Bhlhe40 Promotes CD4+ T Helper 1 Cell and Suppresses T Follicular Helper Cell Differentiation during Viral Infection

In response to acute infection, naive CD4+ T cells primarily differentiate into T helper 1 (Th1) or T follicular helper (Tfh) cells that play critical roles in orchestrating cellular or humoral arms of immunity, respectively. However, despite the well established role of T-bet and BCL-6 in driving Th1 and Tfh cell lineage commitment, respectively, whether additional transcriptional circuits also underlie the fate bifurcation of Th1 and Tfh cell subsets is not fully understood. In this article, we study how the transcriptional regulator Bhlhe40 dictates the Th1/Tfh differentiation axis in mice. CD4+ T cell-specific deletion of Bhlhe40 abrogates Th1 but augments Tfh differentiation. We also assessed an increase in germinal center B cells and Ab production, suggesting that deletion of Bhlhe40 in CD4+ T cells not only alters Tfh differentiation but also their capacity to provide help to B cells. To identify molecular mechanisms by which Bhlhe40 regulates Th1 versus Tfh lineage choice, we first performed epigenetic profiling in the virus specific Th1 and Tfh cells following LCMV infection, which revealed distinct promoter and enhancer activities between the two helper cell lineages. Furthermore, we identified that Bhlhe40 directly binds to cis-regulatory elements of Th1-related genes such as Tbx21 and Cxcr6 to activate their expression while simultaneously binding to regions of Tfh-related genes such as Bcl6 and Cxcr5 to repress their expression. Collectively, our data suggest that Bhlhe40 functions as a transcription activator to promote Th1 cell differentiation and a transcription repressor to suppress Tfh cell differentiation.

Exhausted CD8+ T cells face a developmental fork in the road

Reinvigorating the function of exhausted CD8+ T cells during chronic viral infection and cancer is a major goal of current immunotherapy regimens. Here, we discuss recent advances in our understanding of exhausted CD8+ T cell heterogeneity as well as the potential differentiation trajectories that exhausted T cells follow during chronic infection and/or cancer. We highlight surmounting evidence suggesting that some T cell clones are divergent in nature and can develop into either terminally differentiated effector or exhausted CD8+ T cells. Lastly, we consider the potential therapeutic implications of such a bifurcation model of CD8+ T cell differentiation, including the intriguing hypothesis that redirecting progenitor CD8+ T cell differentiation along an effector pathway may serve as a novel approach to mitigate T cell exhaustion.

Clonal lineage tracing reveals mechanisms skewing CD8+ T cell fate decisions in chronic infection

Although recent evidence demonstrates heterogeneity among CD8+ T cells during chronic infection, developmental relationships and mechanisms underlying their fate decisions remain incompletely understood. Using single-cell RNA and TCR sequencing, we traced the clonal expansion and differentiation of CD8+ T cells during chronic LCMV infection. We identified immense clonal and phenotypic diversity, including a subset termed intermediate cells. Trajectory analyses and infection models showed intermediate cells arise from progenitor cells before bifurcating into terminal effector and exhausted subsets. Genetic ablation experiments identified that type I IFN drives exhaustion through an IRF7-dependent mechanism, possibly through an IFN-stimulated subset bridging progenitor and exhausted cells. Conversely, Zeb2 was critical for generating effector cells. Intriguingly, some T cell clones exhibited lineage bias. Mechanistically, we identified that TCR avidity correlates with an exhausted fate, whereas SHP-1 selectively restricts low-avidity effector cell accumulation. Thus, our work elucidates novel mechanisms underlying CD8+ T cell fate determination during persistent infection and suggests two potential pathways leading to exhaustion.

Spatial transcriptomics demonstrates the role of CD4 T cells in effector CD8 T cell differentiation during chronic viral infection

CD4 T cell help is critical to sustain effector CD8 T cell responses during chronic infection, notably via T follicular helper (Tfh)-derived interleukin-21 (IL-21). Conversely, CD4 depletion results in severe CD8 T cell dysfunction and lifelong viremia despite CD4 T cell reemergence following transient depletion. These observations suggest that repopulating CD4 subsets are functionally or numerically insufficient to orchestrate a robust CD8 response. We utilize spatial transcriptomics and single-cell RNA sequencing (scRNA-seq) to investigate CD4 T cell heterogeneity under CD4-replete and -deplete conditions and explore cellular interactions during chronic infection. Although IL-21-producing Tfh cells repopulate following transient CD4 depletion, they are outnumbered by immunomodulatory CD4 T cells. Moreover, the splenic architecture appears perturbed, with decreases in white pulp regions, coinciding with germinal center losses. These disruptions in splenic architecture are associated with diminished Tfh and progenitor CD8 T cell colocalization, providing a potential mechanism for impaired progenitor-to-effector CD8 T cell differentiation during "un-helped" conditions.

