The significance of N-linked glycosylation in pig endogenous retrovirus infectivity.

The significance of the envelope glycoprotein in the transmission of pig endogenous retrovirus (PERV) to human cells was investigated. Pig endothelial cells (PEC) were transduced with the LacZ gene by a pseudotype infection and then infected with PERV subtype B. Culture supernatants of the infected PEC previously incubated with several types of drugs were inoculated into HEK293 cells. The inoculated cells were then stained and the number of LacZ-positive foci was counted. PERV from tunicamycin treated PEC was not transmitted to human cells, indicating the importance of N-linked sugars in this process. Moreover, while inhibition of the terminal alpha-glucose residues from the precursor N-glycan by castanospermine and 1-deoxynojirimycin attenuated PERV infectivity, the mannosidase inhibitors, 1-deoxymannojirimycin and swainsonine, upregulated the infectivity. In addition, treatment with alpha-mannosidase and incubation with concanavalin A completely abrogated the transmission of PERV to HEK293. These data imply that the high-mannose type of N-glycan plays a key role in PERV infectivity.