Significant elevation of B cells at the acute stage in enterovirus 71-infected children with central nervous system involvement

Suppression of innate and acquired immunity in severe hand foot and mouth disease caused by EV71 infections in children

Hand, foot, and mouth disease (HFMD) is a common children infectious disease caused by human enteroviruses. Most of the cases have minimal symptoms, however, some patients may develop serious neurological, cardiac complications, or even death. The pathological mechanism leading to severe HFMD is not clearly understood, and the immunological status of the individual patient may play an important role. Transcriptomes of peripheral blood mononuclear cells from EV71-infected patients (n = 45) and healthy controls (n = 36) were examined. Immune pathways were up-regulated in patients with mild disease symptoms (n = 11, M) compared to the healthy controls (n = 36, H), demonstrating an effective anti-viral response upon EV71 infection. However, in patients with severe symptoms (n = 23, S) as well as severe patients following treatment (n = 11, A), their innate and acquired immune pathways were down-regulated, indicating a global immunity suppression. Such immune suppression characteristics could thus provide an opportunity for early EV-71 infection prognosis prediction. Based on our cohort, an SVM model using RNA-seq expression levels of five genes (MCL1, ZBTB37, PLEKHM1P, IFNAR2 and YEATS2) was developed and achieved a high ROC-AUC (91·3%) in predicting severe HFMD. Meanwhile, qPCR fold-changes method was performed based three genes (MCL1, IFNAR2 and YEATS2) on additional cohort. This qPCR method achieved a ROC-AUC of 78.6% in predicting severe HFMD, which the patients could be distinguished in 2-3 h. Therefore, our models demonstrate the possibility of HFMD severity prediction based on the selected biomarkers that predict severe HFMD effectively.

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.

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.

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.

Chronic viral infections in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Background and main text

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex and controversial clinical condition without having established causative factors. Increasing numbers of cases during past decade have created awareness among patients as well as healthcare professionals. Chronic viral infection as a cause of ME/CFS has long been debated. However, lack of large studies involving well-designed patient groups and validated experimental set ups have hindered our knowledge about this disease. Moreover, recent developments regarding molecular mechanism of pathogenesis of various infectious agents cast doubts over validity of several of the past studies.

Conclusions

This review aims to compile all the studies done so far to investigate various viral agents that could be associated with ME/CFS. Furthermore, we suggest strategies to better design future studies on the role of viral infections in ME/CFS.

Association analysis of polymorphisms in OAS1 with susceptibility and severity of hand, foot and mouth disease

Hand, foot and mouth disease (HFMD) is a common childhood illness that mainly affects Asian children under the age of 5 years. Human enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the most common pathogens of HFMD. It is imperative that the susceptible population is screened early and that the severe illness population can be identified via genetic variation detection in children. Four single-nucleotide polymorphisms (SNP) [2'-5'-oligoadenylate synthetase1 (OAS1) rs10774671, selectin P ligand (SELPLG) rs2228315, scavenger receptor class B member 2 (SCARB2) rs41284767 and interleukin 28B (IL28B) rs12979860] were determined by Taqman assays in 333 HFMD samples and 163 control samples. The rs2228315, rs41284767 and rs12979860 polymorphisms did not differ significantly between HFMD patients and the controls, but the prevalence of the rs10774671 polymorphism was significantly different between the control children and children infected with CA16 (GG genotype vs. AA + AG genotype, P < 0.05). Children with the GG genotype were more susceptible to CA16-type HFMD. Furthermore, the rs10774671 genotype distribution was clearly different between children with severe HFMD and those with mild HFMD [P < 0.05, OR 0.240, 95% CI (0.071-0.809)]. HFMD children with the AA+AG genotype were more likely to progress to encephalitis than were those with the GG genotype. Plasma γ-interferon (IFN) expression levels among control children and the mild and severe HFMD children were detected by ELISA. Those with mild HFMD had higher γ-IFN expression levels compared with those with severe HFMD (P < 0.05). In addition, there is a significant correlation between γ-IFN levels and OAS1 rs10774671 SNP, as analysed by linear correlation assay. The GG genotype correlated with higher γ-IFN levels (P < 0.05). In short, the OAS1 rs10774671 SNP GG genotype contributed to CA16 susceptibility and was associated with the development of mild HFMD.

