Interleukin-21 Regulates Natural Killer Cell Responses During Mycobacterium tuberculosis Infection

Immune response of BALB/c mice infected with two strains of Corynebacterium pseudotuberculosis

This work evaluated aspects of the immune response of BALB/c mice infected with Corynebacterium pseudotuberculosis (T1 and C57). The fifteen BALB/c mice were euthanized after 70 days of infection and morphologically evaluated, also analyzing the innate and adaptive immune responses. The C57 strain induced more pronounced morphological changes than the T1 strain. There was an increase in CD4+ and CD8+ T cells identified during infection with the C57 strain. Cytokines of the inflammatory profile IL-1α and IL-6 and regulatory IL-13 and IL-10 presented significant differences. Cytokines IL-2, IL-4, INF-γ, IL-22, IL-21, and IL-27 did not differ significantly between groups. The obtained results contribute to a better understanding of the type of response and the immunological mechanisms involved during infection with different strains of C. pseudotuberculosis.

Pro-inflammatory cytokine IL-21 correlates with the reactive oxygen species and 25-hydroxy vitamin D in rheumatoid arthritis patients

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disorder and its characteristics include the immune system's invasion of the healthy lining of the joints and the articular structures degeneration. The IL-21 pro-inflammatory cytokine, and the reactive oxygen species (ROS) might have a role in the RA etiopathogenesis. The present study assessed the correlation of IL-21 with vitamin 25(OH)D and the ROS.

METHODS

The study included 120 RA patients and 60 healthy group. The RA patients were categorized based on rheumatoid factor (RF) seropositivity or seronegativity and the RA severity. Chemiluminescent immunoassay and 10% hematocrit were used to check levels of vitamin 25(OH)D and ROS, respectively. ELISA was used for the detection of IL-21 in the plasma.

RESULTS

The RA patients had a significantly reduced vitamin 25(OH)D level compared to the healthy controls. The IL-21 and ROS were however significantly increased in the RA patients compared to the controls. Further, the seropositive RF and the high RA severity patients had significant IL-21 and ROS increase in comparison with the seronegative RF and the low severity RA patients. Finally, IL-21 negatively correlated with vitamin 25(OH)D, but positively correlated with the ROS.

CONCLUSION

This is the first investigation to confirm the relationship between IL-21 with vitamin 25(OH)D and the ROS among the RA patients. The findings indicate that vitamin 25(OH)D is reduced in the RA patients' serum. ROS and IL-21 are also associated with increased RA severity.

NK-derived exosome miR-1249-3p inhibits Mycobacterium tuberculosis survival in macrophages by targeting SKOR1

Murine Natural Killer cells were cultivated in vitro to isolate NK-derived exosomes. Subsequent quantification via qPCR confirmed enrichment of miR-1249-3p. Ana-1 murine macrophages were cultured in vitro and subsequently inoculated with Mycobacterium tuberculosis (MTB) strain H37Rv. NK-exo and NK-exo miR-1249-3p were separately applied to the infection model, followed by immunological assays conducted post-48-hour co-culture. Western blot analyses corroborated that NK-exo exhibited exosomal marker proteins Granzyme A (GzmA), Granzyme B (GzmB), and Perforin (PFN), alongside a notable enrichment of miR-1249-3p. Functionally, NK-exo augmented the expression levels of Caspase-9,-8, and -3, as well as PARP, while attenuating the expression of NLRP3, ASC, and Cleaved-Caspase-1. Furthermore, qPCR demonstrated an up-regulation of Caspase-9, -8, and -3, along with pro-apoptotic factors Bax and Bid, and a concomitant down-regulation of the anti-apoptotic factor Bcl-2. The expression levels of inflammatory markers ASC, NLRP3, Cleaved-Caspase-1, and IL-1β were concomitantly decreased. ELISA findings indicated diminished levels of TNF-α and ROS secretion. NK-exo miR-1249-3p specifically targeted and attenuated the expression of SKOR-1, engendering up-regulation of apoptosis-associated proteins and down-regulation of inflammation-related proteins, consequently affecting cellular fate.Our empirical evidence substantiates that NK-exo induces macrophage apoptosis, thereby mitigating MTB survival. Furthermore, NK-exo miR-1249-3p directly targets and inhibits SKOR-1 expression, leading to macrophage apoptosis and consequently hampering the proliferation of MTB. The data implicate the potential therapeutic relevance of NK-exo and miR-1249-3p in managing drug-resistant tuberculosis.

