Synthesis and preliminary biological evaluation of a 99mTc‐labeled hypericin derivative as a necrosis avid imaging agent

Mono‐[¹²³I]iodohypericin and mono‐[¹²³I]iodohypericin monocarboxylic acid are iodine‐123‐labeled hypericin derivatives which have shown great promise in preclinical studies as necrosis avid imaging agents in animal models of infarction. In view of the more attractive properties of a ^99mTc‐labeled hypericin derivative, we have synthesized a conjugate of protohypericin monocarboxylic acid with S‐benzoylmercaptoacetyldiglycyl‐diaminopentane in an overall yield of 15%. The conjugate was labeled with technetium‐99m by exchange labeling at pH 10 in a labeling yield of 95% followed by photocyclization to yield ^99mTc‐mercaptoacetyldiglycyl‐1,5‐diaminopentylene hypericincarboxamide (^99mTc‐13). The negatively charged ^99mTc‐13 complex was purified by reversed phase high‐pressure liquid chromatography and the log P_7.4 was determined to be 2.36. In normal NMRI mice, the complex showed slow hepatobiliary clearance while plasma clearance was rapid. The tracer was evaluated in rats with reperfused hepatic infarction by ex vivo autoradiography, gamma counting and histochemical techniques. Unlike the radioiodinated hypericin derivatives, the new tracer agent did not show preferential uptake in necrotic tissue on autoradiography and gamma counting techniques. Conjugation of hypericin with a ^99mTc‐chelate, resulting in a change in size, charge and lipophilicity, had a profound effect on the necrosis avidity of the tracer agent. The results show that ^99mTc‐13 is not suitable for imaging necrosis. Copyright © 2008 John Wiley & Sons, Ltd.     

Delayed expansion of a restricted T cell repertoire by low-density TCR ligands

The role of TCR ligand density (i.e. the number of antigen-MHC complexes) in modulating the diversity of a T cell response selected from a pool of naive precursors remains largely undefined. By measuring early-activation markers up-regulation and proliferation following stimulation with staphylococcal enterotoxin A (SEA), we demonstrate that decreasing the ligand dose below an optimal concentration leads to the delayed activation of a restricted set of TCRVbeta-bearing T cells, with the specific, non-stochastic exclusion of some TCRVbeta+ T cells from the activated pool. Our results suggest that the failure of these TCRVbeta-bearing T cells to reach the activation threshold at sub-optimal ligand concentration is due to the inefficiency of TCR engagement, as measured by TCR internalization, and does not correlate with the relative precursor frequency in the non-immune repertoire. Moreover, even at SEA concentrations that lead to the simultaneous proliferation of all SEA-reactive T cells, we observe marked differences in the ability to secrete cytokines among the different responsive TCRVbeta-bearing T cells. Altogether, our results indicate that the development of a T cell response to a scarce display of ligand significantly narrows TCR repertoire diversity by mechanisms that involve focusing of the repertoire on the expansion of those T cells with the highest avidity of TCR engagement.     

Avidity and titer of immunoglobulin G subclasses to Porphymmonas gingivalis in adult periodontitis patients

The relative avidity and titer of antibodies representing the 4 immunoglobulin G (IgG) subclasses (IgG1-4) reactive with Porphyromonas gingivalis, P. gingivalis-lipopolysaccharide (-LPS), streptokinase (SK) and tetanus toxoid (TT) in the sera of patients having adult periodontitis and of healthy controls were measured. Patient antibody titers to P. gingivalis and P. gingivalis-LPS were found to be significantly elevated for IgG, IgG1 (no P. gingivalis-LPS antibodies) and IgG2. The predominant antibody response to P. gingivalis and P. gingivalis-LPS occurred in the IgG2 subclass. When the relative avidity of the antibodies to P. gingivalis and P. gingivalis-LPS were examined, no significant differences between control and patient sera could be identified. However, anti-P. gingivalis and P. gingivalis-LPS antibodies were found to possess significantly lower relative avidity than either SK or TT antibodies. The IgG1 subclass antibodies to P. gingivalis, SK and TT all appeared to be of high relative avidity. In contrast, anti-P. gingivalis and P. gingivalis-LPS of the IgG2 subclass were of significantly lower relative avidity. Since the predominant humoral response to P. gingivalis occurs in the IgG2 subclass, the low relative avidity of these antibodies predominates in measurements of whole serum activity.     

