A sensitive enzyme immunoassay of human thyroid-stimulating hormone (TSH) using bispecific F(ab')2 fragments recognizing polymerized alkaline phosphatase and TSH

Relationship between inflammatory biomarkers and testosterone levels in male master athletes and non-athletes

BACKGROUND

Aging is often associated with low-grade systemic inflammation and reduced anabolic hormone levels. To investigate whether lifelong exercise training can decrease the age-related low-grade inflammation and anabolic hormone levels, we examined hormonal and inflammatory parameters among highly-trained male masters athletes and age-matched non-athletes.

METHODS

From 70 elite power and endurance master athletes - EMA (51.3 ± 8.0 yr), 32 young controls - YC (23.7 ± 3.9 yr) and 24 untrained age-matched controls - MAC (47.2 ± 8.0 yr) venous blood was drawn to measure inflammatory parameters (interleukin-6 [IL-6], tumor necrosis factor-α [TNF-α] and interleukin-10 [IL-10]) and circulating hormones (luteinizing hormone [LH], total testosterone, estradiol, sex hormone-binding globulin [SHBG] and free androgen index [FAI]).

RESULTS

EMA showed a better anti-inflammatory status than MAC (higher IL-10 and IL-10/IL-6 ratio and lower IL-6), but a lower anti-inflammatory status than YC (higher TNF-α) (p < 0.05). The MAC group had lower testosterone levels compared to the YC and EMA group (p < 0.05), and lower estradiol levels and testosterone/LH ratio compared to YC (p < 0.05). In the control groups (MAC and YC), testosterone correlated negatively with age and proinflammatory parameters, and positively with anti-inflammatory parameters.

CONCLUSION

Elite master athletics elevated levels of anti-inflammatory cytokines above that seen in non-athlete peers and mitigated the age-related reduction in testosterone levels.

Predicting relapse of Graves' disease following treatment with antithyroid drugs

The aim of the present study was to monitor long term antithyroid drug treatments and to identify prognostic factors for Graves' disease (GD). A total of 306 patients with GD who were referred to the Endocrinology Clinic at Weifang People's Hospital (Weifang, China) between August 2005 and June 2009 and treated with methimazole were included in the present study. Following treatment, patients were divided into non-remission, including recurrence and constant treatment subgroups, and remission groups. Various prognosis factors were analyzed and compared, including: Patient age, gender, size of thyroid prior to and following treatment, thyroid hormone levels, disease relapse, hypothyroidism and drug side-effects, and states of thyrotropin suppression were observed at 3, 6 and 12 months post-treatment. Sixty-five patients (21.2%) were male, and 241 patients (78.8%) were female. The mean age was 42±11 years, and the follow-up was 31.5±6.8 months. Following long-term treatment, 141 patients (46%) demonstrated remission of hyperthyroidism with a mean duration of 18.7±1.9 months. The average age at diagnosis was 45.6±10.3 years in the remission group, as compared with 36.4±8.8 years in the non-remission group (t=3.152; P=0.002). Free thyroxine (FT)3 levels were demonstrated to be 25.2±8.9 and 18.7±9.4 pmol/l in the non-remission and remission groups, respectively (t=3.326, P=0.001). The FT3/FT4 ratio and thyrotrophin receptor antibody (TRAb) levels were both significantly higher in the non-remission group (t=3.331, 3.389, P=0.001), as compared with the remission group. Logistic regression analysis demonstrated that elevated thyroid size, FT3/FT4 ratio and TRAb at diagnosis were associated with poor outcomes. The ratio of continued thyrotropin suppression in the recurrent subgroup was significantly increased, as compared with the remission group (P=0.001), as thyroid function reached euthyroid state at 3, 6 and 12 months post-treatment. Patients with GD exhibiting large thyroids, high pre-mediation TRAb levels and elevated FT3/FT4 ratios responded less markedly to antithyroid drug treatments, as compared with patients not exhibiting these prognostic factors. Furthermore, patients with large thyroids, post-medication ophthalmopathy and continued thyrotropin suppression demonstrated higher rates of recurrence.