Delineating the transcriptional landscape and clonal diversity of virus-specific CD4+ T cells during chronic viral infection

Although recent evidence indicates that CD4+ T cells responding to chronic viral infection are functionally heterogenous, our understanding of the developmental relationships between these subsets, and a determination of how their transcriptional landscape compares to their acute infection counterparts remains unclear. Additionally, whether cell-intrinsic factors such as TCR usage influence CD4+ T cell fate commitment during persistent infection has not previously been studied. Herein, we perform single-cell RNA sequencing (scRNA-seq) combined with single-cell T cell receptor sequencing (scTCR-seq) on virus-specific CD4+ T cells isolated from mice infected with chronic lymphocytic choriomeningitis virus (LCMV) infection. We identify several transcriptionally distinct states among the Th1, Tfh, and memory-like T cell subsets that form at the peak of infection, including the presence of a previously unrecognized Slamf7+ subset with cytolytic features. We further show that the relative distribution of these populations differs substantially between acute and persistent LCMV infection. Moreover, while the progeny of most T cell clones displays membership within each of these transcriptionally unique populations, overall supporting a one cell-multiple fate model, a small fraction of clones display a biased cell fate decision, suggesting that TCR usage may impact CD4+ T cell development during chronic infection. Importantly, comparative analyses further reveal both subset-specific and core gene expression programs that are differentially regulated between CD4+ T cells responding to acute and chronic LCMV infection. Together, these data may serve as a useful framework and allow for a detailed interrogation into the clonal distribution and transcriptional circuits underlying CD4+ T cell differentiation during chronic viral infection.

Tfh-cell-derived interleukin 21 sustains effector CD8+ T cell responses during chronic viral infection

CD4+ T cell-derived interleukin 21 (IL-21) sustains CD8+ T cell responses during chronic viral infection, but the helper subset that confers this protection remains unclear. Here, we applied scRNA and ATAC-seq approaches to determine the heterogeneity of IL-21+CD4+ T cells during LCMV clone 13 infection. CD4+ T cells were comprised of three transcriptionally and epigenetically distinct populations: Cxcr6+ Th1 cells, Cxcr5+ Tfh cells, and a previously unrecognized Slamf6+ memory-like (Tml) subset. T cell differentiation was specifically redirected toward the Tml subset during chronic, but not acute, LCMV infection. Although this subset displayed an enhanced capacity to accumulate and some developmental plasticity, it remained largely quiescent, which may hinder its helper potential. Conversely, mixed bone marrow chimera experiments revealed that Tfh cell-derived IL-21 was critical to sustain CD8+ T cell responses and viral control. Thus, strategies that bolster IL-21+Tfh cell responses may prove effective in enhancing CD8+ T cell-mediated immunity.

BATF promotes group 2 innate lymphoid cell-mediated lung tissue protection during acute respiratory virus infection

[Figure: see text].

Single-cell lineage mapping of a diverse virus-specific naive CD4 T cell repertoire

Tracking how individual naive T cells from a natural TCR repertoire clonally expand, differentiate, and make lineage choices in response to an infection has not previously been possible. Here, using single-cell sequencing technology to identify clones by their unique TCR sequences, we were able to trace the clonal expansion, differentiation trajectory, and lineage commitment of individual virus-specific CD4 T cells during an acute lymphocytic choriomeningitis virus (LCMV) infection. Notably, we found previously unappreciated clonal diversity and cellular heterogeneity among virus-specific helper T cells. Interestingly, although most naive CD4 T cells gave rise to multiple lineages at the clonal level, ∼28% of naive cells exhibited a preferred lineage choice toward either Th1 or TFH cells. Mechanistically, we found that TCR structure, in particular the CDR3 motif of the TCR α chain, skewed lineage decisions toward the TFH cell fate.

