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1.  Requirement of NK cells for selective A2A receptor blockade to suppress CD73+ tumor metastasis 
Immunotherapy  2014;6(1):19-21.
CD73 is becoming an emerging therapeutic target for the prevention of tumor growth and metastasis. However, the mechanism by which CD73 promotes tumor metastasis is unclear. Beavis et al. evaluated the efficacy of A2A and A2B adenosine receptor antagonists in inhibiting the metastasis of tumors expressing CD73, either endogenously or ectopically. They demonstrate distinct mechanisms whereby A2A versus A2B adenosine receptors could contribute to CD73+ tumor metastasis. As A2Areceptor (R)/A2BR antagonists have been tested in clinical trials in other disease settings, this study highlights the potential therapeutic application of an A2AR/A2BR blockade strategy for treatment of CD73+ metastatic tumors.
PMCID: PMC3968679  PMID: 24341879
adenosine receptor; CD73; ecto-5′-nucleotidase; metastasis; NK cell
3.  A delicate balance 
Oncoimmunology  2013;2(1):e22107.
The utility of allogeneic stem cell transplantation for treating hematologic malignancies is enhanced by the graft vs. tumor (GvT) effect, but limited by graft vs. host disease (GvHD). Studies involving the inhibition of CD73 by genetic or pharmacologic means suggest that the levels of CD73-generated adenosine may be manipulated to control GvHD, while maintaining the GvT effect.
PMCID: PMC3583907  PMID: 23482243
adenosine receptor; CD73; graft vs. host disease; graft vs. tumor effect
4.  Ectonucleotidases in Cancer and Inflammation 
PMCID: PMC3480712  PMID: 23125527
5.  The TCR ligand-inducible expression of CD73 marks γδ lineage commitment and a metastable intermediate in effector specification 
CD73 expression is induced in response to TCR ligation and identifies a population of thymocytes that are committed to the γδ T cell fate.
Numerous studies indicate that γδ T cell receptor (γδTCR) expression alone does not reliably mark commitment of early thymic progenitors to the γδ fate. This raises the possibility that the γδTCR is unable to intrinsically specify fate and instead requires additional environmental factors, including TCR–ligand engagement. We use single cell progenitor assays to reveal that ligand acts instructionally to direct adoption of the γδ fate. Moreover, we identify CD73 as a TCR ligand-induced cell surface protein that distinguishes γδTCR-expressing CD4−CD8− progenitors that have committed to the γδ fate from those that have not yet done so. Indeed, unlike CD73− γδTCR+ progenitors, which largely adopt the αβ fate upon separation from the intrathymic selecting environment, those that express CD73 remain CD4−CD8− and committed to the γδ fate. CD73 is expressed by >90% of peripheral γδ cells, suggesting this is a common occurrence during development. Moreover, CD73 induction appears to mark a metastable intermediate stage before acquisition of effector function, suggesting that γδ lineage and effector fate are specified sequentially. These findings have important implications for the role of ligand in γδ lineage commitment and its relationship to the specification of effector fate.
PMCID: PMC3920555  PMID: 24493796
6.  Restoration of adenosine deaminase-deficient human thymocyte development in vitro by inhibition of deoxynucleoside kinases1,2 
Mutations in the gene encoding adenosine deaminase (ADA), a purine salvage enzyme, lead to immunodeficiency in humans. Although ADA deficiency has been analyzed in cell culture and murine models, information is lacking concerning its impact on the development of human thymocytes. We have used chimeric human/mouse fetal thymic organ culture (hu/moFTOC) to study ADA-deficient human thymocyte development in an “in vivo-like” environment where toxic metabolites accumulate in situ. Inhibition of ADA during human thymocyte development resulted in a severe reduction in cellular expansion as well as impaired differentiation, largely affecting mature thymocyte populations. Thymocyte differentiation was not blocked at a discrete stage; rather, the paucity of mature thymocytes was due to the induction of apoptosis as evidenced by activation of caspases and was accompanied by the accumulation of intracellular deoxyadenosine triphosphate (dATP). Inhibition of adenosine kinase and deoxycytidine kinase prevented the accumulation of dATP and restored thymocyte differentiation and proliferation. Our work reveals that multiple deoxynucleoside kinases are involved in the phosphorylation of deoxyadenosine when ADA is absent, and suggests an alternate therapeutic strategy for treatment of ADA-deficient patients.