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.

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.

Comparative study of the cytokine/chemokine response in children with differing disease severity in enterovirus 71-induced hand, foot, and mouth disease

Background

Enterovirus 71 (EV71) infection can lead to a rapidly progressing, life-threatening, and severe neurological disease in young children, including the development of human hand, foot, and mouth disease (HFMD). This study aims to further characterize the specific immunological features in EV71–mediated HFMD patients presenting with differing degrees of disease severity.

Methodology

Comprehensive cytokine and chemokine expression were broadly evaluated by cytokine antibody array in EV71–infected patients hospitalized for HFMD compared to Coxsackievirus A16-infected patients and age-matched healthy controls. More detailed analysis using Luminex-based cytokine bead array was performed in EV71–infected patients stratified into diverse clinic outcomes. Additionally, immune cell frequencies in peripheral blood and EV71–specific antibodies in plasma were also examined.

Principal Findings

Expression of several cytokines and chemokines were significantly increased in plasma from EV71–infected patients compared to healthy controls, which further indicated that: (1) GM-CSF, MIP-1β, IL-2, IL-33, and IL-23 secretion was elevated in patients who rapidly developed disease and presented with uncomplicated neurological damage; (2) G-CSF and MCP-1 were distinguishably secreted in EV71 infected very severe patients presenting with acute respiratory failure; (3) IP-10, MCP-1, IL-6, IL-8, and G-CSF levels were much higher in cerebrospinal fluid than in plasma from patients with neurological damage; (4) FACS analysis revealed that the frequency of CD19⁺HLADR⁺ mature B cells dynamically changed over time during the course of hospitalization and was accompanied by dramatically increased EV71–specific antibodies. Our data provide a panoramic view of specific immune mediator and cellular immune responses of HFMD and may provide useful immunological profiles for monitoring the progress of EV71–induced fatal neurological symptoms with acute respiratory failure.

The Pathogenesis and Prevention of Encephalitis due to Human Enterovirus 71

Human enterovirus 71 (HEV71) has emerged as a major cause of viral encephalitis in Southeast Asia, with increased epidemic activity observed since 1997. This is reflected in a large increase in scientific publications relating directly to HEV71. New research is elucidating details of the viral life cycle, confirming similarities between HEV71 and other enteroviruses. Scavenger receptor B2 (SCARB2) is a receptor for HEV71, although other receptors are likely to be identified. Currently, the only strategies to prevent HEV71-associated disease are early diagnosis and aggressive supportive management of identified cases. As more information emerges regarding the molecular processes of HEV71 infection, further advances may lead to the development of effective antiviral treatments and ultimately a vaccine-protection strategy. The protective efficacies of several inactivated HEV71 vaccines have been confirmed in animal models, suggesting that an effective vaccine may become available in the next decade.

Enterovirus infections of the central nervous system

Enteroviruses (EV) frequently infect the central nervous system (CNS) and induce neurological diseases. Although the CNS is composed of many different cell types, the spectrum of tropism for each EV is considerable. These viruses have the ability to completely shut down host translational machinery and are considered highly cytolytic, thereby causing cytopathic effects. Hence, CNS dysfunction following EV infection of neuronal or glial cells might be expected. Perhaps unexpectedly given their cytolytic nature, EVs may establish a persistent infection within the CNS, and the lasting effects on the host might be significant with unanticipated consequences. This review will describe the clinical aspects of EV-mediated disease, mechanisms of disease, determinants of tropism, immune activation within the CNS, and potential treatment regimes.