Determination of Domoic Acid Toxins in Shellfish by Biosense ASP ELISAA Direct Competitive Enzyme-Linked Immunosorbent Assay: Collaborative Study

A collaborative study was conducted on the Biosense amnesic shellfish poisoning (ASP) enzyme-linked immunosorbent assay (ELISA) for the determination of domoic acid (DA) toxins in shellfish in order to obtain interlaboratory validation data for the method. In addition, a method comparison study was performed to evaluate the ASP ELISA as an alternative to the current liquid chromatography (LC) reference method for DA determination. The study material comprised 16 shellfish samples, including blue mussels, Pacific oysters, and king scallops, spiked with contaminated mussel homogenates to contain 0.120 mg DA/kg shellfish flesh. The shellfish samples were extracted with 50% aqueous methanol, and the supernatants were directly analyzed. Sixteen participating laboratories in 10 countries reported data from the ASP ELISA, and 4 of these laboratories also reported data from instrumental LC analysis. The participating laboratories achieved interlaboratory precision estimates for the 8 Youden paired shellfish samples in the range of 1020% for RSDr (mean 14.8 4%), and 1329% for RSDR (mean 22.7 6%). The precision estimates for the ELISA data did not show a strong dependence on the DA concentration in the study samples, and the overall precision achieved was within the acceptable range of the Horwitz guideline with HorRat values ranging from 1.1 to 2.4 (mean HorRat 1.7 0.5). The analysis of shellfish samples spiked with certified reference material (CRM)-ASP-MUS-b gave recoveries in the range of 88122%, with an average recovery of 104 10%. The estimate on method accuracy was supported by a correlation slope of 1.015 (R2 = 0.992) for the determined versus the expected DA values. Furthermore, the correlation of the ASP ELISA results with those for the instrumental LC analyses of the same sample extracts gave a correlation slope of 1.29 (R2 = 0.984). This indicates some overestimation of DA levels in shellfish by the ELISA, but it is also a result of apparent low recoveries for the LC methods. This interlaboratory study demonstrates that the ASP ELISA is suitable for the routine determination and monitoring of DA toxins in shellfish, and that it offers a rapid and cost-effective methodology with high sample throughput.

Single-Laboratory Validation of the Biosense Direct Competitive Enzyme-Linked Immunosorbent Assay (ELISA) for Determination of Domoic Acid Toxins in Shellfish

Method validation was conducted for an enzyme-linked immunosorbent assay (ELISA) for the determination of domoic acid (DA) toxins, known to give amnesic shellfish poisoning (ASP) symptoms, in shellfish. The calibration curve range of the assay is approximately 10260 pg/mL, with a dynamic working range for DA toxins in shellfish from 0.01 to at least 250 mg/kg. The ASP ELISA showed no significant cross-reactivity to structural analogs, and proved to be robust to deliberate alterations of the optimal running conditions. The shellfish matrix effects observed with mussels, oysters, and scallops were eliminated by diluting shellfish extracts 1:200 prior to analysis, leading to a limit of detection at 0.003 mg/kg. Thirteen blank shellfish homogenates were spiked with certified mussel material containing DA to levels in the range of 0.125 mg DA/kg, and analyzed in quadruplicate on 3 different days. The relative standard deviation (RSD) under intra-assay repeatability conditions ranged from 6.5 to 13.1%, and under interassay repeatability conditions the RSD ranged from 5.7 to 13.4%, with a mean value of 9.3%. The recoveries ranged from 85.5 to 106.6%, with a mean recovery of 102.2%. A method comparison was conducted with liquid chromatography with ultraviolet detection, using naturally contaminated scallop samples (n = 27) with DA levels at 0244 mg/kg. The overall correlation coefficient was 0.960 and the slope of the regression was 1.218, indicating a good agreement between the methods.

Determination of domoic acid toxins in shellfish by biosense ASP ELISA--a direct competitive enzyme-linked immunosorbent assay: collaborative study

A collaborative study was conducted on the Biosense amnesic shellfish poisoning (ASP) enzyme-linked immunosorbent assay (ELISA) for the determination of domoic acid (DA) toxins in shellfish in order to obtain interlaboratory validation data for the method. In addition, a method comparison study was performed to evaluate the ASP ELISA as an alternative to the current liquid chromatography (LC) reference method for DA determination. The study material comprised 16 shellfish samples, including blue mussels, Pacific oysters, and king scallops, spiked with contaminated mussel homogenates to contain 0.1-20 mg DA/kg shellfish flesh. The shellfish samples were extracted with 50% aqueous methanol, and the supernatants were directly analyzed. Sixteen participating laboratories in 10 countries reported data from the ASP ELISA, and 4 of these laboratories also reported data from instrumental LC analysis. The participating laboratories achieved interlaboratory precision estimates for the 8 Youden paired shellfish samples in the range of 10-20% for RSD(r) (mean 14.8 +/- 4%), and 13-29% for RSDR (mean 22.7 +/- 6%). The precision estimates for the ELISA data did not show a strong dependence on the DA concentration in the study samples, and the overall precision achieved was within the acceptable range of the Horwitz guideline with HorRat values ranging from 1.1 to 2.4 (mean HorRat 1.7 +/- 0.5). The analysis of shellfish samples spiked with certified reference material (CRM)-ASP-MUS-b gave recoveries in the range of 88-122%, with an average recovery of 104 +/- 10%. The estimate on method accuracy was supported by a correlation slope of 1.015 (R2 = 0.992) for the determined versus the expected DA values. Furthermore, the correlation of the ASP ELISA results with those for the instrumental LC analyses of the same sample extracts gave a correlation slope of 1.29 (R2 = 0.984). This indicates some overestimation of DA levels in shellfish by the ELISA, but it is also a result of apparent low recoveries for the LC methods. This interlaboratory study demonstrates that the ASP ELISA is suitable for the routine determination and monitoring of DA toxins in shellfish, and that it offers a rapid and cost-effective methodology with high sample throughput.

