Synthesis, Electrochemical and Fluorescence Properties of the First Fluorescent Member of the Ferrocifen Family and of Its Oxidized Derivatives

The first fluorescent ferrociphenol derivative (P797) has been synthesized via McMurry cross-coupling followed by copper-catalyzed [3 + 2] azide-alkyne cycloaddition of the fluorescent group coumarin. Cyclic voltammograms of P797 exhibit either a monoelectronic oxidation wave ascribed to the ferrocene Fe(II) → Fe(III) conversion or a three-electron oxidation process in the presence of a base, leading to a Fe(III) quinone methide adduct. This general sequence is consistent with those previously described for non-fluorescent ferrociphenols. Furthermore, the fluorescence properties of P797 and its oxidized intermediates appear to strongly depend on the redox state of the ferrocene group. Indeed, electrochemical generation of Fe(III) (ferrocenium) states markedly increases the fluorescence emission intensity. In contrast, the emission of the Fe(II) (ferrocene) states is partially quenched by photoinduced electron transfer (PET) from the Fe(II) donor to the coumarin acceptor and by concentration-dependent self-quenching. Owing to its switchable fluorescence properties, complex P797 could represent an innovative and useful tool to study the biodistribution and the redox state of ferrocifens in cancer cells.

Emergency ward ultrasound: clinical audit on disinfection practices during routine and sterile examinations

Context

In the emergency ward, where the use of ultrasound is common (including for sterile procedures), ward equipment is constantly exposed to high risks of microbiological contamination. There are no clear guidelines for disinfection control practices in emergency departments, and it is not known how emergency ward doctors follow good hygiene practices.

Method

A multi-centre audit was conducted in 16 emergency services from Northern France regional hospitals, in form of a questionnaire. It was proposed to all emergency ward physicians. We excluded questionnaires when physicians mentioned that they did not use ultrasound on a daily basis. The questionnaire was designed using existing hygiene and ultrasound disinfection practices guidelines from varying French medical societies. It included three different clinical scenarios: (a) ultrasound on healthy skin, (b) on injured skin, and (c) ultrasound-guided punctures. All questions were closed-ended, with only one answer corresponding to the guidelines. We then calculated compliance rates for each question, each clinical situation, and an overall compliance rate for all the questions.

Results

104 questionnaires were collected, and 19 were excluded. For the 85 analysed questionnaires, the compliance rates were 60.4% 95% CI [56.4–64.7] for ultrasound on healthy skin, 70.9% 95% CI [66.3–76.1] on injured skin and 69.4% 95% CI [65.1–73.6] for ultrasound-guided punctures. The overall compliance rate for the compliance questions was 66.1% 95% CI [62.8–69.1]. Analysis of the questionnaires revealed severe asepsis errors, misuse of gel, ignorance of infection control practices to be applied in the context of ultrasound-guided puncture and exposure of the probe to body fluids.

Conclusion

This study details areas for quality improvement in the disinfection of emergency ultrasound scanner use. Consequently, we propose a standardized protocol based upon the recommendations used for the questionnaire drafting, with a visual focus on the low compliance points that have been revealed in this audit. This protocol has been distributed to all the medical emergency services audited and included in the emergency resident’s ultrasound learning program.

AB0718 DIAGNOSTIC PERFORMANCE OF VARIOUS CLASSIFICATION CRITERIA IN LOW BACK PAIN PATIENTS WITH SUSPECTED AXIAL SPONDYLOARTHRITIS: A PRAGMATIC STUDY

Background:

In routine practice, axial spondyloarthritis (SpA) can be a diagnostic challenge because there is potential overlap with osteoarthritic low back pain or diffuse polyalgic syndrome with axial pain as fibromyalgia. Internationally recognized classification criteria (AMOR, ASAS (1), ESSG (2)) are often used as diagnostic tools in clinical practice (3), but few studies have sought to establish their “real life” diagnostic performances.

Objectives:

This monocentric study aimed to evaluate the diagnostic performance of different sets of classification criteria for SpA in patients with chronic back pain hospitalized for suspected axial SpA. The second objective was to evaluate the impact of the sacroiliac MRI reading according to the ASAS MRI reading or expert musculoskeletal reading.

Methods:

Patients presenting with inflammatory low back pain who underwent standardized sacroiliac MRI protocol were consecutively included. The diagnoses obtained with the classification criteria (AMOR, ESSG, Modified AMOR and Modified ESSG (with sacroiliac MRI)) were compared to the gold standard diagnoses (made by a college of three experienced rheumatologists). Two readings of the sacroiliac MRI were performed (ASAS MRI reading and Expert MRI reading (including all inflammatory or structural T1 or T2 STIR abnormalities)). Diagnostic performance was measured for each set of classification criteria: sensitivity, specificity, predictive positive and negative values (PPV, NPV) and positive and negative likelihood ratios (PLR, PLN). The clinical, biological and MRI factors associated with axial SpA diagnosis were identified in a multivariate logistic regression model.

Results:

83 patients were included of which 27 had axial SpA according to the opinion of the college of rheumatologists. The AMOR modified criteria (with ASAS MRI reading) had the highest diagnostic performance values, with sensitivity = 96%, specificity = 71%, NPV = 97%, PPV = 54%, PLR = 3.3, and NLR = 0.06. Sacroiliac MRI reading demonstrated poor sensitivity (< 60%) for SpA (ASAS or expert reading), while expert reading of MRI had high specificity (98%), NPV = 90%, PPV = 78%, and PLR = 18. In multivariate logistic regression, the presence of enthesitis (OR = 3.51, IC95% [1.10;11.21]; p = 0.024), positive HLA B27 (OR = 4.22, IC95% [1.25;14.18]; p = 0.02)) or sacroiliitis on MRI (ASAS reading) (OR = 3.34, IC95% [1.04; 10.76]; p = 0.043) were independently associated with the final diagnosis of SpA.

Conclusion:

The results of this pragmatic study suggest that the Modified AMOR criteria with ASAS MRI reading can be used to rule out axial spondyloarthritis (NPV = 97%). However, the use of an MRI ASAS reading alone creates a risk of false positives because of the greater impact on ASAS criteria compared to AMOR or ESSG criteria. Further international studies are needed to decrease the rate of false positives in suspected cases of axial spondyloarthritis in routine practice.