Abstract B64: CD4 help is required for the generation of a transcriptionally distinct cytolytic CD8 T-cell subset to control chronic infection and tumor

“CD4 help” is crucial to sustain the function of exhausted CD8 T cells, yet the detailed mechanisms by which CD4 help regulates CD8 T-cell differentiation and function during chronic viral infection remains elusive. Here, using single-cell RNA-sequencing (scRNA-seq) we show that CD8 T cells responding to chronic viral infection are more heterogeneous than previously appreciated, with three transcriptionally distinct subsets dominating the late phase of the antiviral response. Importantly, our findings uncover the formation of a previously unrecognized CD8 T-cell subset that exhibits potent cytolytic function. This subset is characterized by high expression of killer cell lectin-like receptors Klre1 and Klra9, the chemokine receptor CX3CR1, and the transcription factors T-bet and Zeb2. Notably, our data further demonstrate that the formation of this cytotoxic subset is critically dependent on CD4 help and that exploitation of this developmental pathway may be used therapeutically to enhance cytotoxic CD8 T-cell infiltration into the tumor. These findings uncover novel cellular and molecular mechanisms of how “CD4 help” regulates CD8 T-cell differentiation during persistent infection and have implications towards optimizing the generation of protective CD8 T cells in immunotherapy.

Citation Format: Ryan Zander, David Schauder, Weiguo Cui. CD4 help is required for the generation of a transcriptionally distinct cytolytic CD8 T-cell subset to control chronic infection and tumor [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B64.

Pathogen-Boosted Adoptive Cell Transfer Therapy Induces Endogenous Antitumor Immunity through Antigen Spreading

Loss of target antigens in tumor cells has become one of the major hurdles limiting the efficacy of adoptive cell therapy (ACT)-based immunotherapies. The optimal approach to overcome this challenge includes broadening the immune response from the initially targeted tumor-associated antigen (TAA) to other TAAs expressed in the tumor. To induce a more broadly targeted antitumor response, we utilized our previously developed Re-energized ACT (ReACT), which capitalizes on the synergistic effect of pathogen-based immunotherapy and ACT. In this study, we showed that ReACT induced a sufficient endogenous CD8+ T-cell response beyond the initial target to prevent the outgrowth of antigen loss variants in a B16-F10 melanoma model. Sequentially, selective depletion experiments revealed that Batf3-driven cDC1s were essential for the activation of endogenous tumor-specific CD8+ T cells. In ReACT-treated mice that eradicated tumors, we observed that endogenous CD8+ T cells differentiated into memory cells and facilitated the rejection of local and distal tumor rechallenge. By targeting one TAA with ReACT, we provided broader TAA coverage to counter antigen escape and generate a durable memory response against local relapse and metastasis.See related Spotlight on p. 2.

CD4+ T Cell Help Is Required for the Formation of a Cytolytic CD8+ T Cell Subset that Protects against Chronic Infection and Cancer

Although CD4⁺ T cell "help" is crucial to sustain antiviral immunity, the mechanisms by which CD4⁺ T cells regulate CD8⁺ T cell differentiation during chronic infection remain elusive. Here, using single-cell RNA sequencing, we show that CD8⁺ T cells responding to chronic infection were more heterogeneous than previously appreciated. Importantly, our findings uncovered the formation of a CX₃CR1-expressing CD8⁺ T cell subset that exhibited potent cytolytic function and was required for viral control. Notably, our data further demonstrate that formation of this cytotoxic subset was critically dependent on CD4⁺ T cell help via interleukin-21 (IL-21) and that exploitation of this developmental pathway could be used therapeutically to enhance the killer function of CD8⁺ T cells infiltrated into the tumor. These findings uncover additional molecular mechanisms of how "CD4⁺ T cell help" regulates CD8⁺ T cell differentiation during persistent infection and have implications toward optimizing the generation of protective CD8⁺ T cells in immunotherapy.

Smoking and alcohol use among women in Russia: Dual risk for prenatal exposure

Alcohol consumption during pregnancy can produce adverse outcomes; maternal smoking compounds this risk. We examined prevalence of smoking and associations between smoking and alcohol use in Russian women of childbearing age (N = 648). Smoking was reported by 35% of nonpregnant and 14% of pregnant women. Smoking prevalence was higher (45%) among at-risk drinkers and those at risk for an alcohol-exposed pregnancy (AEP). In a multivariate model, smoking status and city of residence significantly predicted AEP risk. Pregnant women in urban locations were more likely to smoke. Smoking and alcohol misuse often co-occur among Russian women, presenting risk for dual prenatal exposure.

