Macrophages act as reservoirs of human immunodeficiency virus type 1 (HIV-1) and play an important role in its transmission to other cells. HIV-1 Vpr is a multi-functional protein involved in HIV-1 replication and pathogenesis; however, its exact role in HIV-1-infected human macrophages remains poorly understood. In this study, we used a microarray approach to explore the effects of HIV-1 Vpr on the transcriptional profile of human monocyte-derived macrophages (MDMs). More than 500 genes, mainly those involved in the innate immune response, the type I interferon pathway, cytokine production, and signal transduction, were differentially regulated (fold change >2.0) after infection with a recombinant adenovirus expressing HIV-1 Vpr protein. The differential expression profiles of select interferon-stimulated genes (ISGs) and genes involved in the innate immune response, including STAT1, IRF7, MX1, MX2, ISG15, ISG20, IFIT1, IFIT2, IFIT3, IFI27, IFI44L, APOBEC3A, DDX58 (RIG-I), TNFSF10 (TRAIL), and RSAD2 (viperin) were confirmed by real-time quantitative PCR and were consistent with the microarray data. In addition, at the post-translational level, HIV-1 Vpr induced the phosphorylation of STAT1 at tyrosine 701 in human MDMs. These results demonstrate that HIV-1 Vpr leads to the induction of ISGs and expand the current understanding of the function of Vpr and its role in HIV-1 immune pathogenesis.

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle, which is closely related to human T‐cell leukemia viruses. BLV has spread worldwide and causes a serious problem for the cattle industry. The cellular receptor specifically binds with viral envelope glycoprotein (Env), and this attachment mediates cell fusion to lead virus entry. BLV Env reportedly binds to cationic amino acid transporter 1 (CAT1)/solute carrier family 7 member 1 (SLC7A1), but whether the CAT1/SLC7A1 is an actual receptor for BLV remains unknown. Here, we showed that CAT1 functioned as an infection receptor, interacting with BLV particles. Cells expressing undetectable CAT1 levels were resistant to BLV infection but became highly susceptible upon CAT1 overexpression. CAT1 exhibited specific binding to BLV particles on the cell surface and colocalized with the Env in endomembrane compartments and membrane. Knockdown of CAT1 in permissive cells significantly reduced binding to BLV particles and BLV infection. Expression of CAT1 from various species demonstrated no species specificity for BLV infection, implicating CAT1 as a functional BLV receptor responsible for its broad host range. These findings provide insights for BLV infection and for developing new strategies for treating BLV and preventing its spread.—Bai, L., Sato, H., Kubo, Y., Wada, S., Aida, Y. CAT1/SLC7A1 acts as a cellular receptor for bovine leukemia virus infection. FASEB J. 33, 14516‐14527 (2019). www.fasebj.org

Bovine leukemia virus (BLV) infects cattle and causes serious problems for the cattle industry, worldwide. Vertical transmission of BLV occurs via in utero infection and ingestion of infected milk and colostrum. The aim of this study was to clarify whether milk is a risk factor in BLV transmission by quantifying proviral loads in milk and visualizing the infectivity of milk. We collected blood and milk from 48 dams (46 BLV seropositive dams and 2 seronegative dams) from seven farms in Japan and detected the BLV provirus in 43 blood samples (89.6%) but only 22 milk samples (45.8%) using BLV-CoCoMo-qPCR-2. Although the proviral loads in the milk tended to be lower, a positive correlation was firstly found between the proviral loads with blood and milk. Furthermore, the infectivity of milk cells with BLV was visualized ex vivo using a luminescence syncytium induction assay (LuSIA) based on CC81-GREMG cells, which form syncytia expressing enhanced green fluorescent protein (EGFP) in response to BLV Tax and Env expressions when co-cultured with BLV-infected cells. Interestingly, in addition to one BLV-infected dam with lymphoma, syncytia with EGFP fluorescence were observed in milk cells from six BLV-infected, but healthy, dams by an improved LuSIA, which was optimized for milk cells. This is the first report demonstrating the infectious capacity of cells in milk from BLV-infected dams by visualization of BLV infection ex vivo. Thus, our results suggest that milk is a potential risk factor for BLV vertical spread through cell to cell transmission.

We examined the proliferative activity, apoptosis, and histogenesis in the early stages of the rat healing socket from just after extraction until new bone formation occurs. Thirty 11-week-old male Wistar rats underwent bilateral maxillary first molar tooth extraction. Five craniomaxillary tissue specimens were dissected at the following time points: at 12 h, days 1, 3, 5, 7 and 10 after surgery. The immunohistochemical expression of both proliferating cell nuclear antigen (PCNA) and the Ki67 counterpart of rodent (MIB5) for proliferative activity and both the TUNEL reaction and the immunohistochemical expression of single-strand DNA for apoptosis were evaluated using 6-µm-thick serial paraffin sections, which were prepared in the coronal plane. The positive cell counts in the socket were converted into the cell numbers per mm2 as either the proliferative index (PI) or the apoptotic index (AI). The PI and the AI showed maximum levels at 5 days and 12 h after extraction, respectively. The proliferative activity in the early stages of extraction wound healing is initially distributed in the remaining periodontium with load-induced apoptosis, next in the proliferative fibrous tissue, and then around the trabeculae of the new bone marking its peak.