A single dose of plasmodium yoelii msp119 immunization formulated with montanide isa51 and cpg oligodeoxynucleotide is enough to induce protection against p. yoelii infection

Abstract

The carboxy-terminal 19kDa-fragment of merozoite surface protein 1 (MSP119), is highly conserved and effective in induction of protective immune response against malaria infection. Our previous studies in mice based on using complete/incomplete Freund’s adjuvant demonstrated that a four-dose immunization was able to induce complete protection. However, the kinetics of MSP119-specific antibody response induced by a single dose-immunization has not been investigated. In this study, we then singly immunized BALB/c mice subcutaneously with MPS119 in the mixture of Montanide ISA51 andCpG oligonucleotide (ODN) and monitored the antibody level. The MSP119-specific antibody reached maximum level by 28 days post immunization. At that day, the IgG or its isotype (IgG1 and IgG2a) levels were comparable to those of mice with four-dose immunization. However, the longevity of the IgG antibody response is shorter, of which the higher IgG1 level decreased rapidly while the lower IgG2a level still persisted 22 weeks of the study period. All immunized mice survived P.yoelii infection post challenge with little patent parasitemia occurring during the first 2 weeks and then being cleared. These findings suggest that one-dose immunization is enough to induce MSP119-specific immunity against parasite infection, and that leaving time longer than three weeks post the first immunization may be helpful in generating more complete memory response.