Driving natural killer cell-based cancer immunotherapy for cancer treatment: An arduous journey to promising ground

Immunotherapy represents one of the most effective strategies for cancer treatment. Recently, progress has been made in using natural killer (NK) cells for cancer therapy. NK cells can directly kill tumor cells without pre-sensitization and thus show promise in clinical applications, distinct from the use of T cells. Whereas, research and development on NK cell-based immunotherapy is still in its infancy, and enhancing the therapeutic effects of NK cells remains a key problem to be solved. An incompletely understanding of the mechanisms of action of NK cells, immune resistance in the tumor microenvironment, and obstacles associated with the delivery of therapeutic agents in vivo, represent three mountains that need to be scaled. Here, we firstly describe the mechanisms underlying the development, activity, and maturation of NK cells, and the formation of NK‑cell immunological synapses. Secondly, we discuss strategies for NK cell-based immunotherapy strategies, including adoptive transfer of NK cell therapy and treatment with cytokines, monoclonal antibodies, and immune checkpoint inhibitors targeting NK cells. Finally, we review the use of nanotechnology to overcome immune resistance, including enhancing the anti-tumor efficiency of chimeric antigen receptor-NK, cytokines and immunosuppressive-pathways inhibitors, promoting NK cell homing and developing NK cell-based nano-engagers.

Clinical manifestations and immune response to tuberculosis

Tuberculosis is a far-reaching, high-impact disease. It is among the top ten causes of death worldwide caused by a single infectious agent; 1.6 million tuberculosis-related deaths were reported in 2021 and it has been estimated that a third of the world's population are carriers of the tuberculosis bacillus but do not develop active disease. Several authors have attributed this to hosts' differential immune response in which cellular and humoral components are involved, along with cytokines and chemokines. Ascertaining the relationship between TB development's clinical manifestations and an immune response should increase understanding of tuberculosis pathophysiological and immunological mechanisms and correlating such material with protection against Mycobacterium tuberculosis. Tuberculosis continues to be a major public health problem globally. Mortality rates have not decreased significantly; rather, they are increasing. This review has thus been aimed at deepening knowledge regarding tuberculosis by examining published material related to an immune response against Mycobacterium tuberculosis, mycobacterial evasion mechanisms regarding such response and the relationship between pulmonary and extrapulmonary clinical manifestations induced by this bacterium which are related to inflammation associated with tuberculosis dissemination through different routes.

Immune checkpoint modulating T cells and NK cells response to Mycobacterium tuberculosis infection

Many subversive mechanisms promote the occurrence and development of chronic infectious diseases and cancer, among which the down-regulated expression of immune-activating receptors and the enhanced expression of immune-inhibitory receptors accelerate the occurrence and progression of the disease. Recently, the use of immune checkpoint inhibitors has shown remarkable efficacy in the treatment of tumors in multiple organs. However, the expression of immune checkpoint molecules on natural killer (NK) cells by Mycobacterium tuberculosis (Mtb) infection and its impact on NK cell effector functions have been poorly studied. In this review, we focus on what is currently known about the expression of various immune checkpoints in NK cells following Mtb infection and how it alters NK cell-mediated host cytotoxicity and cytokine secretion. Unraveling the function of NK cells after the infection of host cells by Mtb is crucial for a comprehensive understanding of the innate immune mechanism of NK cells involved in tuberculosis and the evaluation of the efficacy of immunotherapies using immune checkpoint inhibitors to treat tuberculosis. In view of some similarities in the immune characteristics of T cells and NK cells, we reviewed the molecular mechanism of the interaction between T cells and Mtb, which can help us to further understand and explore the specific interaction mechanism between NK cells and Mtb.