Detection of Antigen-antibody Reaction Using a Fluorescent Probe and Its Application to Homogeneous Competitive-type Immunoassay for Insulin

The interaction of bovine insulin with anti-human insulin antibody (mAb) was examined using a fluorescent probe. The fluorescence intensity of fluoresceinthiocarbamyl (FTC)-insulin was increased by adding mAb, and the increase was saturated at 53% at a molar ratio of FTC-insulin to mAb of 2.0. Based on the change in fluorescence intensity, a standard curve of the homogeneous competitive-type immunoassay was constructed, and the detection range of insulin was found to be 50-400 nM.

Effects of amines and aminoalcohols on bovine intestine alkaline phosphatase activity

Bovine intestine alkaline phosphatase (BIALP) is widely used as a signaling enzyme in sensitive assays such as enzyme immunoassay (EIA). In this study, we evaluated the effects of various aminoalcohols and amines on the activity of BIALP in the hydrolysis of p-nitrophenyl phosphate (pNPP) at pH 9.8, at 20 °C. The k(cat) values at 0.05 M diethanolamine, 0.1 M triethanolamine, and 0.2 M N-methylethanolamine were 190±10, 840±30, and 500±10 s(-1), respectively. The k(cat) values increased with increasing concentrations of diethanolamine, triethanolamine, and N-methylethanolamine and reached 1240±60, 1450±30, and 2250±80 s(-1), respectively, at 1.0M. On the other hand, the k(cat) values at 0.05-1.0M ethanolamine, ethylamine, methylamine, and dimethylamine were in the range of 100-600 s(-1). These results indicate that diethanolamine, triethanolamine and N-methylethanolamine highly activate BIALP and might be suitable as a dilution buffer of BIALP in EIA. Interestingly, the K(m) values increased with increasing concentrations of diethanolamine and N-methylethanolamine, but not triethanolamine: the K(m) value at 1.0M diethanolamine (0.83±0.15 mM) was 12-fold higher than that at 0.05M (0.07±0.01 mM), and that at 1.0M N-methylethanolamine (2.53±0.20 mM) was 14-fold higher than that at 0.2M (0.18±0.02 mM), while that at 1.0M triethanolamine (0.31±0.01 mM) was similar as that at 0.2M (0.25±0.01 mM), suggesting that the mechanisms of BIALP activation are different between the aminoalcohols.

A sensitive TSH assay in spot-coated microwells utilizing recombinant antibody fragments

We have developed a novel TSH immunoassay based on a simplified test protocol suitable for point-of-care testing yet providing 3rd generation TSH assay sensitivity. The antibody density and the functional solid phase capacity were improved up to six-fold by capturing the site-specifically biotinylated recombinant Fab fragment or single chain antibody fragment onto the surface of immobilized streptavidin. An important mechanism for obtaining a low limit of detection (0.003 mIU/l) was the reduction of the coated area to a size ("spot") more closely coinciding with the excitation beam. The reporter technology was based on time-resolved fluorometric detection of inherently fluorescent europium chelates of high quantum yield. The ready-to-use assay concept employed the all-in-one (Aio!) principle--holding all assay components in a dry form in the microtitration well--to provide a simple assay protocol. Direct signal measurement from the surface was done after the washing step without a separate development step. It is concluded that size reduction and site-specific labeling of the antibodies to create a surface with high functional capacity provides a rapid, highly sensitive immunoassay.