References:

[1]Dougados M, van der Linden S, Juhlin R et al. The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy. Arthritis Rheum 1991;34:1218-27.

[2]Rudwaleit M, van der Heijde D, Landewé R et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009;68:777-83.

[3]Gazeau P, Cornec D, Timsit MA et al. Classification criteria versus physician’s opinion for considering a patient with inflammatory back pain as suffering from spondyloarthritis. Joint Bone Spine 2018;85:85-91.

Disclosure of Interests:

None declared

Clinical and laboratory correlates of lung disease and cancer in adults with idiopathic hypogammaglobulinaemia

Idiopathic hypogammaglobulinaemia, including common variable immune deficiency (CVID), has a heterogeneous clinical phenotype. This study used data from the national UK Primary Immune Deficiency (UKPID) registry to examine factors associated with adverse outcomes, particularly lung damage and malignancy. A total of 801 adults labelled with idiopathic hypogammaglobulinaemia and CVID aged 18-96 years from 10 UK cities were recruited using the UKPID registry database. Clinical and laboratory data (leucocyte numbers and serum immunoglobulin concentrations) were collated and analysed using uni- and multivariate statistics. Low serum immunoglobulin (Ig)G pre-immunoglobulin replacement therapy was the key factor associated with lower respiratory tract infections (LRTI) and history of LRTI was the main factor associated with bronchiectasis. History of overt LRTI was also associated with a significantly shorter delay in diagnosis and commencing immunoglobulin replacement therapy [5 (range 1-13 years) versus 9 (range 2-24) years]. Patients with bronchiectasis started immunoglobulin replacement therapy significantly later than those without this complication [7 (range 2-22) years versus 5 (range 1-13) years]. Patients with a history of LRTI had higher serum IgG concentrations on therapy and were twice as likely to be on prophylactic antibiotics. Ensuring prompt commencement of immunoglobulin therapy in patients with idiopathic hypogammaglobulinaemia is likely to help prevent LRTI and subsequent bronchiectasis. Cancer was the only factor associated with mortality. Overt cancer, both haematological and non-haematological, was associated with significantly lower absolute CD8(+) T cell but not natural killer (NK) cell numbers, raising the question as to what extent immune senescence, particularly of CD8(+) T cells, might contribute to the increased risk of cancers as individuals age.

Accuracy assessment of online glucose monitoring by a subcutaneous enzymatic glucose sensor during exercise in patients with type 1 diabetes treated by continuous subcutaneous insulin infusion

AIM

Online continuous glucose monitoring (CGM) during physical exercise would be highly useful in patients with insulin-treated diabetes. For this reason, this study assessed whether such a goal could be reached with a subcutaneous 'needle-type' enzymatic sensor.

METHODS

Ten patients (five women/five men), aged 51 ± 12 years, with type 1 diabetes for 24 ± 11 years treated by continuous subcutaneous insulin infusion (CSII) for more than 1 year (HbA1c: 7.5 ± 0.8%) performed a 30-min bout of exercise at a constant high-intensity load (15% above their individual ventilatory threshold) on a cycle ergometer. All patients wore a subcutaneous 'needle-type' enzymatic glucose sensor linked to a portable monitor (Guardian(®) RT, Medtronic-MiniMed, Northridge, CA, USA) that had been inserted the previous evening. Sensor calibration was performed against capillary blood glucose immediately before the exercise. CGM values were recorded every 5 min from T(-10) to T(+30), then every 10 min during the recovery period from T(+30) to T(+90). These recorded values were compared with blood glucose assays performed on simultaneously collected venous samples.

RESULTS

Sensor functioning and tolerability raised no problems except for one sensor that could not be adequately calibrated. Data from this patient were excluded from the data analysis. An average blood glucose decrease of 63 ± 63 mg/dL (3.5 ± 3.5 mmol/L) (median decrease: 58 mg/dL [3.22 mmol/L]; range: -3 mg/dL [0.16 mmol/L] to 178 mg/dL [9.8 mmol/L]) occurred during exercise bouts, while CGM values decreased by 38 ± 49 mg/dL (2.11 ± 2.72 mmol/L) (median: 32 mg/dL [1.7 mmmol/L]; range: -15 mg/dL [0.83 mmol/L] to 58 mg/dL [3.22 mmol/L]). Cumulative paired glucose values (n = 135) could be analyzed. The correlation factor between CGM and blood glucose values was 0.957 with an intercept of 0.275. The mean difference between paired values according to Bland-Altman analysis was 10 ± 31 mg/dL (0.56 ± 1.72 mmol/L). Clarke error grid analysis showed 91% of paired points in A and B zones, while 0%, 9% and 0% of paired points were in the C, D and E zones, respectively.

CONCLUSION

Blood glucose changes during intensive physical-exercise bouts performed by CSII-treated type 1 diabetes patients can be estimated with acceptable clinical accuracy by online CGM.

Actinides and decay products in selected produce and bioindicators in the vicinity of a uranium plant

Cypress needles collected at the edge of the Malvési uranium facility (SW France) exhibit enhanced activities of actinides and some decay products (uranium, americium, plutonium, (230)Th, (226)Ra) compared to a remote site. These enhanced activities resulted from the release of U via smokestacks and passive release from former artificial ponds located inside the nuclear site. Enhanced activities are also observed in selected produce (wheat, lettuce, fruits) sampled from the edge of the site. However, excess actinides measured in wheat grains in 2007 are inconsistent with the activities and the uranium ratio measured in the soils. This result suggests that the studied annual crops were contaminated mainly through the short-term release of airborne actinides, and that other transfer pathways, such as, uptake through the roots or adhesion of soil particles, were negligible.

Isotopic evidence of natural uranium and spent fuel uranium releases into the environment

Uranium and plutonium isotopes were measured in soils, sediments and waters in an area subject to the past and present discharges from the uranium conversion plant of Malvési (France). The isotopes (236)U and (239)Pu are well known activation products of uranium and they prove to be powerful tracers of spent fuel releases in soils and sediments. On the other hand (234)U and (238)U activities measured in waters can be used to distinguish between releases and background uranium sources. Such findings contribute to improve the monitoring of the actinides releases by nuclear fuel facilities (mining sites, conversion, enrichment and fuel plants, reprocessing plants).

