title: An ELISA for detecting anti-Plasmodium spp. antibodies in African black-footed penguins (Spheniscus demersus).
abstract: An enzyme-linked immunosorbent assay (ELISA) utilizing 3 Plasmodium falciparum antigens, R32tet32, P.F.R27, and crude red blood cell extract, was developed for the detection of circulating anti-Plasmodium relictum or anti-Plasmodium elongatum antibodies in sera from naturally infected adult African black-footed penguins (Spheniscus demersus) at The Baltimore Zoo, Maryland. A concentration of 2.0 micrograms/ml of each antigen was optimal in terms of specificity, sensitivity, and test speed. It was possible to detect anti-Plasmodium spp. antibodies at a dilution of 10(-4.11). Low absorbance values (less than 0.050) of nonspecific background were observed. The binding efficacy of anti-penguin IgG coupled to alkaline phosphatase to antibodies in the penguin sera was significantly higher than the binding efficacy of anti-chicken IgG. All penguins, bled in the winter time, in controlled mosquito-free conditions had anti-Plasmodium spp. antibodies reactive with P. falciparum antigens. The penguins showed age-dependent variation in antibody levels. There was a decrease in antibody titration units that was significantly correlated with the number of outdoor exposure years experienced by the birds, despite the season-comparable epizootiologic conditions in their summer open-air habitat. We concluded that the decrease of anti-malarial antibodies could be explained by an antibody-mediated equilibrium of immunity in naturally immunized birds harboring endothelial-stage parasites. The ELISA described is sensitive, and it requires a minimal amount of equipment to collect the blood samples. The assay can be used for detecting and monitoring levels of anti-Plasmodium spp. antibodies in selected groups of penguins.
authors.affiliation: Department of Immunology and Infectious Diseases, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: T K
authors.initials: TK
authors.lastname: Graczyk
authors.forename: M R
authors.initials: MR
authors.lastname: Cranfield
authors.forename: M L
authors.initials: ML
authors.lastname: Skjoldager
authors.forename: M L
authors.initials: ML
authors.lastname: Shaw
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D001717:Birds; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary*; D005260:Female; D008289:Malaria, Avian / Q000175:diagnosis*; D008297:Male; D010961:Plasmodium / Q000276:immunology*; D010963:Plasmodium falciparum / Q000276:immunology; D012044:Regression Analysis
chemical_list: D000913:Antibodies, Protozoan