Dodoo, D

Dodoo, D., T. occurred regardless of whether improving of the anti-MSP119 response was observed. Improving of anti-MSP119 did not appear to be due to contaminating endotoxin in the EcMSP4/5 material since enhanced protection was observed in C3H/HeJ mice, which are endotoxin insensitive. Collectively, these experiments show that multiantigen combinations offer enhanced levels of protection against asexual stage contamination and suggest that combinations of MSP1, MSP4, and MSP5 should be evaluated further for use in humans. The development of an effective vaccine against contamination by malaria asexual stages faces numerous hurdles, CETP-IN-3 including antigenic diversity and antigenic variance on the part of the parasite, lack of a reliable delivery system, and potent adjuvants approved for clinical use, as well as difficulties with large-scale production of clinical-grade vaccine antigen (10). Despite the significant progress that has been made in the identification of vaccine candidates, an effective vaccine against human malaria has not yet been developed. Antigen selection and characterization has been hampered by the lack of a readily available challenge system for genes inserted into a highly attenuated vaccinia computer virus, and CDC/NIIMALVAC-1 (34), composed of a synthetic gene that encodes numerous B- and T-cell epitopes, as well as cytotoxic-T-lymphocyte epitopes derived from nine antigens. Another approach CETP-IN-3 to the multivalent vaccine is usually immunization with a combination of recombinant proteins. A combination of different recombinant malaria antigens has been tested in humans. The vaccine consisted of MSP1, MSP2, and RESA (19), and although antibodies were CETP-IN-3 induced against all three antigens, they did not have any significant effect on parasite growth after challenge compared to a placebo group. However, use of this combination in a field trial resulted in modest levels of protection (B. Genton, Proc unpublished data). Despite the screening of a number of multiple-component formulations, convincing proof of greater efficacy for such combinations versus single-antigen formulations is not available. We describe here immunization experiments with a combination of the defined merozoite surface protein 4/5 (MSP4/5) and MSP119. The results demonstrate that immunization CETP-IN-3 with a combination of recombinant MSP4/5 and MSP119 induces enhanced protection in mice compared to protection observed after immunization with a single antigen. The groups of mice immunized with both antigens showed higher survival rates and significantly lower peak parasitemias compared to mice immunized with either of the two antigens alone. Patent parasitemia could not be detected in the majority of animals vaccinated with a combination of antigens, and the same end result was obtained in mice with different genetic backgrounds. MATERIALS AND METHODS Parasites and animals. YM parasites were kindly supplied by Michael F. Good (Queensland Institute of Medical Research, Brisbane, Queensland, Australia). Female BALB/c and C3H/HeJ mice, aged 6 to 8 8 weeks, were purchased from your Central Animal Services (Monash University or college, Melbourne, Victoria, Australia). Recombinant proteins, expression, and purification. The full-length PyMSP4/5 sequence lacking the predicted signal peptide and glycosylphosphatidylinositol (GPI) anchor, was expressed as a His6-tagged recombinant protein (EcMSP4/5) and purified on Talon metal affinity resin (Clontech, Palo Alto, Calif.) as explained previously (14). The full-length yMSP4/5 (lacking signal sequence and GPI attachment site) and yMSP119 were expressed in as explained previously (13). Vaccination and challenge contamination. Groups of female BALB/c or C3H/HeJ mice were immunized with either 25 or 30 g of various recombinant proteins emulsified in total Freund adjuvant CETP-IN-3 (Difco Laboratories, Detroit, Mich.) administered intraperitoneally (i.p.). Recombinant proteins for combination immunization were mixed in answer prior to coformulation in adjuvant. Two subsequent boosters of antigen emulsified in incomplete Freund adjuvant (Difco Laboratories) were delivered i.p. at monthly intervals. Control mice were injected with phosphate-buffered saline emulsified in the appropriate Freund adjuvant. Sera were collected prior to the initial injection and 2 days before challenge. At 12 to 14 days after the second booster, mice were challenged i.p..