Foot-and-Mouth Disease Virus Virulent for Cattle Utilizes the Integrin α(v)β(3) as Its Receptor

Adsorption and plaque formation of foot-and-mouth disease virus (FMDV) serotype A(12) are inhibited by antibodies to the integrin α(v)β(3) (A. Berinstein et al., J. Virol. 69:2664–2666, 1995). A human cell line, K562, which does not normally express α(v)β(3) cannot replicate this serotype unless cells are transfected with cDNAs encoding this integrin (K562-α(v)β(3) cells). In contrast, we found that a tissue culture-propagated FMDV, type O(1)BFS, was able to replicate in nontransfected K562 cells, and replication was not inhibited by antibodies to the endogenously expressed integrin α(5)β(1). A recent report indicating that cell surface heparan sulfate (HS) was required for efficient infection of type O(1) (T. Jackson et al., J. Virol. 70:5282–5287, 1996) led us to examine the role of HS and α(v)β(3) in FMDV infection. We transfected normal CHO cells, which express HS but not α(v)β(3), and two HS-deficient CHO cell lines with cDNAs encoding human α(v)β(3), producing a panel of cells that expressed one or both receptors. In these cells, type A(12) replication was dependent on expression of α(v)β(3), whereas type O(1)BFS replicated to high titer in normal CHO cells but could not replicate in HS-deficient cells even when they expressed α(v)β(3). We have also analyzed two genetically engineered variants of type O(1)Campos, vCRM4, which has greatly reduced virulence in cattle and can bind to heparin-Sepharose columns, and vCRM8, which is highly virulent in cattle and cannot bind to heparin-Sepharose. vCRM4 replicated in wild-type K562 cells and normal, nontransfected CHO (HS(+) α(v)β(3(−))) cells, whereas vCRM8 replicated only in K562 and CHO cells transfected with α(v)β(3) cDNAs. A similar result was also obtained in assays using a vCRM4 virus with an engineered RGD→KGE mutation. These results indicate that virulent FMDV utilizes the α(v)β(3) integrin as a primary receptor for infection and that adaptation of type O(1) virus to cell culture results in the ability of the virus to utilize HS as a receptor and a concomitant loss of virulence.