Background: In a recent enterovirus outbreak in Taiwan, serotype 71 was the culprit of encephalitis causing rapid clinical deterioration and death among young children.
Objectives: Since knowledge of enterovirus 71 (EV71) infection in the central nervous system is still limited, the purpose of the present case study was attempted to uncover the pathogenesis of the virus.
Study design: We performed a detailed pathological examination, virological and molecular studies on a case of EV71 infection with a rapidly fatal outcome. In addition, the whole genome of the virus was sequenced to determine the genetic relationships to other enteroviruses and two other EV71 strains (a prototype BrCr and a neurovirulent MS strain), and to provide the genetic basis of its neurovirulence of the new isolate, NCKU9822 strain.
Results: Characteristic features of acute encephalomyelitis were observed, with most prominent lesions in the spinal cord and brain stem. Mild myocarditis and pancreatitis were also noticed. EV71 antigen was localized to neurons on immunohistochemical staining. EV71 was recovered from all organs with inflammatory reaction. Sequence analysis showed that overall NCKU9822 and the two EV71 strains shared 80% nucleotide identity and 95% amino acid identity. It had only 45% amino acid and 52% nucleotide identities with polioviral P1 capsid region.
Conclusion: The spinal cord and brain stem were the main targets of EV71 in the fatal cases in this outbreak, however, heart and pancreas might also be involved. Since the amino acid sequences in the P1 region are conserved (97% identity) among the three EV71 strains as compared to other enteroviruses and polioviruses, these EV71 neurovirulent strains might share the same mechanisms of neurovirulence, and the mechanisms might be different from those in polioviruses.