Involvement of neutrophil hyporesponse and the role of Toll-like receptors in human immunodeficiency virus 1 protection

Role of the human vaginal microbiota in the regulation of inflammation and sexually transmitted infection acquisition: Contribution of the non-human primate model to a better understanding?

The human vaginal microbiota has a central role in the regulation of the female reproductive tract (FRT) inflammation. Indeed, on one hand an optimal environment leading to a protection against sexually transmitted infections (STI) is associated with a high proportion of Lactobacillus spp. (eubiosis). On the other hand, a more diverse microbiota with a high amount of non-Lactobacillus spp. (dysbiosis) is linked to a higher local inflammation and an increased STI susceptibility. The composition of the vaginal microbiota is influenced by numerous factors that may lead to a dysbiotic environment. In this review, we first discuss how the vaginal microbiota composition affects the local inflammation with a focus on the cytokine profiles, the immune cell recruitment/phenotype and a large part devoted on the interactions between the vaginal microbiota and the neutrophils. Secondly, we analyze the interplay between STI and the vaginal microbiota and describe several mechanisms of action of the vaginal microbiota. Finally, the input of the NHP model in research focusing on the FRT health including vaginal microbiota or STI acquisition/control and treatment is discussed.

RIG-I-like Receptor Regulation of Immune Cell Function and Therapeutic Implications

Retinoic acid-inducible gene I-like receptors (RLRs) are cytosolic RNA sensors critical for initiation of antiviral immunity. Activation of RLRs following RNA recognition leads to production of antiviral genes and IFNs for induction of broad antiviral immunity. Although the RLRs are ubiquitously expressed, much of our understanding of these molecules comes from their study in epithelial cells and fibroblasts. However, RLR activation is critical for induction of immune function and long-term protective immunity. Recent work has focused on the roles of RLRs in immune cells and their contribution to programming of effective immune responses. This new understanding of RLR function in immune cells and immune programming has led to the development of vaccines and therapeutics targeting the RLRs. This review covers recent advances in our understanding of the contribution of RLRs to immune cell function during infection and the emerging RLR-targeting strategies for induction of immunity against cancer and viral infection.

Therapeutic role of inflammasome inhibitors in neurodegenerative disorders

Neuroinflammation, characterized by the activation of glial cells, is a hallmark in several neurological and neurodegenerative disorders. Inadequate inflammation cannot eliminate the infection of pathogens, while excessive or hyper-reactive inflammation can cause chronic or systemic inflammatory diseases affecting the central nervous system (CNS). In response to a brain injury or pathogen invasion, the pathogen recognition receptors (PRRs) expressed on glial cells are activated via binding to cellular damage-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs). This subsequently leads to the activation of NOD (nucleotide-binding oligomerization domain)-like receptor proteins (NLRs). In neurodegenerative diseases such as HIV-1-associated neurocognitive disorders (HAND), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), chronic inflammation is a critical contributing factor for disease manifestation including pathogenesis. Emerging evidence points to the involvement of "inflammasomes", especially the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) complex in the development of these diseases. The activated NLRP3 results in the proteolytic activation of caspase-1 that facilitates the cleavage of pro-IL-1β and the secretion of IL-1β and IL-18 proinflammatory cytokines. Accordingly, these and other seminal findings have led to the development of NLRP-targeting small-molecule therapeutics as possible treatment options for neurodegenerative disorders. In this review, we will discuss the new advances and evidence-based literature concerning the role of inflammasomes in neurodegenerative diseases, its role in the neurological repercussions of CNS chronic infection, and the examples of preclinical or clinically tested NLRP inhibitors as potential strategies for the treatment of chronic neurological diseases.

The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic exercise in recreational athletes

BACKGROUND

To examine the effects of varying doses of caffeine on autonomic reactivation following anaerobic exercise.

METHODS

Recreationally active males (N = 20; 24 ± 2y) participated in a randomized, double-blind, placebo-controlled, crossover study where participants ingested: [1] Control (CON; no supplement), [2] a non-caffeinated placebo (PLA), [3] 3-mg∙kg- 1 of caffeine (CAF3) or [4] 6-mg∙kg- 1 of caffeine (CAF6) prior to Wingate testing. Parasympathetic (lnRMSSD, primary outcome) and global HRV (lnSDNN, secondary outcome) were assessed at rest (i.e., pre-ingestion), 45-min post-ingestion, and 5-min and 35-min post-exercise recovery. We used a GLM to assess mean (95% CI) changes from pre-ingestion baseline.

