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Neospora caninum is an Apicomplexa parasite that in the last two decades was acknowledged as the main pathogenic agent responsible for economic losses in the cattle industry. In the present study, the effectiveness of intranasal immunization with N. caninum membrane antigens plus Cp G adjuvant was assessed in a murine model of intragastrically established neosporosis. Immunized mice presented a lower parasitic burden in the brain on infection with 5 × 107 tachyzoites, showing that significant protection was achieved by this immunization strategy. Intestinal Ig A antibodies raised by immunization markedly agglutinated live N. caninum tachyzoites whereas previous opsonization with Ig G antibodies purified from immunized mice sera reduced parasite survival within macrophage cells. Although an Ig G1 : Ig G2a ratio < 1 was detected in the immunized mice before and after infection, indicative of a predominant T helper type 1 immune response, no increased production of interferon-γ was detected in the spleen or mesenteric lymph nodes of the immunized mice. Altogether, these results show that mucosal immunization with N. caninum membrane proteins plus Cp G adjuvant protect against intragastrically established neosporosis and indicate that parasite-specific mucosal and circulating antibodies have a protective role against this parasitic infection. [ABSTRACT FROM AUTHOR]

Re-expression of recombinase activating genes ( RAG) in mature B cells may support autoreactivity by enabling revision of the B-cell receptor ( BCR). Recent reports suggest that administration of Toll-like receptor 9 ( TLR9) -stimulating Cp G oligodeoxynucleotides ( ODN) could trigger the manifestation of autoimmune disease and that TLR are involved in the selection processes eliminating autoreactive BCR. The mechanisms involved remain to be elucidated. This prompted us to ask, whether TLR9 could be involved in receptor revision. We found that phosphorothioate-modified Cp G ODN ( Cp GPTO) induced expression of Ku70 and re-expression of RAG-1 in human peripheral blood B lymphocytes and Igλ expression in sorted Igκ+ B cells. Further results revealed unselective binding specificity of Cp GPTO-induced immunoglobulin and suggested that Cp GPTO engage and/or mimic Ig M receptor signalling, an important prerequisite for the initialization of receptor editing or revision. Altogether, our data describe a potential role for TLR9 in receptor revision and suggest that Cp GPTO could mimic chromatin-bearing autoantigens by simultaneously engaging the BCR and TLR9 on Ig M+ B cells. [ABSTRACT FROM AUTHOR]

Cyclooxygenase (Cox) inhibitors are among the most widely used and commonly prescribed medications. Relatively little is understood about their influence on human immune responses. Herein, we discovered a novel and important mechanism whereby non-steroidal anti-inflammatory drugs (NSAIDs) blunt human B-cell antibody production. We demonstrate that the Cox-2 selective small molecule inhibitors SC-58125 and NS-398 attenuate the production of human antibody isotypes including immunoglobulin M (IgM), IgG1, IgG2, IgG3 and IgG4. In addition, inhibition of Cox-2 significantly reduced the generation of CD38+ IgM+ and CD38+ IgG+ antibody-secreting cells. Interestingly, we discovered that inhibition of Cox-2 activity in normal human B cells severely reduced the messenger RNA and protein levels of the essential plasma cell transcription factor, Blimp-1. These observations were mirrored in Cox-2-deficient mice, which had reduced CD138+ plasma cells and a near loss of Blimp-1 expression. These new findings demonstrate a critical role for Cox-2 in the terminal differentiation of human B lymphocytes to antibody-secreting plasma cells. The use of NSAIDs may adversely influence the efficacy of vaccines, especially in the immunocompromised, elderly and when vaccines are weakly immunogenic. [ABSTRACT FROM AUTHOR]

B-cell expression of certain Toll-like receptors (TLRs) is important in linking innate and adaptive immune responses in normal and pathological conditions. The expression of TLR9 plays a role in the recognition of conserved pathogen motifs in a manner that is dependent on B-cell localization, deduced from B-cell phenotype. The nature of TLR9 function is unclear. A first step in unravelling the function of this pattern recognition receptor is to discover the precise nature of the cell types that express TLR9. This study used three-colour flow cytometry to characterize the B lymphocytes from human peripheral blood mononuclear cells (PBMCs) that express TLR9 on the surface. We sorted TLR9-positive B and non-B cells from the PBMC population and detected TLR9 expression on naïve and memory B cells. Moreover, we identified two discrete subpopulations of B cells: CD19+ CD27− CD23+ cells and CD19+ CD27high CD80+ cells. These subpopulations expressed high levels of membrane TLR9 and exhibited a strong in vitro response to binding a relevant CpG motif by secreting high levels of interleukin-6 (compared to controls). Our finding that this pattern recognition receptor is expressed on a variety of cell subsets adds to the current understanding of the functional complexity of B-cell membrane TLR9. [ABSTRACT FROM AUTHOR]

Immunostimulatory sequences (ISS) that contain CpG motifs have been demonstrated to exert antipathogen and antitumour immunity in animal models through several mechanisms, including the activation of natural killer (NK) cells to secrete interferon-γ (IFN-γ) and to exert lytic activity. Since NK cells lack the ISS receptor TLR9, the exact pathway by which NK cells are activated by ISS is unclear. We determined that ISS-induced IFN-γ from NK cells is primarily dependent upon IFN-α release from plasmacytoid dendritic cells (PDCs), which directly activates the NK cell. However, further analysis indicated that other PDC-released soluble factor(s) may contribute to IFN-γ induction. Indeed, tumour necrosis factor-α (TNF-α) was identified as a significant contributor to ISS-mediated activation of NK cells and was observed to act in an additive fashion with IFN-α in the induction of IFN-γ from NK cells and to up-regulate CD69 expression on NK cells. This activity of TNF-α, however, was dependent upon the presence of PDC-derived factors such as type I interferon. These results illustrate an important function for type I interferon in innate immunity, which is not only to activate effectors like NK cells directly, but also to prime them for enhanced activation by other factors such as TNF-α. [ABSTRACT FROM AUTHOR]

Oligodeoxynucleotides (ODN) with unmethylated CpG dinucleotides mimic the immune stimulatory activity of bacterial DNA in vertebrates and are recognized by Toll-like receptor 9 (TLR9). It is also possible to detect immune activation with certain phosphorothioate sequences that lack CpG motifs. These ODN are less potent than CpG ODN and the mechanism by which they stimulate mammalian leucocytes is not understood. We here provide several lines of evidence demonstrating that the effects induced by non-CpG ODN are mediated by TLR9. First, non-CpG ODN could not stimulate cytokine secretion from the splenocytes of TLR9-deficient (TLR9–/–) mice. Second, immunization of TLR9+/+ but not TLR9–/– mice with non-CpG ODN enhanced antigen-specific antibody responses, although these were T helper type 2 (Th2)-biased. Third, reactivity to non-CpG ODN could be reconstituted by transfection of human TLR9 into non-responsive cells. In addition, we define a new efficient immune stimulatory motif aside from the CpG dinucleotide that consists of a 5′-TC dinucleotide in a thymidine-rich background. Non-CpG ODN containing this motif induced activation of human B cells, but lacked stimulation of Th1-like cytokines and chemokines. Our study indicates that TLR9 can mediate either efficient Th1- or Th2-dominated effects depending on whether it is stimulated by CpG or certain non-CpG ODN. [ABSTRACT FROM AUTHOR]