XIAP regulates cytosol-specific innate immunity to Listeria infection

The inhibitor of apoptosis protein (IAP) family has been implicated in immune regulation, but the mechanisms by which IAP proteins contribute to immunity are incompletely understood. We show here that X-linked IAP (XIAP) is required for innate immune control of Listeria monocytogenes infection. Mice deficient in XIAP had a higher bacterial burden 48 h after infection than wild-type littermates, and exhibited substantially decreased survival. XIAP enhanced NF-kappaB activation upon L. monocytogenes infection of activated macrophages, and prolonged phosphorylation of Jun N-terminal kinase (JNK) specifically in response to cytosolic bacteria. Additionally, XIAP promoted maximal production of pro-inflammatory cytokines upon bacterial infection in vitro or in vivo, or in response to combined treatment with NOD2 and TLR2 ligands. Together, our data suggest that XIAP regulates innate immune responses to L. monocytogenes infection by potentiating synergy between Toll-like receptors (TLRs) and Nod-like receptors (NLRs) through activation of JNK- and NF-kappaB-dependent signaling.

IFN-alpha enhances poly-IC responses in human keratinocytes by inducing expression of cytosolic innate RNA receptors: relevance for psoriasis

Keratinocytes play a key role in innate immune responses of the skin to bacterial and viral pathogens. Viral double-stranded RNA and its synthetic analogue polyriboinosinic-polyribocytidylic acid (poly-IC) are recognized via multiple pathways involving the receptors Toll-like receptor 3 (TLR3), protein kinase R (PKR), and the recently described cytosolic RNA helicases retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). We show that preincubation of human keratinocytes with IFN-alpha enhances the proinflammatory responses to poly-IC. Kinetic studies suggest that this is mediated via upregulation of the receptors TLR3, PKR, RIG-I, and MDA5. Interestingly, expression of RIG-I, MDA5, and PKR was significantly increased in lesional skin from patients with psoriasis, a chronic inflammatory skin disease that is characterized by high IFN-alpha levels. These results suggest that psoriatic keratinocytes show increased sensitivity to viral RNA intermediates, thereby leading to excessive proinflammatory responses and maintenance of the inflammatory skin phenotype. Here, we provide early evidence that point toward a role for the recently described cytosolic innate RNA receptors in non-viral chronic inflammatory diseases.

Cytosolic antiviral RNA recognition pathway activates caspases 1 and 3

During an innate immune response, macrophages recognize viruses by their pattern recognition receptors. In this study, we have studied the role of membrane-associated TLRs and cytoplasmic retinoic acid inducible gene-I (RIG-I)-like receptors (RLR) in regulation of IFN-beta, IL-29, IL-1beta, and IL-18 production and caspases 1 and 3 activation in human macrophages. We provide evidence that TLRs are mainly involved in transcriptional up-regulation of IL-1beta gene expression, whereas cytosolic dsRNA recognition pathway stimulates powerful IFN-beta and IL-29 gene transcription. However, robust IL-1beta secretion occurred only if two TLRs were triggered simultaneously or if a single TLR was activated in conjunction with the RLR pathway. Markedly, TLR activation did not stimulate IL-18 processing or secretion. In contrast, triggering of cytosolic RNA recognition pathway with poly(I:C) transfection or influenza A virus infection resulted in caspase-1- and -3-mediated proteolytic processing of pro-IL-18 and secretion of biologically active IL-18. Furthermore, caspase 3-dependent processing of pro-IL-18 was also observed in human HaCaT keratinocytes, and forced expression of RIG-I and its downstream effector, mitochondrial antiviral signaling protein, activated proteolytic processing of pro-IL-18, caspase-3, and apoptosis in these cells. The present results indicate that in addition to robust IFN-beta, IL-29, IL-1beta, and IL-18 generation, RIG-I/mitochondrial antiviral signaling protein pathway activates caspase-3, suggesting a role for these RIG-I-like receptors beyond the innate cytokine response, hence, in the induction of apoptosis of the virus-infected cell.