Analysis of the binding of bispecific monoclonal antibodies with immobilized antigens (human IgG and horseradish peroxidase) using a resonant mirror biosensor

The interaction between two monoclonal antibodies (mAbs) and their corresponding bispecific antibody (bAb) with immobilized antigens has been examined using a resonant mirror biosensor (IAsys). BAbs were produced by cell fusion. The analysed panel of affinity-purified antibodies included two parental mAbs, one specific to human IgG (hIgG), and another specific to horseradish peroxidase (HRP), and a bAb derived thereof (anti-hIgG/HRP). The real-time analysis showed the drastic differences in the avidity of bivalent anti-HRP mAbs and anti-HRP shoulder of bAbs. Thus, the observed equilibrium association constant (K(ass)) of anti-HRP mAbs was about 50 times higher that of anti-HRP shoulder of bAbs. The ratio of association rate constants (k(ass)) of mAbs and bAbs was about two, due to the statistical factor of two binding sites per bivalent antibody molecule. However, the dissociation rate constant (k(diss)) of anti-HRP shoulder of bAbs was 21 times higher k(diss) of anti-HRP mAbs. The comparison with the theoretical model shows that these observations are consistent only with a situation in which bivalent binding of mAbs with immobilized HRP predominates over monovalent binding. On the contrary, the second parental mAb (anti-hIgG) did not show the increase in avidity due to bivalent binding, compared to the anti-hIgG shoulder of bAbs, suggesting that this mAb was bound monovalently to immobilized hIgG. The K(ass) values determined by solid-phase radioimmunoassay (RIA) yielded figures almost overlapping with those obtained by IAsys. The results of the comparison of bAbs and mAbs are discussed from the viewpoint of the use of bAbs in heterogeneous systems. On the other hand, these data demonstrate that real-time analysis of antibody binding parameters in IAsys biosensor is valuable for the selection of mAbs and bAbs with desired features, for different fields of application.

The comparison of the ability of monoclonal antibodies directed to different proteins (human IgG, human myoglobin and HRP) and bispecific antibodies derived thereof to bind antigens immobilized on a surface of a solid phase

BACKGROUND

Bindings of mouse monoclonal antibodies (mAbs) and affinity purified bispecific antibodies (bAbs), derived thereof, to antigens adsorbed on immunoplates have been compared, using ELISA and RIA methods.

METHODS

The analysed panel of antibodies included mAbs specific to human myoglobin (Mb), human IgG (hIgG) and horseradish peroxidase (HRP) and biologically produced bAbs with double specificity to Mb and HRP, and to hIgG and HRP.

RESULTS

The degree of difference between different mAbs and corresponding bAbs varied markedly from antibody to antibody, depending on whether the parental mAbs could bind immobilized antigens bivalently. The observed equilibrium binding constant (K(obs)) for anti-HRP mAbs was 21-38 times higher that of anti-HRP site of bAbs (anti-hIgG/HRP or anti-Mb/HRP, respectively), due to bivalent binding of mAbs. Anti-Mb mAbs also bound bivalently with immobilized Mb. On the contrary, anti-hIgG mAbs bound monovalently with immobilized hIgG in the same conditions. The avidity of anti-Mb/HRP bAbs increased, if both antigens were simultaneously adsorbed on a solid phase.

CONCLUSIONS

The obtained data indicate that the use of bAbs in heterogeneous immunoassays instead of traditional mAb-enzyme conjugates hardly can provide the significant gain in assay performance if parental mAbs bind bivalently.

Pepsin digestion of a mouse monoclonal antibody of IgG1 class formed F(ab')(2) fragments in which the light chains as well as the heavy chains were truncated

In the preparation of F(ab')(2) fragments of monoclonal antibodies (mAbs) of IgG class, heavy (H) chains are truncated by pepsin and light (L) chains are remained intact. However, F(ab')(2) fragments formed by pepsin-digestion of a mouse mAb PM373, which was of the IgG1 class and raised against human prostate specific antigen (PSA), indicated that the L chains of 31 kDa were cleaved into 23-kDa fragments as well as the cleavage of H chains of 50 kDa into 28-kDa fragments. On the other hand, F(ab')(2) fragments formed by digesting the mAb by cathepsin D showed that the L chains were intact and the H chains were truncated. The immunoreactivities against PSA of the F(ab')(2) fragments containing the intact L chains and those containing the truncated L chains were almost the same as that of the parental mAb, suggesting that the truncation of the L chains does not affect the interaction of the mAb with its specific antigen.

