Expression of SARS coronavirus S protein functional receptor ACE2 in human and rabbit cornea and conjunctiva

Objective The spike proteins of SARS-CoV assoc ia te with cellular receptors of sensitive cells to mediate infection of their tar get cells.Recently,a metallopeptidase named angiotensin-converting enzyme 2( ACE2)has been identified as the functional receptor for SARS-CoV.The present s tudy investigated the expression of ACE2 in human and rabbit cornea and conjunct iva in an attempt to provide evidence about the possible route of SARS-CoV entr y via eyes. Methods ACE2 expression in human and rabbit cornea and conjunctiva was detected by RT-PCR and immunohistochemistry. Results Positive expression of ACE2 was det ected in human and rabbit cornea and conjunctiva.Amplified strands of ACE2 were detected by RT-PCR in corneal and conjunctival tissues and cells.The amplifie d strands were weaker in fetal,adult and rabbit cornea and conjunctiva than in hearts and lungs.Luminosity of the amplif ied strands of various tissues in rabbits was similar to that of the correspondi ng human tissue s.The product of ACE2 immunohistochemical reaction was mainly in the cytoplasm and cytomembrane,looking dark brown.Expression of ACE2 was significantly posit ive in corneal and conjunctival epithelia and corneal endothelia,and weakly pos itive in corneal and conjunctival fibroblasts.Positive expression of ACE2 was also detected in cultured human conjunctival fibroblasts and rabbit corneal epithelia.The strength of ACE2 expression and histological a pposition in the rabbit tissues were similar to those in human tissues. Conclusion These results indicate that there exist SARS-CoV S protein functional receptor -A CE2 in human and rabbit cornea and conjunctiva.So it is possible for SARS-CoV to enter by the cornea and conjunctiva.It is also po ssible to use rabbits as an animal model in investigating the possible route of SARS-CoV transmission.