Variable domain N-linked glycosylation and negative surface charge are key features of monoclonal ACPA: implications for B-cell selection

Autoreactive B cells have a central role in the pathogenesis of rheumatoid arthritis (RA), and recent findings have proposed that anti-citrullinated protein autoantibodies (ACPA) may be directly pathogenic. Herein, we demonstrate the frequency of variable-region glycosylation in single-cell cloned mAbs. A total of 14 ACPA mAbs were evaluated for predicted N-linked glycosylation motifs in silico and compared to 452 highly-mutated mAbs from RA patients and controls. Variable region N-linked motifs (N-X-S/T) were strikingly prevalent within ACPA (100%) compared to somatically hypermutated (SHM) RA bone marrow plasma cells (21%), and synovial plasma cells from seropositive (39%) and seronegative RA (7%). When normalized for SHM, ACPA still had significantly higher frequency of N-linked motifs compared to all studied mAbs including highly-mutated HIV broadly-neutralizing and malaria-associated mAbs. The Fab glycans of ACPA-mAbs were highly sialylated, contributed to altered charge, but did not influence antigen binding. The analysis revealed evidence of unusual B-cell selection pressure and SHM-mediated decreased in surface charge and isoelectric point in ACPA. It is still unknown how these distinct features of anti-citrulline immunity may have an impact on pathogenesis. However, it is evident that they offer selective advantages for ACPA+ B cells, possibly also through non-antigen driven mechanisms

Therapeutic efficacy of antibodies lacking FcgammaR against lethal Dengue virus infection Is due to neutralizing potency and blocking of enhancing antibodies

<div><p>Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are life-threatening complications following infection with one of the four serotypes of dengue virus (DENV). At present, no vaccine or antiviral therapies are available against dengue. Here, we characterized a panel of eight human or mouse-human chimeric monoclonal antibodies (MAbs) and their modified variants lacking effector function and dissected the mechanism by which some protect against antibody-enhanced lethal DENV infection. We found that neutralizing modified MAbs that recognize the fusion loop or the A strand epitopes on domains II and III of the envelope protein, respectively, act therapeutically by competing with and/or displacing enhancing antibodies. By analyzing these relationships, we developed a novel <em>in vitro</em> suppression-of-enhancement assay that predicts the ability of modified MAbs to act therapeutically against antibody-enhanced disease <em>in vivo</em>. These studies provide new insight into the biology of DENV pathogenesis and the requirements for antibodies to treat lethal DENV disease.</p> </div

Presentation of peptides by cultured monocytes or activated T cells allows specific priming of human cytotoxic T lymphocytes in vitro

The conditions favouring effective specific cytotoxic T lymphocyte (CTL) priming have been exploited to set up a simple and reproducible method to induce a primary CTL response in vitro. We report that cultured monocytes, as well as activated T cells, pulsed with exogenous HLA-A2 binding immunogenic peptides, can induce primary peptide-specific CTL responses in vitro in a Th-independent manner. Primary viral peptide-induced CTL were HLA-A2 restricted, and recognized both peptide-pulsed target cells and targets infected with recombinant vaccinia virus expressing viral endogenous antigens. In addition, both cultured monocytes and activated T cells primed peptide-specific CD8+ T cells depleted from the CD45RO+ memory cell fraction. The efficiency of CTL priming by monocytes was dependent upon the strong up-regulation of class I, adhesion and co-stimulatory molecules occurring spontaneously upon in vitro culture. The inability of unseparated peripheral blood mononuclear cells to mount a peptide-specific CTL response could be reverted by direct co-stimulation of responding CD8+ T cells by soluble B7.1 or a stimulatory anti-CD28 antibody, that allowed a specific response to take place. Although co-stimulation via the B7-CD28 interaction appeared sufficient to trigger CTL responses, It was not essential for CTL priming, since neither anti-B7.1 mAb nor soluble CTLA-4 inhibited induction of primary CTL response. This new method for induction of specific CD8+ T cell response in vitro may be exploited in adoptive immunotherapy in cancer or in HIV-infected patient

Dissecting human antibody responses: useful, basic and surprising findings

Human memory B cells and plasma cells represent a rich source of antibodies that have been selected in response to human pathogens. In the last decade, different methods have been developed to interrogate the human memory repertoire and isolate monoclonal antibodies. I will discuss how a target‐agnostic approach based on high‐throughput screening of antibodies produced by cultured B cells and plasma cells has not only provided potent and broadly neutralizing antibodies against a range of pathogens, but has also advanced our understanding of basic aspects of the immune response, from host–pathogen interaction to the role of somatic mutations in affinity maturation and in the diversification of the antibody response. Most surprisingly, this approach has also revealed a new mechanism of diversification based on templated insertion of non‐Ig DNA into antibody genes that we discovered in the context of the immune response to malaria infection

Cytokine-driven Proliferation and Differentiation of Human Naive, Central Memory, and Effector Memory CD4+ T Cells

Memory T lymphocytes proliferate in vivo in the absence of antigen maintaining a pool of central memory T cells (TCM) and effector memory T cells (TEM) with distinct effector function and homing capacity. We compared human CD4+ naive T, TCM, and TEM cells for their capacity to proliferate in response to cytokines, that have been implicated in T cell homeostasis. Interleukin (IL)-7 and IL-15 expanded with very high efficiency TEM, while TCM were less responsive and naive T cells failed to respond. Dendritic cells (DCs) and DC-derived cytokines allowed naive T cells to proliferate selectively in response to IL-4, and potently boosted the response of TCM to IL-7 and IL-15 by increasing the expression of the IL-2/IL-15Rβ and the common γ chain (γc). The extracellular signal regulated kinase and the p38 mitogen-activated protein (MAP) kinases were selectively required for TCR and cytokine-driven proliferation, respectively. Importantly, in cytokine-driven cultures, some of the proliferating TCM differentiated to TEM-like cells acquiring effector function and switching chemokine receptor expression from CCR7 to CCR5. The sustained antigen-independent generation of TEM from a pool of TCM cells provides a plausible mechanism for the maintenance of a polyclonal and functionally diverse repertoire of human CD4+ memory T cells