HIV-Differentiated Metabolite N-Acetyl-L-Alanine Dysregulates Human Natural Killer Cell Responses to Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) has latently infected over two billion people worldwide (LTBI) and caused ~1.6 million deaths in 2021. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared with HIV- LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals. Plasma samples collected from healthy and HIV-infected individuals were investigated using liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using the online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, and quantitative reverse-transcription PCR (qRT-PCR) were performed using standard procedures to determine the surface markers, cytokines, and other signaling molecule expressions. Seahorse extra-cellular flux assays were used to measure mitochondrial oxidative phosphorylation and glycolysis. Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared with healthy donors. One of the HIV-upregulated metabolites, N-acetyl-L-alanine (ALA), inhibits pro-inflammatory cytokine IFN-γ production by the NK cells of LTBI+ individuals. ALA inhibits the glycolysis of LTBI+ individuals' NK cells in response to Mtb. Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK-cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV-Mtb interaction and providing insights into the implication of nutrition intervention and therapy for HIV-Mtb co-infected patients.

HIV-differentiated metabolite N-Acetyl-L-Alanine dysregulates human natural killer cell responses to Mycobacterium tuberculosis infection

Background

Mycobacterium tuberculosis ( Mtb ) has latently infected over two billion people worldwide (LTBI) and causes 1.8 million deaths each year. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared to the HIV-LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals.

Methods

Plasma samples collected from healthy and HIV-infected individuals were investigated by liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using an online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, quantitative reverse transcription PCR (qRT-PCR) were performed by standard procedure to determine the surface markers, cytokines and other signaling molecule expression. Seahorse extra cellular flux assays were used to measure the mitochondrial oxidative phosphorylation and glycolysis.

Results

Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared to healthy donors. One of the HIV-upregulated metabolites, N-Acetyl-L-Alanine (ALA), inhibits pro-inflammatory cytokine IFN-□ production by NK cells of LTBI+ individuals. ALA inhibits glycolysis of LTBI+ individuals' NK cells in response to Mtb .

Conclusions

Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV- Mtb interaction and providing the implication of nutrition intervention and therapy for HIV- Mtb co-infected patients.

Deciphering the virulence factors, regulation, and immune response to Acinetobacter baumannii infection

Deciphering the virulence factors, regulation, and immune response to Acinetobacter baumannii infectionAcinetobacter baumannii is a gram-negative multidrug-resistant nosocomial pathogen and a major cause of hospital acquired infetions. Carbapenem resistant A. baumannii has been categorised as a Priority1 critial pathogen by the World Health Organisation. A. baumannii is responsible for infections in hospital settings, clinical sectors, ventilator-associated pneumonia, and bloodstream infections with a mortality rates up to 35%. With the development of advanced genome sequencing, molecular mechanisms of manipulating bacterial genomes, and animal infection studies, it has become more convenient to identify the factors that play a major role in A. baumannii infection and its persistence. In the present review, we have explored the mechanism of infection, virulence factors, and various other factors associated with the pathogenesis of this organism. Additionally, the role of the innate and adaptive immune response, and the current progress in the development of innovative strategies to combat this multidrug-resistant pathogen is also discussed.

Leveraging Natural Killer Cell Innate Immunity against Hematologic Malignancies: From Stem Cell Transplant to Adoptive Transfer and Beyond

Numerous recent advancements in T-cell based immunotherapies have revolutionized the treatment of hematologic malignancies. In the race towards the first approved allogeneic cellular therapy product, there is growing interest in utilizing natural killer (NK) cells as a platform for off-the-shelf cellular therapies due to their scalable manufacturing potential, potent anti-tumor efficacy, and superior safety profile. Allogeneic NK cell therapies are now being actively explored in the setting of hematopoietic stem cell transplantation and adoptive transfer. Increasingly sophisticated gene editing techniques have permitted the engineering of chimeric antigen receptors, ectopic cytokine expression, and tumor recognition signals to improve the overall cytotoxicity of NK cell therapies. Furthermore, the enhancement of antibody-dependent cellular cytotoxicity has been achieved through the use of NK cell engagers and combination regimens with monoclonal antibodies that act synergistically with CD16-expressing NK cells. Finally, a greater understanding of NK cell biology and the mechanisms of resistance have allowed the preclinical development of NK checkpoint blockade and methods to modulate the tumor microenvironment, which have been evaluated in early phase trials. This review will discuss the recent clinical advancements in NK cell therapies in hematologic malignancies as well as promising avenues of future research.

