Evaluation of Immune Responses in Mice after DNA Immunization with Putative Toxoplasma gondii Calcium-Dependent Protein Kinase 5

Abstract

dToxoplasma gondii can cause serious public health problems and economic losses worldwide. Calcium-dependent protein kinases (CDPKs) are key mediators of T. gondii signaling pathways and are implicated as important virulence factors. In the present study, we cloned a novel T. gondii CDPK gene, named TgCDPK5, and constructed the eukaryotic expression vector pVAX-CDPK5. Then, we evaluated the immune protection induced by pVAX-CDPK5 in Kunming mice. After injection of pVAX-CDPK5 intramuscularly, immune responses, determined with lymphoproliferative assays and cytokine and antibody measurements, were monitored, and mouse survival times and brain cyst formation were evaluated following challenges with the T. gondii RH strain (genotype I) and the PRU strain (genotype II). pVAX-CDPK5 effectively induced immune responses with increased specific antibodies, a predominance of IgG2a production, and a strong lymphocyte proliferative response. The levels of gamma interferon (IFN-␥), interleukin 2 (IL-2), and IL-12(p70) and the percentages of CD3 ؉ CD4 ؉ and CD3 ؉ CD8 ؉ cells in mice vaccinated with pVAX-CDPK5 were significantly increased. However, IL-4 and IL-10 were not produced in the vaccinated mice. These results demonstrate that pVAX-CDPK5 can elicit strong humoral and cellular Th1 immune responses. The survival time of immunized mice challenged with the T. gondii RH strain (8.67 ؎ 4.34 days) was slightly, but not significantly, longer than that in the control groups within 7 days (P > 0.05). The numbers of brain cysts in the mice in the pVAX-CDPK5 group were reduced by ϳ40% compared with those in the control groups (P < 0.05), which provides a foundation for the further development of effective subunit vaccines against T. gondii.

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.…”

Protective efficacy of two novel DNA vaccines expressingToxoplasma gondiirhomboid 4 and rhomboid 5 proteins against acute and chronic toxoplasmosis in mice

“…The obtained tachyzoites were also used for Toxoplasma lysate antigen (TLA) preparation according to our previous studies [12,20] and for total RNA extraction following the instruction of the RNAprep Pure Tissue Kit (TIANGEN, China).…”

Recent Advances in Toxoplasma gondii Immunotherapeutics

“…An analysis across T. gondii DNA vaccination studies reveals that the inducement of a Th1-type cellular immune response with significantly elevated levels of IFN-γ and IL-2 does not correlate with the degree of protective outcomes in mice. This means that the level of immunogenicity is not necessarily predictive of survival rates, as can be appreciated in several recent examples [ 33 , 34 , 35 , 36 ]. However, DNA vaccinations in general has shown to be effective at inducing the activation and proliferation of CD4 + and CD8 + T cells, along with eliciting specific antibodies essential for control of chronic infection.…”

“…Another subset of these DNA vaccine studies produced a significant increase in survival time (≥3 weeks) but no survivors following a lethal challenge, which was the ROP13, ROP16, ROP18, MIC13, and eIF4A [ 34 , 36 , 55 , 56 , 57 ]. There was a less significant survival outcome (≤2 weeks) from yet another subset of antigens, such as TgROM1, TgPLP1, TgCDPK3, and TgCDPK5 [ 33 , 58 , 59 , 60 ]. For effective comparisons, these recent studies in DNA vaccinations against toxoplasmosis are summarized in Table 2 .…”