TRITIUM ANALYSIS IN URINE BY THE TRIPLE-TO-DOUBLE COINCIDENCE RATIO METHOD WITH THE HIDEX 300 SL LIQUID SCINTILLATION COUNTER.

The triple-to-double coincidence ratio (TDCR) method is a liquid scintillation primary method for the absolute activity measurement of pure ß- and pure electron capture emitters. This method requires specific three-photomultiplier liquid scintillation counters. The aim of the present work is to assess the TDCR method performance for routine tritium analysis in urine using an HIDEX 300 SL, the only three-photomultiplier liquid scintillation counter designed for routine laboratories. The physical parameters and the semi-empirical Birks parameter (kB) of the prepared liquid scintillation source were firstly determined. TDCR model equations solving and detection efficiencies calculations for measured samples were performed by TDCR07c computing program. Accuracy, uncertainties and detection limit of TDCR method were assessed through the tritium analysis of six intercomparison urine samples. The results demonstrate that the analytical performance of the TDCR method implemented on the HIDEX 300 SL is conform to the recommendations for the monitoring of workers exposed to tritium.

Vaccine-induced Aß-specific CD8+ T cells do not trigger autoimmune neuroinflammation in a murine model of Alzheimer's disease.

BACKGROUND: Active immunization against Aß was reported to have a therapeutic effect in murine models of Alzheimer's disease. Clinical Aß vaccination trial AN1792 was interrupted due to the development in 6 % of the patients of meningoencephalitis likely involving pro-inflammatory CD4(+) T cells. However, the potential implication of auto-aggressive anti-Aß CD8(+) T cells has been poorly investigated. METHODS: Potential MHC-I-restricted Aß-derived epitopes were first analyzed for their capacity to recruit functional CD8(+) T cell responses in mouse models. Their impact on migration of CD8(+) T cells into the brain parenchyma and potential induction of meningoencephalitis and/or neuronal damage was investigated upon vaccination in the APPPS1 mouse model of AD. RESULTS: We identified one nonamer peptide, Aß33-41, which was naturally processed and presented in association with H-2-D(b) molecule on neurons and CD11b(+) microglia. Upon optimization of anchor residues for enhanced binding to H-2-D(b), immunization with the modified Aß33-41NP peptide elicited Aß-specific IFNγ-secreting CD8(+) T cells, which are cytotoxic towards Aß-expressing targets. Whereas T cell infiltration in the brain of APPPS1 mice is dominated by CD3(+)CD8(-) T cells and increases with disease evolution between 4 and 7 months of age, a predominance of CD3(+)CD8(+) over CD3(+)CD8(-) cells was observed in 6- to 7-month-old APPPS1 but not in WT animals, only after vaccination with Aß33-41NP. The number of CD11b(+) mononuclear phagocytes, which significantly increases with age in the brain of APPPS1 mice, was reduced following immunization with Aß33-41NP. Despite peripheral activation of Aß-specific CD8(+) cytotoxic effectors and enhanced infiltration of CD8(+) T cells in the brain of Aß33-41NP-immunized APPPS1 mice, no clinical signs of severe autoimmune neuroinflammation were observed. CONCLUSIONS: Altogether, these results suggest that Aß-specific CD8(+) T cells are not major contributors to meningoencephalitis in response to Aß vaccination.

UPLC-ESI-Q-TOF-MS(E) identification of urinary metabolites of the emerging sport nutrition supplement methoxyisoflavone in human subjects.

Methoxyisoflavone (5-methyl-7-methoxyisoflavone) is a synthetic isoflavone used by bodybuilders for its ergogenic properties. A recent study demonstrated that methoxyisoflavone metabolites can induce false-positive results in urinary immunoassay screening tests for cannabinoids, and only one metabolite has been identified. To improve the knowledge on the metabolic pathways of methoxyisoflavone, ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF) was applied. Urine samples were obtained from methoxyisoflavone regular users. After enzymatic hydrolysis and liquid-liquid extraction, the samples were analyzed by UPLC-Q-TOF fitted with an electrospray ionization source (ESI) operating under positive ion mode. Mass data were acquired with the MS(E) method. Five metabolites were identified. Those were divided into two metabolic pathways, depending on whether the B ring hydroxylation was preceded or not by the O-demethylation of the methoxy group. The MS(E) mass spectra of methoxyisoflavone and its metabolites are specific of isoflavones structures and revealed 1,3 retro Diels-Alder fragmentation and double CO loss. Losses of small neutral molecules CO and H2O, and radical CH3, typical of flavonoids, were also observed. This study illustrates the capacity of the sensitive UPLC-Q-TOF analytical system, combined with the MS(E) method of collection of fragmentation data, to rapidly elucidate the unknown xenobiotics metabolism.