Evaluation of early innate and adaptive immune responses to the TB vaccine Mycobacterium bovis BCG and vaccine candidate BCGΔBCG1419c

The vaccine Mycobacterium bovis Bacillus Calmette-Guérin (BCG) elicits an immune response that is protective against certain forms of tuberculosis (TB); however, because BCG efficacy is limited it is important to identify alternative TB vaccine candidates. Recently, the BCG deletion mutant and vaccine candidate BCGΔBCG1419c was demonstrated to survive longer in intravenously infected BALB/c mice due to enhanced biofilm formation, and better protected both BALB/c and C57BL/6 mice against TB-induced lung pathology during chronic stages of infection, relative to BCG controls. BCGΔBCG1419c-elicited protection also associated with lower levels of proinflammatory cytokines (i.e. IL6, TNFα) at the site of infection in C57BL/6 mice. Given the distinct immune profiles of BCG- and BCGΔBCG1419c-immunized mice during chronic TB, we set out to determine if there are early immunological events which distinguish these two groups, using multi-dimensional flow cytometric analysis of the lungs and other tissues soon after immunization. Our results demonstrate a number of innate and adaptive response differences between BCG- and BCGΔBCG1419c-immunized mice which are consistent with the latter being longer lasting and potentially less inflammatory, including lower frequencies of exhausted CD4⁺ T helper (T_H) cells and higher frequencies of IL10-producing T cells, respectively. These studies suggest the use of BCGΔBCG1419c may be advantageous as an alternative TB vaccine candidate.

IL-21/IL-21R Regulates the Neutrophil-Mediated Pathologic Immune Response during Chlamydial Respiratory Infection

IL-21/IL-21R was documented to participate in the regulation of multiple infection and inflammation. During Chlamydia muridarum (C. muridarum) respiratory infection, our previous study had revealed that the absence of this signal induced enhanced resistance to infection with higher protective Th1/Th17 immune responses. Here, we use the murine model of C. muridarum respiratory infection and IL-21R deficient mice to further identify a novel role of IL-21/IL-21R in neutrophilic inflammation. Resistant IL-21R^−/− mice showed impaired neutrophil recruitment to the site of infection. In the absence of IL-21/IL-21R, pulmonary neutrophils also exhibited reduced activation status, including lower CD64 expression, MPO activity, and neutrophil-produced protein production. These results correlated well with the decrease of neutrophil-related chemokines (KC and MIP-2), inflammatory cytokines (IL-6, IL-1β, and TNF-α), and TLR/MyD88 pathway mediators (TLR2, TLR4, and MyD88) in infected lungs of IL-21R^−/− mice than normal mice. Complementarily, decreased pulmonary neutrophil infiltration, activity, and levels of neutrophilic chemotactic factors and TLR/MyD88 signal in infected lungs can be corrected by rIL-21 administration. These results revealed that IL-21/IL-21R may aggravate the neutrophil inflammation through regulating TLR/MyD88 signal pathway during chlamydial respiratory infection.

A Bovine Enteric Mycobacterium Infection Model to Analyze Parenteral Vaccine-Induced Mucosal Immunity and Accelerate Vaccine Discovery

Mycobacterial diseases of cattle are responsible for considerable production losses worldwide. In addition to their importance in animals, these infections offer a nuanced approach to understanding persistent mycobacterial infection in native host species. Mycobacteriumavium ssp. paratuberculosis (MAP) is an enteric pathogen that establishes a persistent, asymptomatic infection in the small intestine. Difficulty in reproducing infection in surrogate animal models and limited understanding of mucosal immune responses that control enteric infection in the natural host have been major barriers to MAP vaccine development. We previously developed a reproducible challenge model to establish a consistent MAP infection using surgically isolated intestinal segments prepared in neonatal calves. In the current study, we evaluated whether intestinal segments could be used to screen parenteral vaccines that alter mucosal immune responses to MAP infection. Using Silirum^® – a commercial MAP bacterin – we demonstrate that intestinal segments provide a platform for assessing vaccine efficacy within a relatively rapid period of 28 days post-infection. Significant differences between vaccinates and non-vaccinates could be detected using quantitative metrics including bacterial burden in intestinal tissue, MAP shedding into the intestinal lumen, and vaccine-induced mucosal immune responses. Comparing vaccine-induced responses in mucosal leukocytes isolated from the site of enteric infection versus blood leukocytes revealed substantial inconsistences between these immune compartments. Moreover, parenteral vaccination with Silirum did not induce equal levels of protection throughout the small intestine. Significant control of MAP infection was observed in the continuous but not the discrete Peyer’s patches. Analysis of these regional mucosal immune responses revealed novel correlates of immune protection associated with reduced infection that included an increased frequency of CD335⁺ innate lymphoid cells, and increased expression of IL21 and IL27. Thus, intestinal segments provide a novel model to accelerate vaccine screening and discovery by testing vaccines directly in the natural host and provides a unique opportunity to interrogate mucosal immune responses to mycobacterial infections.