The use of bispecific antibodies in tumor cell and tumor vasculature directed immunotherapy

To overcome dose limiting toxicities and to increase efficacy of immunotherapy of cancer, a number of strategies are under development for selectively redirecting effector cells/molecules towards tumor cells. Many of these strategies exploit the specificity of tumor associated antigen recognition by monoclonal antibodies. Using either hybridoma fusion, chemical derivatization or molecular biology technology, antibodies with dual specificity can be constructed. These so called biospecific antibodies (BsAbs) have been used to redirect the cytolytic activity of a variety of immune effector cells such as cytotoxic T lymphocytes, natural killer cells, neutrophils and monocytes/macrophages to tumor cells. Local administration of BsAbs, either alone or in combination with autologous effector cells, is highly effective in eradicating tumor cells. In contrast, systemic application of BsAb at present is only suitable for adjuvant treatment of minimal residual disease due to poor tumor cell accessibility. As an alternative, angiogenesis related determinants on tumor blood vessels can be exploited for the selective delivery of effector cells/molecules apart from being used to inhibit angiogenesis. Important advantages of this strategy is that the endothelial cell associated target epitope(s) are easy accessible. The dependence of tumor growth on the tumor's blood supply also renders tumor endothelial cells an attractive target for therapy. Although still in its infancy, attacking the tumor's blood supply for example by delivering coagulation factors or toxins, or by BsAb directed immunotherapies holds great promise for antineoplastic therapy.

Method for the preparation of bispecific F(ab')2mu fragments from mouse monoclonal antibodies of the immunoglobulin M class and characterization of the fragments

Bispecific F(ab')2mu fragments (Bs F(ab')2mu) binding simultaneously both sialyl Lewis A antigen (SLA) and human carcinoembryonic antigen (CEA) were prepared by disulfide bond exchange between F(ab')2mu fragments derived from IgM monoclonal antibodies (mAbs) against SLA and CEA, and were purified to homogeneity in a one-step procedure of hydrophobic interaction HPLC. The final yield of Bs F(ab')2mu from F(ab')2mu fragments was 70-78%, and the purity was higher than 98%. The immunoreactivities of the Bs F(ab')2mu fragments against SLA and CEA were almost the same as those of the respective parental F(ab')2mu fragments. The dissociation constant (0.17 microM) of the Bs F(ab')2mu for CEA was in good agreement with that of the parental F(ab')2mu fragments. Although the number of applications of IgM mAbs is restricted because of the large molecular mass and low solubility, Bs F(ab')2mu might, nevertheless, be a useful tool for immunotherapy and immunodiagnosis.

A biotin-avidin labeled enzyme immunoassay for the quantitation of serum TSH using protein-layered solid phase

A sensitive enzyme immunoassay for serum TSH has been developed utilizing the tight binding between biotin and avidin, and three layered protein polystyrene beads as solid phase. To increase binding capacity of TSH and sensitivity of the assay, the polystyrene beads were coated sequentially with mouse immunoglobulin as first layer, rabbit antimouse immunoglobulin as second layer and monoclonal anti-TSH as third layer. A serum sample was incubated simultaneously with a monoclonal anti-TSH immobilized polystyrene beads and a second monoclonal anti-TSH covalently attached to biotin. After washing, the antibody bound serum TSH-anti-TSH-biotin complex is reacted with horseradish peroxidase (HRP)-labeled avidin. Following a second wash, the bound HRP activity was measured colorimetrically. Reproducible results were obtained within 4 hours for serum TSH in the range between 0 microIU/ml and 50 microIU/ml with detection limit of 0.1 microIU per test.