Increased frequency of Th17 cells in the peripheral blood of children infected with enterovirus 71

A surge in serum mucosal cytokines associated with seroconversion in children at risk for type 1 diabetes

AIMS/INTRODUCTION

Autoantibodies to pancreatic islet antigens identify young children at high risk of type 1 diabetes. On a background of genetic susceptibility, islet autoimmunity is thought to be driven by environmental factors, of which enteric viruses are prime candidates. We sought evidence for enteric pathology in children genetically at-risk for type 1 diabetes followed from birth who had developed islet autoantibodies ("seroconverted"), by measuring mucosa-associated cytokines in their sera.

MATERIALS AND METHODS

Sera were collected 3 monthly from birth from children with a first-degree type 1 diabetes relative, in the Environmental Determinants of Islet Autoimmunity (ENDIA) study. Children who seroconverted were matched for sex, age, and sample availability with seronegative children. Luminex xMap technology was used to measure serum cytokines.

RESULTS

Of eight children who seroconverted, for whom serum samples were available at least 6 months before and after seroconversion, the serum concentrations of mucosa-associated cytokines IL-21, IL-22, IL-25, and IL-10, the Th17-related cytokines IL-17F and IL-23, as well as IL-33, IFN-γ, and IL-4, peaked from a low baseline in seven around the time of seroconversion and in one preceding seroconversion. These changes were not detected in eight sex- and age-matched seronegative controls, or in a separate cohort of 11 unmatched seronegative children.

CONCLUSIONS

In a cohort of children at risk for type 1 diabetes followed from birth, a transient, systemic increase in mucosa-associated cytokines around the time of seroconversion lends support to the view that mucosal infection, e.g., by an enteric virus, may drive the development of islet autoimmunity.

Laboratory Indicators for Identifying Hand, Foot, and Mouth Disease Severity: A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study is to study laboratory indicators for the identification of hand, foot, and mouth disease (HFMD) severity.

METHODS

We searched PubMed, Embase, and the Web of Science for literature that was published before May 2022. The main results are presented as forest plots. Subgroup analyses, sensitivity analyses, and publication bias were also performed.

RESULTS

Our study indicated that white blood cells (WBC) (95%CI: 0.205-0.778), blood glucose (95%CI: 0.505-0.778), lymphocytes (95%CI: 0.072-0.239), creatinine (95%CI: 0.024-0.228), interleukin (IL)-2 (95%CI: 0.192-1.642), IL-6 (95%CI: 0.289-0.776), IL-8 (95%CI: 0.499-0.867), IL-10 (95%CI: 0.226-0.930), interferon-γ (IFN-γ) (95%CI: 0.193-2.584), tumor necrosis factor-α (TNF-α) (95%CI: 1.078-2.715), and creatine kinase MB isoenzyme (CK-MB) (95%CI: 0.571-1.459) were associated with an increased risk of HFMD severity, and the results of the sensitivity analysis of these indicators were stable and free of publication bias.

CONCLUSIONS

Our results suggest that various deleterious immune and metabolic changes can increase the risk of HFMD severity, which can provide a basis for predicting the prognosis and useful evidence for clinicians to manage patients efficiently.

Low-frequency, exhausted immune status of CD56dim NK cells and disordered inflammatory cytokine secretion of CD56bright NK cells associated with progression of severe HFMD, especially in EV71-infected patients

BACKGROUND

The roles of CD56^bright and CD56^dim natural killer (NK) subsets in the viral clearance and inflammatory processes of hand, foot, and mouth disease (HFMD) remain undefined.

METHODS

A total of 39 HCs and 55 patients were enrolled to analyze peripheral CD56^bright and CD56^dim NK cells according to cell number, surface receptors, cytotoxic activities, and cytokine production. The plasma concentrations of IL-2, IL-6, IL-10, IFN-γ, TNF-α,and MCP-1 were detected using ELSA.

RESULTS

Peripheral blood NK cells was significantly lower in severe patients than in HCs due to the dramatic loss of CD56^dim NK cells with no changes in the cell count of CD56^bright NK cells. For mild patients, decreased NKp46 expression coincided with enhanced cytolysis (CD107a, GNLY, and GrB) in CD56^dim NK cells and decreased NKG2A expression with enhanced IL-10 production in CD56^bright NK cells. In contrast, severe patients showed the dominant expression of NKG2A and decreased expression of NKG2D accompanied by cytotoxic dysfunction in CD56^dim NK cells. Imbalanced receptor expression coincided with the increased concentrations of TNF-α in CD56^bright NK cells. Moreover, EV71+ patients showed significantly decreased counts of CD56^dim NK cells with cytolysis dysfunction, displayed cytokine hypersecretion in CD56^bright NK cells, while the EV71- patients displayed significantly higher plasma cytokine concentrations. The changes in the immune function of NK subsets and their subpopulations were closely related to clinical inflammatory parameters.

