Role of Integrin Cross-Regulation in Parvovirus B19 Targeting

Abstract

Most viral vectors used for gene therapy lack the ability to target a defined cell population. Parvovirus B19 has a restricted tropism for human erythroid progenitor cells and uses activated α₅β₁ integrins as coreceptors for entry [Weigel-Kelley, K.A., Yoder, M.C., and Srivastava, A. (2003). Blood 102, 3927–3933]. In this study we examined the role of coexpressed integrins in α₅β₁ integrin coreceptor function. Antibody-mediated cross-linking of β₁, β₂, and β₃ integrins and the integrin-associated protein (IAP) increased parvovirus B19 entry into nontarget K562 cells. Functional silencing of one integrin group, however, reduced the virus uptake- promoting function of a subsequently activated integrin group, indicating that the three integrins did not operate in isolation but through shared signaling pathways. This was further corroborated by direct competition between simultaneously clustered β₂ and β₁ integrins that could be overcome by stabilizing clusteredβ₁ integrins in a high-affinity conformation. In contrast, parvovirus B19 entry into primary erythroid progenitor cells was characterized by strong clustering-induced β₁ integrin coreceptor activity that was not abolished by subsequent β₂ and β₃ integrin activation and was, in fact, substantially increased in the presence of preclustered β₂ and β₃ integrins. Thus, integrin function is regulated in a cell type-specific manner through coexpressed integrins and preferential parvovirus B19 entry into erythroid progenitor cells is promoted by a robust β₁ integrin response that is enhanced through stable preclustering of coexpressed integrins. These results have implications for other viral vectors that use integrins as receptors/coreceptors and for gene therapy of hematopoietic progenitor cells using parvovirus B19 vectors.