Abstract
Introduction: The enterovirus A71 (EV-A71)-caused central nerve system (CNS) damage seriously endangers the health of infants and young children, but the underlying mechanisms by which EV-A71 crosses the blood-brain barrier (BBB) are still largely unknown. This study developed a tree shrew (Tupaia belangeri) model to examine EV-A71 neurotropism and the disruption of the BBB. Methods: A cohort of twenty-two tree shrews, aged three months, were inoculated intranasally and orally with EV-A71 to establish an in vivo infection model. Complementary in vitro experiments were conducted using primary brain microvascular endothelial cells (MVECs) and astrocytes (AS) isolated from tree shrews. Results: Tree shrews infected with EV-A71 demonstrated symptoms of fever, vesicular lesions, and sustained viremia. Viral replication was observed in neural tissues, including the brain and spinal cord, as well as in select non-neural organs, accompanied by histopathological changes. Evans blue permeation assessment showed increased BBB permeability. EV-A71 infection down-regulated tight junction proteins Claudin-5 and junctional adhesion molecule A in the brain. In vitro studies showed that EV-A71 replicated efficiently in MVECs and AS, inducing cytopathic effects. Scavenger Receptor Class B Member 2 (SCARB2) and Annexin A2 (ANXA2) were identified as potential functional receptors facilitating viral entry. EV-A71 infection led to the dysregulation of tight junction proteins, matrix metalloproteinases, and Major facilitator superfamily domain-containing protein 2a. EV-A71 also stimulated the immune activity of AS. Discussion: This study indicated that SCARB2 and ANXA2 play a role in the invasion of EV-A71 into the CNS of tree shrews. EV-A71 infection down-regulated tight junction proteins and increased the BBB permeability. This model provides a novel platform for studying EV-A71 neuropathogenesis.