CONCLUSIONS

Low-frequency, exhausted immune status of CD56^dim NK cells and disordered inflammatory cytokine secretion of CD56^bright NK cells were associated with the progression of severe HFMD, especially in EV71-infected patients. This promoted the severity of inflammatory disorders, leading to enhanced disease pathogenesis.

The Binary Model of Chronic Diseases Applied to COVID-19

A binary model for the classification of chronic diseases has formerly been proposed. The model classifies chronic diseases as “high Treg” or “low Treg” diseases according to the extent of regulatory T cells (Treg) activity (frequency or function) observed. The present paper applies this model to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The model correctly predicts the efficacy or inefficacy of several immune-modulating drugs in the treatment of severe coronavirus disease 2019 (COVID-19) disease. It also correctly predicts the class of pathogens mostly associated with SARS-CoV-2 infection. The clinical implications are the following: (a) any search for new immune-modulating drugs for the treatment of COVID-19 should exclude candidates that do not induce “high Treg” immune reaction or those that do not spare CD8+ T cells; (b) immune-modulating drugs, which are effective against SARS-CoV-2, may not be effective against any variant of the virus that does not induce “low Treg” reaction; (c) any immune-modulating drug, which is effective in treating COVID-19, will also alleviate most coinfections; and (d) severe COVID-19 patients should avoid contact with carriers of “low Treg” pathogens.

Immunomodulatory Effects of Rhinovirus and Enterovirus Infections During the First Year of Life

Early childhood infections have been implicated in the development of immune-mediated diseases, such as allergies, asthma, and type 1 diabetes. We set out to investigate the immunomodulatory effects of early viral infections experienced before the age of one year on the peripheral regulatory T cell population (Treg) and circulating cytokines in a birth-cohort study of Estonian and Finnish infants. We show here a temporal association of virus infection with the expression of FOXP3 in regulatory T cells. Infants with rhinovirus infection during the preceding 30 days had a higher FOXP3 expression in Treg cells and decreased levels of several cytokines related to Th1 and Th2 responses in comparison to the children without infections. In contrast, FOXP3 expression was significantly decreased in highly activated (CD4+CD127-/loCD25+FOXP3high) regulatory T cells (TregFOXP3high) in the infants who had enterovirus infection during the preceding 30 or 60 days. After enterovirus infections, the cytokine profile showed an upregulation of Th1- and Th17-related cytokines and a decreased activation of CCL22, which is a chemokine derived from dendritic cells and associated with Th2 deviation. Our results reveal that immunoregulatory mechanisms are up-regulated after rhinovirus infections, while enterovirus infections are associated with activation of proinflammatory pathways and decreased immune regulation.

Increased effector γδ T cells with enhanced cytokine production are associated with inflammatory abnormalities in severe hand, foot, and mouth disease

BACKGROUND

Although γδ T cells have been reported to be closely related to the immunopathogenesis of some viral infectious diseases, the changes or roles of γδ T cells in the development of hand, foot, and mouth disease (HFMD) remain unclear.

METHODS

Peripheral γδ T cells and their subsets were determined by surface (γδ TCR, Vδ1 TCR, Vδ2 TCR, CD45RA, and CD27) or intracellular (IFN-γ, TNF-α, CD107a, and Granzyme B) markers in healthy controls (HCs) and HFMD patients with FACS. The plasma levels of IFN-γ, TNF-α, IL-6, and MCP-1 were measured by ELISA. Differences in γδ T cells or their subsets and correlations between γδ T cells and inflammation indicators were statistically analyzed.

RESULTS

Compared to HCs, HFMD patients showed increased effector γδ T and TNF-α⁺γδ T cells and plasma TNF-α levels, especially in severe cases. In addition, significantly increased Vδ1 T and IFN-γ⁺γδ T cells and other plasma inflammatory cytokines were further found in severe patients. Furthermore, EV71+ severe patients showed significantly increased effector and cytokine-producing γδ T cells, while the EV71- severe patients displayed significantly greater plasma cytokine levels. The percentage of IFN-γ⁺γδ T or TNF-α⁺γδ T cells was positively correlated with that of effector γδ T cells. There was a positive correlation between the proportion of Vδ1 T cells and white blood cell (WBC) count or the proportion of IFN-γ⁺γδ T or TNF-α⁺γδ T cells and neutrophil (N) count, while there was a negative correlation between Vδ2 T cells and WBC or N count. Moreover, the percentages of Vδ1 T and effector γδ T cells in the acute phase of disease declined significantly to normal levels during the recovery phase.

