INFLUENCE OF FIBRONECTIN ON HIV-1 INFECTION AND CAPABILITY OF BINDINGTO PLATELETS

We have previously demonstrated that fibronectin (FN) can bind HIV-1 e nvelope proteins, in particular gp120. The aim of the present study wa s to determine some biological effects of this phenomenon. Pretreating HIV-1 with human FN increased the infectivity of HIV-1, when a low co ncentration of the virus was used. In contrast, an RGD-containing pent apeptide (Gly-Arg-Gly-Asp-Ser), which is a fundamental binding site of FN, reduced the infectivity of a suspension of HIV-1 at high concentr ations of the virus. It is likely that FN bridges the cell surface and the virions, while the RGD-containing pentapeptide may saturate the H IV-1 binding sites for cell surface receptors. Moreover, gp120 was bou nd to the FN present on the surface of platelets. The specifity of thi s binding was confirmed by the inhibition obtained by pretreating plat elets with anti-FN antibodies. The consequence of the surface modifica tions of the platelets could explain the thrombocytopenia that frequen tly occurs in patients infected with HIV and suggests also the possibi lity that platelets could be a vehicle for the virus in the circulatio n.