Quantification analyses were performed assessing the mean fluorescence per nuclei stained. Statistics. but no significant activity in 5 Pfs25-EPA recipients, and combination with Pfs25-EPA did not increase activity over Pfs230D1-EPA alone. CONCLUSION The complement-dependent functional immunogenicity of Pfs230D1-EPA represents a significant improvement over Pfs25-EPA in this comparative study. The rhesus model is usually more predictive of the functional human immune response to Pfs230D1 than is the mouse model. TRIAL REGISTRATION ClinicalTrials.gov NCT02334462. FUNDING Intramural Research Program of the National Institute of Allergy and Infectious Diseases, National Institutes of Health. Keywords: Infectious disease, Vaccines Keywords: Malaria Introduction The world has achieved substantial strides in malaria control, with roughly half of the countries endemic for malaria having eliminated the disease in the past 50 years. However, existing tools failed to achieve elimination despite comprehensive application in African settings (1, 2), and recent progress to reduce malaria cases has stalled globally and been reversed in some areas (3). Vaccines have been essential for elimination of infectious brokers such as PF-2545920 smallpox, polio, and measles by halting the onward transmission of these diseases, conferring major benefits to human health and economies (4C6). Malaria transmission-blocking vaccines (TBVs) were conceived in the 1970s as a tool to interrupt parasite transmission with antibodies that attack sexual-stage parasites in the mosquito vector (7, 8). Monoclonal antibodies to mosquito sexual-stage (gamete) parasites were used to identify candidate TBV antigens, including gamete surface proteins P230 and PF-2545920 P48/45, first expressed by gametocytes in mammalian host blood (9), and zygote surface proteins P25 and P28, expressed only after fertilization in the mosquito host (10, 11). These antigens are multidomain cysteine-rich proteins and generally difficult to produce as properly folded recombinant protein. P25 (Pfs25) antigen was the first expressed as recombinant protein (12) and has remained the leading TBV candidate for 3 decades. In preclinical studies, Pfs25 vaccines have induced equal or greater serum activity versus other candidate antigens or antigen combinations (13, 14). TBV activity is usually measured in mosquito feeding assays that assess whether immune sera reduce the parasite burden (transmission-reducing activity, TRA) or the proportion of infected mosquitoes (transmission-blocking activity, TBA). While earlier P25 candidates failed to meet safety or activity Rabbit Polyclonal to NCAM2 criteria to PF-2545920 advance in the clinic (15, 16), we recently reported that a Pfs25 protein-protein conjugate vaccine formulated in alum adjuvant induced serum functional activity in both US and Malian adults (17, 18). However, few vaccinees developed TRA greater than 50% or significantly increased their TRA after 2 or 3 3 doses of Pfs25 vaccine. This occurred in 2 of 17 subjects after 2 doses and 2 of 15 subjects after 3 doses in US adults (17), and no significant activity was seen in vaccinees (versus comparators) after 3 doses in Malian adults (18). In each study, significant functional activity required 4 vaccine doses, and antibody levels declined rapidly, suggesting functional immunogenicity and sturdiness must be improved before advancing TBV further in clinical development. Preclinical evidence suggested that TBV combinations might enhance vaccine activity (19), and we have proposed that Pfs25 should be assessed in combination with other antigens to improve human vaccine activity (18). Specifically, we hypothesized that this combination of Pfs230 prefertilization activity and Pfs25 postfertilization activity might exceed their individual activities. To assess the contribution of Pfs230 to a TBV, a fragment (Ser542 to Gly736) encompassing domain name 1 of Pfs230 cloned and expressed in (Pfs230D1, previously referred to as Pfs230D1M) as described in (20) was chemically conjugated to EPA (21), a nontoxic mutant of exoprotein A from using methods previously described for development of the Pfs25-EPA vaccine (22). Here, we compare Pfs230D1-EPA to our benchmark TBV (Pfs25-EPA) formulated in alum in 3 models (mice, nonhuman primates, and humans) and assess their activity in combination. Results To confirm the benefit of conjugation of Pfs230D1, groups of CD-1 mice were PF-2545920 immunized twice (0, 28 days) by intramuscular injection with either Pfs230D1 or PF-2545920 Pfs230D1-EPA, both formulated in Alhydrogel, which was the clinical formulation. Antibody levels induced by Pfs230D1-EPA were approximately 100-fold greater than those induced by Pfs230D1 monomer (Supplemental Physique 1; supplemental material available online with this article; https://doi.org/10.1172/JCI146221DS1). For clinical development planning, we assessed Pfs230D1 and Pfs25 for their relative capacities to induce functional antibodies, to determine if one antigen should be prioritized over the other for clinical testing. Initial dose ranging studies with Pfs230D1-EPA were performed in mice.
Quantification analyses were performed assessing the mean fluorescence per nuclei stained