CONCLUSIONS

Increased effector γδ T cells with enhanced cytokine production were remarkably observed in severe HFMD patients, which was also associated with clinical inflammation parameters. These data indicated that γδ T cells might be involved in inflammatory abnormalities in severe HFMD.

Celiac Disease in Children, Particularly with Accompanying Type 1 Diabetes, Is Characterized by Substantial Changes in the Blood Cytokine Balance, Which May Reflect Inflammatory Processes in the Small Intestinal Mucosa

Cytokines play a pivotal role in the maintenance of intestinal homeostasis inducing pro- or anti-inflammatory response and mucosal barrier function in celiac disease (CD) and type 1 diabetes (T1D). We aimed to compare the levels of pro- and anti-inflammatory cytokines in CD patients without and with coexisting T1D, as well as to evaluate its association with the presence of enteroviruses (EV), regulatory T cells (Tregs), and dendritic cells (DCs) in small bowel mucosa. Altogether, 72 patients (median age 10.1 years) who had undergone small bowel biopsy were studied. The study group consisted of 24 patients with CD (median age 6.5 years), 9 patients with CD and concomitant T1D (median age 7.0 years), two patients with T1D (median age 8.5 years), and 37 patients (median age 14.0 years) with functional gastrointestinal disorders (FGD) and a normal small bowel mucosa as controls. The levels of 33 cytokines in serum were measured by multiple analysis using the Milliplex® MAP Magnetic Bead assay. The densities of FOXP3+ Tregs, CD11c+ DC, indoleamine 2,3-dioxygenase+ (IDO+) DC, langerin+ (CD207+) DCs, and EV were evaluated by immunohistochemistry as described in our previous studies. Circulating anti-EV IgA and IgG were evaluated using ELISA. The most important finding of the study is the significant increase of the serum levels of IL-5, IL-8, IL-13, IL-15, IL-17F, IL-22, IL-27, IP-10, MIP-1β, sIL-2Rα, sTNFRII, and TNFα in CD patients compared to controls and its correlation with the degree of small bowel mucosa damage graded according to the Marsh classification. The leptin level was higher in females in all study groups. The levels of IL-2, IL-6, IL-12 (P70), IL-15, IP-10, and IFNγ correlated significantly with the density of FOXP3+ Tregs in lamina propria of the small bowel mucosa, which supports the evidence about the signaling role of these cytokines in the peripheral maintenance of FOXP3+ Tregs. At the same time, a significant negative correlation occurred between the level of IL-4 and density of FOXP3+ Tregs in controls. Another important finding of our study was the correlation of IL-17F, IP-10, sTNFRII, MCP-1, and GM-CSF with the density of EV-positive cells in the lamina propria of the small bowel mucosa. Correlation of MIP-1 (CCL-4) with CD103+ DC and langerin+ DC densities may point to their significance in the recruitment of immune cells into the lamina propria and in driving the inflammatory response in CD patients. Our results suggest the predominance of Th1 and Th17 immune responses over EV VP1 protein in CD and T1D patients. The significant elevation of Th2 cytokines, like IL-5 and IL-13, but not IL-4, in CD patients and its correlation with the degree of small bowel mucosa damage could reflect the role of these cytokines in gut defense and inflammation.

Characterization of lymphocyte subsets in peripheral blood cells of children with EV71 infection

BACKGROUND

Enterovirus 71 (EV71) is one of the major causative pathogens of hand, foot, and mouth disease (HFMD). Immune cells play a critical role in determining the outcomes of virus infection. We aimed to characterize the lymphocyte subsets and transcriptional levels of T lymphocytes-associated transcription factors in peripheral blood cells of children with EV71 infection.

METHODS

Peripheral blood samples from 32 children with EV71 infection and 32 control subjects were included in this study. The frequencies of T-, B-lymphocytes, and their subsets were determined by flow cytometry. The expression of transcription factors, including T-bet, Gata3, ROR γ t, Foxp3, TCF-1, and BCL-6 in the whole blood cells were evaluated by real-time reverse-transcription quantitative polymerase chain reaction (RT-qPCR).

RESULTS

The frequencies of T cells, helper T cells (Th), cytotoxic T cells (Tc), IFN-γ⁺ Th1, IFN-γ⁺ Tc1, and regulatory T (Treg) cells were significantly decreased (P < 0.01) in children with EV71 infection. As for IL-4⁺ Th2, IL-4⁺ Tc2, IL-17⁺ Th17, IL-17⁺ Tc17, follicular helper T cells (Tfh), CD3⁺CD8⁺IL-21⁺ T cells, CD19⁺ B cells, and CD19⁺IL-10⁺ B10 cells, their frequencies were significantly increased in the EV71 group (P < 0.01). The EV71 group had lower mRNA expressions of T-bet, Gata3, and Foxp3 than the control group (P < 0.05), whereas the expressions of ROR γ t, TCF-1, and BCL-6 showed no significant difference between two groups.

