Helminth Infection-Induced Increase in Virtual Memory CD8 T Cells Is Transient, Driven by IL-15, and Absent in Aged Mice.

CD8 virtual memory T (TVM) cells are Ag-naive CD8 T cells that have undergone partial differentiation in response to common γ-chain cytokines, particularly IL-15 and IL-4. TVM cells from young individuals are highly proliferative in response to TCR and cytokine stimulation but, with age, they lose TCR-mediated proliferative capacity and exhibit hallmarks of senescence. Helminth infection can drive an increase in TVM cells, which is associated with improved pathogen clearance during subsequent infectious challenge in young mice. Given the cytokine-dependent profile of TVM cells and their age-associated dysfunction, we traced proliferative and functional changes in TVM cells, compared with true naive CD8 T cells, after helminth infection of young and aged C57BL/6 mice. We show that IL-15 is essential for the helminth-induced increase in TVM cells, which is driven only by proliferation of existing TVM cells, with negligible contribution from true naive cell differentiation. Additionally, TVM cells showed the greatest proliferation in response to helminth infection and IL-15 compared with other CD8 T cells. Furthermore, TVM cells from aged mice did not undergo expansion after helminth infection due to both TVM cell-intrinsic and -extrinsic changes associated with aging.

Sex-bias in CD8+ T-cell stemness and exhaustion in cancer.

This commentary article highlights two recently published studies, which for the first time revealed the immunological underpinnings of sex-bias in cancer incidence and mortality. These studies showed that the androgen receptor restrains anti-tumour immunity in males by repressing cytotoxic genes in CD8+ T cells.

Targeting BMI-1 in B cells restores effective humoral immune responses and controls chronic viral infection.

Ineffective antibody-mediated responses are a key characteristic of chronic viral infection. However, our understanding of the intrinsic mechanisms that drive this dysregulation are unclear. Here, we identify that targeting the epigenetic modifier BMI-1 in mice improves humoral responses to chronic lymphocytic choriomeningitis virus. BMI-1 was upregulated by germinal center B cells in chronic viral infection, correlating with changes to the accessible chromatin landscape, compared to acute infection. B cell-intrinsic deletion of Bmi1 accelerated viral clearance, reduced splenomegaly and restored splenic architecture. Deletion of Bmi1 restored c-Myc expression in B cells, concomitant with improved quality of antibody and coupled with reduced antibody-secreting cell numbers. Specifically, BMI-1-deficiency induced antibody with increased neutralizing capacity and enhanced antibody-dependent effector function. Using a small molecule inhibitor to murine BMI-1, we could deplete antibody-secreting cells and prohibit detrimental immune complex formation in vivo. This study defines BMI-1 as a crucial immune modifier that controls antibody-mediated responses in chronic infection.

Increase in Penicillin and multidrug resistance in Streptococcus pneumoniae (1993-2016): Report from a tertiary care hospital laboratory, Pakistan.

OBJECTIVE: To determine the trend of resistance to antimicrobials in Streptococcus pneumoniae infections, and the impact of new Clinical and Laboratory Standards Institute guidelines on 1211 among meningeal isolates. METHODS: The descriptive observational retrospective study was conducted at the Aga Khan University Hospital laboratory in Karachi, and comprised Streptococcus pneumoniae isolation and antimicrobial susceptibility data over a period of 24 years, from 1993 to 2016, which was compared in terms of pre-2008 and post-2008 data, which was analysed using SPSS 19. RESULTS: Of the 7415 non-duplicate isolates identified, 4700(63.4%) were from male patients and 2,715(36.6%) were from female patients. The overall mean age of the patients was 38±27 years. Penicillin resistance in non-meningeal isolates during the two periods was not significantly different (p>0.05), but a significant rise in penicillin resistance in meningeal isolates was observed in the second period (p<0.05). High resistance rates were observed for co-trimoxazole, tetracycline and erythromycin, and an increased trend of multi-drug resistant strains was also noted from 1999 {n=35/317(11%)} to 2016 {n=110/314 (36%)}. CONCLUSIONS: The emergence of multi-drug resistant strains was evident. The spike in penicillin-resistant Streptococcus pneumoniae in meningeal isolates may have been due to the revised guidelines by the Clinical and Laboratory Standards Institute.

Hiding in Plain Sight: Virtually Unrecognizable Memory Phenotype CD8+ T cells.

