Linear and multiple antigen peptides containing defined T and B epitopes of the Plasmodium yoelii circumsporozoite protein: antibody- mediated protection and boosting by sporozoite infection

Abstract

We previously reported the identification of a T cell epitope in the N-terminal part of the circumsporozoite protein (CSP) of Plasmodium yoelii yoelii (Pyy). CD4+ T cell clones derived from mice immunized with a 21-mer peptide (amino acids 59-79, referred to as Py1) containing this epitope confer complete protection after passive transfer in mice. These clones proliferate in vitro in the presence of a 13-mer peptide (amino acids 59-71, referred to as Py1T). This shorter peptide was found to behave as a Th epitope in vivo, allowing overcoming of the genetic restriction for production of anti-repeat antibodies in BALB/c mice, when cross-linked to three (QGPGAP) repeats of the Pyy CSP. In this study, we report protection in BALB/c mice, against a challenge with Pyy sporozoites after immunization with linear and multiple antigen peptides containing Py1T as T epitope and three repeats QGPGAP (Py3) as B epitope. Multiple antigen peptide (MAP4-Py1T-Py3)-induced immunity was shown to be more effective than immunity induced by the linear form of the conjugate (Py1T-Py3), protecting against challenges with higher numbers of sporozoites. In both cases, levels of anti-repeat antibodies were strongly correlated with anti-parasite antibodies and protection. When tested in vitro, sera from mice immunized with the protective constructs strongly inhibited Pyy liver stages, while lymph node T cells displayed no cytotoxicity. In vivo, depletion of CD4+ or CD8+ T cells did not affect protection. Furthermore, MAP4-Py1T-Py3-immunized mice were not protected against a challenge with P. yoelii nigeriensis sporozoites, a parasite which has the same Py1T sequence but differs from Pyy in its repeated sequence. These results demonstrate that anti-repeat antibodies raised by immunization with the linear or the MAP form are exclusively responsible for the protection. Furthermore, this antibody response is boosted by a sporozoite challenge, allowing protection against a second challenge.

Development of Peptide Mimotopes of Lipooligosaccharide from NontypeableHaemophilus influenzaeas Vaccine Candidates

“…To produce an experimental vaccine candidate for human use, these promising peptides need to be conjugated to clinically acceptable carriers, such as TT, and conventionally tested in animal models, such as in active protection models of mouse pulmonary clearance and chinchilla OM by systemic or mucosal administration. Meanwhile, these peptides can be rationally designed with multivalent LOS mimotopes, multiple Ag peptides, or to contain additional structures, including Th cell epitopes and built-in adjuvants (53)(54)(55)(56). These applications might further improve immunogenicity of these LOS mimotopes in vivo.…”

A Subdominant CD8+Cytotoxic T Lymphocyte (CTL) Epitope from thePlasmodium yoeliiCircumsporozoite Protein Induces CTLs That Eliminate Infected Hepatocytes from Culture

“…Indeed, a large panel of CD4 ϩ T-cell clones belonging to the TH1 and TH2 subsets were derived from BALB/c mice immunized with a peptide (PyCSP59-79) from this region (12,13,25,34). It has previously been shown, unequivocally, that these CD4 ϩ T-cell clones inhibit parasite development in vitro (5,18,26) and in vivo (34). However, none of the clones were shown to lyse target cells coated with the peptide (PyCSP59-79) in a CTL assay (25).…”

Antibodies against MAEBL Ligand Domains M1 and M2 Inhibit Sporozoite Development In Vitro

“…Rabbit antisera (at a 1:100 dilution) were tested in triplicate for inhibition of sporozoite penetration and development in primary hepatocyte cultures as previously described (13). Sporozoites were added to cultures with immune serum (prepared against M1, M2, and C-Cys) or with preimmune serum as a negative control at a concentration in serum of 1:100.…”

“…Therefore, rabbit antisera (1:100 dilution) were tested for the inhibition of sporozoite penetration and development in primary hepatocyte cultures as previously described (13). Antiserum to the M1 domain had the highest level of inhibition, reducing the number of developing liver-stage parasites by greater than 42% (Fig.…”