Abstract B200: Single-cell RNA-sequencing (ScRNA-seq) reveals broad heterogeneity among CD8 T-cells during chronic viral infection and identifies a critical role for CD4 help in promoting the differentiation of a potent cytotoxic CD8 T-cell subset

During chronic viral infection and cancer, CD8 T-cells undergo a differentiation process commonly referred to as T-cell exhaustion. This process is traditionally defined by a stepwise loss of effector functions, eventually leading to cell death. Despite their inability to completely clear the infection, exhausted T-cells are still necessary for limiting viral replication during infection. Thus, it has been proposed that functional adaptation is a more appropriate term for T-cell exhaustion, as CD8 T-cells may be undergoing a multifaceted process of differentiation to better meet the needs of a chronic infection. In line with this hypothesis, it has recently been demonstrated that CD8 T-cells responding to chronic infection are non-homogenous and can be compartmentalized into at least two major subsets, with a TCF-1+ subset serving as a progenitor population that can give rise to a more terminally exhausted TCF-1- subset. However, whether additional heterogeneity exists among CD8 T-cells responding to persistent infection remains unclear. Here, we used ScRNA-seq to fully characterize the heterogeneity of CD8 T-cells during chronic LCMV Cl13 infection. We identified that several transcriptionally distinct subsets of CD8 T-cells develop during chronic LCMV infection, with 3 particular clusters, Slamf6, Pdcd1, and Cx3cr1 cell subsets dominating the antiviral CD8 T-cell response. Importantly both ScRNA-seq and flow cytometric analyses demonstrated that differential expression of cell surface receptors CX3CR1 and Ly108 (encoded by Slamf6) can distinguish these 3 major T-cell subsets. Notably, Ly108 cells shared similar characteristics to the previously described progenitor population and displayed elevated expression of TCF-1. Conversely, CX3CR1 CD8 T-cells displayed increased expression of killer cell lectin-like receptors Klre1 and Klra9, and the TFs T-bet and Zeb2, whereas CX3CR1-Ly108- (DN) cells exhibited elevated expression of multiple co-inhibitory receptors and the TFs Eomes and Nr4a2. Ex vivo functional analyses further indicated that Ly108 CD8 T-cells exhibit an enhanced capacity to co-produce IFN-γ and TNF-α upon GP33 peptide stimulation, whereas CX3CR1 CD8 T-cells display augmented cytotoxicity against peptide-pulsed targeT-cells. Sc trajectory modeling using Monocle analyses predicted that Ly108 CD8 T-cells give rise to both CX3CR1 and DN subsets, with the DN subset branch appearing closer in pseudotime to the Ly108 progenitor subset. To determine the in vivo differentiation trajectory, proliferative potential, and phenotypic stability of these 3 subsets, we performed adoptive transfer experiments using congenically marked CD8 T-cells. Importantly, and consistent with our Monocle predictions, our results demonstrate that Ly108 CD8 T-cells display robust secondary proliferation and give rise to both CX3CR1 and DN subsets. By contrast, CX3CR1 cells retained high CX3CR1 and T-bet expression and did not differentiate into Ly108 or DN CD8 T-cells. Intriguingly, although the DN subset appeared to be the most phenotypically and functionally exhausted subset, more than half of their progeny acquired high CX3CR1 and T-bet expression, indicating that this subset may not be as terminally differentiated as its CX3CR1 counterpart. Notably, our ScRNA-seq analyses also identified that DN cells displayed the highest levels of IL-21R expression, suggesting a potential role for CD4 help in regulating the differentiation of this subset. Strikingly, depletion of CD4 T-cells or deletion of IL-21R signaling in P14 transgenic CD8 T-cells abrogated the development of the CX3CR1 CD8 subset, indicating a critical role for CD4 help in facilitating the differentiation of exhausted CD8 T-cells into a potent cytotoxic CD8 subset. Collectively, our work supports a new model of CD8 T-cell differentiation during chronic viral infection and has important implications for T-cell-based immunotherapies aimed at treating persistent infections and/or cancer.

Citation Format: Ryan Zander, David Schauder, Gang Xin, Christine Nguyen, Xiaopeng Wu, Weiguo Cui. Single-cell RNA-sequencing (ScRNA-seq) reveals broad heterogeneity among CD8 T-cells during chronic viral infection and identifies a critical role for CD4 help in promoting the differentiation of a potent cytotoxic CD8 T-cell subset [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B200.

