Comparing crop land net primary production estimates from inventory , a satellite-based model , and a process-based model in the Midwest of the United States Zhengpeng

An enzyme-linked immunosorbent assay (ELISA) was developed on the basis of testing a single dilution of serum to quantify the level of antibody to the p57 protein of Renibacterium salmoninarum in sockeye salmon (Oncorhynchus nerka). The levels of antibody were interpolated from a standard curve constructed by relating the optical densities (OD) produced by several dilutions of a high-titer rainbow trout (O. mykiss) antiserum to the p57 protein. The ELISA OD values produced by as many as 36 test sera on each microplate were compared with the standard curve to calculate the antigen-specific antibody activity. Repeated measurements of 36 samples on 3 microplates on each of 6 assay dates indicated that the mean intraassay coefficient of variation (CV) was 6.68% (range, 0–23%) and the mean interassay CV was 8.29% (range, 4–16%). The antibody levels determined for the serum sample from 24 sockeye salmon vaccinated with a recombinant p57 protein generally were correlated with the levels determined by endpoint titration (r2 5 0.936) and with results from another ELISA that was based on extrapolation of antibody levels from a standard curve (r2 5 0.956). The single-dilution antibody ELISA described here increases the number of samples that can be tested on each microplate compared with immunoassays based on analysis of several dilutions of each test serum. It includes controls for interassay standardization and can be used to test fish weighing ,3 g. Regular monitoring of the health of fish reared in intensive aquaculture is an important step toward reducing the introduction and spread of infectious diseases.32 The immune system of fish may be adversely affected by changes in physiologic processes resulting from an inattention to water quality or fish rearing density,4,30 diet formulation,7,21,40 or fish handling methods.4,5 Serum antibody levels are an indicator of the overall immune system activity of a fish. The amount of antibody can be estimated using a variety of assays, including agglutination, radial immunodiffusion, or neutralization reactions, although the sensitivity of these tests is limited.1,27,31,41 Monoclonal antibodies to fish antibody3,11,37 have been adapted to the enzyme-linked immunosorbent assay (ELISA) and used to quantify low levels of specific antibody activity.2,9,24,38 When estimating fish antibody levels in an ELISA, several dilutions of each serum sample are usually analyzed to arrive at an endpoint dilution or units of antibody.2,8,20,24,26,41 Replicate analyses of several dilutions of each test serum, however, can limit the number of fish evaluated on each ELISA microplate and increase reagent costs. In an effort to analyze greater numbers of fish on each microplate, the optical density (OD) of a single dilution of test serum has been used for antibody concentration comparisons.13,15,18,38 However, From The US Geological Survey, Biological Resources Division, Western Fisheries Research Center, 6505 NE 65th Street, Seattle,