CONCLUSIONS

EV71 infection in children caused a decreased frequency of total Th, Tc and Treg cells, and increased percentages of B cell, Th2 and Th17 cells in blood.

Enterovirus A71 Infection Activates Human Immune Responses and Induces Pathological Changes in Humanized Mice

Since the discovery of enterovirus A71 (EV-A71) half a century ago, it has been recognized as the cause of large-scale outbreaks of hand-foot-and-mouth disease worldwide, particularly in the Asia-Pacific region, causing great concern for public health and economic burdens. Detailed mechanisms on the modulation of immune responses after EV-A71 infection have not been fully known, and the lack of appropriate models hinders the development of promising vaccines and drugs. In the present study, NOD-scid IL2Rγ^-/- (NSG) mice with a human immune system (humanized mice) at the age of 4 weeks were found to be susceptible to a human isolate of EV-A71 infection. After infection, humanized mice displayed limb weakness, which is similar to the clinical features found in some of the EV-A71-infected patients. Histopathological examination indicated the presence of vacuolation, gliosis, or meningomyelitis in brain stem and spinal cord, which were accompanied by high viral loads detected in these organs. The numbers of activated human CD4⁺ and CD8⁺ T cells were upregulated after EV-A71 infection, and EV-A71-specific human T cell responses were found. Furthermore, the secretion of several proinflammatory cytokines, such as human gamma interferon (IFN-γ), interleukin-8 (IL-8), and IL-17A, was elevated in the EV-A71-infected humanized mice. Taken together, our results suggested that the humanized mouse model permits insights into the human immune responses and the pathogenesis of EV-A71 infection, which may provide a platform for the evaluation of anti-EV-A71 drug candidates in the future.IMPORTANCE Despite causing self-limited hand-food-and-mouth disease in younger children, EV-A71 is consistently associated with severe forms of neurological complications and pulmonary edema. Nevertheless, only limited vaccines and drugs have been developed over the years, which is possibly due to a lack of models that can more accurately recapitulate human specificity, since human is the only natural host for wild-type EV-A71 infection. Our humanized mouse model not only mimics histological symptoms in patients but also allows us to investigate the function of the human immune system during infection. It was found that human T cell responses were activated, accompanied by an increase in the production of proinflammatory cytokines in EV-A71-infected humanized mice, which might contribute to the exacerbation of disease pathogenesis. Collectively, this model allows us to delineate the modulation of human immune responses during EV-A71 infection and may provide a platform to evaluate anti-EV-A71 drug candidates in the future.

Th17 cytokine profiling of colorectal cancer patients with or without enterovirus 71 antigen expression

OBJECT

Th17 cytokines have been identified in several types of human cancers. In this pilot study, the expression of Th17 cytokines profiling in enteroviruses 71 (EV71) associated colorectal cancer (CRC) were explored.

METHODS

66 patients with CRC were enrolled in this study; immune- histochemical analyses were performed on cancerous tissues and adjacent non- cancerous tissues of the patients. Serum Th17 cytokines of CRC patients and healthy controls were measured using a Luminex 200 analyzer.

RESULTS

Cancerous tissues had more positive EV71 antigen expression than adjacent non- cancerous tissues. In TNM II-III CRC, 59.9% of cancerous tissues were observed to be EV71 positive; on the contrary, 65.2% of the adjacent non- cancerous epithelium was EV71 negative. In TNM I CRC, all adjacent non- cancerous epithelium was virus negative, but in TNM IV, half of adjacent non- cancerous tissues were virus positive. Serum IL-10 were significantly higher in CRC patients than in healthy controls, and IL-10 concentrations in the EV71 positive group were higher than those of the EV71 negative group, with the highest IL-10 levels being observed in CRC patients with strong positive group (P < 0.05). Similar results were found for IL-21 and IL-23. IL-17 levels were higher in CRC patients than in healthy controls, there was no significant difference in IL-17 between the viral positive and viral negative groups (P > 0.05).

CONCLUSION

Persistent existing EV71 viral antigens in intestinal tissues are positively associated with TNM III/IV CRC. EV71 latent infection recruits Th17 cells in the colorectal tumor site, stimulating Th17 cytokine production that closely associated with CRC carcinogenesis.