PMCID: PMC2673198  PMID: 19018008
human; immunodeficiency diseases; apoptosis; thymus
7.  CD73-generated Adenosine Restricts Lymphocyte Migration into Draining Lymph Nodes1 
After an inflammatory stimulus, lymphocyte migration into draining lymph nodes increases dramatically to facilitate the encounter of naïve T cells with antigen-loaded dendritic cells. Here we show that CD73 (ecto-5′-nucleotidase) plays an important role in regulating this process. CD73 produces adenosine from AMP and is expressed on high endothelial venules (HEV) and subsets of lymphocytes. Cd73-/- mice have normal sized lymphoid organs in the steady state, but approximately 1.5-fold larger draining lymph nodes and 2.5-fold increased rates of L-selectin-dependent lymphocyte migration from the blood through HEV compared to wild type mice 24 hours after LPS administration. Migration rates of cd73+/+ and cd73-/- lymphocytes into lymph nodes of wild type mice are equal, suggesting that it is CD73 on HEV that regulates lymphocyte migration into draining lymph nodes. The A2B receptor is a likely target of CD73-generated adenosine, as it is the only adenosine receptor expressed on the HEV-like cell line KOP2.16 and it is up regulated by TNFα. Furthermore, increased lymphocyte migration into draining lymph nodes of cd73-/- mice is largely normalized by pretreatment with the selective A2B receptor agonist BAY 60-6583. Adenosine receptor signaling to restrict lymphocyte migration across HEV may be an important mechanism to control the magnitude of an inflammatory response.
PMCID: PMC2709497  PMID: 18424752
Rodent; Cell Trafficking; Spleen and lymph nodes; Inflammation
8.  Human αβ and γδ Thymocyte Development: TCR Gene Rearrangements, Intracellular TCRβ Expression and γδ Developmental Potential – Differences between Men and Mice1,2 
To evaluate the role of the TCR in the αβ/γδ lineage choice during human thymocyte development, molecular analyses of the TCRβ locus in γδ cells and the TCRγ and δ loci in αβ cells were undertaken. TCRβ variable gene segments remained largely in germline configuration in γδ cells, indicating that commitment to the γδ lineage occurred prior to complete TCRβ rearrangements in most cases. The few TCRβ rearrangements detected were primarily out-of-frame, suggesting that productive TCRβ rearrangements diverted cells away from the γδ lineage. In contrast, in αβ cells, the TCRγ locus was almost completely rearranged with a random productivity profile; the TCRδ locus contained primarily non-productive rearrangements. Productive γ rearrangements were, however, depleted compared to pre-selected cells. Productive TCRγ and δ rearrangements rarely occurred in the same cell, suggesting that αβ cells developed from cells unable to produce a functional γδ TCR. Intracellular TCRβ expression correlated with the up regulation of CD4 and concomitant down regulation of CD34, and plateaued at the early double positive stage. Surprisingly, however, some early double positive thymocytes retained γδ potential in culture. We present a model for human thymopoiesis which includes γδ development as a default pathway, an instructional role for the TCR in the αβ/γδ lineage choice, and a prolonged developmental window for β-selection and γδ lineage commitment. Aspects that differ from the mouse are the status of TCR gene rearrangements at the non-expressed loci, the timing of β-selection, and maintenance of γδ potential through the early double positive stage of development.
PMCID: PMC1592528  PMID: 16424183
cell differentiation; gene rearrangement; human; T cell receptors; thymus
9.  Further Differentiation of Murine Double Positive Thymocytes Is Inhibited in Adenosine Deaminase-Deficient Murine Fetal Thymic Organ Culture1 
Murine fetal thymic organ culture (FTOC) was used to investigate the mechanism by which a lack of adenosine deaminase (ADA) leads to a failure of T cell production in the thymus. We previously showed that T cell development was inhibited beginning at the CD4−CD8−CD25+CD44lo stage in ADA-deficient FTOCs initiated at day 15 of gestation when essentially all thymocytes are CD4−CD8−. In the present study, we asked whether thymocytes at later stages of differentiation would also be sensitive to ADA inhibition by initiating FTOCs when substantial numbers of CD4+CD8+ thymocytes were already present. dATP was highly elevated in ADA-deficient cultures and the recovery of αβ TCR+ thymocytes was inhibited by 94%, indicating that the later stages of thymocyte differentiation are also dependent upon ADA. ADA-deficient cultures were partially rescued by the pan-caspase inhibitor carbobenzoxy-Val-Ala-Asp-fluoromethyl ketone (z-VADfmk) or by the use of Apaf-1-deficient mice. Rescue was even more dramatic, with 60- to >200-fold increases in the numbers of CD4+CD8+ cells, when FTOCs were performed with an inhibitor of adenosine kinase, the major thymic deoxyadenosine phosphorylating enzyme, or with bcl-2 transgenic mice. dATP levels were normalized by treatment with either z-VADfmk or an adenosine kinase inhibitor, but not in cultures with fetal thymuses from bcl-2 transgenic mice. These data suggest that ADA deficiency leads to the induction of mitochondria-dependent apoptosis as a consequence of the accumulation of dATP derived from thymocytes failing the positive/negative selection checkpoint.
