Passive transfer of humoral resistance against adults of the tsetse fly, Glossina palpalis palpalis (Diptera, Glossinidae), in rabbits.

The possibility of passive transfer of rabbit humoral immunity against tsetse fly bites was investigated for the first time. Partial immunity of recipient animals was achieved after two intravenous injections of 15 ml of serum from immunized (donor) rabbits during 48 hrs. This treatment induced an apparent increase of resistance in the passively immunized group of rabbits expressed as direct mortality ("killing effect") of sucking flies within the following 72 hr period. The immunological state of immune sera of both donors and recipients was examined by ELISA, using the water-soluble proteins of tsetse salivary glands as antigen. No direct correlation between the titre of antibodies and the killing of Glossina was detected. These results indicate that these antibodies were not the only humoral factor responsible for tsetse mortality since their titre did not substantially change in the course of 7 days while the "killing effect" had disappeared from the recipient's blood within 72 hrs.