Enumeration of lymphocyte subsets during follow-up in the pulmonary tuberculosis patients with co morbid diabetes mellitus

The present study was designed to evaluate percentage of lymphocyte subsets in peripheral blood mononuclear cells of pulmonary tuberculosis patients with diabetes mellitus (TBDM) and household contacts (HHC) at the time of diagnosis and at different intervals of follow-up. T-lymphocyte subsets, monocytes and natural killer cells were evaluated using fluorescence associated cell sorting (FACS) in a total of 125 subjects including TBDM, pulmonary tuberculosis (PTB) patients, HHC, diabetes mellitus (DM) patients and healthy controls (HC), 25 in each category. CD4 proportion was significantly low in TBDM (p = 0.003), PTB (p = 0.0008) and HHC (p = 0.005) when compared to HCs and increased with treatment in PTB at 6 M and 12 M (p = 0.008). CD8 percentage was significantly low in DM (p = 0.01); Significantly high mean percentage was observed with respect to CD14 in TBDM (p = 0.008), PTB (p = 0.018), HHC (p = 0.008) and DM (p = 0.014); with CD16 in TBDM (p = 0.0001), PTB (p = 0.0001), HHC (p = 0.045); with CD56 in TBDM (p = 0.0003), PTB (p = 0.002) and HHC (p = 0.015) respectively when compared to HCs. These results indicate that TBDM patients have altered lymphocyte homeostasis and FACS analysis might have the potential of a non-invasive clinical indicator for the early detection and monitoring of TB in HHC.

Exploiting Pre-Existing CD4+ T Cell Help from Bacille Calmette-Guérin Vaccination to Improve Antiviral Antibody Responses

The continuing emergence of viral pathogens and their rapid spread into heavily populated areas around the world underscore the urgency for development of highly effective vaccines to generate protective antiviral Ab responses. Many established and newly emerging viral pathogens, including HIV and Ebola viruses, are most prevalent in regions of the world in which Mycobacterium tuberculosis infection remains endemic and vaccination at birth with M. bovis bacille Calmette-Guérin (BCG) is widely used. We have investigated the potential for using CD4⁺ T cells arising in response to BCG as a source of help for driving Ab responses against viral vaccines. To test this approach, we designed vaccines comprised of protein immunogens fused to an immunodominant CD4⁺ T cell epitope of the secreted Ag 85B protein of BCG. Proof-of-concept experiments showed that the presence of BCG-specific Th cells in previously BCG-vaccinated mice had a dose-sparing effect for subsequent vaccination with fusion proteins containing the Ag 85B epitope and consistently induced isotype switching to the IgG2c subclass. Studies using an Ebola virus glycoprotein fused to the Ag 85B epitope showed that prior BCG vaccination promoted high-affinity IgG1 responses that neutralized viral infection. The design of fusion protein vaccines with the ability to recruit BCG-specific CD4⁺ Th cells may be a useful and broadly applicable approach to generating improved vaccines against a range of established and newly emergent viral pathogens.

Insights in tuberculosis immunology: Role of NKT and T regulatory cells

Background

Tuberculosis (TB) control is challenging due to poor drug compliance and emerging resistance. The need of the hour is to determine the prediction of disease cure and relapse. Patients' immune response is crucial to the disease outcome. This study was designed to study the immune profile of TB patients during treatment and cure.

