated from treated individuals co-expressing PD-1 alongside other IC molecules are enriched for HIV DNA. Administration of a IC blocking antibodies resulted in an increase of cell-associated HIV RNA within an individual, indicating the potential for this therapeutic to be utilized as a latency reversing agent. IC inhibitors could target CD4+ T cells expressing IC molecules and possibly enhance HIV transcription, allowing for the elimination of these cells by either ART or the immune system. However, treatment with IC inhibitors has been associated with toxicities such as immune-related adverse events and therefore future studies should proceed with caution

Animal models for liver disease – A practical approach for translational research

Animal models are crucial for improving our understanding of human pathogenesis, enabling researchers to identify therapeutic targets and test novel drugs. In the current review, we provide a comprehensive summary of the most widely used experimental models of chronic liver disease, starting from early stages of fatty liver disease (non-alcoholic and alcoholic) to steatohepatitis, advanced cirrhosis and end-stage primary liver cancer. We focus on aspects such as reproducibility and practicality, discussing the advantages and weaknesses of available models for researchers who are planning to perform animal studies in the near future. Additionally, we summarise current and prospective models based on human tissue bioengineering

The elusive source of HIV-1 rebound after treatment interruption

Identifying the source of viral rebound during a monitored analytical treatment interruption (ATI) would reveal potential targets for cure strategies. Therefore, we examined the genetic composition of proviral DNA in different subsets from participants on antiretroviral therapy and compared this to rebounding virus after an ATI. Eleven participants underwent a monitored ATI and were sampled from different anatomical sites prior to and after the ATI. From the peripheral blood, Naïve (TNA), central (TCM), transitional (TTM) and effector (TEM) memory CD4+ T cells were sorted as were CD45 cells from gut-associated lymphoid tissue (GALT). Using single-genome sequencing (SGS) the env region of HIV DNA and plasma-derived RNA was sequenced. In an ongoing study, Full-Length Individual Proviral Sequencing (FLIPS) and Integration Site Loop Amplification (ISLA) assays were performed on the T cell subsets from 2 participants. For participant STAR10, 87 integration sites (IS) and 113 proviral genomes were sequenced while only 3 unique intact proviruses (3%) were identified. A cluster of 17 identical defective proviruses were linked to an IS (9% of all IS) in STAT5B located in TCM, TNA, TEM and TTM. When comparing the FLIPS to SGS env sequences a 100% match was found between one defective provirus and one plasma HIV RNA sequence after rebound. For participant STAR11, 37 IS and 105 proviral genomes were sequenced yielding 14 intact proviruses (13%) with the highest proportion found predominantly in the TEM subset (n=13, 45%). Four different clusters of identical sequences could be identified of which 2 (n=3 and n=9) consisted of intact TEM sequences with the smaller cluster linked to an IS in ZNF274. A 99% match between 2 env from rebounding plasma RNA and this smaller cluster of intact proviral genomes was identified. Comparing proviral sequences and their IS to plasma-derived RNA sequences after an ATI reveals additional information in terms of the source of viral rebound. However, this comparison is complicated by multiple factors. For example, we found a plasma-derived RNA sequence obtained during viral rebound matched a defective proviral sequence which highlights the problem of using one HIV RNA subgenomic region for identifying replication-competent virus. In addition, ongoing viral replication during rebound may prevent a 100% match with genetically intact proviral sequences making it challenging to determine the absolute source of rebound

Unequal distribution of genetically-intact HIV-1 proviruses in cells expressing the immune checkpoint markers PD-1 and/or CTLA-4

