Multistage Multiantigen Heterologous Prime Boost Vaccine forPlasmodium knowlesiMalaria Provides Partial Protection in Rhesus Macaques

Abstract

A nonhuman primate model for malaria vaccine development allowing reliable, stringent sporozoite challenge and evaluation of both cellular and antibody responses is needed. We therefore constructed a multicomponent, multistage DNA vaccine for the simian malaria species Plasmodium knowlesi including two preerythrocytic-stage antigens, the circumsporozoite protein (PkCSP) and sporozoite surface protein 2 (PkSSP2), and two blood stage antigens, apical merozoite antigen 1 (PkAMA1) and merozoite surface protein 1 (PkMSP1p42), as well as recombinant canarypox viruses encoding the four antigens (ALVAC-4). The DNA vaccine plasmids expressed the corresponding antigens in vitro and induced antiparasite antibodies in mice. Groups of four rhesus monkeys received three doses of a mixture of the four DNA vaccine plasmids and a plasmid encoding rhesus granulocyte-monocyte colony-stimulating factor, followed by boosting with a single dose of ALVAC-4. Three groups received the priming DNA doses by different routes, either by intramuscular needle injection, by intramuscular injection with a needleless injection device, the Biojector, or by a combination of intramuscular and intradermal routes by Biojector. Animals immunized by any route developed antibody responses against sporozoites and infected erythrocytes and against a recombinant PkCSP protein, as well as gamma interferon-secreting Tcell responses against peptides from PkCSP. Following challenge with 100 P. knowlesi sporozoites, 1 of 12 experimental monkeys was completely protected and the mean parasitemia in the remaining monkeys was significantly lower than that in 4 control monkeys. This model will be important in preclinical vaccine development.Malaria is a major cause of morbidity and mortality throughout tropical and subtropical regions of the world, accounting for an estimated 300 to 500 million infections and 1.5 to 3.0 million deaths annually (35). In the face of the spread of drugresistant malaria, efforts to develop an effective vaccine have become increasingly critical. Two observations suggest that a malaria vaccine may be achievable. First, immunization with radiation-attenuated sporozoites induces sterile protection in mice and humans (5, 17), mediated predominantly by CD8 ϩ T cells and gamma interferon (IFN-␥) and directed against the intrahepatocytic stage of the parasite. Second, adults in areas endemic for malaria develop partial clinical immunity, which is largely mediated by antibodies directed against blood stage antigens (23). A vaccine may need to induce both types of responses to provide optimal protection. DNA vaccines represent a flexible vaccine delivery system, capable of inducing both antibodies and cell-mediated immune responses to a wide variety of antigens. The flexibility of DNA vaccine technology permits the combination of multiple antigens from both the preerythrocytic and erythrocytic stages of the parasite. Previous studies from our laboratory have shown that DNA vaccines directed against either preerythrocytic-stage antigens (7, 26) or...

Effect on antibody and T-cell responses of mixing five GMP-produced DNA plasmids and administration with plasmid expressing GM-CSF

“…1 Because of their ease and simplicity of production, stability, and potential ease of combination, DNA vaccines have seemed to be an ideal method for establishing such immune responses. Our lab has systematically studied DNA malaria vaccines, either as single plasmids or as combinations in mice, 2-4 rabbits, 5 non-human primates, [6][7][8][9] and humans. [10][11][12] Additionally, we have also studied multiple methods to enhance the immunogenicity and protective efficacy of DNA vaccines in murine and non-human primate systems.…”

Prime-boost strategies for malaria vaccine development

“…Reproduced with permission from Schneider et al (1998). Prime-boost strategies for malaria vaccine development encoding two pre-erythrocytic antigens and two blood-stage antigens, with better protection obtained with a DNA/NYVAC regimen than a DNA/canarypox prime-boost regime (Rogers et al, 2001).…”

DNA Immunization with the Cysteine-Rich Interdomain Region 1 of the Plasmodium falciparum Variant Antigen Elicits Limited Cross-Reactive Antibody Responses

“…Immunization with naked DNA is possibly the only efficient way to accomplish such a task. Generation of a large number of immunogens (vectors) is relatively easy, and the method permits coinjection of many members of a variant gene family at the same time (14,15,27,38,39,43). A limited number of domains may be sufficient, as immunization with one domain appears to prime the immune response against other heterologous CIDR1 domains (3).…”