Fibroblast-stimulating lipopeptide-1 as a potential mucosal adjuvant enhances mucosal and systemic immune responses to enterovirus 71 vaccine

To prevent viral infection at the site of entry, mucosal vaccines are potent tools for inducing IgA secretion for defense. Because Toll-like receptor (TLR) ligands serve as strong adjuvants, two ligands that mimic the structure of mycoplasmal and bacterial lipopeptides represent interesting vaccine candidates. Pam3CSK4, a synthetic triacylated lipopeptide, interacts with TLR2/1. Because fibroblast-stimulating lipopeptide-1 (FSL-1), a synthetic diacylated lipopeptide, is recognized by TLR2/6, we targeted the potential immuno-inducibility of Pam3CSK4 and FSL-1 as adjuvants of an enterovirus 71 (EV71) mucosal vaccine. Naïve BALB/c mice were used for intranasal immunization three times over a 3-week interval, with results showing that EV71-specific IgG and IgA in serum, nasal washes, bronchoalveolar lavage fluid, and feces from the EV71 + FSL-1 group were significantly higher than levels observed in mice treated with EV71 + Pam3CSK4, EV71 alone, or the control group treated with phosphate-buffered saline. Furthermore, we observed more EV71-specific IgG and IgA-producing cells in treatments using EV71 formulated with FSL-1. Additionally, T cell-proliferative responses and interferon-γ and interleukin-17 secretion were significantly increased when inactivated EV71 was formulated using FSL-1. Moreover, serum from immunized mice was capable of neutralizing the infectivity of EV71 (C2 genotype) and was able to cross-neutralize the B4 and B5 genotypes of EV71. Our data suggested that FSL-1 could be used as an efficient adjuvant for intranasal EV71-vaccine immunization.

Association of Interleukin-17F gene polymorphisms with susceptibility to severe enterovirus 71 infection in Chinese children

Enterovirus 71 (EV71) is a single-strand RNA virus that causes hand, foot and mouth disease (HFMD) in infants and young children, leading to neurological complications with significant morbidity and mortality. Unfortunately, the pathogenesis of EV71 infection is not well understood. In this study, we investigated the IL-17F rs1889570 and rs4715290 gene polymorphisms in a Chinese Han population. Severe cases and cases with EV71 encephalitis had a significantly higher frequency of the rs1889570 T/T genotype and T allele. The serum IL-17F levels in rs1889570 T/T and C/T genotypes were also significantly elevated when compared to C/C genotypes. However, there was no significant difference observed in rs4715290 genotype distribution and allele frequency. These findings suggest that IL-17F rs1889570 gene polymorphisms are significantly associated with the susceptibility to severe EV71 infection in Chinese Han children.

Changes of circulating Th22 cells in children with hand, foot, and mouth disease caused by enterovirus 71 infection

Interleukin (IL)-22+CD4+T (Th22) cells play crucial roles in the pathogenesis of autoimmune diseases and infectious diseases, although the role of Th22 cells remains largely unclear in children with hand, foot, and mouth disease (HFMD) caused by enterovirus 71 (EV71). This study aims to explore the role of circulating IL-22+IL-17A-CD4+T (cTh22) cells in children with EV71-associated HFMD. We found that during the acute stage of illness, the frequencies of cTh22 and circulating IL-22+IL-17A+CD4+T (IL-22+cTh17) cells in CD4+T cells infrom affected patients, and especially in severely affected patients, were significantly higher than in healthy controls (HC). The major source of IL-22 production was cTh22 cells, partially from cTh17 cells. Moreover, the protein and mRNA levels of IL-22, IL-17A, IL-23, IL-6, and TNF-α were significantly different among the mild patients, severe patients and HC, as well as AHR and RORγt mRNA levels. A positive correlation was found between plasma IL-22 levels and cTh22 cell frequencies, and cTh17 cell and IL-22+ cTh17 cell frequencies. Furthermore, the frequencies of cTh22 were significantly decreased in the convalescent patients. Our findings indicated that cTh22 cells could play critical roles in the pathogenesis of EV71 infection, and are potential therapeutic targets for patients with EV71-associated HFMD.

Enterovirus 71 Proteins 2A and 3D Antagonize the Antiviral Activity of Gamma Interferon via Signaling Attenuation