IntroductionHIV-1 persists in resting CD4+ T-cells despite antiretroviral therapy (ART). Determining the cell surface markers that enrich for genetically-intact HIV-1 genomes is vital in developing targeted curative strategies. Previous studies have found that HIV-1 proviral DNA is enriched in CD4+ T-cells expressing the immune checkpoint markers programmed cell death protein-1 (PD-1) or cytotoxic T-lymphocyte associated protein-4 (CTLA-4). There has also been some success in blocking these markers in an effort to reverse HIV-1 latency. However, it remains unclear whether cells expressing PD-1 and/or CTLA-4 are enriched for genetically-intact, and potentially replication-competent, HIV-1 genomes. MethodsWe obtained peripheral blood from 16 HIV-1-infected participants, and paired lymph node from four of these participants, during effective ART. Memory CD4+ T-cells from either site were sorted into four populations: PD-1-CTLA-4- (double negative, DN), PD-1+CTLA-4- (PD-1+), PD-1-CTLA-4+ (CTLA-4+) and PD-1+CTLA-4+ (double positive, DP). We performed an exploratory study using the full-length individual proviral sequencing (FLIPS) assay to identify genetically-intact and defective genomes from each subset, as well as HIV-1 genomes with specific intact open reading frames (ORFs). Results and DiscussionIn peripheral blood, we observed that proviruses found within PD-1+ cells are more likely to have intact ORFs for genes such as tat, rev and nef compared to DN, CTLA-4+ and DP cells, all of which may contribute to HIV-1 persistence. Conversely, we observed that CTLA-4 expression is a marker for cells harbouring HIV-1 provirus that is more likely to be defective, containing low levels of these intact ORFs. In the lymph node, we found evidence that CTLA-4+ cells contain lower levels of HIV-1 provirus compared to the other cell subsets. Importantly, however, we observed significant participant variation in the enrichment of HIV-1 proviruses with intact genomes or specific intact ORFs across these memory CD4+ T-cell subsets, and therefore consideration of additional cellular markers will likely be needed to consistently identify cells harbouring latent, and potentially replication-competent, HIV-1

A Nutraceutical Rich in Docosahexaenoic Acid Improves Portal Hypertension in a Preclinical Model of Advanced Chronic Liver Disease

Inflammation and oxidative stress play a key role in the pathophysiology of advanced chronic liver disease (ACLD) and portal hypertension (PH). Considering the current lack of effective treatments, we evaluated an anti-inflammatory and antioxidant nutraceutical rich in docosahexaenoic acid (DHA) as a possible therapy for ACLD. We investigated the effects of two-week DHA supplementation (500 mg/kg) on hepatic fatty acids, PH, oxidative stress, inflammation, and hepatic stellate cell (HSC) phenotype in rats with ACLD. Additionally, the effects of DHA were evaluated in murine macrophages and human HSC. In contrast to vehicle-treated animals, cirrhotic rats receiving DHA reestablished a healthy hepatic fatty acid profile, which was associated with an improvement in PH. The mechanisms underlying this hemodynamic improvement included a reduction in oxidative stress and inflammation, as well as a marked HSC deactivation, confirmed in human HSC. Experiments with cultured macrophages showed that treatment with DHA protects against pro-inflammatory insults. The present preclinical study demonstrates that a nutraceutical rich in DHA significantly improves PH in chronic liver disease mainly by suppressing inflammation and oxidative stress-driven HSC activation, encouraging its evaluation as a new treatment for PH and cirrhosis

Overview of the MOSAiC expedition-Atmosphere INTRODUCTION

With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore crosscutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system scientific research and provide an important foundation for advancing multiscale modeling capabilities in the Arctic.Peer reviewe

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

Warm and moist air-mass intrusions into the Arctic are more frequent than the past decades. Here, the authors show that warm air mass intrusions from northern Eurasia inject record amounts of aerosols into the central Arctic Ocean strongly impacting atmospheric chemistry and cloud properties. Frequency and intensity of warm and moist air-mass intrusions into the Arctic have increased over the past decades and have been related to sea ice melt. During our year-long expedition in the remote central Arctic Ocean, a record-breaking increase in temperature, moisture and downwelling-longwave radiation was observed in mid-April 2020, during an air-mass intrusion carrying air pollutants from northern Eurasia. The two-day intrusion, caused drastic changes in the aerosol size distribution, chemical composition and particle hygroscopicity. Here we show how the intrusion transformed the Arctic from a remote low-particle environment to an area comparable to a central-European urban setting. Additionally, the intrusion resulted in an explosive increase in cloud condensation nuclei, which can have direct effects on Arctic clouds' radiation, their precipitation patterns, and their lifetime. Thus, unless prompt actions to significantly reduce emissions in the source regions are taken, such intrusion events are expected to continue to affect the Arctic climate.Peer reviewe