Nod-like receptors: cytosolic watchdogs for immunity against pathogens

In mammals, tissue-specific sets of pattern-recognition molecules, including Nod-like receptors (NLR), enable concomitant and sequential detection of microbial-associated molecular patterns from both the extracellular and intracellular microenvironment. Repressing and de-repressing the cytosolic surveillance machinery contributes to vital immune homeostasis and protective responses within specific tissues. Conversely, defective biology of NLR drives the development of recurrent infectious, autoimmune and/or inflammatory diseases by failing to mount barrier functions against pathogens, to tolerate commensals, and/or to instruct the adaptive immune response against microbes. Better decoding microbial strategies that are evolved to circumvent NLR sensing will provide clues for the development of rational therapies aimed at curing and/or preventing common and emerging immunopathologies.

Up-regulation of Bcl-2 through ERK phosphorylation is associated with human macrophage survival in an estrogen microenvironment

Estrogen is a known immunomodulator with pleiotropic effects on macrophage function that partly accounts for the gender bias observed in numerous autoimmune, cardiovascular, and neurodegenerative disorders. The effect of estrogen on the survival of human macrophages is largely unknown, and in this study we demonstrate that 17beta-estradiol (E2) provokes a death response in human THP-1 macrophages by initiating Bax translocation from cytosol to the mitochondria; however, a concomitant up-regulation of Bcl-2 creates a Bax to Bcl-2 ratio favorable for Bcl-2, thus ensuring cell survival. Both Bcl-2 up-regulation and Bax translocation are estrogen receptor-dependent events; however, Bcl-2 augmentation but not Bax translocation is dependent on Ca(2+) increase, activation of protein kinase C, and ERK phosphorylation. This estrogen-induced Bcl-2 increase is crucial for the survival of THP-1 macrophages as well as that of human peripheral blood monocyte-derived macrophages, which is evident from E2-induced cell death under small interfering RNA-mediated Bcl-2 knockdown conditions. Hence, this study demonstrates that E2-induced Bcl-2 up-regulation is a homeostatic survival mechanism necessary for the manifestation of immunomodulatory effect of estrogen on human macrophages.

Identification by proteomic tool of atypical anti-liver/kidney microsome autoantibodies targets in de novo autoimmune hepatitis after liver transplantation

De novo autoimmune hepatitis (AIH) occurs after liver transplantation for nonautoimmune disorders. Autoantibodies so-called atypical anti-liver/kidney microsome antibodies (LKMA) with an unusual liver/kidney cytoplasmic staining as judged by indirect immunofluorescence, can be detected in some patients' sera. Few studies investigated their molecular targets, and the aim of this work was to identify the atypical anti-LKMA targets by proteomic tool. This proteomic approach consisted of (a) two-dimensional gel electrophoresis of cytosolic and microsomal proteins obtained by differential centrifugations of rat liver and rat kidney, followed by (b) two-dimensional immunoblotting with sera of patients with de novo AIH (n = 8, including 2 with anti-LKMA antibodies) and then (c) identifications of interest spots performed by ion trap mass spectrometry. By this way several proteins at 25 kDa were unambiguously identified: isoforms of carbonic anhydrase III, members of different glutathione S-transferase (GST) families, and subunit beta1 of proteasome. This is the first report of proteasome and carbonic anhydrase III as autoantigens in de novo AIH. These results could lead to a better diagnosis of this disease using identified autoantigens in diagnostic tests, and strengthen proteomic approach as a new way of autoantigens investigation.

Injection of flagellin into the host cell cytosol by Salmonella enterica serotype Typhimurium

Bacterial flagellins are potent inducers of innate immunity. Three signaling pathways have been implicated in the sensing of flagellins; these involve toll-like receptor 5 (TLR5) and the cytosolic proteins Birc1e/Naip5 and Ipaf. Although the structural basis of TLR5-flagellin interaction is known, little is known about how flagellin enters the host cell cytosol to induce signaling via Birc1e/Naip5 and Ipaf. Here we demonstrate for the first time the translocation of bacterial flagellin into the cytosol of host macrophages by the vacuolar pathogen, Salmonella enterica serotype Typhimurium. Translocation of flagellin into the host cell cytosol was directly demonstrated using beta-lactamase reporter constructs. Flagellin translocation required the Salmonella Pathogenicity Island 1 Type III secretion system (SPI-1 T3SS) but not the flagellar T3SS.