PMCID: PMC1550651  PMID: 16670300
apoptosis; cell differentiation; immunodeficiency diseases; thymus
10.  Crucial Role for Ecto-5′-Nucleotidase (CD73) in Vascular Leakage during Hypoxia 
The Journal of experimental medicine  2004;200(11):1395-1405.
Extracellular adenosine has been widely implicated in adaptive responses to hypoxia. The generation of extracellular adenosine involves phosphohydrolysis of adenine nucleotide intermediates, and is regulated by the terminal enzymatic step catalyzed by ecto-5′-nucleotidase (CD73). Guided by previous work indicating that hypoxia-induced vascular leakage is, at least in part, controlled by adenosine, we generated mice with a targeted disruption of the third coding exon of Cd73 to test the hypothesis that CD73-generated extracellular adenosine functions in an innate protective pathway for hypoxia-induced vascular leakage. Cd73−/− mice bred and gained weight normally, and appeared to have an intact immune system. However, vascular leakage was significantly increased in multiple organs, and after subjection to normobaric hypoxia (8% O2), Cd73−/− mice manifested fulminant vascular leakage, particularly prevalent in the lung. Histological examination of lungs from hypoxic Cd73−/− mice revealed perivascular interstitial edema associated with inflammatory infiltrates surrounding larger pulmonary vessels. Vascular leakage secondary to hypoxia was reversed in part by adenosine receptor agonists or reconstitution with soluble 5′-nucleotidase. Together, our studies identify CD73 as a critical mediator of vascular leakage in vivo.
PMCID: PMC1237012  PMID: 15583013
adenosine; inflammation; edema; endothelium; knockout; ANOVA, analysis of variance; APCP, α,β -methylene ADP; E-Ado, etheno-adenosine; E-AMP, etheno-AMP; ES, embryonic stem; NECA, 5′-(N-ethylcarboxamido)-adenosine; 5′-NT, 5′-nucleotidase
11.  Crucial Role for Ecto-5′-Nucleotidase (CD73) in Vascular Leakage during Hypoxia 
The Journal of Experimental Medicine  2004;200(11):1395-1405.
Extracellular adenosine has been widely implicated in adaptive responses to hypoxia. The generation of extracellular adenosine involves phosphohydrolysis of adenine nucleotide intermediates, and is regulated by the terminal enzymatic step catalyzed by ecto-5′-nucleotidase (CD73). Guided by previous work indicating that hypoxia-induced vascular leakage is, at least in part, controlled by adenosine, we generated mice with a targeted disruption of the third coding exon of Cd73 to test the hypothesis that CD73-generated extracellular adenosine functions in an innate protective pathway for hypoxia-induced vascular leakage. Cd73−/− mice bred and gained weight normally, and appeared to have an intact immune system. However, vascular leakage was significantly increased in multiple organs, and after subjection to normobaric hypoxia (8% O2), Cd73−/− mice manifested fulminant vascular leakage, particularly prevalent in the lung. Histological examination of lungs from hypoxic Cd73−/− mice revealed perivascular interstitial edema associated with inflammatory infiltrates surrounding larger pulmonary vessels. Vascular leakage secondary to hypoxia was reversed in part by adenosine receptor agonists or reconstitution with soluble 5′-nucleotidase. Together, our studies identify CD73 as a critical mediator of vascular leakage in vivo.
