Efficient induction and expansion of human alloantigen-specific CD8 regulatory T cells from naive precursors by CD40-activated B cells

CD40: novel association with Crohn's disease and replication in multiple sclerosis susceptibility

BACKGROUND

A functional polymorphism located at -1 from the start codon of the CD40 gene, rs1883832, was previously reported to disrupt a Kozak sequence essential for translation. It has been consistently associated with Graves' disease risk in populations of different ethnicity and genetic proxies of this variant evaluated in genome-wide association studies have shown evidence of an effect in rheumatoid arthritis and multiple sclerosis (MS) susceptibility. However, the protective allele associated with Graves' disease or rheumatoid arthritis has shown a risk role in MS, an effect that we aimed to replicate in the present work. We hypothesized that this functional polymorphism might also show an association with other complex autoimmune condition such as inflammatory bowel disease, given the CD40 overexpression previously observed in Crohn's disease (CD) lesions.

METHODOLOGY

Genotyping of rs1883832C>T was performed in 1564 MS, 1102 CD and 969 ulcerative colitis (UC) Spanish patients and in 2948 ethnically matched controls by TaqMan chemistry.

PRINCIPAL FINDINGS

The observed effect of the minor allele rs1883832T was replicated in our independent Spanish MS cohort [p = 0.025; OR (95% CI) = 1.12 (1.01-1.23)]. The frequency of the minor allele was also significantly higher in CD patients than in controls [p = 0.002; OR (95% CI) = 1.19 (1.06-1.33)]. This increased predisposition was not detected in UC patients [p = 0.5; OR (95% CI) = 1.04 (0.93-1.17)].

CONCLUSION

The impact of CD40 rs1883832 on MS and CD risk points to a common signaling shared by these autoimmune conditions.

Cytotoxic T lymphocytes established by seasonal human influenza cross-react against 2009 pandemic H1N1 influenza virus

While few children and young adults have cross-protective antibodies to the pandemic H1N1 2009 (pdmH1N1) virus, the illness remains mild. The biological reasons for these epidemiological observations are unclear. In this study, we demonstrate that the bulk memory cytotoxic T lymphocytes (CTLs) established by seasonal influenza viruses from healthy individuals who have not been exposed to pdmH1N1 can directly lyse pdmH1N1-infected target cells and produce gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). Using influenza A virus matrix protein 1 (M1(58-66)) epitope-specific CTLs isolated from healthy HLA-A2(+) individuals, we further found that M1(58-66) epitope-specific CTLs efficiently killed both M1(58-66) peptide-pulsed and pdmH1N1-infected target cells ex vivo. These M1(58-66)-specific CTLs showed an effector memory phenotype and expressed CXCR3 and CCR5 chemokine receptors. Of 94 influenza A virus CD8 T-cell epitopes obtained from the Immune Epitope Database (IEDB), 17 epitopes are conserved in pdmH1N1, and more than half of these conserved epitopes are derived from M1 protein. In addition, 65% (11/17) of these epitopes were 100% conserved in seasonal influenza vaccine H1N1 strains during the last 20 years. Importantly, seasonal influenza vaccination could expand the functional M1(58-66) epitope-specific CTLs in 20% (4/20) of HLA-A2(+) individuals. Our results indicated that memory CTLs established by seasonal influenza A viruses or vaccines had cross-reactivity against pdmH1N1. These might explain, at least in part, the unexpected mild pdmH1N1 illness in the community and also might provide some valuable insights for the future design of broadly protective vaccines to prevent influenza, especially pandemic influenza.

CD8+ Tregs in lupus, autoimmunity, and beyond

While CD4(+)CD25(high) regulatory T cells (Tregs) have garnered much attention for their role in the maintenance of immune homeostasis, recent findings have shown that subsets of CD8(+) T cells (CD8(+) Tregs) display immunoregulatory functions as well. Both CD4(+) Tregs and CD8(+) Tregs appear impaired in number and/or function in several autoimmune diseases and in experimental animal models of autoimmunity, suggesting the possibility of immunotherapeutic targeting of these cells for improved management of autoimmune conditions. Our group has developed a strategy to induce CD8(+) Tregs in autoimmune mice through the use of a tolerogenic self-peptide, and new information has been gained on the phenotype, function and role of induced CD8(+) Tregs in autoimmunity. Here we present an overview of the role and mechanisms of action of CD8(+) Tregs in autoimmunity, with a special focus on lupus. We also discuss the potential role of CD8(+) Tregs in other diseases, including chronic infection and cancer.

CD40-activated B cells are more potent than immature dendritic cells to induce and expand CD4(+) regulatory T cells

CD4(+) regulatory T cells (Tregs) play an important role in maintaining immune tolerance by suppressing pathologic immune responses. The generation of large numbers of antigen-specific Tregs ex vivo is critical for the development of clinical immunotherapy based on the adoptive transfer of Tregs. Both CD40-activated B cells (CD40-B) and immature dendritic cells (imDCs) have been used as professional antigen-presenting cells (APCs) to generate antigen-specific Tregs. However, the efficiencies of CD40-B and imDCs to generate CD4(+) Tregs have not been compared directly and the mechanism driving the generation of these Tregs remains largely unknown. In this study, we found that CD40-B exhibited mature phenotypes and were more able to induce and expand CD4(high)CD25(+) Tregs than imDCs. Moreover, Tregs induced by CD40-B had greater suppressive capacity than those induced by imDCs. The generation of CD4(high)CD25(+) Tregs by CD40-B and imDCs is cell-cell contact dependent and partially relies on the expression of human leukocyte antigen (HLA)-DR and CD80/86. Differences in CD4(high)CD25(+) Treg generation efficiency were largely explained by the production of endogenous IL-2 by CD40-B. Our results suggest that CD40-B is better able to generate large numbers of antigen-specific Tregs than imDCs. Additionally, using CD40-B to generate Tregs may accelerate the clinical use of Treg-based immunotherapy in the treatment of allograft rejection, graft versus host disease (GVHD) and autoimmune diseases.

Inhibition of human natural killer cell activity by influenza virions and hemagglutinin

Natural killer (NK) cells keep viral infections under control at the early phase by directly killing infected cells. Influenza is an acute contagious respiratory viral disease transmitted from host-to-host in the first few days of infection. The evasion of host innate immune defenses including NK cells is important for its success as a viral pathogen of humans and animals. NK cells encounter influenza virus within the microenvironment of infected cells. It therefore is important to investigate the direct effects of influenza virus on NK cell activity. Recently we demonstrated that influenza virus directly infects human NK cells and induces cell apoptosis to counter their function (H. Mao, W. Tu, G. Qin, H. K. W. Law, S. F. Sia, P.-L. Chan, Y. Liu, K.-T. Lam, J. Zheng, M. Peiris, and Y.-L. Lau, J. Virol. 83:9215-9222, 2009). Here, we further demonstrated that both the intact influenza virion and free hemagglutinin protein inhibited the cytotoxicity of fresh and interleukin-2 (IL-2)-activated primary human NK cells. Hemagglutinin bound and internalized into NK cells via the sialic acids. This interaction did not decrease NKp46 expression but caused the downregulation of the zeta chain through the lysosomal pathway, which caused the decrease of NK cell cytotoxicity mediated by NKp46 and NKp30. The underlying dysregulation of the signaling pathway involved zeta chain downregulation, leading to decreased Syk and ERK activation and granule exocytosis upon target cell stimulation, finally causing reduced cytotoxicity. These findings suggest that influenza virus developed a novel strategy to evade NK cell innate immune defense that is likely to facilitate viral transmission and also contribute to virus pathogenesis.