Monoclonal antibodies to Mycobacterium tuberculosis CDC 1551 reveal subcellular localization of MPT51

Mycobacterium tuberculosis CDC 1551, a highly immunogenic outbreak strain, previously reported to have unique surface distribution of capsular polysaccharide, was used to generate novel monoclonal antibodies (mabs) to surface mycobacterial targets. Two immunoglobulin G1 (IgG1) mAbs, 16a1 and 16a6 were generated. The mAbs originated from the same B cell, bound strongly to whole cell M. tuberculosis CDC1551 and to its cell wall, membrane and cytosol fractions recognizing a 90kDa protein. Immunoprecipitation using mAb 16a1 isolated a protein with amino acid peptide sequences matching MPT51 from the cytosol. This immunogenic protein of unknown function was previously reported only in culture filtrates of M. tuberculosis. Our findings suggest for the first time that this protein is found within the M. tuberculosis cell.

Cdc42-interacting protein-4 functionally links actin and microtubule networks at the cytolytic NK cell immunological synapse

An essential function of the immunological synapse (IS) is directed secretion. NK cells are especially adept at this activity, as they direct lytic granules to the synapse for secretion, which enables cytotoxicity and facilitates host defense. This initially requires rearrangement of the actin cytoskeleton and, subsequently, microtubule-dependent trafficking of the lytic granules. As these two steps are sequential, specific linkages between them are likely to serve as critical regulators of cytotoxicity. We studied Cdc42-interacting protein-4 (CIP4), which constitutively interacts with tubulin and microtubules but focuses to the microtubule organizing center (MTOC) after NK cell activation, when it is able to associate with Wiskott-Aldrich syndrome protein (WASp) and the actin filament-rich IS. WASp deficiency, overexpression of CIP4, or parts of CIP4 interfere with this union and block normal CIP4 localization, MTOC polarization to the IS, and cytotoxicity. Reduction of endogenous CIP4 expression using small interfering RNA similarly inhibits MTOC polarization and cytotoxic activity but does not impair actin filament accumulation at the IS, or Cdc42 activation. Thus, CIP4 is an important cytoskeletal adaptor that functions after filamentous actin accumulation and Cdc42 activation to enable MTOC polarization and NK cell cytotoxicity.

Autoantibodies to novel membrane and cytosolic antigens of the lachrymal gland in primary Sjögren's syndrome

Sjögren's syndrome (SS) is a prototypical systemic autoimmune disease, where autoimmune processes lead to the dysfunction of the exocrine glands. The key feature of the disease is autoimmune exocrinopathy, causing reduced tear secretion and subsequent keratoconjunctivitis sicca (KCS). The aim of this study was to investigate the connection between the presence of autoantibodies to lachrymal gland antigens and the reduced tear production in patients with primary SS. Ninety-nine patients, 90 women and 9 men, were investigated in the study. Twenty healthy young women served as controls. Enzyme-linked immunosorbent assay (ELISA) and Western blotting were applied to detect autoantibodies to antigen fractions prepared from the human lachrymal gland membrane and cytosolic fractions. Autoantibodies of the IgG, IgA and IgM isotypes to the lachrymal membrane and cytosolic fractions were detected in about one third (27%) of the patients with primary SS. IgA antobodies to the membrane and cytosolic fractions occurred most frequently in SS patients. A significant difference was found in the presence of IgA antibodies to the membrane lachrymal fraction between patients and controls given in ELISA indices (1.23 +/- 0.3 vs 1 +/- 0.19, p < 0.001). IgG, IgA, and IgM isotypes of autoantibodies directed to the membrane lachrymal fraction of 200-180, 120-116, 80-70, 58, 50, 48.5, 40 and 28.8 kDa were also identified in patients. Membrane IgG antibody levels showed a positive correlation (R = 0.998; p = 0.045) with the clinical loss of secretory function (Schirmer's test values). Positive correlation was found between membrane IgM and anti-SS-A levels (R = 0.962; p = 0.038) and also between cytosolic IgM antibodies and anti-SS-A levels (R = 0.982; p = 0.018). IgG, IgA and IgM types of autoantibodies may play a role in the development of the impaired lachrymal secretion and therefore may be involved in the pathogenesis of KCS.

