EIMERIA-MAXIMA GAMETOCYTE ANTIGENS - POTENTIAL USE IN A SUBUNIT MATERNAL VACCINE AGAINST COCCIDIOSIS IN CHICKENS

Affinity-purified gametocyte antigens (APGA) from Eimeria maxima, emul sified in Freund's adjuvant, were injected intramuscularly into breedi ng hens on two or three occasions, As a result, progeny of the immuniz ed hens were partially immune to infection with E. maxima, Eimeria ten ella and Eimeria acervulina (with a reduction in total oocyst output o f 45-63% as compared with progeny of untreated hens). Thus, APGA in Fr eund's adjuvant appears to have great potential as part of a maternall y applied vaccine against coccidiosis. The ability of APGA to induce p artial cross-species protection is most probably due to the existence of conserved epitopes in the different species as indicated by compara tive Western blots of E. maxima and E. tenella. Surprisingly, Freund's adjuvant by itself also induced significant levels of maternal immuni ty to coccidiosis (with a 12-35% reduction in oocyst output in the pro geny). In contrast to the purified antigens or Freund's alone, crude e xtracts from gametocytes as well as other developmental stages, induce d little if any significant maternal immunity despite provoking the pr oduction of large amounts of parasite-specific IgG, including antibodi es to APGA, This result indicates that a successful maternal vaccine a gainst coccidiosis requires, in addition to good recognition of protec tive antigens, the exclusion of irrelevant antigens from the vaccine p reparation.