Non-invasive detection and quantification of acute myocardial infarction in rabbits using mono-[123I]iodohypericin microSPECT.

AIMS: Mono-[(123)I]iodohypericin ([(123)I]MIH) has been reported to have high avidity for necrosis. In the present study, by using rabbit models of acute myocardial infarction, we explored the suitability of [(123)I]MIH micro single photon emission computed tomography (microSPECT) for non-invasive visualization of myocardial infarcts in comparison with [(13)N]ammonia micro positron emission tomography (microPET) imaging, postmortem histomorphometry, and [(123)I]MIH autoradiography. METHODS AND RESULTS: Fourteen rabbits were divided into four groups. The left circumflex coronary artery was permanently occluded in group A (n = 3), reperfused by releasing the ligature after 15 min in group B (n = 3) or 90 min in group C (n = 6), or not occluded in group D (n = 2). Animals received [(13)N]ammonia microPET perfusion imaging 18 h after infarct induction followed by microSPECT imaging at 2-3.5, 9-11, and 22-24 h post injection (p.i.) of [(123)I]MIH. The cardiac images were assembled into polar maps for assessment of tracer uptake. Animals were sacrificed and the excised heart was sliced for autoradiography, triphenyl tetrazolium chloride, and haematoxylin-eosin staining. Using [(123)I]MIH microSPECT, infarcts were well delineated at 9 h p.i. Mean microSPECT infarct size was 38.8 and 32.7% of left ventricular area for groups A and C, respectively, whereas group B showed low uptake of [(123)I]MIH. Highest mean infarct/viable tissue activity ratio of 61/1 was obtained by autoradiography in group C animals at 24 h p.i. CONCLUSION: The study indicates the suitability of [(123)I]MIH for in vivo visualization of myocardial infarcts.     

Antibody response of Echinococcus granulosus infected mice: Protoscolex specific response during infection is associated with decreasing specific IgG1/IgG3 ratio as well as decreasing avidity

The antibody response was followed during 68 weeks in 17 Balb/c mice intraperitoneally (i.p.) infected with Echinococcus granulosus protoscoleces (PSC) and in three mice i.p. immunized with dead PSC. Titres of antibodies recognizing peptidic and glucidic PSC epitopes, as well as their isotypic and avidity profiles were followed by ELISA. In addition, antigen recognition patterns were analysed by immunoblot. The response against carbohydrate epitopes was dominant in infected and immunized mice but stronger in the first group. Infected mice showed similar profiles of specific IgG and IgM with maximum titres from week 38 to 53. Although IgG1 and IgG3 were the predominant antibody subclasses, the ratio of IgG1/IgG3 antibody titres as well as antibody avidity decreased during the experiment, encompassing a decrease in recognition of peptidic epitopes. Immunized mice did not show significant levels of specific IgM and, after week 15, showed IgG titres lower than the infected mice. IgG1 was the predominant IgG subclass during all the experiment with background levels of IgG3. The mean Ab avidity was high and showed no significant changes during immunization. Different patterns of response were thus produced by dead and developing live parasites. Although high avidity IgG1 antibodies were early found in both cases, lower avidity IgG3 antibodies were increasingly produced afterwards only in infected animals. The isotype switch and avidity decrease observed only during infection are consistent with a possible parasitic mechanism to evade host immunity .     

Human Antibody Responses to Avian Influenza A(H7N9) Virus, 2013

Understanding host antibody response is crucial for predicting disease severity and for vaccine development. We investigated antibody responses against influenza A(H7N9) virus in 48 serum samples from 21 patients, including paired samples from 15 patients. IgG against subtype H7 and neutralizing antibodies (NAbs) were not detected in acute-phase samples, but ELISA geometric mean titers increased in convalescent-phase samples; NAb titers were 20–80 (geometric mean titer 40). Avidity to IgG against subtype H7 was significantly lower than that against H1 and H3. IgG against H3 was boosted after infection with influenza A(H7N9) virus, and its level in acute-phase samples correlated with that against H7 in convalescent-phase samples. A correlation was also found between hemagglutinin inhibition and NAb titers and between hemagglutinin inhibition and IgG titers against H7. Because of the relatively weak protective antibody response to influenza A(H7N9), multiple vaccinations might be needed to achieve protective immunity.     