Virtual memory T (TVM) cells are a recently described population of conventional CD8+ T cells that, in spite of their antigen inexperience, express markers of T cell activation. TVM cells exhibit rapid responsiveness to both antigen-specific and innate stimuli in youth but acquire intrinsic antigen-specific response defects in the elderly. In this article, we review how the identification of TVM cells necessitates a re-evaluation of accepted paradigms for conventional memory T (TMEM) cells, the potential for heterogeneity within the TVM population, and the defining characteristics of TVM cells. Further, we highlight recent literature documenting the development of TVM cells as a distinct CD8+ T cell lineage as well their biological significance in the context of disease.

Publisher Correction: Metabolic characteristics of CD8+ T cell subsets in young and aged individuals are not predictive of functionality.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Metabolic characteristics of CD8+ T cell subsets in young and aged individuals are not predictive of functionality.

Virtual memory T (TVM) cells are antigen-naïve CD8+ T cells that exist in a semi-differentiated state and exhibit marked proliferative dysfunction in advanced age. High spare respiratory capacity (SRC) has been proposed as a defining metabolic characteristic of antigen-experienced memory T (TMEM) cells, facilitating rapid functionality and survival. Given the semi-differentiated state of TVM cells and their altered functionality with age, here we investigate TVM cell metabolism and its association with longevity and functionality. Elevated SRC is a feature of TVM, but not TMEM, cells and it increases with age in both subsets. The elevated SRC observed in aged mouse TVM cells and human CD8+ T cells from older individuals is associated with a heightened sensitivity to IL-15. We conclude that elevated SRC is a feature of TVM, but not TMEM, cells, is driven by physiological levels of IL-15, and is not indicative of enhanced functionality in CD8+ T cells.

Inflammatory and immunometabolic consequences of gut dysfunction in HIV: Parallels with IBD and implications for reservoir persistence and non-AIDS comorbidities.

The gastrointestinal mucosa is critical for maintaining the integrity and functions of the gut. Disruption of this barrier is a hallmark and a risk factor for many intestinal and chronic inflammatory diseases. Inflammatory bowel disease (IBD) and HIV infection are characterized by microbial translocation and systemic inflammation. Despite the clinical overlaps between HIV and IBD, significant differences exist such as the severity of gut damage and mechanisms of immune cell homeostasis. Studies have supported the role of metabolic activation of immune cells in promoting chronic inflammation in HIV and IBD. This inflammatory response persists in HIV+ persons even after long-term virologic suppression by antiretroviral therapy (ART). Here, we review gut dysfunction and microbiota changes during HIV infection and IBD, and discuss how this may induce metabolic reprogramming of monocytes, macrophages and T cells to impact disease outcomes. Drawing from parallels with IBD, we highlight how factors such as lipopolysaccharides, residual viral replication, and extracellular vesicles activate biochemical pathways that regulate immunometabolic processes essential for HIV persistence and non-AIDS metabolic comorbidities. This review highlights new mechanisms and support for the use of immunometabolic-based therapeutics towards HIV remission/cure, and treatment of metabolic diseases.

Similar but different: virtual memory CD8 T cells as a memory-like cell population.

Immunological memory is a phenomenon where the immune system can respond more rapidly to pathogens and immunological challenges that it has previously encountered. It is defined by several key hallmarks. After an initial encounter, immune cells (1) expand and (2) differentiate to form memory cell populations. Memory cells are (3) long-lived and (4) facilitate more rapid immune responses to subsequent infection because of (i) an increase in cell number, (ii) a decrease in the signaling threshold required for entry into cell cycle or effector function and (iii) localization of cells to tissue sites for surveillance. Classically, immunological memory has been antigen specific but it is becoming apparent that mechanisms of immunological memory can be co-opted by innate or antigen-inexperienced immune cells to generate heterogeneity in immune responses. One such cell is the virtual memory CD8 T (TVM ) cell, which is a semi-differentiated but antigen-naïve CD8 T-cell population. This review will summarize current knowledge of how TVM cells are generated, their memory-like hallmarks, how they are maintained during steady state, infection and aging, and propose a model to integrate key signaling pathways during their generation.

Comparison of chitinase-3-like protein 1, aspartate aminotransferase-to-platelet ratio index, and fibrosis-4 index with shear-wave elastography.

