Iduronic acid-containing glycosaminoglycans on target cells are required for efficient respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is an important human respiratory pathoge n, particularly in infants. Glycosaminoglycans (GAGs) have been implicated in the initiation of RSV infection of cultured cells, but it is not clear w hat type of GAGs and GAG components are involved, whether the important GAG s are on the virus or the cell, or what the magnitude is of their contribut ion to infection. We constructed and rescued a recombinant green fluorescen t protein (GFP)-expressing RSV (rgRSV) and used this virus to develop a sen sitive system to assess and quantify infection by flow cytometry. Evaluatio n of a panel of mutant Chinese hamster ovary cell lines that are geneticall y deficient in various aspects of GAG synthesis showed that infection was r educed up to 80% depending on the type of GAG deficiency. Enzymatic removal of heparan sulfate and/or chondroitin sulfate from the surface of HEp-2 ce lls also reduced infection, and the removal of both reduced infection even further. Blocking experiments in which RSV was preincubated with various so luble GAGs revealed the relative blocking order of: heparin > heparan sulfa te > chondroitin sulfate B. Iduronic acid is a component common to these GA Gs, GAGs that do not contain iduronic acid, namely, chondroitin sulfate A a nd C and hyaluronic acid, did not inhibit infection. A role for iduronic ac id-containing GAGs in RSV infection was confirmed by the ability of basic f ibroblast growth factor to block infection, because basic fibroblast growth factor binds to GAGs containing iduronic acid. Pretreatment of cells with protamine sulfate, which binds and blocks GAGs, also reduced infection. In these examples, infection was reduced by pretreatment of the virus with sol uble GAGs, pretreatment of the cells with GAG-binding molecules, pretreatme nt of the cells with GAG-destroying enzymes or in cells genetically deficie nt in GAGs. These results establish that the GAGs involved in RSV infection are present on the cell rather than on the virus particle. Thus, the prese nce of cell surface GAGs containing iduronic acid, like heparan sulfate and chondroitin sulfate B, is required for efficient RSV infection in cell cul ture. (C) 2000 Academic Press.