Interleukin-13-induced type II polarization of inflammatory macrophages is mediated through suppression of nuclear factor-kappaB and preservation of IkappaBalpha in a T cell lymphoma

Spontaneously arising transplantable T cell lymphoma, designated as Dalton's lymphoma (DL), is characterized by a highly invasive and deleterious nature almost completely paralysing the host immune system. The level of interleukin (IL)-13 is elevated in serum and ascitic fluid of the DL-bearing host. IL-13 is a potent immunosuppressive cytokine and is an alternative activator of macrophages that suppresses the production of nitric oxide (NO) and expression of inducible nitric oxide synthase (iNOS), and proinflammatory cytokines. The expression of iNOS and proinflammatory cytokines are dependent largely upon the activation of nuclear factor-kappaB (NF-kappaB). Activation of NF-kappaB involves the degradation of cytoplasmic inhibitor IkappaBalpha, allowing the nuclear translocation of NF-kappaB and thereby transcription of the iNOS gene. Therefore, in this study we sought to determine whether the alternative activation or type II polarization of macrophages induced by IL-13 is mediated by the suppression of NF-kappaB and cytoplasmic preservation of IkappaBalpha. Western blot analysis and electrophoretic mobility shift assay (EMSA) indicate that tumour-associated macrophages (TAM) or polarized type II macrophages are due to preserved protein expression of IkappaBalpha, and therefore suppressed NF-kappaB nuclear translocation. These findings suggest that IL-13 may operate through the suppression of NF-kappaB activation and preservation of IkappaBalpha.

Regulation of T-cell antigen receptor-mediated inside-out signaling by cytosolic adapter proteins and Rap1 effector molecules

Integrins are critical for the migration of T cells to lymphoid organs and to sites of inflammation and are also necessary for productive interactions between T cells and antigen-presenting cells. Integrin activation is enhanced following T-cell receptor (TCR) engagement, as signals initiated by the TCR increase affinity and avidity of integrins for their ligands. This process, known as inside-out signaling, has been shown to require several molecular components including the cytosolic adapter proteins adhesion and degranulation-promoting adapter protein and Src homology 2 domain-containing adapter protein of 55 kDa, the low molecular weight guanosine triphosphatase Rap1, and the Rap1 effector proteins Rap1 guanosine triphosphate-interacting adapter molecule, regulator of adhesion and cell polarization enriched in lymphoid tissues, and protein kinase D1. Herein, we review recent findings about how the TCR is linked to integrin activation through inside-out signaling.

DAI (DLM-1/ZBP1) is a cytosolic DNA sensor and an activator of innate immune response

Central to innate immunity is the sensing of pathogen-associated molecular patterns by cytosolic and membrane-associated receptors. In particular, DNA is a potent activator of immune responses during infection or tissue damage, and evidence indicates that, in addition to the membrane-associated Toll-like receptor 9, an unidentified cytosolic DNA sensor(s) can activate type I interferon (IFN) and other immune responses. Here we report on a candidate DNA sensor, previously named DLM-1 (also called Z-DNA binding protein 1 (ZBP1)), for which biological function had remained unknown; we now propose the alternative name DAI (DNA-dependent activator of IFN-regulatory factors). The artificial expression of otherwise IFN-inducible DAI (DLM-1/ZBP1) in mouse fibroblasts selectively enhances the DNA-mediated induction of type I IFN and other genes involved in innate immunity. On the other hand, RNA interference of messenger RNA for DAI (DLM-1/ZBP1) in cells inhibits this gene induction programme upon stimulation by DNA from various sources. Moreover, DAI (DLM-1/ZBP1) binds to double-stranded DNA and, by doing so, enhances its association with the IRF3 transcription factor and the TBK1 serine/threonine kinase. These observations underscore an integral role of DAI (DLM-1/ZBP1) in the DNA-mediated activation of innate immune responses, and may offer new insight into the signalling mechanisms underlying DNA-associated antimicrobial immunity and autoimmune disorders.

Bacterial ligands generated in a phagosome are targets of the cytosolic innate immune system

