Chun Keung Yu

Pathogenesis of Enterovirus 71 Brainstem Encephalitis in Pediatric Patients: Roles of Cytokines and Cellular Immune Activation in Patients with Pulmonary Edema

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 Strain Causes Neurological Disease in Mice after Oral Infection

ABSTRACT 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, 102 and 104 PFU/mouse, respectively). Strain MP4 (5 × 106 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.

IL-19 Induced Th2 Cytokines and Was Up-Regulated in Asthma Patients

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.

Retrograde Axonal Transport: a Major Transmission Route of Enterovirus 71 in Mice

ABSTRACT Inoculation of enterovirus 71 (EV71) by the oral (p.o.), intramuscular (i.m.), or intracranial route resulted in brain infection, flaccid paralysis, pulmonary dysfunction, and death of 7-day-old mice. The lag time of disease progression indicated that neuroinvasion from the inoculation sites was a prerequisite for the development of the clinical signs. Although EV71 p.o. inoculation led to a persistent viremia and a transient increase in blood-brain barrier permeability at the early stage of the infection, only low levels of virus, which led to neither severe infection nor clinical illness, could be detected in the brain, suggesting that hematogenous transport might not represent a major transmission route. In the spinal cord, following both p.o. and hind limb i.m. inoculation, the virus first appeared and increased rapidly in the lower segments, especially at the anterior horn areas, and then spread to the upper segments and brain in the presence of viremia. A reverse pattern, with the virus being first detected in the upper segment, was observed when the virus was i.m. inoculated in the forelimb. Colchicine, a fast axonal transport inhibitor, but not sciatic nerve transection reduced EV71 neuroinvasion in a dose-dependent manner, indicating a neuronal transmission of the virus.

Acute Chemokine Response in the Blood and Cerebrospinal Fluid of Children with Enterovirus 71-Associated Brainstem Encephalitis

BACKGROUNDnBrainstem encephalitis (BE) is a serious neurological complication of enterovirus 71 (EV71) infection. The present study was designed to determine the characteristics of the chemokine response in the blood and cerebrospinal fluid (CSF) of patients with EV71-associated BE.nnnMETHODSnThirty-one patients with BE were studied. They consisted of 12 with uncomplicated BE, 9 with autonomic nervous system (ANS) dysregulation, and 10 with pulmonary edema (PE); 13 healthy control subjects were also studied. Plasma and CSF concentrations of various chemokines were determined by a particle-based flow cytometry immunoassay.nnnRESULTSnPlasma levels of interferon (IFN)-gamma-induced protein (IP)-10, monocyte chemoattractant protein (MCP)-1, monokine induced by IFN-gamma (MIG), and interleukin (IL)-8 were significantly higher in patients with PE than in those with uncomplicated BE. CSF levels of MIG were significantly higher in patients with PE than in those with uncomplicated BE and ANS dysregulation. The ratios of mean CSF to plasma levels for MCP-1 and IL-8 were highest in patients with uncomplicated BE and tended to fall with increasing severity of the disease.nnnCONCLUSIONSnOverexpression of the chemokine cascade in the central nervous system compartment appears to play an important role in the elicitation of the immune response to EV71. The chemokine CSF to plasma ratios suggest that IL-8, IP-10, MCP-1, and possibly MIG-but not RANTES-are synthesized in the brain in response to encephalitis.

Neutralizing antibody provided protection against enterovirus type 71 lethal challenge in neonatal mice

Experimental infection with enterovirus type 71 (EV71) induced death in neonatal mice in an age- and dose-dependent manner. The mortality rate was 100% following intraperitoneal inoculation 1-day-old ICR mice and this gradually decreased as the age at the time of inoculation increased (60% in 3-day-old mice and no deaths occurred in mice older than 6 days of age). A lethal dose greater than 10(8) PFU was necessary. Lethargy, failure to gain weight, rear limb tremors and paralysis were observed in the infected mice before death. EV71 was isolated from various tissues of the dead mice. Using a reverse transcription polymerase chain reaction technique with a specific primer pair, a 332-bp product was detected in the tissues that produced a culture positive for EV71. Protection against EV71 challenge in neonatal mice was demonstrated following passive transfer of serum from actively immunized adult mice 1 day after inoculation with the virus. Pups from hyperimmune dams were resistant to EV71 challenge. Additionally, maternal immunization with a formalin-inactivated whole-virus vaccine prolonged the survival of pups after EV71 lethal challenge.

Ribavirin Reduces Mortality in Enterovirus 71–Infected Mice by Decreasing Viral Replication

Abstract Enterovirus 71 (EV71) causes fatal encephalitis in young children. However, there is no effective antiviral drug available for infected patients. Ribavirin is currently used for the treatment of several RNA virus infections clinically, so its anti-EV71 efficacy was evaluated. In vitro results showed that ribavirin effectively reduced the viral yields (with an IC50 of 65 μg/mL) and virus-induced cytopathic effect in human and mouse cell lines. In vivo results showed that ribavirin reduced the mortality, morbidity, and subsequent paralysis sequelae in infected mice by decreasing viral loads in tissues. Thus, ribavirin could be a potential anti-EV71 drug

Isolation and Characterization of a Vibrio vulnificus Mutant Deficient in Both Extracellular Metalloprotease and Cytolysin

ABSTRACT We isolated a Vibrio vulnificus mutant that was deficient in both metalloprotease and cytolysin by allelic exchange. The virulence of this mutant in mice and its cytotoxicity for HEp-2 cells were comparable to those of the wild-type strain, indicating that neither factor was essential for these properties. The cytolysin, but not the protease, seemed to be important for causing damage in the alimentary tract of the mice.

Allergen-induced bronchial inflammation is associated with decreased levels of surfactant proteins A and D in a murine model of asthma.

Background Increasing evidence suggests that pulmonary surfactant protein A (SP‐A) and D (SP‐D) participate in the lung defence against pathogens. However, the role of surfactant proteins in the pathogenesis of allergen‐induced airway inflammation has not been elucidated. In this study we examined the levels and distributions of SP‐A and SP‐D in a dust mite (Dermatophagoides pteronyssinus, Der p) allergen‐induced murine model of asthma.

The effect of Chinese herbal medicine, xiao-qing-long tang (XQLT), on allergen-induced bronchial inflammation in mite-sensitized mice.

Background: There are detailed descriptions of the clinical experiences and prescriptions of asthma in traditional Chinese medicine. Xiao‐qing‐long tang (XQLT), or sho‐seiryo‐to by its Japanese name, is one of the Chinese herbal medicines used to treat bronchial asthma and allergic rhinitis for centuries. However, the therapeutic mechanisms of this medication are still far from clear. In this study, a house‐dust‐mite (Dermatophagoides pteronyssinus [Der p])‐sensitized murine model of asthma was used to evaluate the immunomodulatory effect of XQLT on the allergen‐induced airway inflammation in asthma.