Methods

The cross-sectional study included newly diagnosed pulmonary TB patients and healthy controls. Levels of serum cytokines/chemokines (Th1/Th2/Th17) were measured by BD cytometric bead array. The cell surface markers assessed in the study were CD3, CD4, CD8, CD16, CD56, and BD human regulatory T cell cocktail (CD4/CD25/CD127).

Results

Data analysis observed statistically significant differences in CD3dim/CD56 + natural killer T (NKT) among TB patients with significantly low levels in healthy controls and after treatment completion (P < 0.0001). The analysis also revealed a high percentage of CD3dim/CD56 + NKT in fast responders. The percentage of T regulatory was found to be high in patients when compared with healthy controls; the values were statistically significant (0.0002). Interleukin-6 was significantly associated with the disease (P < 0.0485).

Discussion

A comprehensive understanding of role of CD3dim/CD56+ NKT in antimycobacterial immunity may enable new possibilities for NK cell-based prophylactic and/or therapeutic strategies against TB.

Characterization and bioactivity of grass carp (Ctenopharyngodon idella) interleukin-21: Inducible production and involvement in inflammatory regulation

In mammals, interleukin 21 (IL-21) is a broad pleiotropic cytokine that plays critical roles in the development of several inflammatory and autoimmune diseases. In fish, functional information of Il-21 is limited, and its role in immune response is largely unknown. In the present study, we cloned a coding sequence of grass carp (Ctenopharyngodon idella) il21 gene (gcil21). To characterize the release patterns and biological activity of gcIl-21, we prepared recombinant gcIl-21 (rgcIl-21) and obtained the polyclonal antibody with gcIl-21 specificity. Western blotting analysis showed that in grass carp head kidney leukocytes (HKLs), gcIl-21 was undetected in culture supernatant of untreated cells but drastically induced by heat-killed Aeromonas hydrophila (A. hydrophila), uncovering the release features of gcIl-21 and its possible involvement in immune response. Subsequent functional experiments revealed that rgcIl-21 did not affect the mRNA expression of grass carp il1b and tgfb, but induced a strong expression of grass carp il10, and to a lesser extent of grass carp tnfa in HKLs, suggesting a dominant effect of gcIl-21 in modulating Il-10 signaling as seen in rainbow trout and mammals. Furthermore, in vivo studies showed that intraperitoneal injection of rgcIl-21 was able to increase the survival rate of grass carp infected with live A. hydrophila, and reduce the pathological responses caused by the same pathogenic bacteria in head kidney and intestine. Taken together, these results for the first time revealed the close relationship of fish Il-21 production and function with inflammatory responses, and highlighted its anti-bacterial and anti-inflammatory ability, thereby providing a new insight into host defense mechanisms in fish.

Thinking Outside the Box: Innate- and B Cell-Memory Responses as Novel Protective Mechanisms Against Tuberculosis

Tuberculosis (TB) is currently the deadliest infectious disease worldwide. Failure to create a highly effective vaccine has limited the control of the TB epidemic. Historically, the vaccine field has relied on the paradigm that IFN-γ-mediated CD4+ T cell memory responses are the principal correlate of protection in TB. Nonetheless, the demonstration that other cellular subsets offer protective memory responses against Mycobacterium tuberculosis (Mtb) is emerging. Among these are memory-like features of macrophages, myeloid cell precursors, natural killer (NK) cells, and innate lymphoid cells (ILCs). Additionally, the dynamics of B cell memory responses have been recently characterized at different stages of the clinical spectrum of Mtb infection, suggesting a role for B cells in human TB. A better understanding of the immune mechanisms underlying such responses is crucial to better comprehend protective immunity in TB. Furthermore, targeting immune compartments other than CD4+ T cells in TB vaccine strategies may benefit a significant proportion of patients co-infected with Mtb and the human immunodeficiency virus (HIV). Here, we summarize the memory responses of innate immune cells and B cells against Mtb and propose them as novel correlates of protection that could be harnessed in future vaccine development programs.