Prolongation of prion disease-associated symptomatic phase relates to CD3+ T cell recruitment into the CNS in murine scrapie-infected mice.

Prion diseases are caused by the transconformation of the host cellular prion protein PrP(c) into an infectious neurotoxic isoform called PrP(Sc). While vaccine-induced PrP-specific CD4(+) T cells and antibodies partially protect scrapie-infected mice from disease, the potential autoreactivity of CD8(+) cytotoxic T lymphocytes (CTLs) received little attention. Beneficial or pathogenic influence of PrP(c)-specific CTL was evaluated by stimulating a CD8(+) T-cell-only response against PrP in scrapie-infected C57BL/6 mice. To circumvent immune tolerance to PrP, five PrP-derived nonamer peptides identified using prediction algorithms were anchored-optimized to improve binding affinity for H-2D(b) and immunogenicity (NP-peptides). All of the NP-peptides elicited a significant number of IFNγ secreting CD8(+) T cells that better recognized the NP-peptides than the natives; three of them induced T cells that were lytic in vivo for NP-peptide-loaded target cells. Peptides 168 and 192 were naturally processed and presented by the 1C11 neuronal cell line. Minigenes encoding immunogenic NP-peptides inserted into adenovirus (rAds) vectors enhanced the specific CD8(+) T-cell responses. Immunization with rAd encoding 168NP before scrapie inoculation significantly prolonged the survival of infected mice. This effect was attributable to a significant lengthening of the symptomatic phase and was associated with enhanced CD3(+) T cell recruitment to the CNS. However, immunization with Ad168NP in scrapie-incubating mice induced IFNγ-secreting CD8(+) T cells that were not cytolytic in vivo and did not influence disease progression nor infiltrated the brain. In conclusion, the data suggest that vaccine-induced PrP-specific CD8(+) T cells interact with prions into the CNS during the clinical phase of the disease.

MHC-independent genetic factors control the magnitude of CD4+ T cell responses to amyloid-ß peptide in mice through regulatory T cell-mediated inhibition.

Accumulation of amyloid-ß peptide (Aß) is considered the triggering factor of pathogenic lesions in Alzheimer's disease (AD), and vaccines targeting Aß are promising therapeutic options. However, the occurrence of meningoencephalitides attributed to T cell responses in 6% of Aß-immunized patients underscores the need for a better understanding of T cell responses to Aß. We characterized the parameters controlling the magnitude of Aß-specific CD4(+) T cell responses in mice. T cell responsiveness to Aß1-42 was highly heterogeneous between mouse strains of different H-2 haplotypes, with SJL/J (H-2(s)) mice displaying a strong response, mainly specific for Aß10-24, and C57BL/6 (H-2(b)) mice displaying a weak response to Aß16-30. Surprisingly, C57BL/6 mice congenic for the H-2(s) haplotype (B6.H-2(S)), which display a "permissive" MHC class II allele for presentation of the immunodominant Aß10-24 epitope, showed a very weak CD4(+) T cell response to Aß, suggesting that MHC-independent genes downmodulate Aß-specific CD4(+) T cell responses in C57BL/6 background. Vaccine-induced CD4(+) T cell responses to Aß were significantly enhanced in both C57BL/6 and B6.H-2(S) mice upon depletion of regulatory T cells (Tregs), whereas Treg-depleted SJL/J mice displayed unaltered Aß-specific T cell responses. Finally, Treg depletion in C57BL/6 transgenic APPPS1 mice, a mouse model of AD, results in enhanced vaccine-induced CD4(+) T cell responses in AD compared with wild-type animals. We concluded that the magnitude of Aß-specific CD4(+) T cell responses is critically controlled in both physiological and pathological settings by MHC-independent genetic factors that determine the overall potency of Aß-specific Treg responses.

Mouse vaccination with dendritic cells loaded with prion protein peptides overcomes tolerance and delays scrapie.

Prion diseases are presumed to be caused by the accumulation in the brain of a pathological protein called prion protein (PrP) scrapie which results from the transconformation of cellular PrP, a ubiquitous glycoprotein expressed in all mammals. Since all isoforms of PrP are perceived as self by the host immune system, a major problem in designing efficient immunoprophylaxis or immunotherapy is to overcome tolerance. The present study was aimed at investigating whether bone-marrow-derived dendritic cells (DCs) loaded with peptides previously shown to be immunogenic in PrP-deficient mice, can overcome tolerance in PrP-proficient wild-type mice and protect them against scrapie. Results show that, in such mice, peptide-loaded DCs elicit both lymphokine release by T cells and antibody secretion against native cellular PrP. Repeated recalls with peptide-loaded DCs reduces the attack rate of 139A scrapie inoculated intraperitoneally and retards disease duration by 40 days. Most interestingly, survival time in individual mice appears to be correlated with the level of circulating antibody against native cellular PrP.