Enterovirus 71 (EV71) infection causes severe mortality involving multiple possible mechanisms, including cytokine storm, brain stem encephalitis, and fulminant pulmonary edema. Gamma interferon (IFN-γ) may confer anti-EV71 activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. This study, investigating the role of IFN-γ in EV71 infection using a murine model, showed that IFN-γ was elevated. Moreover, IFN-γ receptor-deficient mice showed higher mortality rates and more severe disease progression with slower viral clearance than wild-type mice. In vitro results showed that IFN-γ pretreatment reduced EV71 yield, whereas EV71 infection caused IFN-γ resistance with attenuated IFN-γ signaling in IFN regulatory factor 1 (IRF1) gene transactivation. To study the immunoediting ability of EV71 proteins in IFN-γ signaling, 11 viral proteins were stably expressed in cells without cytotoxicity; however, viral proteins 2A and 3D blocked IFN-γ-induced IRF1 transactivation following a loss of signal transducer and activator of transcription 1 (STAT1) nuclear translocation. Viral 3D attenuated IFN-γ signaling accompanied by a STAT1 decrease without interfering with IFN-γ receptor expression. Restoration of STAT1 or blocking 3D activity was able to rescue IFN-γ signaling. Interestingly, viral 2A attenuated IFN-γ signaling using another mechanism by reducing the serine phosphorylation of STAT1 following the inactivation of extracellular signal-regulated kinase without affecting STAT1 expression. These results demonstrate the anti-EV71 ability of IFN-γ and the immunoediting ability by EV71 2A and 3D, which attenuate IFN-γ signaling through different mechanisms.

IMPORTANCE

Immunosurveillance by gamma interferon (IFN-γ) may confer anti-enterovirus 71 (anti-EV71) activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. IFN-γ receptor-deficient mice showed higher mortality and more severe disease progression, indicating the anti-EV71 property of IFN-γ. However, EV71 infection caused cellular insusceptibility in response to IFN-γ stimulation. We used an in vitro system with viral protein expression to explore the novel IFN-γ inhibitory properties of the EV71 2A and 3D proteins through the different mechanisms. According to this study, targeting either 2A or 3D pharmacologically and/or genetically may sustain a cellular susceptibility in response to IFN-γ, particularly for IFN-γ-mediated anti-EV71 activity.

Coxsackievirus A16 infection stimulates imbalances of T cells in children

Immune reaction plays a crucial role in the regulation of the progression of Coxsackievirus A16 (CA16)-infected hand, foot and mouth disease (HFMD). However, no details of T-cell subset frequency or imbalance during the CA16 infection process have been revealed. In the present study, whether CA16-induced HFMD changes the frequency of different T-cell subsets and associated immune mediators was determined in children. The results indicate that the percentages of Th1 and Tc1 cells were significantly increased in children with HFMD compared with those in healthy children. In addition, the Th1/Th2 ratio and interferon (IFN)-γ levels were significant higher in children with HFMD. Furthermore, the percentage of Th17 cells and the Th17/Treg ratio as well as interleukin (IL)-17A levels were higher in HFMD cases. In conclusion, the present study demonstrated the dysregulation of T-cell subsets following CA16 infection. The Th1/Th2 and Th17/Treg ratios were imbalanced following infection. Also, the imbalance Th1/Th2 and Th17/Treg ratios contributed to the increased levels of IFN-γ and IL-17A. Based on this information, the present study provides new insights for the future study of CA16-induced HFMD and offers new data of diagnostic and therapeutic value for CA16 infection.

Serum inflammatory cytokine levels correlate with hand-foot-mouth disease severity: a nested serial case-control study

Background

Hand-food-mouth disease (HFMD) cases can be fatal. These cases develop rapidly, and it is important to predict the severity of HFMD from mild to fatal and to identify risk factors for mild HFMD. The objective of this study was to correlate the levels of serum inflammatory cytokines with HFMD severity.

Methods

This study was designed as a nested serial case-control study. The data collected included general information, clinical symptoms and signs, laboratory findings and serum cytokine levels.

Results

The levels of IL-4, IL-6, IL-10, TNF-α and IFN-γ in patients with severe HFMD were significantly higher than in mild patients during the 2nd to 5th day after disease onset. The levels of IL-4, IL-6, IL-10 and IFN-γ increased from the 2nd day to the 4th day and later decreased. The levels of TNF-α were high on the first two days and subsequently decreased. The changes of IL-10, TNF-α and IFN-γ in the controls were similar for all cases. The levels of IL-4, IL-6 and IL-17 in the controls were not significantly different with the progression of HFMD.

Conclusions

Our findings indicate that the IL-4, IL-6, IL-10, TNF-α and IFN-γ levels correlate with HFMD severity.

