| Summary: | 碩士 === 國立成功大學 === 微生物及免疫學研究所 === 90 === Enterovirus 71 (EV71), a single positive strand RNA virus, belongs to Picornaviridae. Since the first epidemic in 1973, there have been several outbreaks of hand-foot-mouth disease (HFMD) caused by EV71 in the United States, Australia, and East Asia. An outbreak at Taiwan in 1998, caused 55 children die with central nervous system (CNS) involvement. The fecal-oral route is thought to be the predominant mode of enterovirus transmission. EV71 has been associated with an array of clinical syndromes including HFMD, aseptic meningitis, encephalitis, polio-like myelitis, and paralysis among infants and children. Its pathogenesis is not clearly understood. There is also no animal model to understand how enterovirus spreads to the central nervous system (CNS). Therefore, we established a murine model of EV71 infection by oral route to understand viral spread in vivo. EV71 can infect intestinal epithelial cell line Caco-2 and neuroblastoma cell line SK-N-SH. The cell- or mouse-adapted EV71 was used to infect murine neonatal intestine ex vivo. The EV71 viral protein 1 (VP1) was detected in intestine epithelial cells 2 days post infection, and stronger staining was observed in tissues infected with mouse-adapted strain than those infected with Caco-2 adapted or parental one. Since mouse-adapted EV71 can successfully infect murine neonatal intestine, we further explored the EV71 infection orally. Oral inoculation of 1 x 106 PFU mouse-adapted EV71 into neonate mice caused flaccid paralysis and death in 50 % of mice at 6-9 days post infection while parental EV71 only induced mild skin lesions. The mortality increased to 100 % at day 3 post infection when mice were inoculated with 1 x 107 PFU of virus. EV71 can be re-isolated from intestine, blood, spleen, brain stem, brain, spinal cord, heart, liver, lung, skin, and hind limb muscle of the infected mice. The pathological analysis found cell infiltration in brain stem, spinal cord and intestine. The kinetic study showed that two-phase viremia appeared at 6 and 24 hours post infection, respectively. The EV71 VP1 antigen first occurred in intestinal muscularis externa, then in cervical and lumbar spinal cord, and finally in the brain stem. Furthermore, EV71 can spread between littermates by fecal route or close contact. This animal model mimics the clinical EV71 infection, and can be used for further study of EV71 pathogenesis and screening of antiviral drugs.
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