PASSAGE OF HOST IMMUNOGLOBULIN ACROSS THE MIDGUT EPITHELIUM INTO THE HEMOLYMPH OF BLOOD-FED BUFFALO FLIES HAEMATOBIA-IRRITANS-EXIGUA

Host immunoglobulin G was detected in the haemolymph of blood-fed buffalo flies. Immunoblot analysis of this haemolymph showed that the immunoglobulin was intact by comparison of its molecular weight to that of an affinity purified immunoglobulin G control. The concentrations of total immunoglobulin and anti-myoglobin antibody in the haemolymph were measured using enzyme linked immunosorbent assays (ELISAs). The concentration of total immunoglobulin in pooled haemolymph from flies which had ad libitum access to blood remained relatively constant over the sampling period (range: 2.1-7.3-mu-g/ml). Ninety-four per cent of flies known to have taken a blood meal had detectable levels of immunoglobulin in the haemolymph. Immunoglobulin could be detected in the haemolymph 24 h after flies had fed on a single blood meal. An ingested specific antibody (anti-myoglobin) which passed into the haemolymph retained the capacity to bind antigen. Measurement of antibody concentration in haemolymph is a valuable guide to the feasibility of targeting specific antigens in a vaccine against the buffalo fly.