Functional analysis of porcine reproductive and respiratory syndrome virus N-glycans in infection of permissive cells

The role of envelope protein-linked N-glycans in porcine reproductive and respiratory syndrome virus (PRRSV) infection of permissive cells was examined. N-acetylglucosamine (GlcNAc) and N-acetyllactosamine (LacNAc) oligomer-specific lectins bound to PRRSV and blocked virus attachment, resulting in reduced viral infection. However, addition of GlcNAc oligomers and LacNAc to cell culture together with PRRSV did not block infection. Removal or alteration of envelope protein-linked N-glycans also did not affect virus infection, indicating that PRRSV N-glycans are not required for virus infection. These findings show that steric hindrance of glycans on the PRRSV envelope by lectins or, presumably, other space-filling molecules, may interfere nonspecifically with infection by blocking protein interactions with cell surface receptors. Glycans themselves appear not to be required for infection of permissive cells, but may have important roles in avoidance of host immunity and in protein structure, intracellular virion growth and assembly.