Comparative Immunization Study Using RNA and DNA Constructs Encoding a Part of the Plasmodium falciparum Antigen Pf332

Abstract

Development of nucleic acid-based vaccines against parasitic diseases shows great promise, although certain concerns about safety aspects of conventional DNA vaccines have been raised. This study presents a comparison of antibody responses induced in mice by DNA and RNA-based immunization with vectors encoding a part of the P. falciparum antigen Pf332. Two types of plasmids were used, one conventional DNA plasmid containing a cytomegalovirus promoter and one suicidal DNA plasmid encoding the Semliki Forest virus (SFV) replicase. RNA, encoding the SFV replicase and the relevant antigen, was delivered either as naked RNA or packaged in SFV suicide particles. In general, the antibody responses induced by the DNA plasmids were low and peaking after three injections, the conventional plasmid giving the highest responses. Also the RNA delivered in SFV particles consistently induced antibody responses, although comparatively low. Analyses of the ratio of immunoglobulin (Ig)G1/IgG2a subclasses in the responses indicated that all plasmids resulted in a bias for a Th2-type of response, while the SFV-particles elicited a Th1 type of response. Importantly, all these immunogens induced an immunological memory, which could be efficiently activated by a booster injection with the corresponding protein, with unchanged patterns of IgG subclasses.

Extracellular mRNA Induces Dendritic Cell Activation by Stimulating Tumor Necrosis Factor-α Secretion and Signaling through a Nucleotide Receptor

“…DCs are also responsible for developing immune responses to altered self where antigen loading occurs through the endocytosis and processing of infected or transformed cells. The use of mRNA to load DC with antigen as a vaccine has been observed to be an efficient and potent method for loading antigen-processing pathways for CD4 ϩ T cells, CD8 ϩ T cells (24,25,(55)(56)(57)(58)(59)(60)(61)(62)(63)(64), and B cells 2 that exceeds those observed for DNA, viral, and protein immunization methods (52,(63)(64)(65)(66). A hypothesis, that RNA may be used physiologically to load DC with antigen and activate them to induce immune responses to intracellularly infected and transformed self cells, can be forwarded.…”

Venezuelan Equine Encephalitis Replicon Immunization Overcomes Intrinsic Tolerance and Elicits Effective Anti-tumor Immunity to the ‘Self’ tumor-associated antigen, neu in a Rat Mammary Tumor Model

“…Several strategies using vector systems derived from alpha viruses have been described, including viral replicon particles (VRPs) [17][18][19][20][21][22][23][24][25][26][27][28][29][30]. VRPs are single-cycle vectors containing RNA replicons with an engineered multiple cloning site in place of the viral structural protein genes.…”

An RNA Vaccine Based on Recombinant Semliki Forest Virus Particles Expressing the Cu,Zn Superoxide Dismutase Protein of Brucella abortus Induces Protective Immunity in BALB/c Mice

“…Three weeks after the last immunization, five mice from each group were sacrificed, and their spleens were removed under aseptic conditions. Single-cell suspensions were prepared from the spleens according to a standard procedure (37), and erythrocytes were eliminated with ACK lysis solution (150 mM NH 4 Cl, 1 mM KHCO 3 , 0.1 mM Na 2 EDTA [pH 7.3]). Splenocytes from all five mice of each group were first pooled and then cultured at 37°C with 5% CO 2 in a 96-well flat-bottom plate at a concentration of 4 ϫ 10 5 viable cells/well in the presence of no additives (unstimulated control) or one of the following different stimulants: 0.4 g of crude B. abortus RB51 proteins (CBPs), an extract obtained from bacteria subjected to treatment with a hypertonic salt solution and sonication as described previously (36) Cytotoxicity assay.…”

“…In the first strategy, the naked RNA replicon that is produced through in vitro transcription can be employed directly for immunization (11). However, the main disadvantage of this approach is the short intracellular half-life of RNA because of its degradation by ubiquitous RNases (4,49). In the second method, the RNA replicons are packaged into infectious vector particles by cotransfection of cultured cells (38).…”