RESULTS

Overall, we observed a significant trend for lnRMSSD and lnSDNN (both, p = 0.001, ηp2 = 0.745). Forty-five minutes after treatment ingestion, we observed a significant increase in lnRMSSD for CAF3 (0.15 ms, 95%CI, 0.07,0.24) and CAF6 (0.16 ms, 95%CI, 0.06,0.25), both being significant (both, p <  0.004) vs. CON (- 0.02 ms, 95%CI, - 0.09,0.04). Five-minutes after exercise, all treatments demonstrated significant declines in lnRMSSD vs. baseline (all, p <  0.001). After 35-min of recovery, lnRMSSD returned to a level not significantly different than baseline for CAF3 (0.03 ms, 95%CI, - 0.05, 0.12) and CAF6 (- 0.03 ms, 95%CI, - 0.17, 0.10), while PLA (- 0.16 ms, 95%CI, - 0.25, - 0.06) and CON (- 0.17 ms, 95%CI, - 0.28, - 0.07) treatments remained significantly depressed. A similar pattern was also observed for SDNN.

CONCLUSION

Caffeine ingestion increases resting cardiac autonomic modulation and accelerates post-exercise autonomic recovery after a bout of anaerobic exercise in recreationally active young men. However, no differences between caffeine doses on cardiac autonomic reactivity were observed.

Inflammasome in HIV infection: Lights and shadows

The importance of inflammasome, and related cytokines IL-1ß and IL-18, in host defense against pathogens is well documented, however, at the same time, dysregulation of inflammasome has been associated to multifactorial diseases characterized by chronic inflammation (i.e.: metabolic disorders, cardiovascular diseases, neurodegenerative diseases, autoimmunity, cancer). Inflammasome activation has been described in response to HIV-1 and possibly contributes to the resistance against virus establishment, however, on the other hand, when viral infection becomes chronic, independently from antiretroviral therapy, the increase constitutive activation of inflammasome has been eventually associated to a worse prognosis, raising the question about the role played by inflammasome and/or some specific receptors in this context. Due to the chance to imply targeted therapies that inhibit inflammasome activation and/or cytokines release, it will be important to define the impact of the complex in the pathogenesis of HIV. The purpose of this review is to depict the double-faced inflammasome role in HIV-1 infection, trying to unveil whether besides its role in first line defense against the virus, it exerts a harmful effect during the chronic phase of infection.

The Dual Role of Neutrophils in HIV Infection

PURPOSE OF REVIEW

We summarize what is known about neutrophils in HIV infection, focusing on their potential roles in HIV protection, acquisition, and pathogenesis.

RECENT FINDINGS

Recent studies have demonstrated that neutrophil-associated proteins and cytokines in genital tissue pre-infection associate with HIV acquisition. However, recent in vivo assessment of highly exposed seronegative individuals and in vitro studies of anti-HIV functions of neutrophils add to older literature evidence that neutrophils may be important in a protective response to HIV infection. Neutrophils are important for containment of pathogens but can also contribute to tissue damage due to their release of reactive oxygen species, proteases, and other potentially harmful effector molecules. Overall, there is a clear evidence for both helpful and harmful roles of neutrophils in HIV acquisition and pathogenesis. Further study, particularly of tissue neutrophils, is needed to elucidate the kinetics, phenotype, and functionality of neutrophils in HIV infection to better understand this dichotomy.

Inflammatory status and severity of disease in dengue patients are associated with lipoprotein alterations

INTRODUCTION

The triggering of severe dengue has been associated with an exacerbated inflammatory process characterized by the production of pro-inflammatory cytokines such as IL-1β/IL-18, which are the product of inflammasome activation. Furthermore, alteration in the levels of high-density (HDL) and low-density lipoproteins (LDL) has been observed; and HDL are known to have immunomodulatory properties, including the regulation of inflammasomes. While HDL would be expected to counteract hyperactivation of the inflammasome, the relationship between HDL and dengue severity, has not previously been explored.

