Journal of immunoassay最新文献

Sustainable management of economically important squid requires monitoring of changes in their abundance, which are related inter alia, to their success in the food chain. The highest mortality is expected in the paralarval stages, which are prone to starvation. Causes of starvation may be linked to the lack of suitable prey. A multiple detection system was developed for the simultaneous identification of five putative zooplankton prey in the guts of paralarval Chokka squid, Loligo vulgaris reynaudii, by employing polyclonal rabbit antisera in conjunction with solid phase immunoassays. Specificities of antisera were validated by ELISA screening against different zooplankton taxa. Cross-reactions observed with ELISA were minimized through manipulation of antibody and antigen concentrations resulting in more specific detection of target prey antigens when used in an immunodot assay. Application of this optimised immunoassay detected multiple predation in paralarval squid samples collected from diverse areas in the Agulhas Bank ecosystem on the south coast of South Africa.

The effect of pH of the blocking solution on the non-specific sorption of peroxidase conjugates to the 0.63-cm formylated polystyrene beads was studied. Anti-G-HRP and BSA-HRP sorption was shown to dramatically depend on pH of blocking protein solutions and was minimum at pH=pI. Sorption of G-HRP weakly depended on pH of the blocking buffer. The blocking efficiency of proteins on unmodified beads, as well as of Tween-20 on formylated beads appeared to be pH independent. The optimized blocking step resulted in a multiple decrease in the non-specific sorption of conjugates on formylated beads.

The aim of this study was to investigate whether the ex vivo whole blood culture (WBC) assay system can be used to detect pyrogens in blood from patients with symptoms of sepsis. Blood samples from 35 patients with symptoms of sepsis were assayed for bacterial contamination using the radiometric blood culture assay. Serum from the same patients were screened for IL-6, C-reactive protein (CRP) and pyrogens using the whole blood culture assay. Serum samples from 26 patients tested positive for pyrogens. Of the 26 patients with pyrogenic serum, 15 had elevated serum IL-6 levels and 19 had elevated CRP levels. Only two of the samples had positive blood cultures as detected by the routine radiometric assay. Both of these patients had high serum CRP and pyrogen levels, while only one of them had an elevated serum IL-6 level. These results show that the WBC is very sensitive in detecting pyrogens in serum of patients. This technique can be a useful tool to quantitate pyrogens in sera from patients with symptoms of sepsis and to determine whether their clinical symptoms are caused by pyretic substances in their circulatory system.

Hybridoma cells were prepared by immunizing mice with carboxylic derivatives of atrazine conjugate to bovine serum albumin. After the screening of culture supernatant of hybridomas, five cell lines producing monoclonal antibodies were established and 1.8-5.3 ml of ascitic fluid per mouse was obtained from each cell line. The protein A affinity purification yielded 0.35-0.65 mg per ml of ascitic fluid from each cell line. The characterization studies in terms of sensitivity and specificity indicate that MAb 2F9 and MAb 4B9 showed the best responses with atrazine and its group of ametryne and cyanazine, using microtiter plate coated with simazine derivative of 6-amino hexanoic acid; no cross-reactivity was shown with simazine and cyanuric chloride.

Antisera were raised in rabbits against two mouse monoclonal anti-porcine growth hormone (pGH) antibodies. Anti-idiotypic antibodies were isolated from rabbit sera by successive passage over immunoadsorbent columns of normal mouse Ig (mIg), followed by the specific immunizing monoclonal and elution from the latter. Enzyme linked immunoadsorbent assay (ELISA) for anti-idiotype and free idiotype were established. While showing specificity for their respective inducing monoclonals, anti-idiotypes also cross reacted in varying degrees with other anti-pGH monoclonals regardless of specificity differences between the antibodies, demonstrating the presence of a cross-reactive idiotype.

