The erythrocyte binding ligand 140 (EBA-140) is a member of the Plasmodium falciparum DBL family of erythrocyte binding proteins, which are considered as prospective candidates for malaria vaccine development. The EBA-140 ligand is a paralogue of the well-characterized P. falciparum EBA-175 protein. They share homology of domain structure, including Region II, which consists of two homologous F1 and F2 domains and is responsible for ligand-erythrocyte receptor interaction during invasion. In this report we describe, for the first time, the glycophorin C specificity of the recombinant, baculovirus-expressed binding region (Region II) of P. falciparum EBA-140 ligand. It was found that the recombinant EBA-140 Region II binds to the endogenous and recombinant glycophorin C, but does not bind to Gerbich-type glycophorin C, neither normal nor recombinant, which lacks amino acid residues 36–63 of its polypeptide chain. Our results emphasize the crucial role of this glycophorin C region in EBA-140 ligand binding. Moreover, the EBA-140 Region II did not bind either to glycophorin D, the truncated form of glycophorin C lacking the N-glycan or to desialylated GPC. These results draw attention to the role of glycophorin C glycans in EBA-140 binding. The full identification of the EBA-140 binding site on glycophorin C molecule, consisting most likely of its glycans and peptide backbone, may help to design therapeutics or vaccines that target the erythrocyte binding merozoite ligands.

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BackgroundHepatitis C virus (HCV) infection is a major health problem worldwide, affecting an estimated 2–3 % of human population. An HCV vaccine, however, remains unavailable. High viral diversity poses a challenge in developing a vaccine capable of eliciting a broad neutralizing antibody response against all HCV genotypes. The small surface antigen (sHBsAg) of hepatitis B virus (HBV) has the ability to form highly immunogenic subviral particles which are currently used as an efficient anti-HBV vaccine. It also represents an attractive antigen carrier for the delivery of foreign sequences. In the present study, we propose a bivalent vaccine candidate based on novel chimeric particles in which highly conserved epitope of HCV E2 glycoprotein (residues 412–425) was inserted into the hydrophilic loop of sHBsAg.ResultsThe expression of chimeric protein was performed in an unconventional, Leishmania tarentolae expression system resulting in an assembly of particles which retained immunogenicity of both HCV epitope and sHBsAg protein. Direct transmission electron microscopy observation and immunogold staining confirmed the formation of spherical particles approximately 22 nm in diameter, and proper foreign epitope exposition. Furthermore, the sera of mice immunized with chimeric particles proved reactive not only to purified yeast-derived sHBsAg proteins but also HCV E2 412–425 synthetic peptide. Most importantly, they were also able to cross-react with E1E2 complexes from different HCV genotypes.ConclusionsFor the first time, we confirmed successful assembly of chimeric sHBsAg virus-like particles (VLPs) in the L. tarentolae expression system which has the potential to produce high-yields of properly N-glycosylated mammalian proteins. We also proved that chimeric Leishmania-derived VLPs are highly immunogenic and able to elicit cross-reactive antibody response against HCV. This approach may prove useful in the development of a bivalent prophylactic vaccine against HBV and HCV and opens up a new and low-cost opportunity for the production of chimeric sHBsAg VLPs requiring N-glycosylation process for their proper functionality and immunogenicity.

Influenza A virus infections are the major public health concern and cause significant morbidity and mortality each year worldwide. Vaccination is the main strategy of influenza epidemic prevention. However, seasonal vaccines induce strain-specific immunity and must be reformulated annually based on prediction of the strains that will circulate in the next season. Thus, it is essential to develop vaccines that would induce broad and persistent immunity to influenza viruses. Hemagglutinin is the major surface antigen of the influenza virus. Recent studies revealed the importance of HA stalk-specific antibodies in neutralization of different influenza virus strains. Therefore, it is important to design an immunogen that would focus the immune response on the HA stalk domain in order to elicit neutralizing antibodies. In the present study, we report characterization of a conserved truncated protein, potentially a universal influenza virus antigen from the H5N1 Highly Pathogenic Avian Influenza A virus strain. Our results indicate that exposure of the HA stalk domain containing conserved epitopes results in cross reactivity with different antibodies (against group 1 and 2 HAs). Additionally, we conclude that HA stalk domain contains not only conformational epitopes recognized by universal FI6 antibody, but also linear epitopes recognized by other antibodies. Abbreviations: HA, hemagglutinin; PAb, polyclonal antibody; MAb, monoclonal antibody; HPAI, highly pathogenic avian influenza; pH1N1, pandemic strain H1N1; rHA, recombinant hemagglutinin; WT AcNPV, Autographa californica nuclear polyhedrosis virus wild type strain.