METHODOLOGY

We conducted a cross-sectional study of 30 patients with dengue and 39 healthy controls matched by sex and age. Lipid profile and levels of C-reactive protein were quantified. Serum levels of IL-1β, IL-6, IL-10, IL-18, and TNF-α, were assessed by ELISA. Expression of inflammasome-related genes in PBMC was quantified by qPCR.

RESULTS

Dengue patients presented an alteration in the parameters of the lipid profile, with a significant decrease in HDL levels, which was more pronounced in dengue patients with warning signs. Moreover, a decrease in the expression of the inflammasome-related genes NLRP1, NLRC4, caspase-1, IL-1β and IL-18 was observed, as well as an increase in serum levels of C-reactive protein and IL-10 in dengue patients versus healthy donors. Significant positive correlations between LDL levels and the relative expression of NLRP3, NLRC4, IL-1β and IL-18, were found.

CONCLUSION

The results suggest that there is a relationship between the alteration of LDL and HDL with the imbalance in the inflammatory response, which could be associated with the severity of dengue.

Interleukin 21 (IL-21)/microRNA-29 (miR-29) axis is associated with natural resistance to HIV-1 infection

BACKGROUND

Interleukin-21 (IL-21) modulates HIV-1 infection through the elicitation of different antiviral mechanisms, including Th17 lineage commitment and induction of microRNA (miR)-29, a miRNA endowed with anti-HIV activity. As miR-29 expression is significantly increased in HIV-1-exposed seronegative individuals (HESN), we investigated the role of miR-29/IL21 axis in the natural control of HIV-1 infection.

METHODS

Peripheral blood mononuclear cells (PBMCs) isolated from 15 Italian sexually exposed HESN and 15 HIV-unexposed healthy controls were in-vitro infected with an R5-tropic HIV-1Ba-L strain. Seven days post HIV-1 infection we evaluated: 1) p24 production (ELISA); 2) CD4/IL-21 and CD4/IL-17 T lymphocytes (FACS); 3) IL-17 concentration in supernatants (ELISA); and 4) IL-6, IL-17, IL-21, and miR-29a,b,c expression by CD4 T lymphocytes as well as perforin and granzyme by peripheral blood mononuclear cells (qPCR). The same analyses were performed on the 15 HIV-positive partners.

RESULTS

At baseline IL-6 expression alone was increased in HESN compared to healthy controls. Seven days after in-vitro HIV-1 infection, nevertheless, differences emerged. Thus, CD4/IL21 and CD4/IL17 T lymphocytes, as well as IL-21 and IL-17 expression and production were significantly augmented in HESN compared to healthy controls. Interestingly, IL-21 upregulation correlated with a significantly increased expression of miR-29a,b,c and a reduced susceptibility to in-vitro HIV-1 infection in HESN alone. No differences were observed in perforin and granzyme expression.

CONCLUSION

The IL-21/miR-29 axis is upregulated by HIV-1 infection in HESN suggesting its involvement in the natural resistance to HIV-1 infection in HESN. Approaches that exogenously increase IL-21 production or prompt preexisting cellular IL-21 reservoir could confine the magnitude of the initial HIV-1 infection.

Lower High-Density Lipoproteins Levels During Human Immunodeficiency Virus Type 1 Infection Are Associated With Increased Inflammatory Markers and Disease Progression

Introduction

High-density lipoproteins (HDL) are responsible for the efflux and transport of cholesterol from peripheral tissues to the liver. In addition, HDL can modulate various immunological mechanisms, including the inflammatory response. Inflammasomes are multiprotein complexes that have been reported to be activated during human immunodeficiency virus type 1 (HIV-1) infection, thus contributing to immune hyperactivation, which is the main pathogenic mechanism of HIV-1 progression. However, the relationship between HDL and inflammasomes in the context of HIV-1 infection is unclear. Therefore, this research aims to explore the association between HDL and the components of the inflammatory response during HIV-1 infection.

Methodology

A cross-sectional study, including 36 HIV-1-infected individuals without antiretroviral treatment and 36 healthy controls matched by sex and age, was conducted. Viral load, CD4+ T-cell counts, serum HDL, and C-reactive protein (CRP) were quantified. Serum cytokine levels, including IL-1β, IL-6, and IL-18, were assessed by ELISA. The inflammasome-related genes in peripheral blood mononuclear cells were determined by quantitative real-time PCR.