A direct sandwich enzyme-linked immunosorbent assay (ELISA), employing affinity purified antivenom antibodies specifically recognizing the homologous venom, was developed for species-specific detection of bothropic venom. The method is based on a two-step affinity purification of the specific antibodies. A species monovalent antivenom is adsorbed onto a venom adsorbent containing heterologous venoms from the Bothrops, Crotalus and Lachesis genera. The species-specific antibodies obtained, are then adsorbed onto a second venom adsorbent containing only the homologous venom for the removal of non antivenom antibodies. Venom concentrations of 0.1 and 1,000 ng/ml were specifically identified for Bothrops jararacussu and B. alternatus venom respectively.

Cytokines occur in biological systems at low levels of concentration, therefore assays developed to measure them must be very sensitive. Enzyme linked immunosorbent assays (ELISA's) developed using manufacturers recommended end points can detect cytokines to picogram levels but the lower parts of their standard curves can be unreliable. In this study the relative merits of different substrate systems - 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 2 forms of tetramethyl benzidine (TMB), were investigated with regard to assay sensitivity. Further, a signal amplification method involving biotinylated tyramine has been used to increase the absorbance signal and thus the assay sensitivity and to achieve a sigmoidal standard curve. The amplified assay approach has been applied successfully to achieve more sensitive detection of TNF-alpha and improve the sensitivity of assays for a wide range of other cytokines. The optimised amplification method is the same for all the cytokine ELISA's performed in this work and this enables them to be performed

Purified E.coli endotoxin, Gram negative bacteria and Gram positive bacteria induce IL-6 secretion by whole blood cultures (WBC's). Polymyxin B at concentrations greater than 2 U/ml completely inhibits IL-6 secretion caused by 10 EU/ml of endotoxin. Polymyxin B has no effect on IL-6 secretion by WBC's in the absence of endotoxin. The inhibition of endotoxin induced IL-6 secretion is Polymyxin B concentration dependent at concentrations less than 1 U/ml. IL-6 induction caused by E.coli is only partially inactivated by 8 U/ml Polymyxin B. Polymyxin B has no effect on IL-6 secretion caused by B.subtilis. Two pyrogenic batches of human serum albumin (HSA), as tested by the rabbit assay for pyrogens, were also investigated. Polymyxin B at 4 U/ml inhibits less than 40 % of IL-6 secretion caused by these pyrogenic HSA batches. All the endotoxin activity in HSA samples spiked with purified endotoxin is inhibited by Polymyxin B indicating that HSA does not protect endotoxin against Polymyxin B inhibition. These results indicate that the pyrogenicity of these HSA batches are caused by Polymyxin B inhibitable and non-inhibitable fractions. This study shows that pyrogenic substances other than endotoxin can contaminate batches of pharmaceutical products and that results obtained using the Limulus Amoebocyte Lysate (LAL) assay does not necessarily indicate the pyrogenic status of pharmaceutical products. The WBC assay for pyrogens, having a broader sensitivity range than the LAL assay, is a better indicator of the pyrogenic status of pharmaceutical products.

A procedure for standardizing Brucella abortus smooth lipopolysaccharide used in diagnostic tests for brucellosis is proposed. The procedure is based on the reactivity of antigen preparations with a panel of sera with or without antibody to B. abortus using a set of parameters established with 13 antigen preparations. For each serum dilution, a mean and two standard deviations were calculated in the indirect and competitive enzyme immunoassays. If data obtained with an antigen preparation, using the same serum dilutions, falls within the range established using two standard deviations, the antigen would be considered acceptable for diagnostic use.

It has been traditional to measure drug concentrations using high pressure liquid chromatography (HPLC). While this method is highly accurate, it is time consuming and requires the use of appropriate standards for identification of the compound. In addition, identification and quantification of drugs from patient samples requires significant manipulation to remove protein. In contrast, enzyme-linked immunoassays (EIA) are able to assay samples with a high degree of specificity, and are able to process multiple samples at a time. In addition, serum proteins do not interfere with sample quantification and samples may be tested without significant preparation. We describe the development of an EIA for the detection of ciprofloxacin in serum and dialysate samples. The immunoassay is specific for ciprofloxacin and is sensitive for picogram amounts of the antibiotic.