Poxviruses, including vaccinia virus (VV) and canarypox virus (ALVAC), do not indiscriminately infect all cell types of the primary human leukocytes (PHLs) that they encounter but instead demonstrate an extremely strong bias toward infection of monocytes and monocyte lineage cells. binding to and infection of PHL subsets. CD29 and CD98, two lipid raft-associated membrane proteins that had been found to be important for VV entry into HeLa cells, had no effect on VV binding to and infection of primary activated T cells. Our data indicate that PHL subsets express VV protein receptors enriched in lipid rafts and that receptors are cross-presented on all susceptible PHLs. INTRODUCTION In general, 4-Azido-L-phenylalanine all viruses must bind to their receptors on the surface of target cells to initiate infection. Virus-receptor interactions determine the cell type, organ specificity, and host range and therefore constitute an interspecies barrier. Poxviruses are a family of large, complex, enveloped DNA viruses that show species specificities (1, 2); for example, variola virus is a strict human-specific pathogen that causes smallpox in humans only (1), and myxoma virus is a rabbit-specific poxvirus that causes a lethal disease (myxomatosis) in rabbits only (1, 2). However, the molecular basis underlying the strict species barrier for poxviruses remains mysterious. Specifically, no specific mobile receptor for just about any poxvirus offers yet been determined. Poxviruses infect a multitude of cell lines in tradition, resulting in the presumptions either that particular receptors for these infections may possibly not be needed or that conserved and ubiquitous receptors could be broadly distributed on the top of varied cell types 4-Azido-L-phenylalanine (1). These conjectures might have impeded efforts to identify mobile receptor(s) that mediate poxvirus binding and disease. However, recent reviews from our group among others show that vaccinia pathogen (VV), the prototypical person in the poxvirus family members, and canarypox pathogen (ALVAC) usually do not indiscriminately infect all cell varieties of the primary human being hematopoietic cells which they encounter but rather demonstrate an exceptionally strong choice for disease of monocytes among peripheral bloodstream mononuclear cells (PBMCs) Rabbit Polyclonal to p53 and monocyte lineage cells within the bone tissue marrow (3, 4). Considerably, manifestation of VV receptor(s) could be induced on major human being T cells upon T cell activation (3). As a result, triggered T cells become vunerable to 4-Azido-L-phenylalanine VV binding, disease, and replication, as opposed to relaxing T cells which are non-permissive to VV binding (3, 4). These receptors tend protein because inhibitors of transcription (actinomycin D), proteins synthesis (cycloheximide), and intracellular proteins transportation (brefeldin A) considerably decrease VV binding to triggered major human being T cells and also because treatment of primary human monocytes or activated T cells with trypsin or pronase completely diminishes VV binding and infection (3). Poxviruses not only bind to and infect monocytes but also use these cells to initiate a systematic infection. A recent study using high doses of variola virus, the most virulent member of the poxvirus family, to infect macaques in an attempt to develop an animal model of smallpox has demonstrated that variola virus is disseminated by means of monocytic cell-associated viremia (5), suggesting that monocytes play a significant role in the initiation of systematic infection. Monocytes may use putative viral receptors to grab infectious variola virus particles and then disseminate them to uninfected cells and tissues, resulting in a generalized infection. However, the specific molecular events that determine poxvirus bias toward monocyte binding and infection remain unclear. In the present study, we investigated the susceptibility of major subsets of primary human leukocytes (PHLs) to VV binding and infection. Our data demonstrate that PHL subsets express and share protein VV receptors that are enriched in lipid rafts on the cytoplasmic membrane and that VV receptors are induced on certain but not all PHL subsets. MATERIALS AND METHODS Antibodies and flow cytometric analysis. The following anti-human monoclonal antibodies (MAbs) or polyclonal Abs (pAbs) conjugated with fluorochrome were purchased from BD PharMingen (San Diego, CA): anti-CD3APC, anti-CD4PerCP, anti-CD8PE, anti-CD14APC, anti-CD16PE, anti-CD19PE, anti-CD56PE, and matched-isotype control Abs conjugated with fluorescein isothiocyanate (FITC), phycoerythrin (PE), peridinin chlorophyll protein (PerCP), or allophycocyanin (APC). Anti-human neutrophil lipocalin (HNL) and anti-human CD66bPE Abs were purchased from Novus Biologicals (Littleton, CO) and 4-Azido-L-phenylalanine Biolegend (San Diego, CA), respectively. Rabbit pAbs against full-length human integrin beta-1 (CD29) and rabbit pAbs against human amino acid transporter SLC3A2 (CD98) were purchased from Abnova (Taipei, Taiwan) and Thermo Fisher Scientific (Pittsburgh, PA), respectively. Isolated PHL subsets including monocytes, B cells, T cells, neutrophils, and NK cells were.