Accuracy of continuous subcutaneous glucose monitoring with the GlucoDay in type 1 diabetic patients treated by subcutaneous insulin infusion during exercise of low versus high intensity

AIM

The GlucoDay allows continuous glucose monitoring by subcutaneous microdialysis in sedentary conditions. To validate it when glycaemia may undergo rapid and dramatic changes, we investigated its accuracy during two exercise sessions with markedly different glucose disposal rates.

METHODS

Nine male diabetic patients, aged 32-61, treated by insulin pumps, first underwent a standard maximal exercise-test designed for determining the maximal oxygen consumption and the first ventilatory threshold (Vt1). Then two 30 min steady-state workloads at 15% below and 15% above the Vt1 were performed in random order with the GlucoDay, and measurement of CHO oxidation rates was made by indirect calorimetry.

RESULTS

CHO oxidation during exercise at +15% Vt1 was higher (+943.5 mg/min, ie +45.5%, P<0.01) than during exercise at -15% Vt1 No hypoglycaemia occurred. Due to breakages of 39% of subcutaneous probes, eleven steady-state sessions in 7 subjects allowed to compare 141 paired glucose (sensor vs. venous) determinations. The Clarke error grid situates 92.9% of glucose values within the A zone and 6.4% within the B zone, while only one pair of values (0.7%) falls in the D zone. Venous glucose tended to decrease more rapidly than sensor glucose during exercise. Bland-Altman plots evidence for a few cases of underestimation of venous glucose at high intensity.

CONCLUSIONS

This study showed satisfactory accuracy of the GlucoDay during exercise. A slight lag time in sensor values likely explains a few discrepancies that do not appear as clinically meaningful. Reduction of probe fragility and confirmed sensor accuracy in hypoglycaemia would further support applicability of GlucoDay at exercise.

Glycerol and NEFA kinetics in long-term fasting king penguins: phase IIversusphase III

In spontaneously fasting birds such as penguins, below a body mass threshold corresponding to the phase II—phase III transition, a metabolic and hormonal shift occurs and feeding behaviour is stimulated(`refeeding signal'). The major aim of this study was to determine whether a decrease in non-esterified fatty acid (NEFA) release from adipose tissue could be a component of this signal. Lipolytic fluxes and primary triacylglycerol:fatty acid (TAG:FA) cycling were determined in vivoin breeding, fasting king penguins (Aptenodytes patagonicus) using continuous infusions of 2-[3H]glycerol and 1-[14C]palmitate under field conditions. In phase II (after approximately 8 days of fasting, large fat stores, body protein spared, N=8), the rate of appearance (Ra) of glycerol and of NEFA were 5.7±0.8 and 10.5±0.4 μmol kg-1min-1, respectively, and the percentage of primary TAG:FA cycling was 41±7%. In phase III (after approximately 25 days of fasting, fat stores reduced by fourfold, increased body protein catabolism, N=9), Ra glycerol kg-1 body mass remained unchanged,whereas Ra glycerol kg-1 fat mass and Ra NEFA kg-1 body mass were increased by 2.8-fold and 1.5-fold, respectively. Increased Ra glycerol kg-1 fat mass was possibly the result of a 3.5-fold increase in circulating glucagon, the increased Ra NEFA kg-1 body mass being attributable to decreased primary TAG:FA cycling. Thus, triggering of the refeeding signal that redirects the behavior of fasting, incubating penguins from incubation towards the search for food after entrance into phase III cannot be ascribed to a reduction in lipolytic fluxes and NEFA availability.

Delivery of multiple epitopes by recombinant detoxified adenylate cyclase of Bordetella pertussis induces protective antiviral immunity

CyaA, the adenylate cyclase toxin from Bordetella pertussis, can deliver its N-terminal catalytic domain into the cytosol of a large number of eukaryotic cells and particularly into professional antigen-presenting cells. We have previously identified within the primary structure of CyaA several permissive sites at which insertion of peptides does not alter the ability of the toxin to enter cells. This property has been exploited to design recombinant CyaA toxoids capable of delivering major histocompatibility complex (MHC) class I-restricted CD8(+) T-cell epitopes into antigen-presenting cells and to induce specific CD8(+) cytotoxic T-lymphocyte (CTL) responses in vivo. Here we have explored the capacity of the CyaA vector carrying several different CD8(+) T-cell epitopes to prime multiple CTL responses. The model vaccine consisted of a polyepitope made of three CTL epitopes from lymphocytic choriomeningitis virus (LCMV), the V3 region of human immunodeficiency virus gp120, and chicken ovalbumin, inserted at three different sites of the catalytic domain of genetically detoxified CyaA. Each of these epitopes was processed on delivery by CyaA and presented in vitro to specific T-cell hybridomas. Immunization of mice by CyaA toxoids carrying the polyepitope lead to the induction of specific CTL responses for each of the three epitopes, as well as to protection against a lethal viral challenge. Moreover, mice primed against the vector by mock CyaA or a recombinant toxoid were still able to develop strong CTL responses after subsequent immunization with a recombinant CyaA carrying a foreign CD8(+) CTL epitope. These results highlight the potency of the adenylate cyclase vector for induction of protective CTL responses with multiple specificity and/or broad MHC restriction.

Refeeding signal in fasting-incubating king penguins: changes in behavior and egg temperature

This study is directed toward understanding the process of feeding stimulation ("refeeding signal") that has been suggested to operate below a body mass threshold or critical metabolic status in spontaneously fasting birds. Behavior and egg temperature (T(egg)) were continuously monitored by video monitoring and biotelemetry, respectively, in fasting-incubating king penguins kept in a pen to prevent relief by the partner until spontaneous egg abandonment. Penned birds fasted 10 days more and lost 1.2 kg more than birds relieved normally by their partner, abandoning the egg about 1 wk after reaching a critical body mass. Definitive egg abandonment was preceded by transitory abandonments of progressively increasing duration during which time the birds went further and further away from their egg. There were marked interindividual differences but on average transitory abandonments began 36 +/- 5 h before the definitive abandonment and were paralleled by resumption of display songs signaling the readiness of the bird to depart for feeding. T(egg) was maintained at around 35.7 degrees C during normal incubation but significantly decreased the last 2 days before egg abandonment. These changes are interpreted as reflecting a stimulation to refeed at a threshold body mass corresponding to a critical fat store depletion. Thus the fasting-incubating king penguin appears to be an interesting animal model for understanding the long-term metabolic control of feeding behavior in relation to energy status.

