The cross-reactivity of the enterovirus 71 to human brain tissue and identification of the cross-reactivity related fragments

Abstract

Background: EV71 occasionally cause a series of severe neurological symptoms, including aseptic meningitis, encephalitis, and poliomyelitis-like paralysis. However, the neurological destruction mechanism was remained to be clarified. This study described the cross reaction between EV71 induced IgG and human brain tissue.

Results: Cross reaction of the IgG from 30 EV71 infected patients' sera to human tissues of cerebra was observed, which suggested that some EV71 antigens could induce IgG cross-reactivity to human cerebra. To identify the regions of EV71 virus that containing above antigens, the polypeptide of virus was divided into 19 peptides by expression in prokaryotes cell. Mouse anti-sera of these peptides was prepared and applied in immunohistochemical staining with human adult and fetus brain tissue, respectively. The result indicated the 19 peptides can be classified into three groups: strong cross-reactivity, weak cross-reactivity and no cross-reactivity with human brain tissue according the cross reaction activity. Then, the increased Blood Brain Barrier (BBB) permeability and permits IgG entry in neonatal mice after EV71 infection was determined.

Conclusion: EV71 induced IgG could enter BBB and cross-reacted with brain tissue in EV71 infected neonatal mice, and then the peptides of EV71 that could induce cross-reactivity with brain tissue were identified, which should be avoided in future vaccine designing.

Figure 1

Cross reaction of the IgG from EV71 infected patients' sera with human tissues of cerebra. The serum was replaced by PBS buffer as blank control (a), and naive sera from five health donors were used as negative control (b-f). The sera of CNILASTB-16 (g), CNILASTB-19 (h), CNILASTB-1 (i), CNILASTB-2 (j), CNILASTB-4 (k) and CNILASTB-9 (l) were used as primary antibodies in immunohistochemical staining with the cerebra of adult. The IgG fraction in the sera of NORMAL-1 (m), CNILASTB-12 (n) and CNILASTB-4 (o) were used as primary antibodies in immunohistochemical staining with the cerebra of adult to exclude the interference of the remained ingredients in sera. The stained glial cell, stroma and neuron were denoted with black, green and red arrows respectively (×200).

Figure 2

Diagrams of divided 22 peptides from EV71 and expression construction. The position and length of 22 peptides divided from EV71 (a) and expression constructs for 22 peptides (b) were diagramed.

Figure 3

Identification of EV71 fragments inducing cross immunity to human brain tissue by immunohistochemical staining. Left panel was adult human cerebra and the right panel was human fetus medulla. The naive mice sera was used as negative control (a & b). The serum of immunized mice with peptide of P_646-755 was one of the four strong cross immunity peptides(c & d). P_2072-2193 was one of the ten weak cross immunity peptides (e & f). P_140-249 was one of the five no cross immunity peptides (g & h). The serum of immunized mice with heat inactivated virus was used as positive control (i & j). The staining sites were denoted with arrows (×200).

Figure 4

Detection the intracranial IgG in mice after intravenous injection. The normal neonatal mice injected with naive IgG. (a), EV71 infected neonatal mice injected with mice naïve IgG. (b), normal neonatal mice injected with EV71 induced IgG. (c) and EV71 infected neonatal mice injected with EV71 induced IgG.(d) were compared by the immunohistochemical test. The staining sites were denoted with arrows (× 200).