Compared to HAVLP, HA-incorporated VLPs were significantly endocytosed by A549 cells. illustrated by fluorescence imaging on the Jurkat cells incubated with rhodamine-loaded VLP performed at fusogenic pH. Furthermore, the green fluorescence protein (GFP) was fused to NA to produce VLP with a pH-sensitive probe, expanding the use of VLP as an antigen carrier and a tool for viral tracking. == 1. Introduction == Virus-like particle (VLP) has been extensively studied for its vaccine capacity in the last 20 years. More than a dozen of VLP-based vaccines have been tested in clinical trials. Two of them against hepatitis B and human papilloma viruses are commercially available as prophylactics [1]. The merits of VLP-based vaccine rest on its viral mimicry and devoid of genetic materials, hence alleviating the safety concerns [2]. The repetitive and ordered structures of VLPs are conducive to opsonization, resulting in enhanced phagocytosis [3,4], and are capable to activate B cells in a T cell-independent manner [5,6]. Owing to the virus-like dimension and particulate nature, VLPs are easily taken up by antigen-presenting cells (APCs) [7,8] and more efficient in cross-presentation of antigens to MHC I molecules compared to the soluble antigen and hence the possibility of activating antigen-specific cytotoxic T lymphocytes (CTLs) [9]. Although the VLP-based vaccines have the potential to induce CTL response, most of them favor the production of humoral immunity but poorly evoke CTL response if additional stimuli for innate immune system and, in particular, APC were Taribavirin hydrochloride neglected [1]. It is somewhat surprising that VLPs derived from baculovirus system incorporating viral structural proteins of influenza virus were found to induce both cell-mediated and humoral immunity to confer full protection from viral challenge [1012]. This distinct feature drew our attention on the interaction between VLPs and cells since most of the VLP-based Taribavirin hydrochloride strategies for vaccine development do not involve antigens with functions of ligand binding and membrane fusion in contrast with the hemagglutinin of influenza VLP. Influenza A virus is an enveloped RNA virus with three transmembrane proteins: hemagglutinin (HA), neuraminidase (NA), and ion channel protein (M2) along with matrix protein 1 (M1) underlying the viral envelope. The major tasks of these proteins include ligand binding and Taribavirin hydrochloride membrane fusion for HA [13,14], spreading of viral progeny and facilitating entry of the virus for NA [1517], proton transfer for viral uncoating as well as assembly and budding of the virus for M2 [1820], recruitment of viral components to the assembly site, and a major driving force for viral budding for M1 [21,22]. Several laboratories have produced insect cell-derived VLPs encompassing the above-mentioned influenza proteins for vaccine development [23]. However, there has been no report on the characterization of the interaction between VLPs and cells. Mouse monoclonal to PTH To afford a better understanding of these interactions, we used fluorescent images and dye dequenching in this study in the hope of shedding some light on the mechanism of antigen presentation, and virus-mediated membrane fusion and its inhibition. == 2. Materials and Methods == == 2.1. Plasmid Construction == HA (A/Thailand/1(KAN-1)/2004/H5N1), NA (A/Viet Nam/1203/2004/H5N1), M1 (A/WSN/33/H1N1) and M2 (A/WSN/33/H1N1), influenza cDNA sequences were amplified by PCR (primer sequences were listed in theTable 1). The HA PCR products were cloned intoBamHI/NotIsite under the control of the polyhedron promoter, the M1 PCR products intoXhoI/KpnIsite under p10 promoter of the pFastbac Dual baculovirus transfer vector (Invitrogen), the M2 PCR products intoEcoRI /HindIIIsite under the polyhedron promoter, and the NA PCR products intoXhoI /KpnIsite under p10 promoter of the pFastbac Dual baculovirus transfer vector (Invitrogen), and the NA-EGFP PCR products intoXhoI/KpnIsite under p10 promoter of the pFastbac Dual baculovirus transfer vector (Invitrogen). All the inserted sequences were confirmed by DNA sequence analysis (Mission Biotech Inc., Taipei, Taiwan). == Taribavirin hydrochloride Table 1. == Primer sequence used in pFastbac Dual vector construction. == 2.2. Generation of Recombinant Baculoviruses == Production of recombinant baculoviruses followed the manufacturer’s manual of Bac-to-Bac baculovirus system (Invitrogen). Briefly, the pFastbac Dual plasmids were transformed intoE.colistrain DH10Bac (Invitrogen) and selected on LB plate containing kanamycin (Invitrogen), gentamicin (Invitrogen), tetracycline (Invitrogen), Bluo-gal (Invitrogen), and IPTG (BioRad). The recombinant bacmids were confirmed by sequencing and then transfected intoSpodoptera frugiperda(Sf9) cells for recombinant baculovirus packaging via the aid of Cellfectin Reagent (Invitrogen). After 4.