Lipid composition of blood platelets and erythrocytes of southern elephant seal (Mirounga leonina) and antarctic fur seal (Arctocephalus gazella)

Erythrocyte and blood platelet phospholipid compositions were studied in three elephant seals and two fur seals, two species of marine mammals living in the Subantarctic region feeding on preys rich in (n-3) polyunsaturated fatty acids. Results were compared with those reported for related species and humans. In erythrocytes, the phospholipid (PL) and cholesterol (CHOL) contents were lower in pinnipeds than in humans. Phosphatidylcholine (PC) levels were higher in elephant seals than in fur seals, with a reverse trend for phosphatidylethanolamine (PE) and phosphatidylserine (PS). Both species had lower SM/PC ratios and PE plasmalogen concentrations than human. Erythrocytes were richer in (n-3) fatty acids (FA) in pinnipeds than in humans. In platelets, the PL content was lower and the CHOL content higher in elephant seals than in humans or in other phocid seal species studied to date. The SM/PC ratio was much higher than in other seal species or in man. In both species, the proportion of PE plasmalogens was higher in platelets than in erythrocytes. PL were more saturated in elephant seals than in fur seals. These results suggest that the erythrocytes and platelets of wild marine mammals may prove useful models to study the influence of dietary lipids on the structure and hemostatic function of these cells.

Lipid composition of erythrocytes and thrombocytes of a subantarctic seabird, the king penguin

Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n-3 polyunsaturated FA. Results were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other birds, cardiolipin levels were unexpectedly high (4%). Very long chain n-3 FA were abundant (13-27%) in phosphatidylethanolamine (PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n-3 FA, 22:6n-3 was the most abundant in all PL (2-20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels of n-3 FA (9-12%) were 1.5-2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%). The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of avian thrombocytes and erythrocytes.

In vivo induction of CTL responses by recombinant adenylate cyclase of Bordetella pertussis carrying multiple copies of a viral CD8(+) T-cell epitope

Bordetella pertussis adenylate cyclase toxin (ACT) is one of the few known protein toxins penetrating directly into the cytosol of target cells across their cytoplasmic membrane without the need for endocytosis. This capacity of ACT was recently exploited for in vivo delivery of single viral CD8(+) T-epitopes into MHC class I-presenting cells and induction of protective antiviral cytotoxic T-cell (CTL) responses. Here, we have explored the potential of the cell-invasive adenylate cyclase domain of the toxin to deliver larger antigens by evaluating the epitope-specific CTL responses induced by constructs bearing one to four copies of the CD8(+) T-epitope from the nucleoprotein of the lymphocytic choriomeningitis virus. The increase in the number of copies of the epitope was accompanied by a moderate decrease of the specific cell invasiveness of the ACT protein and did not lead to further enhancement of the level of induced epitope-specific CTL cells in mice, as compared to ACT with a single copy of the epitope. These results demonstrate the capacity of ACT to deliver larger heterologous antigens comprising several epitopes for antigenic presentation in vivo.

Therapy of murine tumors with recombinant Bordetella pertussis adenylate cyclase carrying a cytotoxic T cell epitope

Bordetella pertussis secretes an invasive adenylate cyclase toxin, CyaA, that is able to deliver its N-terminal catalytic domain into the cytosol of eukaryotic target cells directly through the cytoplasmic membrane. We have shown previously that recombinant CyaA can be used to deliver viral CD8+ T cell epitopes to the MHC-class I presentation pathway to trigger specific CTL responses in vivo. In the present study, we show that mice immunized with a detoxified but still invasive CyaA carrying a CD8+ T cell epitope of OVA developed strong epitope-specific CTL responses, which kill tumor cells expressing this Ag. Treating mice with this recombinant molecule after the graft of melanoma cells expressing OVA induced a strong survival advantage compared with control animals. To our knowledge, this study represents the first demonstration that a nonreplicative and nontoxic vector carrying a single CTL epitope can stimulate efficient protective and therapeutic antitumor immunity.

Charge-dependent translocation of Bordetella pertussis adenylate cyclase toxin into eukaryotic cells: implication for the in vivo delivery of CD8(+) T cell epitopes into antigen-presenting cells

Bordetella pertussis secretes a calmodulin-activated adenylate cyclase toxin, CyaA, that is able to deliver its N-terminal catalytic domain (400-aa residues) into the cytosol of eukaryotic target cells, directly through the cytoplasmic membrane. We have previously shown that CyaA can be used as a vehicle to deliver T cell epitopes, inserted within the catalytic domain of the toxin, into antigen-presenting cells and can trigger specific class I-restricted CD8(+) cytotoxic T cell responses in vivo. Here, we constructed a series of recombinant toxins harboring at the same insertion site various peptide sequences of 11-25 amino acids, corresponding to defined CD8(+) T cell epitopes and differing in the charge of the inserted sequence. We show that inserted peptide sequences containing net negative charges (-1 or -2) decreased or completely blocked (charge of -4) the internalization of the toxin into target cells in vitro and abolished the induction of cytotoxic T cell responses in vivo. The blocking of translocation due to the inserted acidic sequences can be relieved by appropriate mutations in the flanking region of CyaA that counterbalance the inserted charges. Our data indicate that (i) the electrostatic charge of the peptides inserted within the catalytic domain of CyaA is critical for its translocation into eukaryotic cells and (ii) the delivery of T cell epitopes into the cytosol of antigen-presenting cells by recombinant CyaA toxins is essential for the in vivo stimulation of specific cytotoxic T cells. These findings will help to engineer improved recombinant CyaA vectors able to stimulate more efficiently cellular immunity.