Macrophages are permissive hosts to intracellular pathogens, but upon activation become microbiocidal effectors of innate and cell-mediated immunity. How the fate of internalized microorganisms is monitored by macrophages, and how that information is integrated to stimulate specific immune responses is not understood. Activation of macrophages with interferon (IFN)–γ leads to rapid killing and degradation of Listeria monocytogenes in a phagosome, thus preventing escape of bacteria to the cytosol. Here, we show that activated macrophages induce a specific gene expression program to L. monocytogenes degraded in the phago-lysosome. In addition to activation of Toll-like receptor (TLR) signaling pathways, degraded bacteria also activated a TLR-independent transcriptional response that was similar to the response induced by cytosolic L. monocytogenes. More specifically, degraded bacteria induced a TLR-independent IFN-β response that was previously shown to be specific to cytosolic bacteria and not to intact bacteria localized to the phagosome. This response required the generation of bacterial ligands in the phago-lysosome and was largely dependent on nucleotide-binding oligomerization domain 2 (NOD2), a cytosolic receptor known to respond to bacterial peptidoglycan fragments. The NOD2-dependent response to degraded bacteria required the phagosomal membrane potential and the activity of lysosomal proteases. The NOD2-dependent IFN-β production resulted from synergism with other cytosolic microbial sensors. This study supports the hypothesis that in activated macrophages, cytosolic innate immune receptors are activated by bacterial ligands generated in the phagosome and transported to the cytosol.

Innate immune recognition of microorganisms has a direct impact on the type and the magnitude of the immune response elicited. While recognition of microorganisms relies on receptors that sense pathogen-associated molecular patterns, (PAMPs), it was reasonable to suspect that immune cells could discriminate between live and dead bacteria. Listeria monocytogenes is an intracellular pathogenic bacterium used extensively as a model system for studying basic aspects of innate and acquired immunity. L. monocytogenes is internalized by macrophages, escapes from a vacuole, multiplies within the cytosol, and spreads from cell to cell without lysing the cells. We used wild-type and bacterial mutants of L. monocytogenes to demonstrate that macrophages not only respond differently to bacteria that are growing in the cytosol and to non-growing bacteria that are trapped in a vacuole, but that they also can discriminate between intact or degraded bacteria in the vacuole. We showed that macrophages induce specific immune response when bacteria are killed and degraded. This response was directly correlated to the ability of macrophages to degrade bacteria and involved receptors that were located in the host cell cytosol. These observations led us to suggest that bacterial degradation products may serve as messengers that inform immune cells that bacteria were killed and degraded. This information might affect directly the immune response, for example, by down-regulating inflammatory responses that can be deleterious. We call these bacterial degradation products PAMP-PM (PAMP–post-mortem).

Type I interferon signaling is required for activation of the inflammasome during Francisella infection

Francisella tularensis is a pathogenic bacterium whose virulence is linked to its ability to replicate within the host cell cytosol. Entry into the macrophage cytosol activates a host-protective multimolecular complex called the inflammasome to release the proinflammatory cytokines interleukin (IL)-1beta and -18 and trigger caspase-1-dependent cell death. In this study, we show that cytosolic F. tularensis subspecies novicida (F. novicida) induces a type I interferon (IFN) response that is essential for caspase-1 activation, inflammasome-mediated cell death, and release of IL-1beta and -18. Extensive type I IFN-dependent cell death resulting in macrophage depletion occurs in vivo during F. novicida infection. Type I IFN is also necessary for inflammasome activation in response to cytosolic Listeria monocytogenes but not vacuole-localized Salmonella enterica serovar Typhimurium or extracellular adenosine triphosphate. These results show the specific connection between type I IFN signaling and inflammasome activation, which are two sequential events triggered by the recognition of cytosolic bacteria. To our knowledge, this is the first example of the positive regulation of inflammasome activation. This connection underscores the importance of the cytosolic recognition of pathogens and highlights how multiple innate immunity pathways interact before commitment to critical host responses.

Pannexin-1-mediated recognition of bacterial molecules activates the cryopyrin inflammasome independent of Toll-like receptor signaling

Cryopyrin is essential for caspase-1 activation triggered by Toll-like receptor (TLR) ligands in the presence of adenosine triphosphate (ATP). However, the events linking bacterial products and ATP to cryopyrin remain unclear. Here we demonstrate that cryopyrin-mediated caspase-1 activation proceeds independently of TLR signaling, thus dissociating caspase-1 activation and IL-1beta secretion. Instead, caspase-1 activation required pannexin-1, a hemichannel protein that interacts with the P2X(7) receptor. Direct cytosolic delivery of multiple bacterial products including lipopolysaccharide, but not flagellin, induced caspase-1 activation via cryopyrin in the absence of pannexin-1 activity or ATP stimulation. However, unlike Ipaf-dependent caspase-1 activation, stimulation of the pannexin-1-cryopyrin pathway by several intracellular bacteria was independent of a functional bacterial type III secretion system. These results provide evidence for cytosolic delivery and sensing of bacterial molecules as a unifying model for caspase-1 activation and position pannexin-1 as a mechanistic link between bacterial stimuli and the cryopyrin inflammasome.

