Abstract
BackgroundImmunization with the spike protein (S) of severe acute respiratory syndrome (SARS)-coronavirus (CoV) in mice is known to produce neutralizing antibodies and to prevent the infection caused by SARS-CoV. Polyethylenimine 25K (PEI) is a cationic polymer which effectively delivers the plasmid DNA.ResultsIn the present study, the immune responses of BALB/c mice immunized via intranasal (i.n.) route with SARS DNA vaccine (pci-S) in a PEI/pci-S complex form have been examined. The size of the PEI/pci-S nanoparticles appeared to be around 194.7 ± 99.3 nm, and the expression of the S mRNA and protein was confirmed in vitro. The mice immunized with i.n. PEI/pci-S nanoparticles produced significantly (P < 0.05) higher S-specific IgG1 in the sera and mucosal secretory IgA in the lung wash than those in mice treated with pci-S alone. Compared to those in mice challenged with pci-S alone, the number of B220+ cells found in PEI/pci-S vaccinated mice was elevated. Co-stimulatory molecules (CD80 and CD86) and class II major histocompatibility complex molecules (I-Ad) were increased on CD11c+ dendritic cells in cervical lymph node from the mice after PEI/pci-S vaccination. The percentage of IFN-γ-, TNF-α- and IL-2-producing cells were higher in PEI/pci-S vaccinated mice than in control mice.ConclusionThese results showed that intranasal immunization with PEI/pci-S nanoparticles induce antigen specific humoral and cellular immune responses.
Highlights
Immunization with the spike protein (S) of severe acute respiratory syndrome (SARS)-coronavirus (CoV) in mice is known to produce neutralizing antibodies and to prevent the infection caused by SARS-CoV
Characterization of Polyethylenimine 25K (PEI)/SARS DNA Vaccine (pci-S) complexes It is well known that transfection efficiency of gene carrier depends upon its ability to condense DNA into nano-sized particles [13]
The formation of PEI/pci-S nanoparticles was further confirmed by morphology observation
Summary
Characterization of PEI/pci-S complexes It is well known that transfection efficiency of gene carrier depends upon its ability to condense DNA into nano-sized particles [13]. SARS S-specific IgG1 antibody was significantly (P < 0.01) increased in mice immunized with SARS-CoV S DNA vaccine plus PEI whereas little increase was observed on SARS-specific IgG2a antibody production (Figure 2A), indicating Th2 dominant response. The result showed that SARS S-specific IgA antibody response was significantly (P < 0.01) increased in lung wash from mice immunized with PEI/pci-S complexes (Figure 2B). The surface expression of CD80 and CD86 co-stimulatory molecules were significantly (P < 0.05) higher on DCs from mice treated with PEI/pci-S complexes than those from SARS-CoV DNA S vaccine alone (Figure 3). Re-stimulation with SARS-CoV S peptide induced the activation of cytokineproducing CD4+ and CD8+ T cells with a predominant production of TNF-a as well as TNF-a and IL-2 double cytokine-producing T cells in mice immunized with PEI/pci-S complexes (Figure 4A and 4B). It is to note that IL4-producing cells were detectable neither in the lung nor spleen (data not shown)
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