Taiwan experienced several epidemics of enterovirus 71 (EV71) infections, which were associated with brainstem encephalitis (BE) and pulmonary edema (PE). To elucidate the role of immune mechanisms in the pathogenesis of BE caused by EV71 and its fatal complication, PE, we analyzed the laboratory findings, cytokine, and immunophenotypes of 73 EV71-infected patients with BE. Patients were stratified by disease: PE (n=14), autonomic nervous system (ANS) dysregulation (n=25), and isolated BE (n=34). The mortality rate for PE was 64.3%. Leukocytosis and thrombocytosis were significantly more frequent among patients with PE. A significant elevation of plasma interleukin (IL)-10, IL-13, and interferon (IFN)-gamma levels observed in patients with PE. Patients with PE also had lower circulating CD4(+) T cells, CD8(+) T cells, and natural killer (NK) cells. An extensive peripheral and central nervous system inflammatory response with abnormal IL-10, IL-13, and IFN-gamma cytokine production and lymphocyte depletion appears to be responsible for the pathogenesis of EV71-associated PE.

A mouse-adapted enterovirus 71 (EV71) strain with increased virulence in mice, MP4, was generated after four serial passages of the parental EV71 strain 4643 in mice. Strain MP4 exhibited a larger plaque size, grew more rapidly, and was more cytotoxic in vitro than strain 4643. Although strains 4643 and MP4 both induced apoptosis of SK-N-SH human neuroblastoma cells, MP4 was more virulent than 4643 in 1-day-old mice (50% lethal doses, 10 2 and 10 4 PFU/mouse, respectively). Strain MP4 (5 ؋ 10 6 PFU/mouse), but not 4643, could orally infect 7-day-old mice, resulting in rear-limb paralysis followed by death 5 to 9 days after inoculation with the virus. Histopathologically, neuronal loss and apoptosis were evident in the spinal cords as well as the brain stems of the infected mice. The limb muscles displayed massive necrosis. There was early and transient virus replication in the intestines, whereas the spinal cord, brain, and muscle became the sites of viral replication during the late phase of the infection. Virus transmission occurred among infected and noninfected cagemates, as demonstrated by the occurrence of seroconversion and the presence of viable viruses in the stool samples of the latter. Protection against EV71 challenge was demonstrated following administration of hyperimmune serum 1 day after inoculation with the virus. Nucleotide sequence analysis of the genome of EV71 strain MP4 revealed four nucleotide changes on the 5 untranslated region, three on the VP2 region, and eight on the 2C region, resulting in one and four amino acid substitutions in the VP2 and 2C proteins, respectively.Enterovirus 71 (EV71), a neurotropic virus with undefined pathogenesis, has caused significant morbidity and mortality worldwide and especially in the Asia-Pacific region since it was first described in 1969 in the United States (1, 2). EV71 infections are generally mild, such as hand-foot-and-mouth disease (HFMD) and herpangina, but occasionally lead to severe diseases such as aseptic meningitis, poliomyelitis-like paralysis, and possibly fatal encephalitis in neonates. The outbreak of EV71 in Taiwan in 1998 killed 78 children, and since then EV71 infection has become endemic in Taiwan (8, 16). Brain stem encephalitis associated with pulmonary edema and cardiac insufficiency were the primary manifestations in patients with neurologic involvement (10, 16, 28). The predominant pathological findings were in the thalamus, pons, midbrain, medulla oblongata, and spinal cord, with intense neutrophil and mononuclear cell infiltrates. There was severe congestion with focal hemorrhage and edema in the lungs (21). Although EV71 was recovered from the mycocardium, there was only mild degeneration of the mycocardium. Neurogenic shock as a result of brain stem encephalitis has been proposed as the cause of pulmonary and cardiac complications (13,16). It has also been postulated that overwhelming virus replication combined with damage in tissues with the induction of toxic inflammatory cytokines is one possible pathogenesis (14,15,27)...

