Uptake and fate of specific antibody in feeding larvae of the sheep blowfly, Lucilia cuprina

Abstract

The quantity of specific antibody ingested by larvae of Lucilia cuprina and its fate after ingestion were studied in larvae grown on sheep and on an artificial diet. Larvae grown to late first or early second instar on sheep vaccinated with horse myoglobin contained 66% less specific antibody detected by enzyme linked immunosorbent assay than larvae grown to a similar stage on an artificial diet containing 75% serum from the same sheep. A similar result was obtained when larvae were grown to mid-third instar. Larvae grown on sheep to first or second instar contained approximately the same quantity of specific antibody per unit weight of larvae as those grown to third instar. Larvae grown on diet to third instar contained 22% less specific antibody per unit weight than those grown to first or second instar. In larvae grown on diet to late third instar, ingested diet retained 91 +/- 12% of its original specific antibody activity in the crop, 50 +/- 11% in the anterior midgut, 8 +/- 2% in the posterior midgut and 13 +/- 6% in the hindgut. The mean concentration of total immunoglobulin detectable in the haemolymph of individual third instar larvae grown on diet was 1.7 +/- 2.8 micrograms/ml. Assays of specific antibody in the haemolymph of similarly reared larvae indicated that all or most of this immunoglobulin remained functional. The implications of the quantities and distribution of ingested functional antibody found in feeding larvae of L.cuprina are discussed in relation to the possibility of vaccinating sheep against these larvae and the selection of likely internal targets as sources of potential protective antigens.