Dendritic cell-mediated-immunization with xenogenic PrP and adenoviral vectors breaks tolerance and prolongs mice survival against experimental scrapie.

In prion diseases, PrP(c), a widely expressed protein, is transformed into a pathogenic form called PrP(Sc), which is in itself infectious. Antibodies directed against PrP(c) have been shown to inhibit PrP(c) to PrP(Sc) conversion in vitro and protect in vivo from disease. Other effectors with potential to eliminate PrPSc-producing cells are cytotoxic T cells directed against PrP-derived peptides but their ability to protect or to induce deleterious autoimmune reactions is not known. The natural tolerance to PrP(c) makes difficult to raise efficient adaptive responses. To break tolerance, adenovirus (Ad) encoding human PrP (hPrP) or control Ad were administered to wild-type mice by direct injection or by transfer of Ad-transduced dendritic cells (DCs). Control Ad-transduced DCs from Tg650 mice overexpressing hPrP were also used for immunization. DC-mediated but not direct administration of AdhPrP elicited antibodies that bound to murine native PrP(c). Frequencies of PrP-specific IFNgamma-secreting T cells were low and in vivo lytic activity only targeted cells strongly expressing hPrP. Immunohistochemical analysis revealed that CD3(+) T cell infiltration was similar in the brain of vaccinated and unvaccinated 139A-infected mice suggesting the absence of autoimmune reactions. Early splenic PrP(Sc) replication was strongly inhibited ten weeks post infection and mean survival time prolonged from 209 days in untreated 139A-infected mice to 246 days in mice vaccinated with DCs expressing the hPrP. The efficacy appeared to be associated with antibody but not with cytotoxic cell-mediated PrP-specific responses.

Contribution of antibody and T cell-specific responses to the progression of 139A-scrapie in C57BL/6 mice immunized with prion protein peptides.

Prion diseases are associated with the conversion of the normal host cellular prion protein to an abnormal protease-resistant (PrPres) associated with infectivity. No specific immune response against prions develops during infection due to the strong tolerance to cellular prion protein. We examined the protective potential on prion diseases of immune responses elicited in C57BL/6 mice with PrP peptides 98-127 (P5) or 158-187 (P9) with CpG. After immunization, P5-treated mice developed high titer and long-lasting Abs, and P9-treated mice developed transient IFN-gamma secreting T cells and poor and variable Ab responses. Both treatments impaired early accumulation of PrPres in the spleen and prolonged survival of mice infected with 139A scrapie. Additional P9 boosts after 139A infection sustained the T cell response and partially inhibited PrPres early accumulation but did not improve the survival. Surprisingly, when P9 injections were started 1 mo after infection and repeated subsequently, specific T cell and Ab responses were impaired and no beneficial effect on prion disease was observed. After a single injection of P9, the number of IFN-gamma secreting CD4+ T cells was also reduced in mice 8- to 10-wk postinfection compared with healthy mice. In vivo and in vitro removal of CD4+CD25+ T cells restored the T cell response to P9 in infected mice. In conclusion, CD4+ T cells as well as Abs might participate to the protection against scrapie. Of importance, the peripheral accumulation of PrPres during infection negatively interferes with the development of T and B cell responses to PrP and regulatory T cells might contribute to this phenomenon.

The murine B cell repertoire is severely selected against endogenous cellular prion protein.

Abs to the prion protein (PrP) can protect against experimental prion infections, but efficient Ab responses are difficult to generate because PrP is expressed on many tissues and induces a strong tolerance. We previously showed that immunization of wild-type mice with PrP peptides and CpG oligodeoxynucleic acid overcomes tolerance and induces cellular and humoral responses to PrP. In this study, we compared Ab and T cell repertoires directed to PrP in wild-type and PrP knockout (Prnp o/o) C57BL/6 mice. Animals were immunized with mouse PrP-plasmid DNA or with 30-mer overlapping peptides either emulsified in CFA or CpG/IFA. In Prnp o/o mice, Abs raised by PrP-plasmid DNA immunization recognized only N-terminal PrP peptides; analyses of Ab responses after PrP peptide/CFA immunization allowed us to identify six distinct epitopes, five of which were also recognized by Abs raised by PrP peptides/CpG. By contrast, in wild-type mice, no Ab response was detected after PrP-plasmid DNA or peptide/CFA immunization. However, when using CpG, four C-terminal peptides induced Abs specific for distinct epitopes. Importantly, immune sera from Prnp o/o but not from wild-type mice bound cell surface PrP. Abs of IgG1 and IgG2b subclasses predominated in Prnp o/o mice while the strongest signals were for IgG2b in wild-type mice. Most anti-PrP Th cells were directed to a single epitope in both Prnp o/o and wild-type mice. We conclude that endogenous PrPC expression profoundly affects the Ab repertoire as B cells reactive for epitopes exposed on native PrPC are strongly tolerized. Implications for immunotherapy against prion diseases are discussed.