Structural aspects of cross-reactivity and its relation toantibody affinity

In the context of IgE/allergen interactions, affinity is largely determined by the stability of the allergen-IgE complex: a low affinity is usually equated with a rapid dissociation of the complex. Regular solid-phase assays are not well suited for affinity estimates because of multivalency effects, unstirred layer effects and invisible antibodies. Elution of IgE bound to solid-phase coupled allergen might be a good measure of intrinsic affinity, provided that reassociation of antibodies is prevented by a high concentration of soluble allergen. Allergen-mediated IgE-dependent triggering of a mast cell is presumably a two-step process. During the first step, the allergen is bound to a cell-bound IgE antibody and dragged over the cell surface. The second step is the interaction between this cell-bound allergen and another IgE antibody. The hypothesis is that the affinity requirements for the first step are higher than for the second. The implication is that a mast cell can be triggered by a single high-affinity antibody in combination with one or more low-affinity antibodies.     

Evaluation of the new LIAISON® CMV IgG,IgM and IgG Avidity II assays

BackgroundThe diagnosis of CMV infection is challenging and the quality of serological laboratory testing is critical, especially in pregnancy and in the determination of transplant recipients and donors serostatus.ObjectivesEvaluate the performances of the new LIAISON^® CMV II line: LIAISON^® CMV IgG II, LIAISON^® CMV IgM II and LIAISON^® CMV IgG Avidity II in comparison with the routine methods used in our laboratory.Study designThe evaluation of LIAISON^® CMV IgG II and LIAISON^® CMV IgM II was performed on both prospective routine samples and retrospective selected samples for a total of 383 sera. CMV IgG avidity was assessed with 88 samples.ResultsThe overall agreement was 98.8% for the IgG and 95% for the IgM on the routine population. On selected retrospective samples, excellent agreement was found in the seronegative and past infection groups. In the recent infection group, discordances were observed in 7.1% of IgG and 13.1% of IgM. No recent infection was missed with LIAISON^®. Avidity agreement with VIDAS^® was 81%. On 51 sera with a known time of infection, no high avidity was found in the group infected for less than 3 months and 82% of the samples showed a high avidity in the group infected for more than 3 months.ConclusionThe performances of the fully automated LIAISON^® CMV II line assays are comparable to those of the reference methods used in our lab for both prospective and selected populations. This new CMV line is a useful tool for the diagnosis of CMV infections and CMV immune status in clinical settings     

影响分化型甲状腺癌肺转移患者预后的临床因素

目的:探讨影响分化型甲状腺癌（DTC）肺转移患者预后的临床因素。方法:回顾性分析西安交通大学第一附属医院2011年至2017年间接受放射性碘治疗的DTC肺转移患者。根据随访患者影像学检查结果、无进展生存率（PFS）和癌症特异性生存率评估其肺转移病灶碘摄取能力和血清甲状腺球蛋白（Tg）水平对预后的影响。结果:最终63例患者被纳入分析。在中位随访35个月（5~91个月）后,多变量分析结果提示肺转移灶摄碘阴性,但Tg分泌阳性是DTC肺转移的独立预后因素,其是导致较短PFS的独立危险因素（P=0.032）。结论:肺转移灶摄碘阴性,但Tg分泌阳性是预测DTC肺转移不良结局最重要的预后因素。     

Salivary anti-RSV IgA antibodies and respiratory infections during the first year of life in atopic and non-atopic infants

Salivary SIgA antibodies against RS virus were studied in 105 children during the first year of life. The infants were divided into groups according to their risk of atopy. At birth 13 neonates showed measurable amounts of SIgA to RS virus. In another 26 children specific antibodies were detected but in concentrations too low for quantitative analysis. During the first year of life this increased to 29 antibody-positive samples with measurable amounts of antibody and 39 with concentrations too low for quantitative determination. At this time 8 children of the high risk group had developed symptoms of allergy. None of these children had measurable amounts of SIgA anti-RSV in their saliva. In comparison, 10 of the remaining 26 high risk infants without symptoms of allergy did have such antibodies. Atopic infants had significantly more respiratory infections during the first year of life than nonatopic infants. The avidity of SIgA anti-RSV in neonatal samples was significantly higher than avidity determined in breast milk SIgA but comparable to the avidity of serum IgG. During the first year of life a continuing decrease of salivary SIgA avidity was observed.