Eosinophils are granulocytic leukocytes that function in both protective and pathological immune responses. They can be infected by HIV-1, but characterization of the infection has been hindered by lack of a productive cell culture model. In the present study, the unique eosinophilic cell line AML14.3D10 was used as a model to test the hypothesis that HIV-1 productively infects eosinophilic cells in a strain-dependent fashion. The AML14.3D10 cell line was cultured with one T cell-tropic (T-tropic) strain and two macrophage-tropic (Mtropic) strains of HIV-1 (HTLV-IIIB, HIV-1Ada-M, and HIV-1Ba-L strains, respectively). Cytopathic effects were evident in living cultures and in stained slide preparations of AML14.3D10 cells infected with the T-tropic strain of HIV-1. Culture supernatants from infected AML14.3D10 cells contained high levels of HIV-1 p24 protein that peaked at approximately 7-10 days postinfection. A line of AML14.3D10 cells chronically infected with HTLV-IIIB and continuously producing high levels of virus was established. In contrast to the T-tropic strain, the M-tropic strains of HIV-1 did not productively infect the eosinophilic cell line. Thus, the AML14.3D10 eosinophilic cell line was permissive for a T-tropic strain but not for M-tropic strains of HIV1. Flow cytometry revealed that uninfected AML14.3D10 cells were positive for the HIV-1 receptor CD4 and coreceptors CXCR4 and CCR5; the cell line was negative for CCR3. The lack of productive infection by M-tropic strains despite CCR5 expression indicates that strain-dependent infection may not be determined at the coreceptor level in AML14.3D10 cells.