Plasmodium falciparum: Immunogenicity of alum-adsorbed clinical-grade TBV25-28, a yeast-secreted malaria transmission-blocking vaccine candidate

Plasmodium falciparum: Immunogenicity of alum-adsorbed clinical-grade TBV25 -28, a yeast-secreted malaria transmission-blocking vaccine candidate. Expe rimental Parasitology 97, 61-69. The fusion of Pfs25 and Pfs28, two major s urface antigens on zygotes and ookinetes of Plasmodium falciparum, as a sin gle recombinant protein (TBV25-28) was previously shown to elicit potent tr ansmission-blocking antibodies in mice. Clinical-grade TBV25-28 was subsequ ently manufactured and its potency was evaluated in rabbits. Rabbits receiv ed three doses of either clinical-grade TBV25H or clinical-grade TBV25-28 a dsorbed to alum with or without QS-21. As measured in a standard membrane-f eeding assay, addition of QS-21 to the formulations appeared to enhance tra nsmission-blocking potency of rabbit sera after two vaccinations but not af ter three vaccinations. Surprisingly, TBV25H elicited more potent transmiss ion blocking antibodies than did TBV25-28, a result strikingly different fr om those of previous mouse experiments using research-grade TBV25-28. The a pparent decrease in potency of clinical-grade TBV25-28 in rabbits appears t o reflect an enhancement in potency of clinical-grade TBV25H in a new formu lation rather than simply a species difference in immunogenicity of TBV25-2 8. (C) 2001 Academic Press.