Abstract B201: Exploration and exploitation of macrophage death pathways: Infection by Mycobacterium tuberculosis as a model

Macrophages can impact the development of tumors and their responses to therapy. However, we lack a full understanding of how macrophage activation and survival are regulated and might be therapeutically modulated. To address these questions, we turned to a host-pathogen interaction that is likely to have impacted the evolution of these processes: infection by Mycobacterium tuberculosis (Mtb), the leading cause of death from infection. Once internalized by macrophages, Mtb resists killing by macrophages and replicates within them. Ultimately, Mtb infection results in death of macrophages, allowing dissemination of the pathogen to other cells. To explore how Mtb induces macrophage cell death and how macrophage cell death might impact host defense against Mtb, we performed a genome-wide CRISPR-Cas9 recessive genetic screen in RAW264.7 macrophages. We discovered that the absence of components of the type I interferon signaling pathway, including the IFN-α/β receptor (IFNAR), delays Mtb-induced cell death. It is known that Mtb infection induces macrophages to produce type I interferon. Our finding directly links type I interferon signaling pathway and Mtb-induced macrophage death. We are currently working on the mechanism of the type I IFN-induced death of bacterially-stimulated macrophages. Meanwhile, we are testing blockers of this pathway as host-directed therapy against TB and have seen striking protective effects of anti-IFNAR1 mAb in Mtb-infected mice, whether the mAb is administered before or after infection. Further exploration of the protective effect of anti-IFNAR mAb could point to an antibody-based, host-directed therapy. Acknowledgment: We thank Prof. R. Schreiber, Washington University, for facilitating access to anti-IFNAR mAb.

Citation Format: Ryan Zander, David Schauder, Gang Xin, Christine Nguyen, Xiaopeng Wu, Weiguo Cui. Exploration and exploitation of macrophage death pathways: Infection by Mycobacterium tuberculosis as a model [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B201.

Transcriptional and Epigenetic Regulation of Effector and Memory CD8 T Cell Differentiation

Immune protection and lasting memory are accomplished through the generation of phenotypically and functionally distinct CD8 T cell subsets. Understanding how these effector and memory T cells are formed is the first step in eventually manipulating the immune system for therapeutic benefit. In this review, we will summarize the current understanding of CD8 T cell differentiation upon acute infection, with a focus on the transcriptional and epigenetic regulation of cell fate decision and memory formation. Moreover, we will highlight the importance of high throughput sequencing approaches and single cell technologies in providing insight into genome-wide investigations and the heterogeneity of individual CD8 T cells.

Single-cell RNA sequencing unveils an IL-10-producing helper subset that sustains humoral immunity during persistent infection

During chronic viral infection, the inflammatory function of CD4 T-cells becomes gradually attenuated. Concurrently, Th1 cells progressively acquire the capacity to secrete the cytokine IL-10, a potent suppressor of antiviral T cell responses. To determine the transcriptional changes that underlie this adaption process, we applied a single-cell RNA-sequencing approach and assessed the heterogeneity of IL-10-expressing CD4 T-cells during chronic infection. Here we show an IL-10-producing population with a robust Tfh-signature. Using IL-10 and IL-21 double-reporter mice, we further demonstrate that IL-10⁺IL-21⁺co-producing Tfh cells arise predominantly during chronic but not acute LCMV infection. Importantly, depletion of IL-10⁺IL-21⁺co-producing CD4 T-cells or deletion of Il10 specifically in Tfh cells results in impaired humoral immunity and viral control. Mechanistically, B cell-intrinsic IL-10 signaling is required for sustaining germinal center reactions. Thus, our findings elucidate a critical role for Tfh-derived IL-10 in promoting humoral immunity during persistent viral infection.

During chronic infection CD4+ T cells can progressively acquire IL-10 producing functionality. Here the authors use single cell RNA sequencing to interrogate the IL10 CD4+ T cell compartment in a murine model of chronic infection and identify Il10-producing Tfh involved in promotion of the antiviral humoral immune response.

The power of combining adoptive cell therapy (ACT) and pathogen-boosted vaccination to treat solid tumors

Recent advancements in adoptive cell therapy (ACT) are opening up new frontiers for cancer immunotherapy. CAR T cells targeting CD19 have emerged as a remarkable T cell-based therapy for the successful treatment of certain types of leukemia and lymphomas. Despite these clinical successes, as well as significant breakthroughs in T cell engineering, the treatment of solid tumors with ACT remains a relentless challenge. Thus, the current consensus of the field is that an urgent need exists for the design of innovative approaches that can improve the efficacy of ACT in treating solid cancers while maintaining a high degree of reliability and safety.