Preparation of polyclonal antibody specific for AtPLC4, an Arabidopsis phosphatidylinositol-specific phospholipase C in rabbits

Phosphoinositide-specific phospholipase Cs (PI-PLCs) are important enzymes in eukaryotes, which catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate into the two second messengers inositol 1,4,5-trisphosphate and diacylglycerol. The Arabidopsis genome contains nine putative PI-PLC genes. AtPLC4, an abiotic stress induced gene, has been reported to encode an active PI-PLC isoform. However, the exact roles of putative AtPLC4 in plant remain to be elicited. The first 108 amino acid residues of the N-terminal of AtPLC4, referred to as AtPLC4 N, was expressed as a recombinant protein in Escherichia coli and used as antigen in generating antibody. Purified recombinant proteins including AtPLC1 to AtPLC5, AtPLC8, AtPLC9 and AtPLC4 N were transferred onto the same blot to test specificity of the prepared antibody. Western blot result shows that only AtPLC4 and AtPLC4 N can be recognized by the antibody. The antibody recognized a protein of approximately 68kDa in the plasma membrane fraction and cytosolic fractions prepared from Arabidopsis thaliana plants. This corresponds very well with the calculated molecular weight of AtPLC4. The results suggest that AtPLC4 may encode a plasma membrane-associated protein.

Identification of CTL epitopes in hepatitis C virus by a genome-wide computational scanning and a rational design of peptide vaccine

Developing a peptide-based vaccine for the highly variable hepatitis C virus (HCV) remains a challenging task. Variant viruses not only escape antigen presentation but also persist in a patient as quasi-species. Such variants are often antagonistic to the responding T cell repertoire. To overcome these problems, we herein propose a cocktail vaccine consisting of a few epitope peptides, which make it possible to outpace the emergence of variant viruses. To design such a vaccine, we developed a way to identify HLA-A*2402-binding peptides efficiently by means of the computational scanning of the whole genome of the pathogen. Most of the predicted peptides exhibited strong binding to the HLA-A*2402 molecule, while also inducing CD8 T cell responses from the patients' peripheral blood mononuclear cells (PBMCs). Peptide-induced T cells were capable of lysing HCV-expressing HepG2 cells which process antigens endogenously. The amount of HCV core antigen in the patients' livers suggested that the lytic activity of the peptide-induced T cells was clearly in a range suitable for therapeutic use. If T cells were activated under optimal conditions by high density peptides, then they tended to be relatively tolerant of single amino acid variations for cytolysis. Finally, an analysis of the viral population isolated in Japan suggested no obvious changes due to immune evasion in the viral genome even in a host population highly biased toward HLA-A*2402.

Pituitary autoantibodies in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED)

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is an autosomal recessive disease due to mutations in the AIRE (AutoImmune REgulator) gene. The role of pituitary autoimmunity in APECED is not known. We determined the prevalence of pituitary autoantibodies in a cohort of 67 Finnish patients with APECED from 217 serum samples collected over 26 years by one investigator. Overall, autoantibodies to the 49 kDa cytosolic autoantigen, human pituitary enolase were detected in 39 of the 67 patients (58%). On their first sample, 25 patients had autoantibodies compared to 5 of 68 controls (chi-square, 1df=17.11, p< 0.001; OR=7.32), but subsequently 14 patients seroconverted between 10 and 53 years of age. Once seropositive, all but two of the patients maintained their positive autoantibody status, even over many years. In the current study all but 7 of the 19 patients known to have high titre anti-candidal enolase antibodies had developed autoantibodies directed against human pituitary enolase. Other pituitary autoantibody reactivities were detected against cytosolic proteins of molecular weights 40-, 45-, 60- and 105 kDa in 15%, 16%, 12% and 3% of patients respectively. Autoantibodies to pituitary enolase are markers of neuroendocrine autoimmunity but seem not to be associated with clinical hypopituitarism in APECED patients.

Expression of a recombinant human sperm-agglutinating mini-antibody in tobacco (Nicotiana tabacum L.)