Results

HIV-1-infected individuals showed a significant decrease in HDL levels, particularly those subjects with higher viral load and lower CD4+ T-cell counts. Moreover, upregulation of inflammasome-related genes (NLRP3, AIM2, ASC, IL-1β, and IL-18) was observed, notably in those HIV-1-infected individuals with higher viral loads (above 5,000 copies/mL). Serum levels of IL-6 and CRP were also elevated in HIV-1-infected individuals. Significant negative correlations between HDL and the mRNA of NLRP3, AIM2, ASC, IL-1β, and IL-18, as well as viral load and CRP were observed in HIV-1-infected individuals. Likewise, a significant positive correlation between HDL and CD4+ T-cell counts was found.

Conclusion

In summary, our results indicate that HDL might modulate the expression of several key components of the inflammasomes during HIV-1 infection, suggesting a novel role of HDL in modifying the inflammatory state and consequently, the progression of HIV-1 infection.

Silica nanoparticles induce NLRP3 inflammasome activation in human primary immune cells

In recent years, the potential use of silica nanoparticles (SiNPs) among different biomedical fields has grown. A deep understanding of the physicochemical properties of nanoparticles (NPs) and their regulation of specific biological responses is crucial for the successful application of NPs. Exposure to NP physicochemical properties (size, shape, porosity, etc.) could result in deleterious effects on cellular functions, including a pro-inflammatory response mediated via activation of the NLRP3 inflammasome. The aim of this study was to evaluate the potential in vitro immunomodulatory effect of 12-nm and 200-nm SiNPs on the expression of pro-inflammatory cytokines and NLRP3 inflammasome components in human primary neutrophils and PBMCs. This study demonstrates that regardless of the size of the nanoparticles, SiNPs induce the production of pro-inflammatory cytokines in a dose-dependent manner. Induced IL-1β production after exposure to SiNPs suggests the involvement of NLRP3 inflammasome components participation in this process. In conclusion, SiNPs induce the production of pro-inflammatory cytokines in a dose-dependent manner. Furthermore, our data suggest that the production and release of IL-1β possibly occurs through the formation of the NLRP3 inflammasome.

The rectal mucosa and condomless receptive anal intercourse in HIV-negative MSM: implications for HIV transmission and prevention

Most HIV transmissions among men who have sex with men (MSM), the group that accounted for 67% of new US infections in 2014, occur via exposure to the rectal mucosa. However, it is unclear how the act of condomless receptive anal intercourse (CRAI) may alter the mucosal immune environment in HIV-negative MSM. Here, we performed a comprehensive characterization of the rectal mucosal immune environment for the phenotype and production of pro-inflammatory cytokines by CD4 and CD8 T cells, global transcriptomic analyses, and the composition of microbiota in HIV-negative MSM. Our results show that compared with men who had never engaged in anal intercourse, the rectal mucosa of MSM engaging in CRAI has a distinct phenotype characterized by higher levels of Th17 cells, greater CD8+ T cell proliferation and production of pro-inflammatory cytokines, molecular signatures associated with mucosal injury and repair likely mediated by innate immune cells, and a microbiota enriched for the Prevotellaceae family. These data provide a high-resolution model of the immunological, molecular, and microbiological perturbations induced by CRAI, will have direct utility in understanding rectal HIV transmission among MSM, and will enhance the design of future biomedical prevention interventions, including candidate HIV vaccines.

Pulmonary Innate Immune Dysfunction in Human Immunodeficiency Virus

The advent of antiretroviral therapy has transformed infection by the type 1 human immunodeficiency virus (HIV) from a rapidly fatal disease to a chronic illness with excellent long-term survival rates. Although HIV primarily targets the adaptive arm of host immunity, it simultaneously impacts the innate immune system, and has profound implications for lung health, even when viral suppression is achieved with antiretroviral therapy. The lung has evolved a unique array of innate immune defenses, and the pathophysiological interactions between HIV and the pulmonary innate immune system deserve particular attention. In this review, we discuss work that elucidates how the components of innate immunity both respond to and are perturbed by infection with HIV.