Identification of two immunogenic domains of the prion protein--PrP--which activate class II-restricted T cells and elicit antibody responses against the native molecule.

Recent reports suggest that immunity against the prion protein (PrP) retards transmissible spongiform encephalopathies progression in infected mice. A major obstacle to the development of vaccines comes from the fact that PrP is poorly immunogenic, as it is seen as self by the host immune system. Additional questions concern the immune mechanisms involved in protection and the risk of eliciting adverse reactions in the central nervous system of treated patients. Peptide-based vaccines offer an attractive strategy to overcome these difficulties. We have undertaken the identification of the immunogenic regions of PrP, which trigger helper T cells (Th) associated with antibody production. Our results identify two main regions, one between the structured and flexible portion of PrP (98-127) and a second between alpha 1 and alpha 2 helix (143-187). Peptides (30-mer) corresponding to these regions elicit class II-restricted Th cells and antibody production against native PrP and could therefore be of potential interest for a peptide-based vaccination.

Breaking immune tolerance to the prion protein using prion protein peptides plus oligodeoxynucleotide-CpG in mice.

The absence of a detectable immune response during transmissible spongiform encephalopathies is likely due to the fact that the essential component of infectious agents, the prion protein (PrP), is a self Ag expressed on the surface of many cells of the host. To overcome self-tolerance to PrP, we used 30-mer PrP peptides previously shown to be immunogenic in Prnp(-/-) mice, together with CFA or CpG-oligodeoxynucleotides (CpG) in IFA. Generation of anti-PrP T and B cell responses was analyzed in the spleen, lymph nodes, and serum of immunized C57BL/6 wild-type mice. Immunization with PrP peptides emulsified in CFA did not trigger an immune response to PrP. When CpG were used, vaccination with peptides P143-172 and P158-187 generated IFN-gamma-secreting splenic T cells, and only P158-187 significantly stimulated IL-4-secreting T cells. Both peptides induced few Ab-producing B cells, and low and variable serum Ab titers. In contrast, immunization with peptide P98-127 did not induce significant levels of T cell responses but elicited specific peptide Abs. T cell epitope mapping, performed using 15-mer peptides covering PrP segment 142-182, revealed that an immunogenic motif lies between positions 156 and 172. These results demonstrate that T and B cell repertoires against PrP can be stimulated in C57BL/6 when adjuvant of the innate immunity such as CpG, but not CFA, is added to PrP peptides, and that the pattern of immune responses varies according to the epitope.

Polyreactive autoantibodies purified from human intravenous immunoglobulins prevent the development of experimental autoimmune diseases.

Intravenous immunoglobulins (IVIg) are therapeutic preparations of normal human polyclonal Ig G (IgG) that exert immunomodulatory effects in patients with autoimmune or systemic inflammatory diseases. Two different IgG subfractions were evaluated for their respective immunomodulatory effects in the treatment of experimental autoimmune diseases: a fraction enriched in antibodies that recognize the F(ab')(2) portion of IVIg and a fraction of natural polyreactive autoantibodies purified on a dinitrophenyl (DNP)-Affiprep immunoadsorbent. A very small fraction of IgG interacting with DNP but not with F(ab')(2) fragments expressed an increased ability to bind to self-antigens. The anti-DNP fraction, but not the anti-idiotype fraction, protected against inflammation observed in collagen-induced arthritis and experimental autoimmune encephalomyelitis in rats. Furthermore, it was able to reduce the occurrence of spontaneous diabetes mellitus in nonobese diabetic mice at lower concentrations than unfractionated IVIg. The therapeutic benefit of the anti-DNP fraction was associated with the inhibition of secretion of proinflammatory cytokines and stimulation of secretion of IL-1 receptor antagonist. Our results provide evidence that polyreactive autoantibodies play a role in the protective effect of IVIg in experimental models of autoimmune diseases in which inflammatory reactions are part of the disease process.