The murine monoclonal antibody (mAB) S19 recognizes an N-linked carbohydrate antigen designated sperm agglutination antigen-1 (SAGA1) located on the membrane protein CD52. This antigen is added to the sperm surface during epididymal maturation. Binding of the S19 mAB to SAGA-1 causes the rapid agglutination of sperm and blocks pre-fertilization events. Previous studies indicated that the S19 mAB may be a potential specific spermicidal agent (termed a spermistatic) capable of replacing current spermicidal products that contain harsh detergents with harmful side effects. The nucleotide sequences encoding the heavy (H) and light (L) chains of the S19 antibody were cloned. A chimeric gene was constructed using the nucleotide sequences encoding the variable regions of both the H and L chains, and this gene (scFv1 9) was expressed in transgenic tobacco (Nicotiana tabacum L.) to produce a recombinant anti-sperm antibody (RASA). Highest levels of RASA expression were observed in BY-2 plant cell suspension cultures and regenerated N. tabacum cv. Xanthi plants transformant in which the RASA coding sequences were expressed under the control of the Cauliflower Mosaic Virus 35S promoter containing a double-enhancer sequence (2X CaMV 35S). Subsequent modifications of the transgene including the addition of a 5'-untranslated sequence from the tobacco etch virus (TEV leader sequence), N-terminal fusion of the coding region with an endoplasmic reticulum targeting signal of patatin (pat) and C-terminal fusion with the endoplasmic reticulum retention signal peptide KDEL showed further enhancement of RASA expression. The plant-expressed RASA formed intrachain disulfide bonds and was primarily soluble in the cytoplasmic fraction of the cells. Introduction of a poly-histidine (6xHIS) tag in the recombinant RASA protein allowed for rapid purification of the recombinant protein using Ni-NTA chromatography. Optimization of scale-up production and purification of this plant-derived recombinant protein should provide large quantities of an inexpensive spermistatic plantibody.

Localization of the hypothetical protein Cpn0797 in the cytoplasm of Chlamydia pneumoniae-infected host cells

Using antibodies raised with chlamydial fusion proteins, we have localized a protein encoded by the hypothetical open reading frame Cpn0797 in the cytoplasm of Chlamydia pneumoniae-infected host cells. The anti-Cpn0797 antibodies specifically recognized Cpn0797 protein without cross-reacting with either CPAFcp or Cpn0796, the only two proteins known to be secreted into the host cell cytosol by C. pneumoniae organisms. Thus, Cpn0797 represents the third C. pneumoniae protein secreted into the host cell cytosol experimentally identified so far.

A recombinant attenuated Salmonella enterica serovar Typhimurium vaccine encoding Eimeria acervulina antigen offers protection against E. acervulina challenge

Coccidiosis is a ubiquitous disease caused by intestinal protozoan parasites belonging to several distinct species of the genus Eimeria. Cell-mediated immunity (CMI) is critically important for protection against Eimeria; thus, our approach utilizes the bacterial type III secretion system (TTSS) to deliver an antigen directly into the cell cytoplasm of the immunized host and into the major histocompatibility complex class I antigen-processing pathway for induction of CMI and antigen-specific cytotoxic T-lymphocyte responses in particular. To accomplish this goal, Eimeria genes encoding the sporozoite antigen EASZ240 and the merozoite antigen EAMZ250 were fused to the Salmonella enterica serovar Typhimurium effector protein gene sptP in the parental pYA3653 vector, yielding pYA3657 and pYA3658, respectively. SptP protein is secreted by the TTSS of Salmonella and translocated into the cytoplasm of immunized host cells. The host strain chromosomal copy of the sptP gene was deleted and replaced by a reporter gene, xylE. The newly constructed vectors pYA3657 and pYA3658 were introduced into host strain chi8879 (DeltaphoP233 DeltasptP1033::xylEDelta asdA16). This strain is an attenuated derivative of the highly virulent strain UK-1. When strain chi8879(pYA3653) as the vector control and strain chi8879 harboring pYA3657 or pYA3658 were used to orally immunize day-of-hatch chicks, colonization of the bursa, spleen, and liver was observed, with peak titers 6 to 9 days postimmunization. In vitro experiments show that the EASZ240 antigen is secreted into the culture supernatant via the TTSS and that it is delivered into the cytoplasm of Int-407 cells by the TTSS. In vivo experiments indicate that both humoral and cell-mediated immune responses are induced in chickens vaccinated with a recombinant attenuated Salmonella serovar Typhimurium vaccine, which leads to significant protection against Eimeria challenge.