Development of antibody responses have been found upon administration of malarial synthetic antigens containing virosomes. In fact, IgG antibodies against UK-39 (a synthetic peptide derived from the circumsporozoite protein of P. faciparum) inhibited invasion of hepatocytes by P. falciparum sporozoites [118]. A second peptide (AMA49-C1) based on domain III of apical membrane antigen 1 induced antibodies that inhibited blood-stage parasite growth in vitro [119]. Combination of both antigens into different

virosomes did not affect negatively the antipeptide antibody titers in mice or rabbits, demonstrating the value of this Inhibitors,research,lifescience,medical system for the development of multivalent vaccines [120]. In addition, a phase I clinical trial has been carried out in order to evaluate the safety and immunogenicity of two virosome-formulated P. falciparum derived synthetic Inhibitors,research,lifescience,medical peptide antigens (AMA 49-CPE and UK39) [121]. Both vaccines resulted safe, as no serious or severe adverse events were observed. In terms of immunogenicity, both formulations elicited already an antibody specific response in all volunteers with Inhibitors,research,lifescience,medical the appropriate dose. 2.6. ISCOMS and ISCOMATRIX Immunostimulatory complexes (ISCOMs) are cage-like structures, approximately

of 40nm in diameter composed of antigen, cholesterol, 5-FU nmr phospholipid, and saponin, held together by hydrophobic interactions, so typically entrapped antigens are amphipathic. The most commonly used saponin is QuilA or its purified compounds [5, 122]. ISCOMATRIX has essentially the same Inhibitors,research,lifescience,medical structure as ISCOMs but lacks the antigen, which can be subsequently added (Figure 7). This fact provides ISCOMATIX for more general applications as they are not

limited to amphipathic antigens [4, 122]. Although numerous studies have been carried out with animal models [123–126], few clinical trials evaluating ISCOMs and ISCOMATRIX are currently in course [127]. Figure 7 Electron micrograph of ISCOMATRIX adjuvant following negative staining. Inhibitors,research,lifescience,medical ISCOMATRIX adjuvant particles are typically rigid, hollow, spherical, and cage-like particles approximately 40nm in diameter. Reproduced with permission from [43]. ISCOMs are not immunogenic by themselves although other saponins different from QuilA are used [43, 128], but when the antigen is incorporated, they can trigger humoral, mucosal, and cellular immune medroxyprogesterone responses [128]. Different results have been obtained when evaluating ISCOMs immunogenicity. For instance, Agrawal et al. [129] administered in the footpad of mice different HIV-1 derived synthetic peptides, with and without an immunoadjuvant, in liposomes or ISCOMs and compared to the administration of peptides with alum. In contrast to alum, both liposomes and ISCOMs induced a predominant Th1 like response. On the other hand, Pahar et al. [123] found that intrarectal immunization of macaques with two HIV-derived peptides (HIV-1env and SIVgag) incorporated into ISCOMs induced low level of immunity against simian-HIV.