Pathological Changes In Respiratory System Of Fatal Hand, Foot And Mouth Disease

Background and ObjectivesHand, foot and mouth disease (HFMD) is a global epidemic, which is reported in many countries and regions. Enterovirus 71 (EV71) and Coxsackievirus A16 (CV A16) are the two major pathogens of HFMD, most frequently affecting children who under 5 years old. Both of them are leading to similar clinical manifestations, including herpes of hand, foot and mouth, fever.HFMD is commonly a mild disease, and the affected children can recover in a week, however, fatal HFMD induced by EV71 can cause brainstem encephalitis, heart failure and pulmonary edema, result in death. In China, fatal HFMD is mostly caused by EV71. Scavenger receptor B2(SCARB2) and P-selectin glycoprotein ligand-1 (PSGL-1) have been identified to be the functional receptors of EV71in cells. so far, the distribution of the receptors SCARB2 and PSGL-1 in fatal HFMD has not been reported.The pathogenesis and prognosis of HFMD is not only associated with EV71 viral virulence and load,but also with the host’s immunological function. Some previous studies have shown that viral related to HFMD can cause immune status changes, abnormal immune response may be involved in the development of HFMD. Our group has demonstrated that the inflammatory lesions present more seriously in the lower parts than in the upper parts in the central nervous system (CNS) of fatal HFMD. The main lesions are midbrain/pons, medulla oblongata and spinal cord, brain and cerebellum are minor. Cellular immune mediated, humoral immune and innate immune are involved corporately in the local immune response of the CNS lesions of HFMD.Based on the above background and research, the location and distribution of EV71 receptors SCARB2 and PSGL-1 is detected by using immunohistochemistry in lung tissues of fatal HFMD to understand the portal of the invasion of EV71. Further more, to detect the expression of the T lymphocyte markers CD3, CD4, CD8, B lymphocyte marker CD20, CD79a, NK cell marker CD57 and macrophage cell marker CD68,CD163 in lung tissues of fatal HFMD by immunohistochemical staining, and to investigate the distribution, quantity and significance of various immunocytes in lung tissues of fatal HFMD.Materials and methodsThe paraffin-embedded tissues of lung tissues from 15 autopsies of HFMD confirmed by pathological examination at the Pathology Department of the First Affiliated Hospital of Guangxi Medical University from 2008-2012 were collected for experiment. Three autopsies of accidental suffocation in 2012 were chosen as the control group of children. Eight samples from adult in 2014 were obtained as the control group of adult. The HE staining was performed to observe the pathological morphological changes in the lung of HFMD. Immunohistochemistry (Supervision) was performed to detect the expression of SCARB2 and PSGL-1 in all specimens, to detect the expression of CD3, CD4, CD8, CD20, CD79a,CD57, CD68 and CD163 in HFMD group and children group. Statistics was performed by using SPSS 20.0 software.Results1. The HE staining observation:Lymphocytes, mononuclear phagocytes gathered together where was in the surrounding of bronchi and bronchiole; Dilatation and congestion of the capillaries and infiltration of lymphocytes and mononuclear phagocytes were observed in widened alveolar septum; Massive edematous fluid, lymphocytes and mononuclear phagocytes were observerd in pulmonary alveoli, some samples accompanied by neutrophil infiltration; Pulmonary emphysema was observerd as alveolar epithelium ruptured in a few cases.2. SCARB2 distributed in bronchial, bronchioli epithelia, alveolar epithelial cells and inflammatory cells among HFMD, healthy children and adults. No significant differences were noted of the positive rates of SCARB2 expression among these three groups (P>0.05). PSGL-1 distributed in bronchial and bronchioli epithelium of adults, but no PSGL-1 expression was found in HFMD and healthy children. The positive rates of PSGL-1 were 100%,0%,0% in bronchial and bronchioli epithelium among the three groups, respectively (P< 0.05). The positive rates of PSGL-1 were 100%,66.7%,100% in inflammatory cells among HFMD, healthy children and adults, respectively. No significant differences were noted of PSGL-1 expression among the three groups (P>0.05). Further, no PSGL-1 expression was observed in alveolar epithelia cells of all groups tested.3.CD3 positive(CD3+), CD4+, CD8+ T cells and CD20+, CD79a+ B cells gathered together surrounding bronchi and bronchiole, CD57+ NK cells were more scattered in widened alveolar septum, CD68+, CD163+ macrophages were mainly distributed in pulmonary alveoli. In addition, the number of CD4+ T cells, CD79a+ B cells, CD57+ NK cells, CD68+, CD163+ macrophages was markedly higher in HFMD group than that in control group (P<0.05). No significant differences were noted of the number of CD3+, CD8+ T cells and CD20+ cell between two groups (P> 0.05).Conclusions1. The pathological morphological changes in the lung tissues of fatal HFMD conform with viral pneumonia and pulmonary edema, and immunocytes including T, B lymphocytes, NK cells and macrophages infiltrate the lung tissues.2. EV71 receptor SCARB2 distributes in bronchial, bronchioli, alveolar epithelial and inflammatory cells of HFMD. Meanwhile, PSGL-1 only distributes in inflammatory cells of HFMD, suggesting that SCARB2 possibly play a crucial role on EV71 infection.