BACKGROUND: In the past, there has been an exponential increase in the potential biomarkers that can be used for staging of liver fibrosis. In light of intraobserver and intralobular variations, criticism has been directed at liver biopsy, and its efficacy has been challenged. Shear-wave elastography (SWE) has become a routine method for pre-assessment of liver fibrosis. Serum markers such as chitinase-3-like protein 1 (CHI3L1) also known as YKL-40, aspartate aminotransferase-to-platelet ratio index, and fibrosis-4 (Fib-4) index have been researched as potential alternates to detect liver fibrosis. STUDY: A total of 150 enrolled patients with chronic hepatitis underwent serum analysis to estimate CHI3L1 or YKL-40 level, aspartate aminotransferase-to-platelet ratio index, and Fib-4 index. These patients also underwent SWE. RESULTS: The distribution of fibrosis grade according to SWE was F0: 46 patients, F1: 31 patients, F2: 16 patients, F3: four patients, and F4: 53 patients. Receiver operating characteristic curve analysis for F0-F1 versus F2-F3, F0-F1 versus F4, and F2-F3 versus F4 gave area under curve values of 0.56 (P>0.05), 0.76 (P<0.01), and 0.75, respectively (P<0.01) for aspartate aminotransferase-to-platelet ratio index; of 0.65 (P<0.05), 0.78 (P<0.01), and 0.7, respectively (P<0.05) for Fib-4 index; and 0.98, 0.99, and 0.95, respectively (P<0.01 for all) for CHI3L1. CONCLUSION: CHI3L1 could be used as a preliminary tool to assess mild/absent fibrosis from significant fibrosis and cirrhosis.

Polymorphism rs1385129 Within Glut1 Gene SLC2A1 Is Linked to Poor CD4+ T Cell Recovery in Antiretroviral-Treated HIV+ Individuals.

Untreated HIV infection is associated with progressive CD4+ T cell depletion, which is generally recovered with combination antiretroviral therapy (cART). However, a significant proportion of cART-treated individuals have poor CD4+ T cell reconstitution. We investigated associations between HIV disease progression and CD4+ T cell glucose transporter-1 (Glut1) expression. We also investigated the association between these variables and specific single nucleotide polymorphisms (SNPs) within the Glut1 regulatory gene AKT (rs1130214, rs2494732, rs1130233, and rs3730358) and in the Glut1-expressing gene SLC2A1 (rs1385129 and rs841853) and antisense RNA 1 region SLC2A1-AS1 (rs710218). High CD4+Glut1+ T cell percentage is associated with rapid CD4+ T cell decline in HIV-positive treatment-naïve individuals and poor T cell recovery in HIV-positive individuals on cART. Evidence suggests that poor CD4+ T cell recovery in treated HIV-positive individuals is linked to the homozygous genotype (GG) associated with SLC2A1 SNP rs1385129 when compared to those with a recessive allele (GA/AA) (odds ratio = 4.67; P = 0.04). Furthermore, poor response to therapy is less likely among Australian participants when compared against American participants (odds ratio: 0.12; P = 0.01) despite there being no difference in prevalence of a specific genotype for any of the SNPs analyzed between nationalities. Finally, CD4+Glut1+ T cell percentage is elevated among those with a homozygous dominant genotype for SNPs rs1385129 (GG) and rs710218 (AA) when compared to those with a recessive allele (GA/AA and AT/TT respectively) (P < 0.04). The heterozygous genotype associated with AKT SNP 1130214 (GT) had a higher CD4+Glut1+ T cell percentage when compared to the dominant homozygous genotype (GG) (P = 0.0068). The frequency of circulating CD4+Glut1+ T cells and the rs1385129 SLC2A1 SNP may predict the rate of HIV disease progression and CD4+ T cell recovery in untreated and treated infection, respectively.

Interleukin-6: A promising cytokine to support liver regeneration and adaptive immunity in liver pathologies.

Liver pathologies (fibrosis, cirrhosis, alcoholic, non-alcoholic diseases and hepatocellular carcinoma) represent one of the most common causes of death worldwide. A number of genetic and environmental factors contribute to the development of liver diseases. Interleukin-6 (IL-6) is a pleiotropic cytokine, exerting variety of effects on inflammation, liver regeneration, and defence against infections by regulating adaptive immunity. Due to its high abundance in inflammatory settings, IL-6 is often viewed as a detrimental cytokine. However, accumulating evidence supports the view that IL-6 has a beneficial impact in numerous liver pathologies, due to its roles in liver regeneration and in promoting an anti-inflammatory response in certain conditions. IL-6 promotes proliferation, angiogenesis and metabolism, and downregulates apoptosis and oxidative stress; together these functions are critical for mediating hepatoprotection. IL-6 is also an important regulator of adaptive immunity where it induces T cell differentiation and regulates autoimmunity. It can augment antiviral adaptive immune responses and mitigate exhaustion of T cells during chronic infection. This review focuses on studies that present IL-6 as a key factor in regulating liver regeneration and in supporting effector immune functions and suggests that these functions of IL-6 can be exploited in treatment strategies for liver pathologies.