PMCID: PMC1237012  PMID: 15583013
adenosine; inflammation; edema; endothelium; knockout
12.  Adenosine kinase inhibition promotes survival of fetal adenosine deaminase–deficient thymocytes by blocking dATP accumulation 
Thymocyte development past the CD4–CD8– stage is markedly inhibited in adenosine deaminase–deficient (ADA-deficient) murine fetal thymic organ cultures (FTOCs) due to the accumulation of ADA substrates derived from thymocytes failing developmental checkpoints. Such cultures can be rescued by overexpression of Bcl-2, suggesting that apoptosis is an important component of the mechanism by which ADA deficiency impairs thymocyte development. Consistent with this conclusion, ADA-deficient FTOCs were partially rescued by a rearranged T cell receptor β transgene that permits virtually all thymocytes to pass the β-selection checkpoint. ADA-deficient cultures were also rescued by the adenosine kinase inhibitor 5′-amino-5′-deoxyadenosine (5′A5′dAdo), indicating that the metabolite responsible for the inhibition of thymocyte development is not adenosine or deoxyadenosine, but a phosphorylated derivative of an ADA substrate. Correction of ADA-deficient FTOCs by 5′A5′dAdo correlated with reduced accumulation of dATP, implicating this compound as the toxic metabolite. In ADA-inhibited FTOCs rescued with a Bcl-2 transgene, however, dATP levels were superelevated, suggesting that cells failing positive and negative selection continued to contribute to the accumulation of ADA substrates. Our data are consistent with dATP-induced mitochondrial cytochrome c release followed by apoptosis as the mechanism by which ADA deficiency leads to reduced thymic T cell production.
PMCID: PMC151094  PMID: 12163459
13.  Metabolites from apoptotic thymocytes inhibit thymopoiesis in adenosine deaminase–deficient fetal thymic organ cultures 
Journal of Clinical Investigation  2000;106(9):1149-1157.
Murine fetal thymic organ culture was used to investigate the mechanism by which adenosine deaminase (ADA) deficiency causes T-cell immunodeficiency. C57BL/6 fetal thymuses treated with the specific ADA inhibitor 2′-deoxycoformycin exhibited features of the human disease, including accumulation of dATP and inhibition of S-adenosylhomocysteine hydrolase enzyme activity. Although T-cell receptor (TCR) Vβ gene rearrangements and pre–TCR-α expression were normal in ADA-deficient cultures, the production of αβ TCR+ thymocytes was inhibited by 95%, and differentiation was blocked beginning at the time of β selection. In contrast, the production of γδ TCR+ thymocytes was unaffected. Similar results were obtained using fetal thymuses from ADA gene-targeted mice. Differentiation and proliferation were preserved by the introduction of a bcl-2 transgene or disruption of the gene encoding apoptotic protease activating factor–1. The pan-caspase inhibitor carbobenzoxy-Val-Ala-Asp-fluoromethyl ketone also significantly lessened the effects of ADA deficiency and prevented the accumulation of dATP. Thus, ADA substrates accumulate and disrupt thymocyte development in ADA deficiency. These substrates derive from thymocytes that undergo apoptosis as a consequence of failing to pass developmental checkpoints, such as β selection.
PMCID: PMC301416  PMID: 11067867
14.  CD73-generated adenosine promotes osteoblast differentiation 
Journal of Cellular Physiology  2012;227(6):2622-2631.
CD73 is a GPI-anchored cell surface protein with ecto-5′-nucleotidase enzyme activity that plays a crucial role in adenosine production. While the roles of adenosine receptors (AR) on osteoblasts and osteoclasts have been unveiled to some extent, the roles of CD73 and CD73-generated adenosine in bone tissue are largely unknown. To address this issue, we first analyzed the bone phenotype of CD73-deficient (cd73−/−) mice. The mutant male mice showed osteopenia, with significant decreases of osteoblastic markers. Levels of osteoclastic markers were, however, comparable to those of wild type mice. A series of in vitro studies revealed that CD73 deficiency resulted in impairment in osteoblast differentiation but not in the number of osteoblast progenitors. In addition, over expression of CD73 on MC3T3-E1 cells resulted in enhanced osteoblastic differentiation. Moreover, MC3T3-E1 cells expressed adenosine A2A receptors (A2AAR) and A2B receptors (A2BAR) and expression of these receptors increased with osteoblastic differentiation. Enhanced expression of osteocalcin (OC) and bone sialoprotein (BSP) observed in MC3T3-E1 cells over expressing CD73 were suppressed by treatment with an A2BAR antagonist but not with an A2AAR antagonist. Collectively, our results indicate that CD73 generated adenosine positively regulates osteoblast differentiation via A2BAR signaling.