RNA Sensing of Mycobacterium tuberculosis and Its Impact on TB Vaccination Strategies

Tuberculosis (TB) is still an important global threat and although the causing organism has been discovered long ago, effective prevention strategies are lacking. Mycobacterium tuberculosis (MTB) is a unique pathogen with a complex host interaction. Understanding the immune responses upon infection with MTB is crucial for the development of new vaccination strategies and therapeutic targets for TB. Recently, it has been proposed that sensing bacterial nucleic acid in antigen-presenting cells via intracellular pattern recognition receptors (PRRs) is a central mechanism for initiating an effective host immune response. Here, we summarize key findings of the impact of mycobacterial RNA sensing for innate and adaptive host immunity after MTB infection, with emphasis on endosomal toll-like receptors (TLRs) and cytosolic sensors such as NLRP3 and RLRs, modulating T-cell differentiation through IL-12, IL-21, and type I interferons. Ultimately, these immunological pathways may impact immune memory and TB vaccine efficacy. The novel findings described here may change our current understanding of the host response to MTB and potentially impact clinical research, as well as future vaccination design. In this review, the current state of the art is summarized, and an outlook is given on how progress can be made.

The Mechanisms of Disease Caused by Acinetobacter baumannii

Acinetobacter baumannii is a Gram negative opportunistic pathogen that has demonstrated a significant insurgence in the prevalence of infections over recent decades. With only a limited number of “traditional” virulence factors, the mechanisms underlying the success of this pathogen remain of great interest. Major advances have been made in the tools, reagents, and models to study A. baumannii pathogenesis, and this has resulted in a substantial increase in knowledge. This article provides a comprehensive review of the bacterial virulence factors, the host immune responses, and animal models applicable for the study of this important human pathogen. Collating the most recent evidence characterizing bacterial virulence factors, their cellular targets and genetic regulation, we have encompassed numerous aspects important to the success of this pathogen, including membrane proteins and cell surface adaptations promoting immune evasion, mechanisms for nutrient acquisition and community interactions. The role of innate and adaptive immune responses is reviewed and areas of paucity in our understanding are highlighted. Finally, with the vast expansion of available animal models over recent years, we have evaluated those suitable for use in the study of Acinetobacter disease, discussing their advantages and limitations.

T helper type cytokines in sepsis: time-shared variance and correlation with organ dysfunction and hospital mortality

Objective

We evaluated the kinetics of cytokines belonging to the T helper1 (Th1), Th2, and Th17 profiles in septic patients, and their correlations with organ dysfunction and hospital mortality.

Methods

This was a prospective observational study in a cohort of septic patients admitted to the intensive care units (ICU) of three Brazilian general hospitals. A total of 104 septic patients and 53 health volunteers (controls) were included. Plasma samples were collected within the first 48 h of organ dysfunction or septic shock (0D), after seven (D7) and 14 days (D14) of follow-up. The following cytokines were measured by flow cytometry: Interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-10, IL-12/23p40, IL-17, IL-21, tumor necrosis factor-α (TNF-α), granulocyte-macrophage colony stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF).

Results

IL-6, IL-8, G-CSF and IL-10 concentrations were higher in septic patients than in controls (p < 0.001), while IL-12/23p40 presented higher levels in the controls (p = 0.003). IL-6, IL-8 and IL-17 correlated with Sequential [Sepsis-related] Organ Failure Assessment (SOFA) D0, D1 and D3 (except for IL-6 at D0). IL-8 was associated with renal and cardiovascular dysfunction. In a mixed model analysis, IL-10 estimated means were lower in survivors than in deceased (p = 0.014), while IL-21 had an estimated mean of 195.8 pg/mL for survivors and 98.5 for deceased (p = 0.03). Cytokines were grouped in four factors according to their kinetics over the three dosages (D0, D7, D14). Group 1 encompassed IL-6, IL-8, IL-10, IL-1β, and G-CSF while Group 3 encompassed IL-17 and IL-12/23p40. Both correlated with SOFA (D0) (p = 0.039 and p = 0.003, respectively). IL-21 (Group 4) was higher in those who survived. IL-2, TNF-α and GM-CSF (Group 2) showed no correlation with outcomes.

Conclusion

Inflammatory and anti-inflammatory cytokines shared co-variance in septic patients and were related to organ dysfunctions and hospital mortality.