Two is better than one: advances in pathogen-boosted immunotherapy and adoptive T-cell therapy

The recent tremendous successes in clinical trials take cancer immunotherapy into a new era and have attracted major attention from both academia and industry. Among the variety of immunotherapy strategies developed to boost patients' own immune systems to fight against malignant cells, the pathogen-based and adoptive cell transfer therapies have shown the most promise for treating multiple types of cancer. Pathogen-based therapies could either break the immune tolerance to enhance the effectiveness of cancer vaccines or directly infect and kill cancer cells. Adoptive cell transfer can induce a strong durable antitumor response, with recent advances including engineering dual specificity into T cells to recognize multiple antigens and improving the metabolic fitness of transferred cells. In this review, we focus on the recent prospects in these two areas and summarize some ongoing studies that represent potential advancements for anticancer immunotherapy, including testing combinations of these two strategies.

Co-inhibitory and co-stimulatory crosstalk regulates helper T cell differentiation and humoral immunity during Plasmodium infection (MPF5P.742)

Pathogen-specific T cells are subject to co-stimulatory and co-inhibitory signals, the balance of which promotes pathogen control while limiting immunopathology. During blood-stage Plasmodium infection, parasite-specific CD4 T cells express PD-1 and LAG-3 co-inhibitory receptors that coordinately limit CD4 T cell function. Blockade of PD-1/LAG-3 co-inhibitory signaling during chronic Plasmodium infection enhances CD4 T cell function and parasite control. In contrast to co-inhibitory receptors, the role of T cell co-stimulatory receptors during established Plasmodium infection has not been investigated. Here we show that CD4 T cells exhibit sustained expression of the co-stimulatory receptor OX40 during both human and experimental malaria. We hypothesized that co-stimulatory signaling can functionally counteract co-inhibitory circuits to maintain protective Plasmodium-specific CD4 T responses. In support of this, therapeutically activating OX40 during established experimental malaria enhances CD4 T cell activity, humoral immunity and parasite clearance. Our data also show that the effects of OX40 signaling are modified following simultaneous PD-1 blockade, which markedly impairs parasite-specific T follicular helper cell responses in an IFN-g-dependent manner. Collectively, our results identify that OX40 can be targeted to limit malaria parasite replication and reveal a previously unrecognized role of IFN-g as a negative regulator of Plasmodium-specific humoral immunity.

Observations of long-lived anthropogenic halocarbons at the high-Alpine site of Jungfraujoch (Switzerland) for assessment of trends and European sources

Anthropogenic halocarbons, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), bromocarbons (halons) and long-lived chlorinated solvents have been measured continuously at the high-Alpine site of Jungfraujoch (Switzerland) since January 2000. Chloro- and bromo-containing halocarbons are responsible for the stratospheric ozone depletion and will be globally banned from usage within the next years. With the exception of the stable CFC-12 (CF2 Cl2), all major CFCs and chlorinated solvents show a negative trend in recent years in their background concentrations at Jungfraujoch. HCFCs, as their first-generation substitute, are still increasing with a few percent per year. However, the frequency and the strength of HCFCs pollution events, which are caused by regional European emissions, are already declining. This can be seen as a sign of the impending ban of these gases within the next years in Europe. On the other hand, HFCs as the second-generation substitutes, are increasing with relative rates of at least 10% per year (e.g. almost 5 ppt per year for HFC-134a). An allocation of European sources was attempted by combining measured concentrations with trajectories of air masses reaching the Jungfraujoch during pollution events. Potential source regions could be detected in Italy, France, Spain and Germany.

Our changing atmosphere: evidence based on long-term infrared solar observations at the Jungfraujoch since 1950

The Institute of Astrophysics of the University of Liège has been present at the High Altitude Research Station Jungfraujoch, Switzerland, since the late 1940s, to perform spectrometric solar observations under dry and weakly polluted high-mountain conditions. Several solar atlases of photometric quality, extending altogether from the near-ultra-violet to the middle-infrared, were produced between 1956 and 1994, first with grating spectrometers then with Fourier transform instruments. During the early 1970s, scientific concerns emerged about atmospheric composition changes likely to set in as a consequence of the growing usage of nitrogen-containing agricultural fertilisers and the industrial production of chlorine-bearing compounds such as the chlorofluorocarbons and hydro-chlorofluorocarbons. Resulting releases to the atmosphere with ensuing photolysis in the stratosphere and catalytic depletion of the protective ozone layer prompted a worldwide consortium of chemical manufacturing companies to solicit the Liège group to help in clarifying these concerns by undertaking specific observations with its existing Jungfraujoch instrumentation. The following pages evoke the main steps that led from quasi full sun-oriented studies to priority investigations of the Earth's atmosphere, in support of both the Montreal and the Kyoto Protocols.