Determination of 226Ra in mineral drinking waters by alpha liquid scintillation with rejection of beta-gamma emitters

The radiotoxicity of radium isotopes (especially the long-half-life 226Ra) requires their monitoring in drinking waters or nuclear wastes. We studied the applicability of the PERALS method of detection (photon electron rejecting alpha liquid scintillation) for radium measurement. This method combines alpha liquid scintillation with pulse shape analysis for beta rejection and specific chemical extractants included in the scintillating cocktail. Radium is separated by an extractive-scintillator cocktail called RADAEX containing 2-methyl-2-heptylnonanoic acid (HMHN) and dicyclohexano-21-crown-7 (Cy(2)21C7) as extractant molecules. The variation of the radium extraction has been studied relative to pH, salt concentrations, anion and cation effects, and the volume ratio between aqueous and organic phases. The main parameter affecting the radium extraction in mineral drinking water is its complexation by inorganic anions, especially sulfate. Due to the lack of thermodynamic data, some complexation constants had to be determined. For instance, the value reported in this paper for radium sulfate (log beta = 2.58 +/- 0.22) is in good agreement with that from the literature. The knowledge of complexation constants allows the determination of radium extraction recovery for any solution when the inorganic anion concentrations had been measured by capillary zone electrophoresis. The detection limit for this technique is found to be equal to 0.006 Bq.L-1 using only 6 mL of sample solution for analysis. Several French mineral waters have been studied and the results compared with determinations of uranium and thorium concentrations by ICPMS and time-resolved laser induced fluorescence (TRLIF).

Intracytoplasmic delivery of listeriolysin O by a vaccinal strain of Bacillus anthracis induces CD8-mediated protection against Listeria monocytogenes

The facultative intracellular pathogen Listeria monocytogenes secretes a 58-kDa hemolysin, listeriolysin O (LLO), that allows bacteria to access the cytoplasm and to multiply inside infected cells. LLO is also a protective Ag required for the development of specific immunity. We studied the capacity of a new bacterial vector, derived from an attenuated strain of Bacillus anthracis, to deliver in vivo LLO and to induce protection against L. monocytogenes infection. The hly gene encoding LLO was fused to a B. anthracis regulatory region induced in vivo and was integrated into a resident plasmid of this bacterium. This recombinant strain secreted a functional LLO in vitro and inside phagosomes of bone marrow macrophages. This LLO production enabled the conversion of the extracellular replicating B. anthracis into an intracytoplasmic bacterium. LLO+ B. anthracis thus mimicked the intracellular behavior of L. monocytogenes in macrophages. Specific protection of mice against lethal doses of L. monocytogenes was induced by immunization with LLO+ B. anthracis. The immunity was mediated by CD8+ T lymphocytes and was associated with the activation of LLO-specific MHC class I-restricted CD8+ CTL, able to recognize the immunodominant H-2d-restricted epitope 91-99 of LLO. This study, therefore, suggests that intracytoplasmic delivery of LLO by B. anthracis is sufficient to induce a MHC class I-restricted CD8-mediated protection against L. monocytogenes. The LLO+ B. anthracis recombinant strain represents a potential vector for delivering foreign Ags involved in CD8-mediated protective responses.

Intracytoplasmic delivery of listeriolysin O by a vaccinal strain of Bacillus anthracis induces CD8-mediated protection against Listeria monocytogenes

The facultative intracellular pathogen Listeria monocytogenes secretes a 58-kDa hemolysin, listeriolysin O (LLO), that allows bacteria to access the cytoplasm and to multiply inside infected cells. LLO is also a protective Ag required for the development of specific immunity. We studied the capacity of a new bacterial vector, derived from an attenuated strain of Bacillus anthracis, to deliver in vivo LLO and to induce protection against L. monocytogenes infection. The hly gene encoding LLO was fused to a B. anthracis regulatory region induced in vivo and was integrated into a resident plasmid of this bacterium. This recombinant strain secreted a functional LLO in vitro and inside phagosomes of bone marrow macrophages. This LLO production enabled the conversion of the extracellular replicating B. anthracis into an intracytoplasmic bacterium. LLO+ B. anthracis thus mimicked the intracellular behavior of L. monocytogenes in macrophages. Specific protection of mice against lethal doses of L. monocytogenes was induced by immunization with LLO+ B. anthracis. The immunity was mediated by CD8+ T lymphocytes and was associated with the activation of LLO-specific MHC class I-restricted CD8+ CTL, able to recognize the immunodominant H-2d-restricted epitope 91-99 of LLO. This study, therefore, suggests that intracytoplasmic delivery of LLO by B. anthracis is sufficient to induce a MHC class I-restricted CD8-mediated protection against L. monocytogenes. The LLO+ B. anthracis recombinant strain represents a potential vector for delivering foreign Ags involved in CD8-mediated protective responses.

Anti-viral protection conferred by recombinant adenylate cyclase toxins from Bordetella pertussis carrying a CD8+ T cell epitope from lymphocytic choriomeningitis virus

The elucidation of the mechanisms of antigen presentation by major histocompatibility complex class I molecules has stimulated the search for nonreplicative vectors that could deliver CD8+ T cell epitopes to the cytosol of antigen-presenting cells to trigger the activation of specific cytotoxic T lymphocytes (CTLs) in vivo. In the present study, we investigated the potential ability of an invasive adenylate cyclase toxin from Bordetella pertussis, carrying a CD8+ T cell epitope from the nucleoprotein of lymphocytic choriomeningitis virus (LCMV), to stimulate protective anti-viral immunity. Mice immunized with this recombinant toxin developed strong CTL responses against LCMV-infected target cells. Moreover, these mice were protected against an intracerebral challenge with a virulent strain of LCMV that killed all nonimmunized mice within 7 days. This protection was abolished after in vivo elimination of CD8+ T cells. A mutant toxin devoid of adenylate cyclase activity (i.e., cAMP synthesizing activity) was constructed by insertion of a dipeptide into the catalytic site of the molecule. This genetically detoxified invasive toxin carrying the LCMV epitope stimulated a strong CTL response against both peptide-coated and virus-infected target cells, and mice immunized with this molecule were fully protected against a lethal intracerebral LCMV challenge. To our knowledge, this study represents the first demonstration that a genetically detoxified bacterial toxin carrying a viral CTL epitope can stimulate efficient protective immunity.

