Newly emerged hantaviruses replicate primarily in the pulmonary endothelium, cause acute platelet loss, and result in hantavirus pulmonary syndrome (HPS). We now report that specific integrins expressed on platelets and endothelial cells permit the cellular entry of HPS-associated hantaviruses. Infection with HPS-associated hantaviruses, NY-1 and Sin Nombre virus (SNV), is inhibited by antibodies to ␤ 3 integrins and by the ␤ 3 -integrin ligand, vitronectin. In contrast, infection with the nonpathogenic (no associated human disease) Prospect Hill virus was inhibited by fibronectin and ␤ 1 -specific antibodies but not by ␤ 3 -specific antibodies or vitronectin. Transfection with recombinant ␣ IIb ␤ 3 or ␣ v ␤ 3 integrins rendered cells permissive to NY-1 and SNV but not Prospect Hill virus infection, indicating that ␣ IIb ␤ 3 and ␣ v ␤ 3 integrins mediate the entry of NY-1 and SNV hantaviruses. Furthermore, entry is divalent cation independent, not blocked by arginine-glycine-aspartic acid peptides and still mediated by, ligand-binding defective, ␣ IIb ␤ 3 -integrin mutants. Hence, NY-1 and SNV entry is independent of ␤ 3 integrin binding to physiologic ligands. These findings implicate integrins as cellular receptors for hantaviruses and indicate that hantavirus pathogenicity correlates with integrin usage.

Hantaviruses infect human endothelial cells and cause two vascular permeability-based diseases: hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. Hantavirus infection alone does not permeabilize endothelial cell monolayers. However, pathogenic hantaviruses inhibit the function of ␣v␤3 integrins on endothelial cells, and hemorrhagic disease and vascular permeability deficits are consequences of dysfunctional ␤3 integrins that normally regulate permeabilizing vascular endothelial growth factor (VEGF) responses. Here we show that pathogenic Hantaan, Andes, and New York-1 hantaviruses dramatically enhance the permeability of endothelial cells in response to VEGF, while the nonpathogenic hantaviruses Prospect Hill and Tula have no effect on endothelial cell permeability. Pathogenic hantaviruses directed endothelial cell permeability 2 to 3 days postinfection, coincident with pathogenic hantavirus inhibition of ␣v␤3 integrin functions, and hantavirus-directed permeability was inhibited by antibodies to VEGF receptor 2 (VEGFR2). These studies demonstrate that pathogenic hantaviruses, similar to ␣v␤3 integrin-deficient cells, specifically enhance VEGF-directed permeabilizing responses. Using the hantavirus permeability assay we further demonstrate that the endothelial-cell-specific growth factor angiopoietin 1 (Ang-1) and the platelet-derived lipid mediator sphingosine 1-phosphate (S1P) inhibit hantavirus directed endothelial cell permeability at physiologic concentrations. These results demonstrate the utility of a hantavirus permeability assay and rationalize the testing of Ang-1, S1P, and antibodies to VEGFR2 as potential hantavirus therapeutics. The central importance of ␤3 integrins and VEGF responses in vascular leak and hemorrhagic disease further suggest that altering ␤3 or VEGF responses may be a common feature of additional viral hemorrhagic diseases. As a result, our findings provide a potential mechanism for vascular leakage after infection by pathogenic hantaviruses and the means to inhibit hantavirus-directed endothelial cell permeability that may be applicable to additional vascular leak syndromes.

Hantaviruses cause two diseases with prominent vascular permeability defects, hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. All hantaviruses infect human endothelial cells, although it is unclear what differentiates pathogenic from nonpathogenic hantaviruses. We observed dramatic differences in interferon-specific transcriptional responses between pathogenic and nonpathogenic hantaviruses at 1 day postinfection, suggesting that hantavirus pathogenesis may in part be determined