Beyond the ostensible: an exploration of barriers to lean implementation and sustainability in healthcare

The barriers to implement lean have been well researched and have generated consistent results; this study identifies these as ostensible barriers. There is a dearth of research that focus on understanding the causes of these ostensible barriers. Thus, this study aims to empirically investigate the deeper causes that produce ostensible barriers to implement lean in emergency areas of the healthcare. To achieve this aim, the paper draws on rich, qualitative data from four different sources of data, using exploratory case studies as the main approach. Undertaking thematic analysis, six main underlying barriers emerge as the root cause of ostensible barriers. The results suggest that addressing each of the underlying barriers in healthcare is likely to support lean implementation and sustainability, by reducing the impact of restraining forces that come from stakeholders and the public healthcare system

Condensed-Phase Photochemistry in the Absence of Radiation Chemistry

We report post-irradiation photochemistry studies of condensed ammonia using photons of energies below condensed ammonia’s ionization threshold of ~ 9 eV. Hydrazine (N2H4), diazene (also known as diimide and diimine) (N2H2), triazane (N3H5), and one or more isomers of N3H3 are detected as photochemistry products during temperature-programmed desorption. Product yields increase monotonically with (1) photon fluence and (2) film thickness. In the studies reported herein, the energies of photons responsible for product formation are constrained to less than 7.4 eV. Previous post-irradiation photochemistry studies of condensed ammonia employed photons sufficiently energetic to ionize condensed ammonia and initiate radiation chemistry. Such studies typically involve ion-molecule reactions and electron-induced reactions in addition to photochemistry. Although photochemistry is cited as a dominant mechanism for the synthesis of prebiotic molecules in interstellar ices, to the best of our knowledge, ours is one of the first astrochemically-relevant studies that has found unambiguous evidence for condensed-phase chemical synthesis induced by photons in the absence of ionization

A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation : insights from the Multidisciplinarydrifting Observatory for the Study of Arctic Climate (MOSAiC) expedition

The Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline in sea ice extent, which thereby enhances feedback loops in the surface energy budget in the Arctic. Arctic aerosols play an important role in the radiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study, we investigate the annual cycle in the aerosol particle number size distribution (PNSD), particle number concentration (PNC), and black carbon (BC) mass concentration in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k-means cluster analysis, FLEXPART simulations, and inverse modeling to evaluate seasonal patterns and the influence of different source regions on the Arctic aerosol population. Furthermore, we compare the aerosol observations to land-based sites across the Arctic, using both long-term measurements and observations during the year of the MOSAiC expedition (2019-2020), to investigate interannual variability and to give context to the aerosol characteristics from within the central Arctic. Our analysis identifies that, overall, the central Arctic exhibits typical seasonal patterns of aerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea ice melting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was the dominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based observatories. We also show that the wintertime Arctic Oscillation (AO) phenomenon, which was reported to achieve a record-breaking positive phase during January-March 2020, explains the unusual timing and magnitude of Arctic haze across the Arctic region compared to longer-term observations. In summer, the aerosol PNCs of the nucleation and Aitken modes are enhanced; however, concentrations were notably lower in the central Arctic over the ice pack than at land-based sites further south. The analysis presented herein provides a current snapshot of Arctic aerosol processes in an environment that is characterized by rapid changes, which will be crucial for improving climate model predictions, understanding linkages between different environmental processes, and investigating the impacts of climate change in future Arctic aerosol studies.Peer reviewe