Expression and immune response to foreign epitopes in bacteria. Perspectives for live vaccine development

We previously developed a general procedure which allows the genetic coupling of a chosen foreign linear epitope in different regions of a carrier protein. By using as carriers, two bacterial envelope proteins, the LamB and MalE proteins of E. coli K12, we were able to express the same epitope in different sites of the two proteins and in different compartments of the bacteria. This allowed us to analyze the influence of the localization in E. coli cells of a foreign B-cell epitope on the induction of specific antibody responses, and the role of the molecular environment on the immunological properties of foreign B- or T-cell epitopes, using either purified hybrid proteins or live recombinant bacteria. Several LamB and MalE hybrid proteins were expressed in the aroA attenuated strain of S. typhimurium, SL3261. Immunizations of mice with live recombinant bacteria by the intravenous route showed that it was possible to induce humoral responses against inserted foreign sequences. In order to improve the in vivo stability of the plasmids carrying the different contructions, and to increase the amounts of recombinant LamB and MalE hybrid proteins expressed in vivo, the LamB and malE genes were placed under the control of the anaerobically inducible pnirBpromoter control. The genetic factors susceptible of influencing the immune response to recombinant Salmonella in mice were also studied.

Peripheral effects of three novel non-peptide tachykinin NK1 receptor antagonists in the anaesthetized rat

Three novel non-peptide tachykinin NK1 receptor antagonists were assessed on the transient fall in mean arterial blood pressure and the salivation induced by i.v. substance P (0.65 nmol/kg) in the urethane-anaesthetized rat. LY303241 ((R)-1-[N-(2-methoxybenzyl)acetylamino]-3-(1H-indol-3-yl)-2-[N-(2-(4- phenylpiperazin-1-yl)acetyl)amino]propane), LY303870 ((R)-1-[N-(2-methoxybenzyl)acetylamino]-3-(1H-indol-3-yl)-2-[N-(2-(4-(++ +piperidin-1 -yl)piperidin-1-yl)acetyl)amino]propane) and LY306740 ((R)-1-[N-(2-methoxybenzyl)acetylamino]-3-(1H-indol-3-yl)-2-[N-(2-(4 -cyclohexylpiperazin-1-yl)acetyl)amino]propane) (65 nmol-9 micromol/kg i.v.; 5 min earlier) inhibited both the vasodepressor and salivary responses to substance P in a dose-dependent manner. LY303241 and LY306740 were more potent in inhibiting the vascular response to substance P while LY303870 was more potent in inhibiting the salivary response. LY303870 and LY306740 were devoid of direct effects while LY303241 decreased blood pressure and heart rate for 1 and 10 min, respectively. The antagonists act in a stereoselective and specific manner since the opposite (S) enantiomers of LY303870 (LY306155) and LY306740 (LY307679) failed to block the effects of substance P. In addition, LY303241, LY303870 and LY306740 neither affected the hypotension and the salivation induced by carbachol nor the increases in mean arterial pressure and heart rate induced by the tachykinin NK2 receptor agonist [beta-Ala8]neurokinin A-(4-10). Only LY303241 attenuated the decreases in mean arterial pressure and heart rate evoked by the tachykinin NK3 receptor agonist senktide. LY303870 and LY306740 appear to be the most interesting antagonists since they act in a specific and selective manner at the tachykinin NK1 receptor. The difference in the order of potency of the three antagonists to inhibit the hypotension and salivation elicited by substance P could be ascribed to their pharmacodynamic features or to the existence of different signal transduction mechanisms or receptor subtypes.

Control by H-2 genes of the Th1 response induced against a foreign antigen expressed by attenuated Salmonella typhimurium

Attenuated salmonellae represent an attractive vehicle for the delivery of heterologous protective antigens to the immune system. Here, we have investigated the influence of the genetic background of the host which regulates the growth and elimination of Salmonella cells on the cellular response induced against a foreign antigen delivered by an aroA Salmonella strain. We have tested CD4+ T-cell responses (cell proliferation and cytokine production) in various mouse strains following immunization with Salmonella typhimurium SL3261 expressing a high level of the recombinant Escherichia coli MalE protein. We were able to detect a CD4+ T-cell response against the recombinant MalE protein only in a restricted number of mouse strains, whereas all mice produced good levels of anti-MalE immunoglobulin G antibodies. The Ity gene did not play a major role in these differences in T-cell responses, since both Ity-resistant and -susceptible strains of mice were found to be unresponsive to MalE delivered by recombinant salmonellae. In contrast, when B10 congenic mice were used, a correlation was established between MalE-specific T-cell unresponsiveness and H-2 genes. The discrepancies described in this paper in the ability of various strains of mice to develop an efficient Th1 response against a recombinant antigen displayed by a live Salmonella vaccine underscore the difficulties that can be encountered in the vaccination of human populations by such a strategy.

Induction of cytotoxic T-cell response by optimal-length peptides does not require CD4+ T-cell help

In several experimental models, synthetic peptides were shown to activate efficiently cytotoxic T-lymphocyte (CTL) responses and therefore represent an attractive strategy to develop new vaccines. However, the mechanisms by which they induce CTL responses are not yet fully understood. Several studies using 15 16-mer peptides previously demonstrated that CD4 helper T cells are required to induce optimal CTL responses with synthetic peptides. However, recently it was suggested that shorter 8 12-mer peptides could have an increased in vivo immunogenicity. In the present study, we therefore investigated if such optimal-length peptides still require CD4+ T-cell help to activate CTL responses. To address this question three synthetic peptides containing different viral CTL epitopes were injected into mice depleted of CD4+ or CD8+ T cells using specific monoclonal antibodies or into mice genetically deficient in those T-cell populations. Our results clearly established that activation of CTL responses by those short optimal peptides does not require CD4+ T-cell help and therefore suggested that high-density binding of peptides to major histocompatibility complex class I molecules on the surface of antigen-presenting cells is required for direct activation of CD8+ T cells, independently of CD4+ T-cell help.

