Exploiting Conformationally Constrained Peptidomimetics and an Efficient Human-Compatible Delivery System in Synthetic Vaccine Design

Abstract

Peptide and protein mimetics are potentially of great value in synthetic vaccine design. The mimetics should function by stimulating the immune system to produce antibodies that recognize the intact parasite. Also the mimetics should be presented to the immune system in a way that leads to efficient antibody production. Here we investigate the application of cyclic peptidomimetics presented on immunopotentiating reconstituted influenza virosomes (IRIVs), a form of antigen delivery that is licensed already for human clinical use, in synthetic vaccine design. We focus on the central (NPNA)(n) repeat region of the circumsporozoite (CS) protein of the malaria parasite Plasmodium falciparum as a model system. Cyclic peptidomimetics of the NPNA repeats were incorporated into both an IRIV and (for comparison) a multiple-antigen peptide (MAP). Both IRIV and MAP delivery forms induced mimetic-specific humoral immune responses in mice, but only with the mimetic-IRIV preparations did a significant fraction of the elicited antibodies cross-react with sporozoites. The results demonstrate that IRIVs are a delivery system suitable for the efficient induction of antibody responses against conformational epitopes by use of cyclic template-bound peptidomimetics. Combined with combinatorial chemistry, this approach may have great potential for the rapid optimization of molecularly defined synthetic vaccine candidates against a wide variety of infectious agents.

Synthesis, Solution Structure and Immune Recognition of an Epidermal Growth Factor‐Like Domain from Plasmodium falciparum Merozoite Surface Protein‐1

“…For preliminary immunological studies, the mimetic 2 was incorporated into virosomes by methods established earlier for short linear peptides and peptidomimetics 17–19. After one immunization with influenza antigens, BALB/c mice were immunized with the 2 ‐loaded virosomes.…”

Synthesis, Solution Structure and Immune Recognition of an Epidermal Growth Factor‐Like Domain from Plasmodium falciparum Merozoite Surface Protein‐1

“…For preliminary immunological studies, the mimetic 2 was incorporated into virosomes by methods established earlier for short linear peptides and peptidomimetics 17–19. After one immunization with influenza antigens, BALB/c mice were immunized with the 2 ‐loaded virosomes.…”

Induction of Parasite Growth-Inhibitory Antibodies by a Virosomal Formulation of a Peptidomimetic of Loop I from Domain III of Plasmodium falciparum Apical Membrane Antigen 1

“…In an attempt to overcome both problems, we are evaluating the use of a human-compatible delivery system comprising IRIVs in synthetic peptide vaccine design (28,34). IRIVs are spherical, unilammelar vesicles prepared by detergent removal from a mixture of natural and synthetic phospholipids and influenza virus surface glycoproteins.…”

“…In the case of the IRIV-based hepatitis A vaccine Epaxal-Berna, which is the first licensed vaccine in which IRIVs are used as a delivery system for a non-influenza virus antigen, the hepatitis A virus antigen spontaneously binds to the IRIVs. For smaller synthetic antigens, we have developed and evaluated a method to link the antigenic molecule to a phospholipid (phosphatidylethanolamine) and to integrate the phosphatidylethanolamine-antigen conjugates into the virosomal membrane during the virosome reconstitution process (28,34). When we compared a virosome formulation loaded with a phosphatidylethanolamine conjugate of a cyclic peptide mimotope of the repeat region of the P. falciparum circumsporozoite protein with an alum-adjuvanted mimotope-multiple antigenic peptide construct, we found that both formulations elicited comparable levels of antimimotope antibody responses in mice.…”

“…However, only the antibodies against the virosomal formulation bind effectively to the parasites, indicating that phosphatidylethanolamine-coupled antigens are located in a more native-like state on the surface of the virosomes. Apparently, adsorption to alum dramatically disturbs the conformation of the mimetic (28).…”

Single-Dose Microparticle Delivery of a Malaria Transmission- Blocking Vaccine Elicits a Long-Lasting Functional Antibody Response

“…Although nano- and microparticle technology has been already shown to potentiate the immune response to pathogen-derived antigens [52, 53], including malaria [44, 45, 49, 54], its use in TBV delivery while previously postulated [9], remained relatively untested [44]. Our small scale study adds to the growing body of data, and moreover, successfully demonstrates that (1) APN1-BMPs with alum adjuvant elicit antigen-specific antibody titers after single dose immunization and induce the production of cell-activation rather than broad-spectrum pro-inflammatory cytokines; (2) the functional transmission-blocking activity of APN1 antisera against P. berghei from mice immunized with a single dose of APN1-BMP in An.…”

Synthesis, Solution Structure and Immune Recognition of an Epidermal Growth Factor‐Like Domain from Plasmodium falciparum Merozoite Surface Protein‐1

“…For preliminary immunological studies, the mimetic 2 was incorporated into virosomes by methods established earlier for short linear peptides and peptidomimetics 17–19. After one immunization with influenza antigens, BALB/c mice were immunized with the 2 ‐loaded virosomes.…”

