Immunization with plasmid DNA expressing Heat Shock Protein 40 confers prophylactic protection against chronicToxoplasma gondiiinfection in Kunming mice

Abstract

Toxoplasma gondii causes one of the most common protozoal diseases of humans and animals worldwide. With the aim of designing an effective vaccine against T. gondii infection, we examined the immunogenicity of a DNA vaccine expressing heat shock protein 40 (HSP40) against challenge with T. gondii (type I RH and type II Pru) strains in Kunming mice. The plasmid pVAX1-HSP40 was constructed and used to immunize mice by intramuscular injection for three sequential immunizations with two-week intervals. This immunization regimen significantly reduced parasite cyst burden in pVAX1-HSP40-immunized mice (1871.9 ± 142.3) compared with control mouse groups immunized with pVAX1 (3479.2 ± 204.4), phosphate buffered saline (3024.4 ± 212.8), or left untreated (3275.0 ± 179.8) as healthy controls (p < 0.01). However, immunization failed to protect mice against challenge with the virulent RH strain. There was a significant increase in T lymphocyte subclasses (CD3e+CD4+ T and CD3e+CD8a+ T lymphocytes) in splenic tissues in immunized mice compared with controls (p < 0.05). However, the level of antibodies, lymphocyte proliferation and concentration of cytokines (IFN-γ, IL-2, IL-4, IL-10 and IL-12p70) were not significantly different between immunized and control mouse groups (p < 0.05). These data indicate that pVAX1-HSP40 induced specific immune responses and achieved a significant reduction in the number of brain cysts in Pru-infected mice, and thus can be tested in future immunization studies along with plasmids containing other immunogenic proteins as a cocktail vaccine to fully abolish chronic toxoplasmosis.

Adjuvantic cytokine IL-33 improves the protective immunity of cocktailed DNA vaccine of ROP5 and ROP18 against toxoplasma gondii infection in mice

“…In particular, CD8+ T cells are specialized cytotoxic T lymphocyte cells that mediate lysis of T. gondii by the production of IFN-c or perforin-mediated cytolysis, in synergy with CD4+ T cells [7,9]. The data in the present study were consistent with some previous reports, underlying the protective effects of these vaccines [18,35,38], with the activated proliferative response of lymphocytes and significant increase in both CD8+ and CD4+ T cells in immunized mice. These high levels of CD4+ and CD8+ T cells further emphasized that type-Th1 immune response holds a dominant position in resistance against T. gondii infection followed by single-gene DNA immunization, which was also boosted by multiple-gene DNA immunization.…”

“…In the present study, significantly increased levels of IFN-c, IL-12p70, IL-23, and IL-2 were detected in all the groups of immunized mice, suggesting that Th1-type mediated immunity was elicited by these DNA candidate injections in mice successfully, which is essential for prolonged survival and reduced brain cysts in the immunized mice. Meanwhile, the combination with pVAX-ROP5 and pVAX-ROP18 boosted this Th1-type-mediated immunity in comparison with a single DNA immunization with pVAX-ROP5 or pVAX-ROP18, emphasizing that a multiple-gene DNA vaccine could elicit greater Th1-type immune responses than a single-gene DNA vaccine [18,40]. The most significantly improved Th1-biased responses, together with the best Th1-type immune responses and the ratio of IgG2a/IgG were also found in mice immunized with pVAX-ROP5 + pVAX-ROP18 supplemented with pVAX-IL-33, which is similar with the efficacy induced by certain other adjuvant cytokines [4,17].…”

Review of DNA Vaccine Approaches Against the Parasite Toxoplasma gondii

“…Heat shock proteins (HSPs) assist the cell with post-translational processes such as stabilization, folding, and translocation ( Li et al, 2018b ). HSPs tested as DNA vaccine candidates include HSP40 and HSP60.…”

Immunization of BALB/c Mice with Killed Tachyzoites of Toxoplasma gondii against Acute Toxoplasmosis

“…The grouped mice include: Group I without any treatment served as blank control; Group II injected with 100 μl of aluminum adjuvant alone named Al(OH) 3 ; Group III injected with 50 μl of aluminum adjuvant and 50 μl of SPSS containing equal formaldehyde-killed RH and GT1 tachyzoites (i.e., 1 × 10 5 parasites each) named RH&GT1+Al(OH) 3 . The spleen tissues of three mice each group were aseptically collected after blood collection prior to challenge ( Table 1 ), and were cut into pieces for the single splenocyte preparation described as previously ( 24 ).…”