Mannose 6-Phosphate Receptor Dependence of Varicella Zoster Virus Infection In Vitro and in the Epidermis during Varicella and Zoster

Varicella zoster virus (VZV) is a highly infectious human pathogen; nevertheless, infectious virions are not released in vitro where infection is cell associated. Four VZV envelope glycoproteins contain mannose 6-phosphate (Man 6-P), and Man 6-P blocks infection of cells by cell-free VZV. Expression of antisense cDNA or siRNA-like transcripts were used to generate five stable human cell lines deficient in cation-independent mannose 6-phosphate receptors (MPR ci). All 5 MPR ci-deficient lines resisted infection by cell-free, but not cell-associated, VZV, secreted lysosomal enzymes, and released infectious virions when infected by cell-associated VZV. Intracellular MPR ci thus appear to divert newly enveloped VZV to late endosomes, and plasmalemmal MPR ci are necessary for entry by cell-free VZV. Biopsies from VZV-infected human skin supported the idea that because MPR ci expression is naturally lost in maturing superficial epidermal cells, these cells do not divert VZV to endosomes and constitutively secrete infectious VZV.