Induction of Parasite Growth-Inhibitory Antibodies by a Virosomal Formulation of a Peptidomimetic of Loop I from Domain III of Plasmodium falciparum Apical Membrane Antigen 1

“…In an attempt to overcome both problems, we are evaluating the use of a human-compatible delivery system comprising IRIVs in synthetic peptide vaccine design (28,34). IRIVs are spherical, unilammelar vesicles prepared by detergent removal from a mixture of natural and synthetic phospholipids and influenza virus surface glycoproteins.…”

“…In the case of the IRIV-based hepatitis A vaccine Epaxal-Berna, which is the first licensed vaccine in which IRIVs are used as a delivery system for a non-influenza virus antigen, the hepatitis A virus antigen spontaneously binds to the IRIVs. For smaller synthetic antigens, we have developed and evaluated a method to link the antigenic molecule to a phospholipid (phosphatidylethanolamine) and to integrate the phosphatidylethanolamine-antigen conjugates into the virosomal membrane during the virosome reconstitution process (28,34). When we compared a virosome formulation loaded with a phosphatidylethanolamine conjugate of a cyclic peptide mimotope of the repeat region of the P. falciparum circumsporozoite protein with an alum-adjuvanted mimotope-multiple antigenic peptide construct, we found that both formulations elicited comparable levels of antimimotope antibody responses in mice.…”

“…However, only the antibodies against the virosomal formulation bind effectively to the parasites, indicating that phosphatidylethanolamine-coupled antigens are located in a more native-like state on the surface of the virosomes. Apparently, adsorption to alum dramatically disturbs the conformation of the mimetic (28).…”

Single-Dose Microparticle Delivery of a Malaria Transmission- Blocking Vaccine Elicits a Long-Lasting Functional Antibody Response

“…Although nano- and microparticle technology has been already shown to potentiate the immune response to pathogen-derived antigens [52, 53], including malaria [44, 45, 49, 54], its use in TBV delivery while previously postulated [9], remained relatively untested [44]. Our small scale study adds to the growing body of data, and moreover, successfully demonstrates that (1) APN1-BMPs with alum adjuvant elicit antigen-specific antibody titers after single dose immunization and induce the production of cell-activation rather than broad-spectrum pro-inflammatory cytokines; (2) the functional transmission-blocking activity of APN1 antisera against P. berghei from mice immunized with a single dose of APN1-BMP in An.…”

Synthesis, Solution Structure and Immune Recognition of an Epidermal Growth Factor‐Like Domain from Plasmodium falciparum Merozoite Surface Protein‐1

“…For preliminary immunological studies, the mimetic 2 was incorporated into virosomes by methods established earlier for short linear peptides and peptidomimetics 17–19. After one immunization with influenza antigens, BALB/c mice were immunized with the 2 ‐loaded virosomes.…”

Induction of Parasite Growth-Inhibitory Antibodies by a Virosomal Formulation of a Peptidomimetic of Loop I from Domain III of Plasmodium falciparum Apical Membrane Antigen 1

“…In an attempt to overcome both problems, we are evaluating the use of a human-compatible delivery system comprising IRIVs in synthetic peptide vaccine design (28,34). IRIVs are spherical, unilammelar vesicles prepared by detergent removal from a mixture of natural and synthetic phospholipids and influenza virus surface glycoproteins.…”

“…In the case of the IRIV-based hepatitis A vaccine Epaxal-Berna, which is the first licensed vaccine in which IRIVs are used as a delivery system for a non-influenza virus antigen, the hepatitis A virus antigen spontaneously binds to the IRIVs. For smaller synthetic antigens, we have developed and evaluated a method to link the antigenic molecule to a phospholipid (phosphatidylethanolamine) and to integrate the phosphatidylethanolamine-antigen conjugates into the virosomal membrane during the virosome reconstitution process (28,34). When we compared a virosome formulation loaded with a phosphatidylethanolamine conjugate of a cyclic peptide mimotope of the repeat region of the P. falciparum circumsporozoite protein with an alum-adjuvanted mimotope-multiple antigenic peptide construct, we found that both formulations elicited comparable levels of antimimotope antibody responses in mice.…”

“…However, only the antibodies against the virosomal formulation bind effectively to the parasites, indicating that phosphatidylethanolamine-coupled antigens are located in a more native-like state on the surface of the virosomes. Apparently, adsorption to alum dramatically disturbs the conformation of the mimetic (28).…”

Single-Dose Microparticle Delivery of a Malaria Transmission- Blocking Vaccine Elicits a Long-Lasting Functional Antibody Response

“…Although nano- and microparticle technology has been already shown to potentiate the immune response to pathogen-derived antigens [52, 53], including malaria [44, 45, 49, 54], its use in TBV delivery while previously postulated [9], remained relatively untested [44]. Our small scale study adds to the growing body of data, and moreover, successfully demonstrates that (1) APN1-BMPs with alum adjuvant elicit antigen-specific antibody titers after single dose immunization and induce the production of cell-activation rather than broad-spectrum pro-inflammatory cytokines; (2) the functional transmission-blocking activity of APN1 antisera against P. berghei from mice immunized with a single dose of APN1-BMP in An.…”