THE EFFECTS OF CONTINUOUS AND INTERMITTENT DELIVERY OF ANTIGENS OF BOOPHILUS-MICROPLUS ON THE DEVELOPMENT OF MURINE ANTIBODIES

Protective antigens solubilised from the membranes of the midgut (LI-G M) of the adult cattle tick Boophilus microplus were delivered to mice either continuously for up to 4 weeks from osmotic pumps implanted su bcutaneously or intermittently in a pulsatile fashion by injections or by a combination of both modes of delivery. The effects of delivery p rofile on antigen specific antibody levels and avidity were compared, LI-GM delivered either by three injections (weeks 0, 2 and 4), or cont inuously from osmotic pumps (over 4 weeks) induced similar levels of a ntibodies in mice. The mode of delivery of LI-GM when in the presence of the adjuvant Quil A did not generally affect either the level or th e avidity of the antibody response; indeed a single injection of LI-GM in the presence of Quil A stimulated an immune response similar to th at induced by several combinations of pulsatile and of continuous deli very where mice were exposed to antigen and adjuvant for up to 4 weeks . LI-GM incubated at 37 degrees C in vitro and in vivo for periods fro m 4 h to 14 days was partly degraded into low molecular weight (less t han 29 kDa) components, The immunogenicity of LI-GM incubated in vitro for 4 h was significantly decreased, although its antigenicity was no t affected after incubation for up to 14 days. In conclusion, delivery of LI-GM continuously from osmotic pumps demonstrated that single-ste p immunisation of mice with tick antigens was feasible. However, it wa s also demonstrated that the continuous delivery of antigen was only a dvantageous (i.e. potential for a decrease in the number of times an a nimal must be handled) compared with delivery by injections when no ad juvant was used. Further work is necessary to establish the effect ant igen degradation has in limiting the immune response resulting from co ntinuous delivery of antigen from osmotic pumps.