IL-19 belongs to the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, melanoma differentiation-associated gene-7 (IL-24), and AK155 (IL-26). IL-10 has been shown to inhibit allergen-induced airway hyperreactivity and inflammation. To determine whether IL-19 was also associated with asthma, we used ELISA to analyze the serum level of IL-19 in patients with asthma and found that their serum IL-19 levels were twice those of healthy controls. Patients with a high level of IL-19 also had high levels of IL-4 and IL-13. In a dust mite-induced murine model of asthma, we found that IL-19 level in asthmatic BALB/cJ mice was also twice that of healthy control mice. IL-19 transcript was also induced in the lungs of asthmatic mice. Electroporation i.m. of the IL-19 gene into healthy mice up-regulated IL-4 and IL-5, but not IL-13. However, IL-19 up-regulated IL-13 in asthmatic mice. In vitro, IL-19 induced IL-4, IL-5, IL-10, and IL-13 production by activated T cells. Activation of T cells was required for induction of IL-13 because IL-19 did not induce IL-13 production on nonstimulated T cells. Taken together, these results demonstrated that IL-19 up-regulates Th2 cytokines on activated T cells and might play an important role in the pathogenesis of asthma.

Enterovirus 71 (EV71) infection causes a myriad of diseases from mild hand-foot-and-mouth disease or herpangina to fatal meningoencephalitis complicated with neurogenic pulmonary oedema. Its pathogenesis, especially the CNS involvement, is not clearly understood. The aim of this study was to set up a mouse EV71 infection model with CNS involvement. EV71 virus was administrated orally to neonatal mice. The EV71-infected mice manifested a skin rash at an early stage and hind limb paralysis or death at a later stage. Immunohistochemical staining and virus isolation demonstrated that EV71 replicated in the small intestine, induced viraemia and spread to various organs. Kinetic studies showed that EV71 antigen was first detected in the intestine at 6 h, in the thoracic spinal cord at 24 h, in the cervical spinal cord at 50 h and in the brain stem at 78 h post-infection. Leukocyte infiltration was evident in the spinal cord and brain stem. Furthermore, EV71 virus could be transmitted to littermates within the same cage.

Enterovirus 71 (EV71), a single-positive-stranded RNA virus that belongs to the Enterovirus genus of the Picornaviridae family, is a highly neurotropic virus and has been regarded as the most important neurotropic EV after the eradication of the poliovirus (11). The brain stem is most likely the major target of EV71 infection (2, 8). However, neither the host cell receptor nor the neurotransmission route of EV71 is fully defined.As for poliovirus (PV), two possible routes by which the virus reaches the central nervous system (CNS) have been suggested: the virus either enters the CNS from the blood across the blood-brain barrier (BBB) or is transmitted to the CNS through peripheral nerves via retrograde axonal transport (1,3,14,23). Expression of certain gene segments would be responsible for determining the capacity of PV to spread to the CNS through bloodstream or neuronal pathways (18).In a cynomologus monkey model (12, 13), EV71 showed a wider-spread distribution pattern in the CNS than PV following both intracranial (i.c.) and intravenous inoculations, and monkeys exhibited extrapyramidal signs, including tremor and ataxia. However, after intraspinal inoculation, monkeys developed flaccid paralysis, a pyramidal sign suggesting direct virus invasion in the inoculation site. EV infection and persistence have been implicated in the pathogenesis of certain chronic muscle diseases (17). Furthermore, PV replicated in muscle cells that maintained constant viremia and spread to CNS from peripheral nerves (23). We previously showed that EV71 propagated more effectively in RD (human rhabdomyosarcoma) cells than in SK-N-SH (neuroblastoma) cells and Caco-2 (colorectal adenocarcinoma) cells. Furthermore, after oral (p.o.) inoculation of a mouse-adapted EV71 strain, EV71/MP4, 7-day-old ICR mice developed paralysis, with a mortality rate of 80%. Virus was first seen in the intestine. The virus then spread to muscle and CNS. A vast amount of virus was detected in the CNS and muscle, which led to neuronal loss and rhabdomyolysis of the mice with severe paralysis (21). In this study, we demonstrated that EV71 possesses strong neurotropism and that retrograde axonal transport in neuron cells might represent the major transmission route of EV71 in mice. MATERIALS AND METHODSCells and virus. RD cells (American Type Culture Collection, Manassas, VA) were maintained in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum plus 2 mM L-glutamine, 100 IU penicillin, and 100 g of streptomycin per ml. EV71/MP4 strain, a mouse-adapted strain derived from parental virus EV71/Tainan/4643/98 (GenBank accession number AF304458) (22), was grown in RD cells. Working stocks contained 2 ϫ 10 7 PFU/ml. Experimental infection. Specific-pathogen-free, 7-day-old ICR mice