PMCID: PMC3237726  PMID: 21882189
CD73; adenosine; osteoblasts; bone; mouse
Journal of Clinical Investigation  1983;71(4):892-899.
T lymphocytes from control subjects were separated into subsets using monoclonal antibodies of the OKT series and complement lysis and analyzed for ecto-5′-nucleotidase activity both by quantitative radiochemical assay and a histochemical stain. T cells from 15 control subjects contained 54±4% OKT4+ (helper/inducer) cells and 32±3% OKT8+ (cytotoxic/suppressor) cells. Total T cell ecto-5′-nucleotidase activity was 10.9±2.1 nmol/h per 106 cells with 25±7% positive by histochemical stain. Ecto-5′-nucleotidase activity in OKT4-enriched populations was 5.43±1.8 nmol/h per 106 cells with 14±2% positive by histochemical stain; that in OKT8-enriched populations was 17.1±5.9 nmol/h per 106 cells with 35±8% positive by histochemical stain.
Two of four patients with congenital agammaglobulinemia and four of seven patients with common variable immunodeficiency had decreased proportions of OKT4+ T cells with corresponding increases in the proportions of OKT8+ T cells (OKT4/OKT8 = 0.60 to 1.0 as compared with 1.7±0.2 for control subjects). All four patients with congenital agammaglobulinemia, and three of seven patients with common variable immunodeficiency also had low T cell ecto-5′-nucleotidase activity (<5.5 nmol/h per 106 cells). Ecto-5′-nucleotidase activity in OKT4- enriched populations isolated from four patients with low total T cell activity was 2.85±0.90 nmol/h per 106 cells with 10±4% positive by histochemical stain; that in OKT8-enriched populations was 6.82±1.7 nmol/h per 106 cells with 7.5±3% positive by histochemical stain. Thus, the number of ecto-5′-nucleotidase positive cells is decreased, especially in the OKT8+ subpopulation, and the low total T cell ecto-5′-nucleotidase activity seen in these patients is due to fewer positive cells rather than to substantially less activity per cell.
Our data indicate that ecto-5′-nucleotidase activity defines two subpopulations of T lymphocytes (ecto-5′-nucleotidase positive and negative), the proportions of which are markedly altered in many patients with hypogammaglobulinemia. In preliminary studies with seven patients, increased numbers of ecto-5′-nucleotidase negative T cells appeared to correlate with increased suppressor T cell activity toward in vitro immunoglobulin synthesis. Therefore, ecto-5′-nucleotidase may be a useful cell surface marker in the study of imbalances of regulatory T cell subsets in patients with antibody synthesis disorders.
PMCID: PMC436946  PMID: 6300192
16.  Influenza vaccination can induce new onset anticardiolipins but not β2-glycoprotein-I antibodies among patients with systemic lupus erythematosus 
Lupus  2012;21(2):168-174.
Antiphospholipid syndrome is characterized by autoantibodies against cardiolipins (aCL), lupus anticoagulant, and independent β2-glycoprotein (β2GPI). Controversy exists as to whether vaccination triggers the development of anti-phospholipid antibodies (aPL) in systemic lupus erythematosus (SLE) patients.
SLE patients (101) and matched controls (101) were enrolled from 2005 to 2009 and received seasonal influenza vaccinations. Sera were tested by ELISA for aCL at baseline, 2, 6, and 12 weeks after vaccination. Vaccine responses were ranked according to an overall anti-influenza antibody response index. Individuals with positive aCL were further tested for β2GPI antibodies.
SLE patients and healthy controls developed new onset aCL post-vaccination (12/101 cases and 7/101 controls, OR 1.81, p=0.34). New onset moderate aCL are slightly enriched in African American SLE patients (5/36 cases; p=0.094). The optical density (OD) measurements for aCL reactivity in patients were significantly higher than baseline at 2 weeks (p<0.05), 6 weeks (p<0.05), and 12 weeks (p<0.05) post vaccination. No new β2GPI antibodies were detected among patients with new aCL reactivity. Vaccine response was not different between patients with and without new onset aCL reactivity (p=0.43).
This study shows transient increases in aCL, but not anti-β2GPI responses, after influenza vaccination.