In vivo induction of CTL responses by recombinant adenylate cyclase of Bordetella pertussis carrying viral CD8+ T cell epitopes

Exogenous Ags enter the endosomal pathway and are presented to CD4+ T cells in association with class II molecules whereas endogenously synthesized Ags, such as viral proteins, are presented to CD8+ T cells in association with MHC class I molecules. Therefore, most CTL activation strategies use live vectors although an alternative possibility could be to deliver the epitope into the cytosol by targeting it to an invasive nonreplicative vector. The adenylate cyclase toxin of Bordetella pertussis is able to invade a large number of eukaryotic cells and to deliver its catalytic domain to the cytosol of the cells. In the present study, we have tested the in vivo immunogenicity of recombinant adenylate cyclase toxins expressing CTL epitopes either from the nucleoprotein of lymphocytic choriomeningitis virus or from the V3 region of HIV-1 gp120. BALB/c mice immunized with these toxins developed high specific CTL responses that were shown to be mediated by class I-restricted CD8+ CTL. The induction of CTL responses by recombinant toxins did not require CD4+ T cells and the cytotoxic activity persisted 2 mo after immunization. The activation of CTL responses by the recombinant adenylate cyclase toxin required the full-length invasive activity of the toxin but did not depend upon its catalytic adenylate cyclase activity as demonstrated with a genetically inactivated recombinant toxin expressing the lymphocytic choriomeningitis virus epitope. This genetically detoxified invasive toxin represents, therefore, an attractive new vector for CTL activation.

In vivo induction of CTL responses by recombinant adenylate cyclase of Bordetella pertussis carrying viral CD8+ T cell epitopes

Exogenous Ags enter the endosomal pathway and are presented to CD4+ T cells in association with class II molecules whereas endogenously synthesized Ags, such as viral proteins, are presented to CD8+ T cells in association with MHC class I molecules. Therefore, most CTL activation strategies use live vectors although an alternative possibility could be to deliver the epitope into the cytosol by targeting it to an invasive nonreplicative vector. The adenylate cyclase toxin of Bordetella pertussis is able to invade a large number of eukaryotic cells and to deliver its catalytic domain to the cytosol of the cells. In the present study, we have tested the in vivo immunogenicity of recombinant adenylate cyclase toxins expressing CTL epitopes either from the nucleoprotein of lymphocytic choriomeningitis virus or from the V3 region of HIV-1 gp120. BALB/c mice immunized with these toxins developed high specific CTL responses that were shown to be mediated by class I-restricted CD8+ CTL. The induction of CTL responses by recombinant toxins did not require CD4+ T cells and the cytotoxic activity persisted 2 mo after immunization. The activation of CTL responses by the recombinant adenylate cyclase toxin required the full-length invasive activity of the toxin but did not depend upon its catalytic adenylate cyclase activity as demonstrated with a genetically inactivated recombinant toxin expressing the lymphocytic choriomeningitis virus epitope. This genetically detoxified invasive toxin represents, therefore, an attractive new vector for CTL activation.

Cell-invasive activity of epitope-tagged adenylate cyclase of Bordetella pertussis allows in vitro presentation of a foreign epitope to CD8+ cytotoxic T cells

The adenylate cyclase (AC) toxin (CyaA) of Bordetella pertussis has an invasive catalytic domain (AC domain) which penetrates the cytoplasmic membrane of a variety of eukaryotic cells and intoxicates them by unregulated synthesis of cyclic AMP. Previous work led to identification of five permissive sites in the AC domain at which heterologous peptides are accommodated without affecting its enzymatic properties. We have constructed a set of CyaA toxins tagged at these permissive sites by insertion of a CD8+ T-cell epitope, RPQASGVYMGNLTAQ, from the nucleoprotein of lymphocytic choriomeningitis virus. Introduction of the epitope at any of the five sites did not affect the capacity of the toxin to deliver its AC domain into target cells. Moreover, the toxin with the inserted epitope was shown to sensitize target cells for lysis by epitope-specific CD8+ cytotoxic T lymphocytes in vitro, showing that the tagged AC was processed for presentation of the lymphocytic choriomeningitis virus epitope in association with the major histocompatibility complex class I molecules. This finding indicates that by virtue of delivery of foreign epitopes into the antigen-presenting cells, purpose-designed recombinant CyaAs may be useful for induction of specific major histocompatibility complex class I-restricted cell-mediated immunity also in vivo.

Genetic control of antibody responses induced against an antigen delivered by recombinant attenuated Salmonella typhimurium

Recombinant derivatives of nonpathogenic bacteria such as attenuated Salmonella typhi have the potential to be used for delivery of heterologous antigens to the immune system. Genetic factors may modulate the immune responses to these live attenuated organisms and could therefore modify the immunogenicity of future human vaccines. In the present study, we compared the antibody responses of Ity or H-2 congenic strains of mice to a foreign antigen expressed by the murine attenuated aroA S. typhimurium strain. Our results demonstrate that the Ity gene may modulate the antibody responses to the foreign antigen but that the major genetic influence is exerted by H-2 genes, which control the capacity of mice to respond to the antigen expressed by recombinant attenuated Salmonella cells. This genetic control is related to differences in responsiveness of different strains of mice to low doses of antigen. Increasing the amount of foreign antigen expressed by recombinant Salmonella cells overcame the genetic restriction of these responses. These findings are potentially of great importance for the design of live vaccines for humans and show that care must be taken to optimize the amount of foreign antigen delivered to the immune system.

Molecular and cellular parameters controlling the immunogenicity of foreign B- or T-cell epitopes expressed by recombinant vectors

Extensive work is being performed to develop live recombinant bacterial vaccines. The use of non-pathogenic bacteria or attenuated strains derived from pathogens may allow protection against the pathogen and at the same time induce immunity against one or several foreign antigens expressed by the recombinant micro-organism. Several bacteria such as attenuated Salmonella or BCG have been used successfully in several experimental models to induce protective immune responses against several pathogens. However, the presentation to the immune system of a foreign antigen in a context different from the natural one may greatly modify the characteristics of elicited immune responses. It is therefore of the utmost importance to establish rules concerning the influence of the vector on the immunogenicity of recombinant antigens. Using a bacterial system that allows the expression of genetically engineered hybrid proteins, we have analysed: 1) the role of the molecular environment on the immunogenicity of foreign B- or T-cell epitopes; 2) the influence of the cellular location of a foreign B-cell epitope on the induction of specific immune responses; 3) the role of the bacterial vector (E. coli or Salmonella typhimurium) on the isotypic characteristic of antibody responses induced against the recombinant antigen. These studies revealed the complexity of the mechanisms which control the immunogenicity of foreign B- or T-cell epitopes expressed by recombinant vectors.

