falciparumblood stage parasites and recombinant GMZ2, MSP3 or GLURP. ELISA with the recombinant antigens exhibited immunodominance of the GLURP component over the MSP3 component. However, compared to the Al(OH)3-adjuvanted formulation the two other formulations elicited in NMRI Nifuroxazide mice a larger proportion of anti-MSP3 antibodies. Analyses of the induced GMZ2-specific IgG subclass profiles showed for all those three formulations a predominance of the IgG1 isotype. Immune sera against all three formulations exhibited cross-reactivity within vitrocultivated blood-stage parasites. Immunofluorescence and immunoblot competition experiments showed that both components of the hybrid protein induced IgG cross-reactive with the corresponding Nifuroxazide native proteins. == Conclusion == A virosomal formulation of the chimeric protein GMZ2 inducedP. falciparumblood stage parasite cross-reactive IgG responses specific for both MSP3 and GLURP. GMZ2 thus represents a candidate component suitable for inclusion into a multi-valent virosomal malaria vaccine and influenza virosomes represent a versatile antigen delivery system suitable for adjuvant-free immunization with recombinant proteins. Keywords:Influenza virosomes, GMZ2 immunogenicity, Vaccine candidate,Plasmodium falciparummalaria == Background == The currently available strategies for malaria control rely on destruction of malaria parasites with drugs and the anopheline vectors with insecticides [1]. This combined approach proved remarkably effective in Europe and North America, whereas malaria continues to represent a huge burden in sub-Saharan Africa, Asia and South and Central America mainly Nifuroxazide due to drug-resistant parasites and insecticide resistant vectors [2]. A malaria vaccine is usually anticipated to be the most effective public health tool for changing this situation. The expected outcome of modern malaria vaccine development has shifted from protecting against the parasite to surviving with the parasite, but without experiencing the noxious effects it can cause. Asexual blood-stage vaccines are aimed to Rabbit Polyclonal to LFA3 primarily protect against the clinical symptoms of severe and moderate malaria disease, and not against the infection, around the assumption that inhibition of parasite invasion cycles will lead to reduced parasite burden and decreased morbidity and mortality [3]. Merozoite surface proteins are, therefore, a major focus of research for blood-stage vaccines. One of the leading candidates for an anti-falciparum vaccine is usually GMZ2, a fusion protein consisting of the N-terminal portion of the Glutamate Rich Protein (GLURP) genetically fused to a C-terminal fragment of Merozoite Surface Protein 3 (MSP3) [4]. Data supporting MSP3 and GLURP as vaccine candidates rely onin vitroandin vivopreclinical models and on immuno-epidemiological studies demonstrating a statistically significant association between protection from clinical malaria and antigen recognition by exposed individuals [5-13]. Development of an effective vaccine against blood-stage contamination will depend not only on antigen quality, but also on the choice of an optimal antigen delivery platform. In general, research on subunit vaccines focused mainly on antigen discovery whereas the method for inducing appropriate immune responses against these antigens has received less attention [14]. The selection of immunopotentiators, however, can have crucial effects on safety, stability, immunogenicity and, consequently, efficacy of a vaccine [15]. The paucity of delivery systems is usually apparent by the fact that aluminium salts identified as immunopotentiators more than 70 years ago have remained the most common Nifuroxazide type of adjuvant licensed worldwide. Alum is regarded as safe and as a stimulator of Th2 immunity and is, therefore, used as a standard to compare to other adjuvants [16]. The need for more effective antigen delivery systems for use in vaccines against malaria is made clear by the poor responses to synthetic and recombinant malarial antigens seen with the use of Alum [17-20]. Two such antigen delivery systems are Montanide ISA 720 and immunopotentiating reconstituted influenza virosomes (IRIV). The experimental Montanide ISA 720 adjuvant forms water-in-oil droplets intended to give a slow release of antigens at the injection site [21]. Montanide ISA 720 based formulations have been shown to elicit high antibody titres in several animal species [22], and have also been investigated in malaria vaccine trials [23-26]. IRIVs are spherical, unilamellar vesicles, prepared by detergent removal from a mixture of natural and synthetic phospholipids and influenza surface glycoproteins. The haemagglutinin membrane glycoprotein of the influenza computer virus is usually a fusion-inducing component, which facilitates antigen delivery to immunocompetent cells. IRIVs represent a universal antigen delivery system for multicomponent subunit vaccines, as antigens can be either coupled to their surface to elicit CD4 T cell and antibody responses or encapsulated in their lumen to elicit CD8 T cell responses. Experience with two licensed vaccines based on virosomes (InflexalV and Epaxal) as well as clinical trials with virosomally-formulated malaria vaccine candidates [27,28] have shown that IRIV-based.