Understanding the molecular mechanisms of NETs and their role in antiviral innate immunity

Polymorphonuclear neutrophils (PMNs) are the most abundant cells in the context of innate immunity; they are one of the first cells to arrive at the site of viral infection constituting the first line of defense in response to invading pathogens. Indeed, neutrophils are provided with several defense mechanisms including release of cytokines, cytotoxic granules and the last recently described neutrophil extracellular traps (NETs). The main components of NETs are DNA, granular antimicrobial peptides, and nuclear and cytoplasmic proteins, that together play an important role in the innate immune response. While NETs were first described as a mechanism against bacteria and fungi, recently, several studies are beginning to elucidate how NETs are involved in the host antiviral response and the prominent characteristics of this new mechanism are discussed in the present review.

HIV-1-derived single-stranded RNA acts as activator of human neutrophils

Neutrophils are key effector cells of the innate immune system and are involved in the host defense against invading pathogens such as viruses. Recently, it was reported that HIV-1-neutrophil interaction triggers neutrophil activation and promotes expression of Toll-like receptors (TLRs). Here, we assessed the role of single-stranded RNA40 (ssRNA40) derived from HIV-1 in neutrophil activation. We observed functional activation of neutrophils in response to HIV-1-derived ssRNA40 based on the expression of TLR7/8, RIG-I, and MDA5, induction of cytokines (IL-6 and TNF-α), and the production of reactive oxygen species (ROS). Additionally, ssRNA40 promoted the expression of CD62L and TNF-α and the production of ROS in the presence of the TLR2 agonist Pam2CSK4. ssRNA40 together with R848 (a TLR7/8 agonist) increased CD11b expression but decreased CD62L expression. Furthermore, decreased IL-6 expression was observed in the presence of the TLR4 agonist LPS. Finally, we found that ssRNA40 promotes RIG-I and MDA5 expression in the presence of the TLR2, TLR4 and TLR7/8 agonists. This study demonstrates a functional response of TLRs in neutrophils challenged with ssRNA40, suggesting that TLRs could be involved in the innate immune response observed during HIV infection, which might be mediated by its genome.

HIV-1-neutrophil interactions trigger neutrophil activation and Toll-like receptor expression

Although neutrophils are the first-line of host defense against infection and express a wide number of pattern recognition receptors (PRRs), the function of these PRRs, including Toll-like receptors (TLRs), in HIV-1 infection remains unclear. TLRs play an important role in innate immunity, and while their involvement in viral immune pathogenesis was recently proposed, little is known about their expression and function during the neutrophil response to HIV-1 exposure. Here, we have shown that freshly isolated human neutrophils from healthy donors exhibited altered TLR expression, which may affect their function, after being challenged with HIV-1, alone or in the presence of TLR agonists. TLRs may promote neutrophil activation, pro-inflammatory cytokine secretion, and the production of reactive oxygen species. To our knowledge, this study is the first demonstration of functional TLR expression on neutrophils in response to HIV-1 treatment, suggesting a possible neutrophil/HIV-1 interaction through TLRs. Although additional studies are required to confirm the function of TLRs in neutrophils, our data clearly suggest that they play a role in the regulation of innate immunity by neutrophils, which could be engaged in HIV-1 pathogenesis or host defense.

HIV-1-exposed seronegative individuals show alteration in TLR expression and pro-inflammatory cytokine production ex vivo: An innate immune quiescence status?

Pattern recognition receptors (PRRs) are involved in direct recognition of viruses, promoting cellular activation and the production of pro-inflammatory cytokines. However, despite the reduced systemic immune activation described in HIV-1-exposed seronegatives (HESNs), few studies have focused on determining the relationship between PRR expression and cytokine production. We have aimed here to evaluate the expression level of PRRs and cytokines in HESNs, HIV-1 patients and healthy donors. Basal PRR expression levels in PBMCs, dendritic cells (DCs) and monocytes, and plasma cytokine levels as well as the PRR ligand-induced cytokine productions were determined by flow cytometry, qPCR and ELISA. Higher TLR2/4 expression in DCs and monocytes from HESNs was observed. Nevertheless, TLR4/8, NOD2 and RIG-I mRNA levels were lower in PBMCs from HESNs than HIV-1-infected patients. Comparable IL-1β, IL-18 and TNF-α mRNA levels were observed among the groups examined; however, at the protein level, production of IL-1β, IL-6 and IL-10 was significantly lower in plasma from HESNs than from HIV-1-infected patients. Our results suggest that exposure to HIV-1 without infection could be associated with reduced basal pro-inflammatory responses. Further studies are required to define the cell subsets responsible for these differences and the role of PRRs on protection against HIV-1 infection.