PMCID: PMC3268677  PMID: 22235049
Influenza; vaccine; antiphospholipid antibodies; systemic lupus erythematosus
17.  B Lymphocyte Stimulator Levels in Systemic Lupus Erythematosus: Higher Circulating Levels in African American Patients and Increased Production after Influenza Vaccination in Patients with Low Baseline Levels 
Arthritis and rheumatism  2011;63(12):3931-3941.
Examine the relationship between circulating B lymphocyte stimulator (BLyS) levels and humoral responses to influenza vaccination in systemic lupus erythematosus (SLE) patients, as well as the effect of vaccination on BLyS levels. Clinical and serologic features of SLE that are associated with elevated BLyS levels will also be investigated.
Clinical history, disease activity measurements and blood specimens were collected from sixty SLE patients at baseline and after influenza vaccination. Sera were tested for BLyS levels, lupus-associated autoantibodies, serum IFN-α activity, 25-hydroxyvitamin D, and humoral responses to influenza vaccination.
Thirty percent of SLE patients had elevated BLyS levels, with African American patients having higher BLyS levels than European American patients (p=0.006). Baseline BLyS levels in patients were not correlated with humoral responses to influenza vaccination (p=0.863), and BLyS levels increased post-vaccination only in the subset of patients in the lowest quartile of BLyS levels (p=0.0003). Elevated BLyS levels were associated with increased disease activity as measured by SLEDAI, PGA, and SLAM in European Americans (p=0.035, p=0.016, p=0.018, respectively), but not in African Americans. Elevated BLyS levels were also associated with anti-nRNP (p=0.0003) and decreased 25(OH)D (p=0.018). Serum IFN-α activity was a significant predictor of elevated BLyS in a multivariate analysis (p=0.002).
African American SLE patients have higher BLyS levels regardless of disease activity. Humoral response to influenza vaccination is not correlated with baseline BLyS levels in SLE patients and only those patients with low baseline BLyS levels demonstrate an increased BLyS response after vaccination.
PMCID: PMC3234134  PMID: 22127709
Systemic lupus erythematosus (SLE); Cytokines
18.  Ecto-5′-nucleotidase (CD73) decreases mortality and organ injury in sepsis1 
The extracellular concentrations of adenosine are elevated during sepsis and adenosine receptors regulate the host’s response to sepsis. Here, we investigated the role of the adenosine generating ectoenzyme, ecto-5′-nucleotidase (CD73) in regulating immune and organ function during sepsis. Polymicrobial sepsis was induced by subjecting CD73 knockout (KO) and wild type (WT) mice to cecal ligation and puncture. CD73 KO mice showed increased mortality in comparison with WT mice, which was associated with increased bacterial counts and elevated inflammatory cytokine and chemokine concentrations in the blood and peritoneum. CD73 deficiency promoted lung injury as indicated by increased myeloperoxidase activity and neutrophil infiltration, and elevated pulmonary cytokine levels. CD73 KO mice had increased apoptosis in the thymus, as evidenced by increased activation of caspase-3, poly(ADP-ribose) polymerase and NF-κB. Septic CD73 KO mice had higher blood urea nitrogen levels and elevated cytokine levels in the kidney, indicating increased renal dysfunction. The increased kidney injury of CD73 KO mice was associated with augmented activation of p38 MAPK and decreased phosphorylation of Akt. Pharmacological inactivation of CD73 in WT mice using AMPCP augmented cytokine levels in the blood and peritoneal lavage fluid. These findings suggest that CD73-derived adenosine may be beneficial in sepsis.
PMCID: PMC3387540  PMID: 21918191
19.  Individual antibody and T cell responses to vaccination and infection with the 2009 pandemic swine-origin H1N1 influenza virus 
Journal of clinical immunology  2011;31(5):900-912.
The 2009 swine origin H1N1 influenza virus (swH1N1) provided an opportunity to study immune responses to a new influenza strain in the context of seasonal influenza vaccination. Our goals were: to assess whether analyzing multiple parameters of immune responsiveness to influenza has an advantage over evaluating hemagglutination inhibition (HAI) titer alone, to determine whether vaccination with the seasonal vaccine induced cross-reactive immunity to swH1N1 in some individuals, and to determine whether the immune response against swH1N1 is higher after infection than vaccination.
Antibody and T cell responses were studied in ten subjects who were first immunized with the 2009-10 seasonal influenza subunit vaccine, then six weeks later with the swH1N1 monovalent subunit vaccine. The amount of antibody against native virus glycoproteins, overall avidity of these antibodies, and HAI titer were measured. T cells were evaluated for proliferation and IFNγ secretion in response to the vaccine in vitro. Individuals with influenza-like illness were also evaluated, adding a microplate neuraminidase-inhibition (NAI) test.
