Dimerization of NKp46 receptor is essential for NKp46-mediated lysis: characterization of the dimerization site by epitope mapping.

NKp46 is a primary activating receptor of NK cells that is involved in lysis of target cells by NK cells. Previous studies showed that the membrane-proximal domain of NKp46 (NKp46D2) retained the binding of NKp46 to its ligands and is involved in lysis. We studied NKp46D2 by using a peptide-based epitope mapping approach and identified an NKp46D2-derived linear epitope that inhibited NKp46-mediated lysis.

NKp46 O-glycan sequences that are involved in the interaction with hemagglutinin type 1 of influenza virus.

Natural killer (NK) cells serve as a crucial first-line defense against tumors and virus-infected cells. We previously showed that lysis of influenza virus (IV)-infected cells is mediated by the interaction between the NK receptor, NKp46, and the IV hemagglutinin (HA) type 1 expressed by the infected cells. This interaction requires the presence of sialyl groups on the NKp46-T225 O-glycoforms.

Preferential translation of Hsp83 in Leishmania requires a thermosensitive polypyrimidine-rich element in the 3' UTR and involves scanning of the 5' UTR.

Heat shock proteins (HSPs) provide a useful system for studying developmental patterns in the digenetic Leishmania parasites, since their expression is induced in the mammalian life form. Translation regulation plays a key role in control of protein coding genes in trypanosomatids, and is directed exclusively by elements in the 3' untranslated region (UTR). Using sequential deletions of the Leishmania Hsp83 3' UTR (888 nucleotides [nt]), we mapped a region of 150 nt that was required, but not sufficient for preferential translation of a reporter gene at mammalian-like temperatures, suggesting that changes in RNA structure could be involved.

Generating NK cell receptor-Fc chimera proteins from 293T cells and considerations of appropriate glycosylation.

The use of recombinant receptors as a scientific tool has become widespread in many research fields. Of particular interest are the natural killer (NK) receptors that play a major role in the immune response against tumors and virus-infected cells. We present here (i) a detailed protocol for the production and purification of soluble recombinant NK cell receptors tagged with human IgG1-Fc (thus termed receptor-Fc chimera or receptor-Ig fusion protein) and (ii) a protocol for cell staining with these recombinant receptor-Fc chimeras.

NKp44 receptor mediates interaction of the envelope glycoproteins from the West Nile and dengue viruses with NK cells.

Dengue virus (DV) and West Nile virus (WNV) have become a global concern due to their widespread distribution and their ability to cause a variety of human diseases. Antiviral immune defenses involve NK cells. In the present study, we investigated the interaction between NK cells and these two flaviviruses.

Dengue virus replicon expressing the nonstructural proteins suffices to enhance membrane expression of HLA class I and inhibit lysis by human NK cells.

Many viruses escape the cellular immune response by downregulating cell surface expression of major histocompatibility complex (MHC) class I molecules. However, infection of cells with flaviviruses can upregulate the expression of these molecules. In this study we analyzed the expression of MHC class I in K562 and THP-1 human cell lines that were stably transfected with self-replicating subgenomic dengue virus RNA (replicons) and express all the dengue virus nonstructural proteins together.

H5-type influenza virus hemagglutinin is functionally recognized by the natural killer-activating receptor NKp44.

Antiviral immune defenses involve natural killer (NK) cells. We previously showed that the NK-activating receptor NKp44 is involved in the functional recognition of H1-type influenza virus strains by NK cells. In the present study, we investigated the interaction of NKp44 and the hemagglutinin of a primary influenza virus H5N1 isolate.

Altered glycosylation of recombinant NKp30 hampers binding to heparan sulfate: a lesson for the use of recombinant immunoreceptors as an immunological tool.

NKp30 is a natural cytotoxicity receptor expressed by human NK cells and involved in NK lytic activity. We previously published that membranal heparan sulfate serves as a coligand for human NKp30. In the present study, we complement our results by showing direct binding of recombinant NKp30 to immobilized heparin.

Expression of ligands to NKp46 in benign and malignant melanocytes.

Human melanoma cell lines were shown to express ligands for the natural cytotoxicity receptor, NKp46, expressed by natural killer (NK) cells. We aimed to examine the expression of ligands for NKp46 by various primary human melanocytic cells and melanocytic lesions. Sections from primary nevi and melanomas were tested for expression of NKp46 ligands employing chimeric NKp46-Fc for staining.

Characterization of the recognition of tumor cells by the natural cytotoxicity receptor, NKp44.

NKp44 is a natural cytotoxicity receptor expressed by human NK cells upon activation. In this study, we demonstrate that cell surface heparan sulfate proteoglycans (HSPGs), expressed by target cells, are involved in the recognition of tumor cells by NKp44. NKp44 showed heparan sulfate-dependent binding to tumor cells; this binding was partially blocked with an antibody to heparan sulfate.

Characterization of the heparin/heparan sulfate binding site of the natural cytotoxicity receptor NKp46.

NKp46 is a member of a group of receptors collectively termed natural cytotoxicity receptors (NCRs) that are expressed by natural killer (NK) cells. NCRs are capable of mediating direct killing of tumor and virus-infected cells by NK cells. We have recently shown that NKp46 recognizes the heparan sulfate moieties of membranal heparan sulfate proteoglycans (HSPGs), thus enabling lysis of tumor cells by NK cells.

Identification of Salmonella typhimurium genes responsible for interference with peptide presentation on MHC class I molecules: Deltayej Salmonella mutants induce superior CD8+ T-cell responses.

Salmonella-derived epitopes are presented on MHC molecules by antigen-presenting cells, and both CD4+ and CD8+ T cells participate in protective immunity to Salmonella. Therefore, mechanisms that allow Salmonella to escape specific immune recognition are likely to have evolved in this bacterial pathogen. To identify Salmonella genes, which potentially interfere with the MHC class I (MHC-I) presentation pathway, Tn10d transposon mutagenesis was performed.