Single-laboratory validation of the biosense direct competitive enzyme-linked immunosorbent assay (ELISA) for determination of domoic acid toxins in shellfish

Method validation was conducted for an enzyme-linked immunosorbent assay (ELISA) for the determination of domoic acid (DA) toxins, known to give amnesic shellfish poisoning (ASP) symptoms, in shellfish. The calibration curve range of the assay is approximately 10-260 pg/mL, with a dynamic working range for DA toxins in shellfish from 0.01 to at least 250 mg/kg. The ASP ELISA showed no significant cross-reactivity to structural analogs, and proved to be robust to deliberate alterations of the optimal running conditions. The shellfish matrix effects observed with mussels, oysters, and scallops were eliminated by diluting shellfish extracts 1:200 prior to analysis, leading to a limit of detection at 0.003 mg/kg. Thirteen blank shellfish homogenates were spiked with certified mussel material containing DA to levels in the range of 0.1-25 mg DA/kg, and analyzed in quadruplicate on 3 different days. The relative standard deviation (RSD) under intra-assay repeatability conditions ranged from 6.5 to 13.1%, and under interassay repeatability conditions the RSD ranged from 5.7 to 13.4%, with a mean value of 9.3%. The recoveries ranged from 85.5 to 106.6%, with a mean recovery of 102.2%. A method comparison was conducted with liquid chromatography with ultraviolet detection, using naturally contaminated scallop samples (n = 27) with DA levels at 0-244 mg/kg. The overall correlation coefficient was 0.960 and the slope of the regression was 1.218, indicating a good agreement between the methods.

Monoclonal antibody enzyme-linked immunosorbent assay to quantify vitellogenin for studies on environmental estrogens in the rainbow trout (Oncorhynchus mykiss)

Vitellogenin (VTG) induction has proved to be a valuable biomarker for assessing exposure to environmental estrogens in fish. The widespread use of VTG in this regard has lead to the need for standardized assays to quantify VTG, and monoclonal antibodies have the potential to help accomplish this. A VTG enzyme-linked immunosorbent assay (ELISA) was developed using a monoclonal antibody prepared against Atlantic salmon (Salmo salar) VTG (MAb BN-5) and its ability to quantify VTG in the rainbow trout (Oncorhynchus mykiss) compared with a rainbow trout vitellogenin (rt-VTG) ELISA that employed homologous polyclonal antibodies (PAb). In routine protocols, the working range of the homologous rt-PAb VTG ELISA was between 9 ng/ml and 70 ng/ml (80- 20% relative maximum binding [B/Bo]) with a 50% B/Bo of 25+/-0.9 ng/ml and inter- and intraassay variations at 50% B/Bo of 7% (n = 7) and 8% (n = 15), respectively. The working range of the MAb BN-5 VTG ELISA was between 60 ng/ml and 850 ng/ml (80-20% B/Bo) with a 50% B/Bo of 227+/-22 ng/ml and inter- and intraassay variations at 50% B/Bo of 5% (n = 10) and 9% (n = 12), respectively. In the routine protocols, detection limits for measurement of plasma VTG in rainbow trout (at 80% B/Bo; and given the requirement to dilute plasma to a minimum of 1:10 for the assays) were 90 ng/ml for the polyclonal rt-VTG assay and approximately 600 ng/ml in the monoclonal antibody assay. In juvenile female rainbow trout exposed to a series of doses of estradiol-17beta (E2) and 4-tert nonylphenol (4-NP), there were no differences in the vitellogenic responses measured in the PAb and MAb BN-5 VTG ELISAs. The monoclonal MAb BN-5 VTG ELISA is likely to be of considerable value for studies on environmental estrogens in juvenile female rainbow trout in standardized tests.

Transient Tat activation of the HIVLAV/Lai-1 LTR by primary HIV-1 phenotypic variants in HeLaT4LTRbeta-gal cells

The rapid/high and slow/low phenotypic variants of primary HIV-1 isolates can be distinguished by their differential co-receptor utilization and their ability to productively infect established cell lines. To reveal possible differences in Tat-mediated transactivation, the potential for primary isolate Tat proteins to transactivate the LTR from the laboratory strain HIVLAV/Lai-1 was examined. Using either cell-mediated or PEG-induced fusion of cells infected with primary HIV-1 isolates and HeLaT4LTRbeta-gal cells, it was clear that the Tat protein encoded by all patient isolates efficiently activated transcription from the HIVLAV/Lai-1 LTR. However, infection of HeLaT4LTRbeta-gal cells by primary HIV-1 isolates was transient, suggesting the development of a postpenetration host control of HIV-1 replication at the level of tat activation, a feature not observed for the laboratory-adapted strain HIVIIIB. Although plasmid vectors based on the HIVLAV/Lai-1 LTR remain useful for the development of susceptible established cell lines for titrating primary HIV-1 isolates, the efficacy of such a system would depend upon the stability/duration of Tat activation.