[The design of the VISEP trial. Critical appraisal]

The survey transcript of the VISEP interventional trial "Prospective randomized multicenter study on the influence of colloid vs crystalloid volume resuscitation and of intensive vs conventional insulin therapy on outcome in patients with severe sepsis and septic shock" [Clinical trials.gov. identifier: NCT00135473; study start April 2003] comprises, according to the data of the year 2003, methodological shortcomings which challenge a priori the study design and thus the resolution of the purpose of the study, i.e., "determination of the influence of the studied volume and insulin interventions on morbidity and mortality of patients with severe sepsis and septic shock". The most important points of criticism are: 1. A volume therapy with exclusively crystalloids or colloids with the chosen colloid hyperoncotic, hyperchloremic HES solution (10% hydroxyethyl starch: 10% Hemohes) or the crystalloid solution with high lactate content (Sterofundin) is neither acceptable nor practicable, even if only due to exceeding the maximum dosage as recommended by the manufacturer. 2. The fact known since the year 2001 that high molecular weight, poorly biodegradable HES preparations can present an independent risk-factor for acute kidney failure in patients with sepsis or septic shock was ignored: the exclusion criterion of a serum-creatinine value of >320 micromol/l (>3.6 mg/dl) was doubled in relation to the manufacturer's specification. 3. The hyperoncotic colloid solution used (10% Hemohes) may only be employed for a brief period: it is highly hyperchloremic and causes extravascular hypohydration with consecutive reduction of renal excretion, which together with HES is a fatal combination. 4. The crystalloid solution used, i.e., Sterofundin, which contains 45 mmol/l lactate, is contraindicated with septic shock as it increases the patient's O2 consumption, hinders lactate diagnostics as a hypoxia marker by simultaneous lactate infusion, and through increased gluconeogenesis leads to hyperglycemia, at least with diabetics. 5. It is doubtful whether an intensified insulin therapy (Actrapid) can be successful if insulin is administered simultaneously with iatrogenic hyperglycemia as a result of lactate influx. Due to these flaws in the design of the VISEP trial, the only consequence can be that the results of the survey are unusable, especially with regard to the point "HES and kidney function". Thus, any further advance presentations and interpretations should be shelved in expectation of the authors' publication of all the data, in order to begin further discussions including the flaws in study design listed here.

Screening California surface waters for estrogenic endocrine disrupting chemicals (EEDC) with a juvenile rainbow trout liver vitellogenin mRNA procedure

Concern regarding the occurrence of chemicals that disrupt endocrine system functions in aquatic species has heightened over the last 15 years. However, little attention has been given to monitoring for estrogenic endocrine disrupting chemicals (EEDCs) in California's freshwater ecosystems. The objective was to screen surface water samples for estrogenic activity using vitellogenin (Vtg) mRNA quantification in livers of juvenile rainbow trout by real-time reverse transcriptase polymerase chain reaction (Q-RT PCR). Vtg mRNA analysis of livers from fish exposed to 113 ambient water samples collected from surface waters in California's Central Valley and northern area indicated that six samples (5% of total) may have contained EEDCs. The six samples induced marginal, but statistically significant, increases of Vtg mRNA. No ambient water sample evoked Vtg mRNA responses equivalent to those in positive controls (all responses were less than 2% of the positive control response). Thus, EEDC concentrations in these samples were low (at or near the threshold for the procedure) or results may have included false positives. To establish a more definitive assessment of EEDC occurrence, follow-up screening at sites where statistically significant, but weak, estrogenic activity was observed is recommended. Overall, results reveal that a majority of the California surface waters tested were below EEDC detection threshold concentration for the screening procedure utilized.