The immune response to influenza was highly variable and immune parameters did not increase in parallel. The seasonal vaccine induced antibodies recognizing the pandemic virus in 50% of subjects. Antibody affinity and NAI activity to swH1N1 were higher after natural infection than vaccination.
Evaluation of several immune parameters gives a more complete measure of immune responsiveness to influenza infection or vaccination than the HAI test alone.
PMCID: PMC3197711  PMID: 21732013
pandemic 2009 H1N1 influenza; vaccine response; antibodies and T cells after infection
20.  Influenza vaccination responses in human systemic lupus erythematosus: impact of clinical and demographic features 
Arthritis and rheumatism  2011;63(8):2396-2406.
Vaccination against common pathogens, such as influenza, is recommended for SLE patients to decrease infections and improve health. However, most vaccination response reports are limited to evaluation of SLE patients with quiescent disease. This study focuses on understanding the clinical, serological, therapeutic, and demographic factors which influence the response to influenza vaccination in patients with a range of disease activities.
Blood specimens and disease activity information were collected from seventy-two SLE patients at baseline and 2, 6 and 12 weeks after influenza vaccination. Influenza-specific antibody responses were assessed for antibody concentration (Bmax), relative affinity (Ka), and hemagglutination inhibition (HAI). Using a cumulative score, the subjects were evenly divided into high and low responders. Autoantibody levels were evaluated at each time-point by immunofluorescence and standard ELISAs.
Low responders to the vaccine were more likely to have hematologic criteria (p=0.009), exhibit more ACR criteria (p=0.05), and be on concurrent prednisone treatment (p=0.04). Interestingly, European American patients were more likely to be low responders than African Americans (p = 0.03). Following vaccination, low responders were more likely to experience disease flares (p=0.01) and to have increased ANA titers (p = 0.04). Baseline serum interferon alpha activity was significantly higher in patients that experienced a flare after vaccination compared to a matched group of patients that did not flare (p= 0.04).
Ancestral background, prednisone treatment, hematological criteria and evidence of increased disease flares were associated with low antibody responses to influenza vaccination in SLE patients.
PMCID: PMC3149742  PMID: 21598235
21.  Immunodominance of Antigenic Site B over Site A of Hemagglutinin of Recent H3N2 Influenza Viruses 
PLoS ONE  2012;7(7):e41895.
H3N2 influenza viruses have now circulated in the human population for 43 years since the pandemic of 1968, accumulating sequence changes in the hemagglutinin (HA) and neuraminidase (NA) that are believed to be predominantly due to selection for escape from antibodies. Examination of mutations that persist and accumulate led to identification of antigenically significant mutations that are contained in five antigenic sites (A–E) mapped on to the H3 HA. In early H3N2 isolates, antigenic site A appeared to be dominant while in the 1990s site B seemed more important. To obtain experimental evidence for dominance of antigenic sites on modern H3 HAs, we have measured antibodies in plasma of human subjects who received the 2006–07 trivalent subunit influenza vaccine (H3 component A/Wisconsin/67/05) or the 2008–09 formulation (H3 component A/Uruguay/716/07). Plasmas were tested against expressed HA of Wisconsin-like influenza A/Oklahoma/309/06 and site-directed mutants in antigenic site A (NNES121-124ITEG, N126T, N133D, TSSS135-138GSNA, K140I, RSNNS142-146PGSG), and antigenic site B (HL156-157KS, KFK158-160GST, NDQI189-192QEQT, A196V). “Native ELISA” analysis and escape mutant selection with two human monoclonal antibodies demonstrated that antibody E05 binds to antigenic site A and 1_C02 binds to site B. We find that most individuals, after vaccination in seasons 2006–07 and/or 2008–09, showed dominance of antigenic site B recognition over antigenic site A. A minority showed dominance of site A in 2006 but these were reduced in 2008 when the vaccine virus had a site A mutation. A better understanding of immunodominance may allow prediction of future antigenic drift and assist in vaccine strain selection.
PMCID: PMC3405050  PMID: 22848649
22.  CD73 has distinct roles in nonhematopoietic and hematopoietic cells to promote tumor growth in mice 
The Journal of Clinical Investigation  2011;121(6):2371-2382.