Enterovirus-71 virus-like particles induce the activation and maturation of human monocyte-derived dendritic cells through TLR4 signaling

Enterovirus 71 (EV71) causes seasonal epidemics of hand-foot-and-mouth disease and has a high mortality rate among young children. We recently demonstrated potent induction of the humoral and cell-mediated immune response in monkeys immunized with EV71 virus-like particles (VLPs), with a morphology resembling that of infectious EV71 virions but not containing a viral genome, which could potentially be safe as a vaccine for EV71. To elucidate the mechanisms through which EV71 VLPs induce cell-mediated immunity, we studied the immunomodulatory effects of EV71 VLPs on human monocyte-derived dendritic cells (DCs), which bind to and incorporate EV71 VLPs. DC treatment with EV71 VLPs enhanced the expression of CD80, CD86, CD83, CD40, CD54, and HLA-DR on the cell surface; increased the production of interleukin (IL)-12 p40, IL-12 p70, and IL-10 by DCs; and suppressed the capacity of DCs for endocytosis. Treatment with EV71 VLPs also enhanced the ability of DCs to stimulate naïve T cells and induced secretion of interferon (IFN)-γ by T cells and Th1 cell responses. Neutralization with antibodies against Toll-like receptor (TLR) 4 suppressed the capacity of EV71 VLPs to induce the production of IL-12 p40, IL-12 p70, and IL-10 by DCs and inhibited EV71 VLPs binding to DCs. Our study findings clarified the important role for TLR4 signaling in DCs in response to EV71 VLPs and showed that EV71 VLPs induced inhibitor of kappaB alpha (IκBα) degradation and nuclear factor of kappaB (NF-κB) activation.

Increased frequency of circulating follicular helper T cells in children with hand, foot, and mouth disease caused by enterovirus 71 infection

Enterovirus 71 (EV71) is a major causative agent of hand, foot, and mouth disease (HFMD) in children. The role of T follicular helper (TFH) cells in EV71-infected children remains unclear in regulating humoral immunity. The frequency of circulating ICOS^high/PD-1^highCXCR5⁺CD4⁺ TFH cells in the children with mild and severe EV71 infection and healthy controls (HC) was detected by flow cytometry, respectively. IL-21 and IL-6 mRNA expression and their serum levels, Bcl-6 mRNA expression, and specific neutralizing antibodies against EV71 (NAb-EV71) were measured. In the acute stage of patients with EV71 infection, increased frequencies of circulating TFH cells with ICOS^high and PD-1^high expression in the mild and severe patients were observed, and the positive correlations among the frequencies of circulating TFH cells and the serum levels of IL-21, IL-6, and NAb-EV71 titres were detected, respectively. Moreover, the expressions of IL-6 and IL-21 mRNA in PBMCs from patients were also significantly higher than those of HC. However, further analysis did not reveal any significant differences between mild and severe patients. These data indicate a role of TFH cells and associated cytokines in modulating the humoral response during the pathogenesis of EV71 infection.

Association of interleukin-17F gene polymorphism with enterovirus 71 encephalitis in patients with hand, foot, and mouth disease

Enterovirus 71 (EV71) is one of the common pathogenic agents of hand, foot, and mouth disease (HFMD) and is associated with severe complications including encephalitis. Interleukin (IL)-17F plays an important role in tissue inflammation by inducing release of proinflammatory cytokines and chemokines. We investigated the association between EV71 encephalitis and of IL-17F 7488T/C (rs763780) gene polymorphism, which is known to cause a His-to-Arg substitution at amino acid 161. The study was performed in 58 Chinese patients with EV71 encephalitis and 127 Chinese patients with EV71-related HFMD without complications. Genotyping was determined by the polymerase chain reaction-restriction fragment length polymorphism technique. The patients with EV71 encephalitis had a significantly lower frequency of the IL-17F 7488TC+CC genotypes (10.3%) as compared to the patients with EV71-related HFMD without complications (27.6%, p = 0.008). The frequency of IL-17F 7488C alleles was also significantly lower among the patients with EV71 encephalitis (5.2%) as compared to that of the patients with EV71-related HFMD without complications (15%, OR = 0.310, 95% CI = 0.127-0.756, p = 0.006). Furthermore, homozygotes with the T allele had significantly higher levels of C-reactive protein, white blood cell count, and neutrophil count as compared to the patients with CC+CT genotypes (p = 0.004, 0.001, and 0.000, respectively). These findings suggested that the IL-17F 7488C allele could be significantly associated with protection against encephalitis in Chinese patients with EV71-related HFMD.

Update of enterovirus 71 infection: epidemiology, pathogenesis and vaccine

Enterovirus 71 (EV71) is a neurotropic human pathogen that is the causative agent of hand foot and mouth disease (HFMD), herpangina and brain stem encephalitis. Recurrent EV71 epidemics of various scales have occurred in the Asia-Pacific region. Several specific cell surface molecules serve as the receptors for EV71. Identification of the receptors is an important step to understand EV71 disease. Cytokines, lymphocytes and monocytes contribute significantly to EV71 pathogenesis. The interaction of EV71 and receptors may be associated with the cytokines immunopathogenesis. Some animal models have been established and aim to explore the pathogenesis of EV71 infections. EV71 antibodies can neutralize or enhance infection at subneutralizing levels. These results are important for EV71 vaccine and therapeutics design. Several clinical trials of human inactivated EV71 vaccine have recently been completed. The purpose of this review is to summarize recent discoveries about the epidemiology and pathogenesis of EV71 and provide insights into human vaccine development.