[Optimisation of the acid-base status in hypothermia]

Under laboratory conditions, it can be demonstrated within sufficient clinical accuracy that the base excess (BE, [mmol/l]) is independent of temperature. In any blood gas analyzer with temperature correction, the results are consistent with tonometry when measuring a sample of hypothermic equilibrated blood at 37 degrees C. Under clinical conditions, it is shown that there is practically no difference in the CO(2) partial pressure, irrespective of whether measured directly by capnometry (p(et)CO(2)) or obtained from arterial blood (p(a)CO(2)) in the blood gas analyzer after correction for the patient's temperature. Hence, the clinical recommendations for hypothermia are: correct artificial ventilation, preferably pCO(2) 40+/-5 mmHg, should be established by capnometry and controlled by temperature-corrected p(a)CO(2): metabolic changes should be diagnosed by temperature-independent BE: the temperature-corrected pH, if at all, should be used only for the diagnosis of acidosis or alkalosis.

Forderungen und Erwartungen an einen optimalen Volumenersatz

A volume replacement should compensate a reduction in the intravascular volume and counteract a hypovolemia so that hemodynamics and vital functions can be maintained. For this therapy, a physiologically-based solution comprising both osmotically and colloid osmotically active components should be administered. A consensus is proposed for this purpose which takes into consideration the following aspects: The optimum colloid, the questionable use of albumin, the physiological electrolyte pattern encompassing sodium, potassium, chloride and phosphate and their contributions to osmolality, an eventual addition of glucose, the physiological acid-base status with bicarbonate or alternately with metabolisable anions, and the importance of a clear declaration of all ingredients. The consensus distinguishes between compulsory requirements derived from evidence-based medicine and physiological data and the potential expectations of an optimal volume replacement, including well-grounded wishes and aspirations for the future.

[Massive transfusion of washed red blood cells: acid-base and electrolyth changes for different wash solutions]

OBJECTIVE

The composition of normal saline (NaCl), the standard wash solution for cell saver autotransfusion, is considerably different from physiologic plasma values in small infants. Therefore, we investigated acid-base and electrolyte changes during massive cell saver autotransfusion with different wash solutions in young pigs.

METHODS

After approval by the animal protection authorities 15 young pigs (weight 10.6 +/- 1.1 kg, blood volume 848 +/- 88 ml, mean+/-SD) underwent 15 cycles of cell saver autotransfusion (Haemolite 2plus, Haemonetics). For each cycle, 100 ml arterial blood was withdrawn, washed with NaCl, physiologic multielectrolyte solution (PME, V Infusionslösung 296 mval Elektrolyte, Baxter) or physiologic erythrocyte protection solution (PEP, 3.2 % gelatine, pH 7.40, cHCO3 24 mmol/l), and then retransfused. Analyses of acid-base, electrolyte, and hematologic parameters were performed for systemic and washed blood samples.

RESULTS

For NaCl there was a progressive decrease in systemic pH, HCO3 and base excess (BE) and an increase in chloride values (Cl) (p < 0.05). Use of PME slightly decreased pH (n. s.), whereas HCO3, BE and Cl remained stable. PEP slightly increased pH, HCO3 and BE, and decreased Cl (n. s.). Free hemoglobin increased in NaCl and PME (p < 0.05) and was below baseline in PEP (n. s.). Lactic acid course was comparable in all groups.

CONCLUSIONS

The use of NaCl as wash solution for massive autotransfusion resulted in metabolic acidosis caused by dilution of HCO3 and increased Cl values. Fewer systemic acid-base and electrolyte changes were observed, when blood was washed with PME or PEP. The decreased hemoglobin release with PEP is possibly due to a gelatine specific electrostatic surface coating of erythrocyte membranes. For massive transfusion of washed red blood cells, physiologic multielectrolyte solution and physiologic erythrocyte protection solution should be preferred to NaCl, especially for small infants.

[Definition of shock types]

Definitions of shock types. Hypovolaemic shock is a state of insufficient perfusion of vital organs with consecutive imbalance of oxygen supply and demand due to an intravascular volume deficiency with critically impaired cardiac preload. Subtypes are haemorrhagic shock, hypovolaemic shock in the narrow sense, traumatic-haemorrhagic shock and traumatic-hypovolaemic shock. Cardiac shock is caused by a primary critical cardiac pump failure with consecutive inadequate oxygen supply of the organism. Anaphylactic shock is an acute failure of blood volume distribution (distributive shock) and caused by IgE-dependent, type-I-allergic, classical hypersensibility, or a physically, chemically, or osmotically induced IgE-independent anaphylactoid hypersensibility. The septic shock is a sepsis-induced distribution failure of the circulating blood volume in the sense of a distributive shock. The neurogenic shock is a distributive shock induced by generalized and extensive vasodilatation with consecutive hypovolaemia due to an imbalance of sympathetic and parasympathetic regulation of vascular smooth muscles.