Immune responses to hybrid maltose-binding proteins

The Escherichia coli maltose-binding protein is a highly versatile carrier protein allowing the construction of genetically engineered hybrid proteins. It accepts large fusions to both C- and N-termini as well as the insertion of shorter peptides at 'permissive sites' within the continuity of the protein. We have genetically inserted immunogenic peptides corresponding to defined viral B- and T-cell epitopes into two permissive sites: one at amino acid site 133, the other at site 303. The hybrid proteins are easily purifiable and immunogenic, inducing peptide-specific B- and T-cell responses. When delivered by live bacteria (E. coli K12 and aroA Salmonella typhimurium) antibody responses can be induced against both the MalE carrier and the inserted B-cell epitope. We discuss the induction of T-cell responses by bacterial delivery systems.

In vivo induction of cytotoxic T cell response by a free synthetic peptide requires CD4+ T cell help

Most attempts to induce CTL responses by in vivo priming with free synthetic peptides have been unsuccessful so far. However, two separate studies have recently succeeded in inducing antiviral CTL responses by immunizing mice with unmodified free synthetic peptides derived from nucleoproteins from either lymphocytic choriomeningitis virus or Sendai virus. In the present study, we have analyzed the cellular mechanisms by which the lymphocytic choriomeningitis virus synthetic peptide induced CTL responses. We demonstrated that this peptide, which was previously shown to be recognized by CD8+ T cells, also contains a helper CD4+ T cell epitope. It stimulates in vivo both CD4+ T cell-mediated CTL response. The in vivo elimination of CD4+ T cells by treatment with a mAb was shown to strongly reduce the antipeptide CTL response. This study therefore demonstrates that to be able to induce CTL responses, a peptide has to stimulate both CD4+ and CD8+ T cell subset.

In vivo induction of cytotoxic T cell response by a free synthetic peptide requires CD4+ T cell help

Most attempts to induce CTL responses by in vivo priming with free synthetic peptides have been unsuccessful so far. However, two separate studies have recently succeeded in inducing antiviral CTL responses by immunizing mice with unmodified free synthetic peptides derived from nucleoproteins from either lymphocytic choriomeningitis virus or Sendai virus. In the present study, we have analyzed the cellular mechanisms by which the lymphocytic choriomeningitis virus synthetic peptide induced CTL responses. We demonstrated that this peptide, which was previously shown to be recognized by CD8+ T cells, also contains a helper CD4+ T cell epitope. It stimulates in vivo both CD4+ T cell-mediated CTL response. The in vivo elimination of CD4+ T cells by treatment with a mAb was shown to strongly reduce the antipeptide CTL response. This study therefore demonstrates that to be able to induce CTL responses, a peptide has to stimulate both CD4+ and CD8+ T cell subset.

Postnatal development of 5-HT1 receptors: [3H]5-HT binding sites and 5-HT induced adenylate cyclase activations in rat brain cortex

The postnatal development of the 5-HT1 receptor system was studied in young rat brain cortex from birth to adulthood (14 successive ages). The high-affinity binding of [3H]5-HT was low at birth but developed markedly between the 8th and the 15th day postnatally. The basal adenylate cyclase activity produced 50 pmoles cAMP/mg protein/min at birth and increased from the 8th to the 15th day. 5-HT could stimulate the adenylate cyclase activity in adult rat brain cortex with two different affinity constants: Km = 1 nM and Km = 0.5 microM; these low- and high-affinity constants presumably correspond to 5-HT1A and 5-HT1non-A.non-B.non-C (5-HT1D) respectively. These two activities developed parallelly from the 14-15th to the 28th day. The 8-hydroxy-2-(di-n-propylamino-tetralin) (8-OH-DPAT)-induced activity described a curve similar to the one that corresponded to 10 microM 5-HT. These results establish that 5-HT1A and 5-HT1non-A.non-B.non-C receptors mainly develop during the synaptogenesis.

5-Hydroxytryptamine stimulates two distinct adenylate cyclase activities in rat brain: high-affinity activation is related to a 5-HT1 subtype different from 5-HT1A, 5-HT1B, and 5-HT1C

5-HT binding sites of the 5-HT1 type are heterogeneous and appear to comprise several subtypes (5-HT1A, 5-HT1B and 5-HT1C); their physiological role is as yet unclear. The stimulation of adenylate cyclase induced by 5-HT has been investigated in membrane fractions prepared from rat brain cortex. Enzymatic activity was determined by measuring cAMP production with an HPLC technique. It was shown that 5-HT stimulates adenylate cyclase activity with 2 activation constants (Kact): one shows a high apparent affinity (Kact = 0.8 nM) and the other a lower apparent affinity (Kact = 0.30 microM). The latter activity, induced by micromolar concentrations of 5-HT, was inhibited by spiperone at concentrations that block 5-HT1A binding. 5-Methoxytryptamine, bufotenin, and LSD also had a stimulatory biphasic effect on adenylate cyclase activity, whereas trifluoromethylphenylpiperazine, 5-carboxyamidotryptamine, 8-hydroxy-(2-di-n-propylamino)tetralin, RU 24969 had a monophasic effect. Enzyme activation by drugs acting in the micromolar range was inhibited by spiperone (1 microM), suggesting a link between this activation and 5-HT1A sites. On the other hand, the high-affinity activation of the enzyme induced by 5-HT, 5-methoxytryptamine, bufotenin, LSD, and the activation induced by TFMPP were not inhibited by spiperone (1 microM), by propranolol (3 microM), or by mesulergine (0.1 microM), which selectively block 5-HT1A, 5-HT1B, and 5-HT1C sites. Inhibition was produced by dihydroergotamine, methysergide, cinanserin, and mianserin, but not by naloxone, phenoxybenzamine, and phentolamine. Therefore, these activations seem related to 5-HT1 receptors but not to 5-HT1A, 5-HT1B, or 5-HT1C sites. Accordingly, binding of [3H]5-HT to 5-HT1-like sites was examined in the presence of spiperone (1 microM) and propranolol (3 microM); in these conditions, a high-affinity site (KD = 3.4 nM) was indeed revealed. The relative potencies of a series of drugs that stimulate or inhibit the activation of the adenylate cyclase with a high affinity and their ability to inhibit this binding of [3H]5-HT showed a positive correlation, strongly suggesting a direct relation between this recognition site for 5-HT and the production of a second messenger (cAMP). Moreover, this potential receptor is shown to be heterogeneously distributed within the brain, and was localized postsynaptically at serotonergic synapses.