Phosphatidylserine treatment relieves the block to retrovirus infection of cells expressing glycosylated virus receptors

BACKGROUND: A major determinant of retrovirus host range is the presence or absence of appropriate cell-surface receptors required for virus entry. Often orthologs of functional receptors are present in a wide range of species, but amino acid differences can render these receptors non-functional. In some cases amino acid differences result in additional N-linked glycosylation that blocks virus infection. The latter block to retrovirus infection can be overcome by treatment of cells with compounds such as tunicamycin, which prevent the addition of N-linked oligosaccharides. RESULTS: We have discovered that treatment of cells with liposomes composed of phosphatidylserine (PS) can also overcome the block to infection mediated by N-linked glycosylation. Importantly, this effect occurs without apparent change in the glycosylation state of the receptors for these viruses. This effect occurs with delayed kinetics compared to previous results showing enhancement of virus infection by PS treatment of cells expressing functional virus receptors. CONCLUSION: We have demonstrated that PS treatment can relieve the block to retrovirus infection of cells expressing retroviral receptors that have been rendered non-functional by glycosylation. These findings have important implications for the current model describing inhibition of virus entry by receptor glycosylation.