In collaboration with Merck Research Laboratories, we have demonstrated that conjugating Pfs25 with OMPC, the Outer Membrane Protein Complex of the Neisseria meningitides subgroup B, significantly increased immunogenicity and response longevity of Pfs25 in multiple animal models, including non human primates. The induced immune sera effectively blocked malaria transmission as evaluated in an ex-vivo membrane feeding assay. Subsequently, the collaborative efforts continued to evaluate conjugates using different carriers and adjuvants, searching for a cost-effective process for vaccine product development, with the result that Pfs25 conjugated to the alternative carrier EPA was produced and further progress on that vaccine candidate is reported elsewehere. During the past year, LMIV and Merck have resumed this collaboration with the following goals: 1) transfer the OMPC conjugation methodologies from Merck to LMIV so that conjugates can be produced in house at LMIV; 2) reproduce the earlier findings in mice and primates showing strong durable antibody responses to the OMPC-Pfs25 conjugate; 3) prepare and assess OMPC-Pfs230 conjugates in a similar fashion. Based on the results of these small animal studies, we will determine whether to proceed to NHP studies to compare the OMPC conjugates to our EPA conjugates for immunogenicity and durability of functional antibody.