PTEN: A potential prognostic marker in virus-induced hepatocellular carcinoma.

PTEN is the second most frequently mutated tumor suppresser gene in cancers after p53. Genetic and epigenetic alterations in the PTEN gene and its regulatory regions have been reported in various studies. PTEN is a crucial downregulator of the pro-survival phosphoinositide 3-kinase/Akt/mammalian target of rapamycin pathway and also suppresses insulin signaling. Failure to regulate these pathways leads to increase in cell proliferation and migration which in turn promotes tumorigenesis. PTEN underexpression is mediated by a variety of cytokines and stress kinases which seem to collectively induce the RAS/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway. In the context of hepatocellular carcinoma, reduced expression of PTEN is seen in nearly half of the cases on average. In some cases, PTEN has been observed to be either mutated or methylated which can also lead to reduced expression or in some cases, complete loss of expression. On the cellular level, PTEN is also a target in the pathogenic pathway of hepatitis C virus core protein and hepatitis B virus X protein. These viruses appear to alter PTEN regulation and pro-apoptotic ability to enhance the process of tumor formation. In perspective of the crucial role PTEN plays in balancing proliferation and apoptosis, we propose PTEN as a valuable marker in the diagnosis, assessment of tumor grade, and disease stage in hepatocellular carcinoma patients.

Regulators of Glucose Metabolism in CD4+ and CD8+ T Cells.

Much like cancer cells, activated T cells undergo various metabolic changes that allow them to grow and proliferate rapidly. By adopting aerobic glycolysis upon activation, T cells effectively prioritize efficiency in biosynthesis over energy generation. There are distinct differences in the way CD4+ and CD8+ T cells process activation signals. CD8+ effector T cells are less dependent on Glut1 and oxygen levels compared to their CD4+ counterparts. Similarly the downstream signaling by TCR also differs in both effector T cell types. Recent studies have explored PI3K/Akt, mTORC, HIF1α, p70S6K and Bcl-6 signaling in depth providing definition of the crucial roles of these regulators in glucose metabolism. These new insights may allow improved therapeutic manipulation against inflammatory conditions that are associated with dysfunctional T-cell metabolism such as autoimmune disorders, metabolic syndrome, HIV, and cancers.

Phylogenetic analysis of Torque Teno Virus genome from Pakistani isolate and incidence of co-infection among HBV/HCV infected patients.

BACKGROUND: Torque Teno Virus (TTV) was the first single stranded circular DNA virus to be discovered that infects humans. Although there have been numerous reports regarding the prevalence of TTV from other countries of South Asia, there is severe lack of information regarding its prevalence in Pakistan. Thus the present study compiles the first indigenous report to comprehensively illustrate the incidence of the virus in uninfected and hepatitis infected population from Pakistan. Another aim of the study was to present the sequence of full length TTV genome from a local isolate and compare it with the already reported genome sequences from other parts of the world. METHODS: TTV DNA was screened in the serum of 116, 100 and 40 HBV infected, HCV infected and uninfected individuals respectively. Nearly full length genome of TTV was cloned from a HBV patient. The genome sequence was subjected to in-silico analysis using CLC Workbench, ClustalW, ClustalX and TreeView. Statistical analysis was carried out in SPSS v17.0. RESULTS: Our results report that 89.7%, 90.0% and 92.5% of HBV, HCV patients and healthy control population were positive for TTV infection. TTV genome of 3603 bp was also cloned from a local isolate and given the identity of TPK01. The TTV genome sequence mentioned in this paper is submitted in the GenBank/EMBL/DDBJ under the accession number JN980171. Phylogenetic analysis of TPK01 revealed that the Pakistani isolate has sequence similarities with genotype 23 and 22 (Genogroup 2). CONCLUSION: The results of the current study indicate that the high frequency of TTV viremia in Pakistan conforms to the reports from other areas of the world, wherever screening of TTV DNA was performed against 5'-UTR of the genome. The high sequence diversity among TTV genome sequences and the high frequency of prevalence makes it harder to study this virus in cellular systems.