CD73 is overexpressed in many types of human and mouse cancers and is implicated in the control of tumor progression. However, the specific contribution from tumor or host CD73 expression to tumor growth remains unknown to date. Here, we show that host CD73 promotes tumor growth in a T cell–dependent manner and that the optimal antitumor effect of CD73 blockade requires inhibiting both tumor and host CD73. Notably, enzymatic activity of CD73 on nonhematopoietic cells limited tumor-infiltrating T cells by controlling antitumor T cell homing to tumors in multiple mouse tumor models. In contrast, CD73 on hematopoietic cells (including CD4+CD25+ Tregs) inhibited systemic antitumor T cell expansion and effector functions. Thus, CD73 on hematopoietic and nonhematopoietic cells has distinct adenosinergic effects in regulating systemic and local antitumor T cell responses. Importantly, pharmacological blockade of CD73 using its selective inhibitor or an anti-CD73 mAb inhibited tumor growth and completely restored efficacy of adoptive T cell therapy in mice. These findings suggest that both tumor and host CD73 cooperatively protect tumors from incoming antitumor T cells and show the potential of targeting CD73 as a cancer immunotherapy strategy.
PMCID: PMC3104756  PMID: 21537079
23.  CD73 on tumor cells impairs anti-tumor T cell responses: a novel mechanism of tumor-induced immune suppression 
Cancer research  2010;70(6):2245-2255.
CD73, originally defined as a lymphocyte differentiation antigen, is thought to function as a co-signaling molecule on T lymphocytes and an adhesion molecule that is required for lymphocyte binding to endothelium. We show here that CD73 is widely expressed on many tumor cell lines and is upregulated in cancerous tissues. Because the ecto-5′-nucleotidase activity of CD73 catalyzes AMP breakdown to immunosuppressive adenosine, we hypothesized that CD73-generated adenosine prevents tumor destruction by inhibiting antitumor immunity. We confirmed this hypothesis by showing that combining tumor CD73 knockdown and tumor-specific T cell transfer cured all tumor-bearing mice. In striking contrast, there was no therapeutic benefit of adoptive T-cell immunotherapy in mice bearing tumors without CD73 knockdown. Moreover, blockade of the A2A adenosine receptor with a selective antagonist also augmented the efficacy of adoptive T cell therapy. These findings identify a potential mechanism for CD73-mediated tumor immune evasion and point to a novel cancer immunotherapy strategy by targeting the enzymatic activity of tumor CD73.
PMCID: PMC2883609  PMID: 20179192
24.  Much Ado about Adenosine: Adenosine Synthesis and Function in Regulatory T Cell Biology 
Recent studies have reported that adenosine is a significant mediator of regulatory T cell (Treg) function. Indeed, activation of the adenosine receptor subtypes expressed by a broad range of immune and inflammatory cells attenuates inflammation in several disease models. This anti-inflammatory response is associated with an increase in intracellular cAMP that inhibits cytokine responses of many immune/inflammatory cells, including T cells and APCs. Thus, adenosine produced by Tregs can provide a paracrine feedback that shapes the host response following an immunologic provocation. This review discusses the evidence that adenosine is an integral part of Treg biology and presents some of the mechanisms that may account for its contribution to the resolution of inflammation and the regulation of the immune/inflammatory cell phenotype.
PMCID: PMC3036969  PMID: 20686167
25.  Antibody quantity versus quality after influenza vaccination 
Vaccine  2009;27(45):6358-6362.
The correlates for protection against influenza infection are incompletely characterized. We have applied an ELISA strategy that distinguishes antibodies against native viral surface antigens (potentially neutralizing) from antibodies directed against internal and denatured viral proteins (not neutralizing) to three groups of vaccinated subjects: (1) participants in a study of repeated annual vaccination (2) elderly subjects and (3) patients with Systemic Lupus Erythematosus compared to control subjects. Antibody increase after vaccination was inversely related to the level of pre-existing antibodies in all groups; most subjects had significant initial antibody levels and showed little increase in amount of antibody after vaccination, but the avidity of their serum antibodies tended to increase. Antibodies against denatured virus proteins varied with vaccine formulation; vaccines that are more recent have less total protein for the same amount of native hemagglutinin. We propose an index consisting of rank order of antibody level plus antibody avidity, both measured against native virus, plus hemagglutination-inhibition antibody titer, as a useful measure of immunity against influenza.
PMCID: PMC2765411  PMID: 19840673

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