Recombinant Pfs25 protein of Plasmodium falciparum elicits malaria transmission-blocking immunity in experimental animals (original) (raw)

1991, Journal of Experimental Medicine

Pfs25 is a sexual stage antigen of Plasmodium falciparum that is expressed on the surface of zygote and ookinete forms of the parasite. Monoclonal antibodies directed against native Pfs25 can block completely the development of P. falciparum oocysts in the midgut of the mosquito vector. Thus, this 25-kD protein is a potential vaccine candidate for eliciting transmission-blocking immunity in inhabitants of malaria endemic regions. We have synthesized, by secretion from yeast, a polypeptide analogue of Pfs25 that reacts with conformation-dependent monoclonal antibodies, and elicits transmission-blocking antibodies when used to immunize mice and monkeys in conjunction with a muramyl tripeptide adjuvant. Our results suggest the further evaluation of recombinant DNA-derived Pfs25 in transmission-blocking vaccination studies in humans.

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Murine Model for Assessment of Plasmodium falciparum Transmission-Blocking Vaccine Using Transgenic Plasmodium berghei Parasites Expressing the Target Antigen Pfs25

Infection and Immunity, 2008

Currently, there is no animal model for Plasmodium falciparum challenge to evaluate malaria transmission-blocking vaccines based on the well-established Pfs25 target antigen. The biological activity of transmission-blocking antibodies is typically assessed using an assay known as the membrane feeding assay (MFA). It is an in vitro method that involves mixing antibodies with cultured P. falciparum gametocytes and feeding them to mosquitoes through an artificial membrane followed by assessment of infection in the mosquitoes. We genetically modified Plasmodium berghei to express Pfs25 and demonstrated that the transgenic parasites (TrPfs25Pb) are susceptible to anti-Pfs25 antibodies during mosquito-stage development. The asexual growth kinetics and mosquito infectivity of TrPfs25Pb were comparable to those of wild-type parasites, and TrPfs25Pb displayed Pfs25 on the surface of ookinetes. Immune sera from nonhuman primates immunized with a Pfs25-based vaccine when passively transferred ...

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Potent Malaria Transmission-Blocking Antibody Responses Elicited by Plasmodium falciparum Pfs25 Expressed in Escherichia coli after Successful Protein Refolding

Infection and Immunity, 2014

ABSTRACTProduction of Pfs25, aPlasmodium falciparumtransmission-blocking vaccine target antigen, in functional conformation with the potential to elicit effective immunogenicity still remains a major challenge. In the current study, codon-harmonized recombinant Pfs25 (CHrPfs25) was expressed inEscherichia coli, and purified protein after simple oxidative refolding steps retained reduction-sensitive conformational epitopes of transmission-blocking monoclonal antibodies. CHrPfs25 formulated in several adjuvants elicited strong immunogenicity in preclinical studies in mice. Antibodies elicited after immunization recognized native Pfs25 on the surface of live gametes ofP. falciparumand demonstrated complete malaria transmission-blocking activity. The transmission-blocking efficacy was 100% even after a 1:128 dilution of sera from immunized mice in the complete Freund's adjuvant and Montanide ISA51 groups and after a 1:16 dilution of sera from mice in the alum group. The blocking was...

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Heterologous Expression and Evaluation of Novel Plasmodium falciparum Transmission Blocking Vaccine Candidates

Frontiers in Immunology

Malaria transmission blocking vaccines (TBV) aim to induce antibodies that can interrupt Plasmodium falciparum development in the mosquito midgut and thereby prevent onward malaria transmission. A limited number of TBV candidates have been identified and only three (Pfs25, Pfs230 and Pfs48/45) have entered clinical testing. While one of these candidates may emerge as a highly potent TBV candidate, it is premature to determine if they will generate sufficiently potent and sustained responses. It is therefore important to explore novel candidate antigens. We recently analyzed sera from naturally exposed individuals and found that the presence and/or intensity of antibodies against 12 novel putative surface expressed gametocyte antigens was associated with transmission reducing activity. In this study, protein fragments of these novel TBV candidates were designed and heterologously expressed in Drosophila melanogaster S2 cells and Lactococcus lactis. Eleven protein fragments, covering ...

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Potent antibody lineage against malaria transmission elicited by human vaccination with Pfs25

Nature Communications, 2019

Transmission-blocking vaccines have the potential to be key contributors to malaria elimination. Such vaccines elicit antibodies that inhibit parasites during their development in Anopheles mosquitoes, thus breaking the cycle of transmission. To date, characterization of humoral responses to Plasmodium falciparum transmission-blocking vaccine candidate Pfs25 has largely been conducted in pre-clinical models. Here, we present molecular analyses of human antibody responses generated in a clinical trial evaluating Pfs25 vaccination. From a collection of monoclonal antibodies with transmission-blocking activity, we identify the most potent transmission-blocking antibody yet described against Pfs25; 2544. The interactions of 2544 and three other antibodies with Pfs25 are analyzed by crystallography to understand structural requirements for elicitation of human transmission-blocking responses. Our analyses provide insights into Pfs25 immunogenicity and epitope potency, and detail an affin...

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Expression of malaria transmission-blocking vaccine antigen Pfs25 in Pichia pastoris for use in human clinical trials

Vaccine, 2003

In previously published studies, Saccharomyces cerevisiae recombinant protein expression systems have been employed to express the malaria parasite antigen Pfs25, a candidate transmission-blocking vaccine antigen against Plasmodium falciparum malaria. However, despite having been in two Phase 1 trials, the recombinant Pfs25 so produced (previously called TBV25H) exists as a mixture of two monomeric protein conformational forms, Pfs25H-A and Pfs25H-B. In this study, we optimized the expression and purification of the two Pfs25H conformers in S. cerevisiae, and characterized their biochemical and antigenic properties, immunogenicities, and transmission-blocking activities. Pfs25H-A is apparently homogeneous, and has the correct conformation as measured by monoclonal antibody recognition. It is, however, expressed at a low yield of only 0.19mg/l. By contrast, Pfs25H-B is produced as a heterogeneous population of molecules that do not seem to have the correct conformation. Nonetheless, ...

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Induction of Plasmodium falciparum Transmission-Blocking Antibodies in Nonhuman Primates by a Combination of DNA and Protein Immunizations

Infection and Immunity, 2004

Malaria transmission-blocking vaccination can effectively reduce and/or eliminate transmission of parasites from the human host to the mosquito vector. The immunity achieved by inducing an antibody response to surface antigens of male and female gametes and parasite stages in the mosquito. Our laboratory has developed DNA vaccine constructs, based on Pfs25 (a Plasmodium falciparum surface protein of 25 kDa), that induce a transmission-blocking immune response in mice (C. A. Lobo, R. Dhar, and N. Kumar, Infect. Immun. 67:1688-1693, 1999). To evaluate the safety, immunogenicity, and efficacy of the Pfs25 DNA vaccine in nonhuman primates, we immunized rhesus macaques (Macaca mulatta) with a DNA vaccine plasmid encoding Pfs25 or a Pfg27-Pfs25 hybrid or with the plasmid (empty plasmid) alone. Immunization with four doses of these DNA vaccine constructs elicited antibody titers that were high but nonetheless unable to reduce the parasite's infectivity in membrane feeding assays. Furth...

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