Peripheral T lymphocyte subset imbalances in children with enterovirus 71-induced hand, foot and mouth disease

Inflammatory mediators (i.e. cytokines) play a pivotal role in the regulation of pathophysiological processes during EV71-induced hand, foot and mouth disease (HFMD). Different T cell subsets have distinct cytokine secretion profiles, and alteration in the T cell subsets frequency (imbalance) during infection leads to changed cytokine patterns. However, the effects of EV71 infection on T cell subsets were not clear. The objective of this study was to determine whether EV71-induced HFMD can be explained by the emergence of particular T-cell subsets (Th1, Th2, Tc1, Tc2, Th17, Tc17 and Treg cells) and the cytokine they produced (IFN-γ, IL-4, IL-17A and TGF-β1), as well as distinct responses to EV71 infection. We found that when compared to the control group, the percentage of Th1 and Tc1 cells was significantly higher in mild and severe HFMD group. Similar results were found in the Th1/Th2 ratio and IFN-γ levels. On the other hand, the percentage of Th17 cells and IL-17A levels were the highest in severe HFMD cases, and lowest in controls. Similar trend was also found for the Th17/Treg cell ratio. An optimal cutoff value of 2.15% for Th17 cell and 6.72 pg/ml for IL-17A provided a discriminatory value for differentiating the severity of HFMD cases by receiver operating characteristic curve analyses. These findings reveal that the Th1/Th2 and Th17/Treg imbalance exist in HFMD patients, suggesting their involvement in the pathogenesis of EV71 infection, which may have potential value as biomarkers.

Implications of Age-Dependent Immune Responses to Enterovirus 71 Infection for Disease Pathogenesis and Vaccine Design

Epidemics of enterovirus serotype 71 (EV71) infection in Asia appear to be increasing in size and severity, and there is increasing concern for pandemic spread. Efforts are underway to develop an effective EV71 vaccine. However, the immunologic correlates of protection against EV71 infection are not fully understood, and studies suggest that severe complications may result from a combination of pathological immune responses and direct viral effects. Severe disease and death typically occur only in young children, which is likely due in part to a lack of EV71-specific adaptive immunity but possibly also due to age-dependent hyperactive innate immune responses. Infants are the primary targets of EV71 vaccination strategies. Therefore, studies are needed to understand the interplay between age, immunopathology, and severity of EV71 infection to distinguish protective from harmful immune responses and to guide the development of effective EV71 vaccines. This review summarizes our current understanding and outlines the next steps forward.

Vaxfectin adjuvant improves antibody responses of juvenile rhesus macaques to a DNA vaccine encoding the measles virus hemagglutinin and fusion proteins

DNA vaccines formulated with the cationic lipid-based adjuvant Vaxfectin induce protective immunity in macaques after intradermal (i.d.) or intramuscular (i.m.) delivery of 0.5 to 1 mg of codon-optimized DNA encoding the hemagglutinin (H) and fusion (F) proteins of measles virus (MeV). To characterize the effect of Vaxfectin at lower doses of H+F DNA, rhesus macaques were vaccinated twice with 20 μg of DNA plus Vaxfectin i.d., 100 μg of DNA plus Vaxfectin i.d., 100 μg of DNA plus Vaxfectin i.m. or 100 μg of DNA plus phosphate-buffered saline (PBS) i.m. using a needleless Biojector device. The levels of neutralizing (P = 0.036) and binding (P = 0.0001) antibodies were higher after 20 or 100 μg of DNA plus Vaxfectin than after 100 μg of DNA plus PBS. Gamma interferon (IFN-γ)-producing T cells were induced more rapidly than antibody, but were not improved with Vaxfectin. At 18 months after vaccination, monkeys were challenged with wild-type MeV. None developed rash or viremia, but all showed evidence of infection. Antibody levels increased, and IFN-γ- and interleukin-17-producing T cells, including cells specific for the nucleoprotein absent from the vaccine, were induced. At 3 months after challenge, MeV RNA was detected in the leukocytes of two monkeys. The levels of antibody peaked 2 to 4 weeks after challenge and then declined in vaccinated animals reflecting low numbers of bone marrow-resident plasma cells. Therefore, Vaxfectin was dose sparing and substantially improved the antibody response to the H+F DNA vaccine. This immune response led to protection from disease (rash/viremia) but not from infection. Antibody responses after challenge were more transient in vaccinated animals than in an unvaccinated animal.