IMMUNOLOGICAL EXAMINATIONS OF SPECIES VARIABILITY IN PREDATOR GUT CONTENT ASSAYS - EFFECT OF PREDATOR PREY PROTEIN RATIO ON IMMUNOASSAY SENSITIVITY/

In qualitative predator gut content immunoassays, sensitivity of an im munoassay is important far determining whether a predator contains a t argeted prey antigen, If the immunoassay employed is insensitive, the probability of obtaining a false-negative reaction is high, The sensit ivity of an indirect enzyme-linked immunosorbent assay (ELISA) develop ed to detect pink bollworm, Pectinophora gossypiella (Saunders) (Lepid optera: Gelechiidae), egg(s) in whole body homogenized predators varie d in efficacy between species, Specifically, the indirect ELISA was mo re effective at detecting egg antigen in small predators than In large predators, In this study, we examined the effect that the predator pr ey protein ratio has on the sensitivity of an indirect ELISA. Our resu lts suggest that when assaying whole body homogenized predators, care must be taken not to overload an ELISA microplate. with nontarget (pre dator) proteins. Predator samples should be diluted to less than 125 m u g of total protein per sample, Any protein concentration above 125 m u g per ELISA microplate well will likely result in an ELISA false-neg ative reaction, In another experiment, we compared the efficacy of an indirect ELISA with a dot blot immunoassay. Adults of Hippodamia conve rgens Guerin-Meneville (Coleoptera: Coccineliidae) that had eaten one pink bollworm egg were homogenized in variable dilutions of phosphate- buffered saline (PBS) and each sample was analyzed for pink bollworm e gg antigen using both immunoassays. The dot blot immunoassay was more reliable than the indirect; ELISA for detecting minute traces of egg a ntigen in the samples. Generally, the volume of PBS that the H. conver gens were homogenized in had little effect on the qualitative outcome of the dot blot, However, the indirect. ELISA was more effective when H. convergens was homogenized in a larger volume of PBS, This suggests that the efficacy of an indirect ELISA can be improved for large, pro tein-rich predators by grinding them in a larger volume of PBS, thus m inimizing the total protein in a given sample. (C) 1997 Academic Press .