Peripheral T Lymphocyte Subset Imbalances In Children With Enterovirus71-induced Hand,Foot And Mouth Disease

BackgroundEnterovirus71(EV71) is a common pathogen that causes hand, foot and mouth disease (HFMD). It also may result in sever neurological complications, such as myocarditis, acute flaccid paralysis, aseptic meningitis, brainstem encephalitis, neurogenic pulmonary edema and even death. So far, the pathogenesis of EV71infection has not been fully elucidated. Limited domestic and international studies have shown that the EV71infection can cause immune dysfunction, and abnormal immune response may be involved in the incidence of EV71infection. However, the specific role of the immune responses in the pathogenesis of severe HFMD is not yet clear. Previous studies on immune status change caused by EV71infection were mostly focused on the detection of cytokines in peripheral blood. There were few reports available on T cell subsets associated with EV71infection.ObjectiveThe objective of this study was to determine whether EV71-induced HFMD can be explained by the emergence of particular T-cell subsets (Thl, Th2, Te1, Tc2, Th17, Te17and Treg cells) and the cytokine they produced (IFN-y, IL-4, IL-17A and TGF-β1), as well as distinct responses to EV71infection. Methods1. EV71infection was defined as the successful detection of EV71nucleic acid in the throat swabs or stool specimens, which were collected from each patient on the day of admission. Thus, a total of95EV71-infected HFMD patients (aged0.3to5.7years), which were admitted to Hangzhou Children’s Hospital during May to August2011were finally enrolled in this study. They were then grouped according to their clinical charateristics. Therefore, of the95HFMD patients,53patients were diagnosed as mild HFMD and42as severe HFMD. Simulataneously,20age-matched children without any symptoms or signs of HFMD were included as controls at the same time.2. T cell subsets were detected by flow cytometry. In detail, the frequency of Treg cells was expressed as a ratio of CD4+CD25+Foxp3+cells/CD4+T cells. Likewise, CD3+CD8-IFN-γ+,CD3+CD8-IL-4+and CD3+CD8-IL-17A+cells were characterized as Thl, Th2and Th17cells respectively, and their ratios in total CD3+CD8-cells were determined accordingly. Similarly, Tc1, Tc2and Tc17cells were classified as CD3+CD8+IFN-γ+, CD3+CD8+IL-4+and CD3+CD8+IL-17A+cells, respectively, and their ratios in total CD3+CD8+cells were calculated. Isotype controls were used to correct compensation and confirm antibody specificity.3. The plasma levels of IFN-y, IL-4, IL-17A and TGF-β3were measured by ELISA.4. Statistics was performed by using SPSS17.0software. Data of normal distribution were presented as Average±Standard Deviation and data of skewed distribution with Median (Quartile Range). One-way analysis of variance and Kruskal-Wallis Rank-Sum test were selected respectively for different comparisons.ResultsWe found that when compared to the control group, the percentage of Thl and Tel cells was significantly higher in mild and severe HFMD group. Similar results were found in the Thl/Th2ratio and IFN-y levels. On the other hand, the percentage of Th17cells 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.ConclusionThese findings reveal that the Th1/Th2and Th17/Treg imbalance exist in HFMD patients, suggesting their involvement in the pathogenesis of EV71infection.