In vitro infection of primary and retrovirus-infected human leukocytes by human foamy virus

The infectivity of human foamy virus (HFV) was examined in primary and cultured human leukocytes; Cell-free infectious viral stocks of HFV were prepared from the human kidney cell line 293 transfected with an infectious molecular clone of HFV. HFV productively infects a variety of human myeloid and lymphoid cell lines. In addition, primary cell cultures enriched for human CD4(+), monocytes and brain-derived microglial cells, were readily infected by HFV. Interestingly, while infected primary CD4(+) lymphocytes and microglial cells showed marked cytopathology characteristic of foamy virus, HFV-infected monocyte-derived macrophages failed to show any cytopathology. In addition, marked cytotoxicity due to HFV infection was seen in both human T-cell leukemia virus type 1- and human immunodeficiency virus type 1-infected T-cell lines and in human immunodeficiency virus type I-infected monocytoid cell lines. Thus, HFV infection produces differential cytopathology in a wide host range of primary human leukocytes and hematopoietic cell lines.