Protective immunity against Toxoplasma gondiiinduced by DNA immunization with the gene encoding a novel vaccine candidate: calcium-dependent protein kinase 3

Abstract

BackgroundToxoplasma gondii can infect almost all warm-blood animals including human beings. The plant-like calcium-dependent protein kinases (CDPKs) harbored by T. gondii are involved in gliding motility, cell invasion, egress and some other developmental processes, and so have been implicated as important virulence factors.MethodsIn the present study, we constructed a DNA vaccine expressing T. gondii CDPK3 (TgCDPK3) and evaluated its protective efficacy against T. gondii infection in Kunming mice. The gene sequence encoding TgCDPK3 was inserted into the eukaryotic expression vector pVAX I, and mice were immunized with pVAX-CDPK3 intramuscularly.ResultsThe results showed that mice immunized with pVAX-CDPK3 developed a high level of specific antibodies and a strong lymphoproliferative response. The significantly increased levels of IFN-γ, IL-2, IL-12 (p70) and IL-23 and high ratio of IgG2a to IgG1 antibody titers indicated that a Th1 type response was elicited after immunization with pVAX-CDPK3. Furthermore, the percentage of CD4+ T cells in mice vaccinated with pVAX-CDPK3 was significantly increased. After lethal challenge with the tachyzoites of the virulent T. gondii RH strain, the mice immunized with pVAX-CDPK3 prolonged the survival time from 10 days to 24 days (13.5 ± 4.89) compared to untreated mice or those received PBS or pVAX I which died within 7 days (P < 0.05). In chronic infection model (10 cysts of the T. gondii PRU strain), the numbers of brain cysts of the mice immunized with pVAX-CDPK3 reduced significantly when compared with those in control groups (P < 0.05), and the rate of reduction could reach to about 50%.ConclusionsTgCDPK3 can generate protective immunity against acute and chronic T. gondii infection in Kunming mice and is a promising vaccine candidate for further development of an effective vaccine against T. gondii.

The effect of chitosan nanospheres on the immunogenicity of Toxoplasma lysate vaccine in mice

“…In the chronic toxoplasmosis model, a statistically significant reduction in the tissue cyst count was found in both vaccinated subgroups. This is similar to the results of Zhang et al (2013) using gene encoding calcium dependent protein kinase 3 in mice immunization, Makino et al (2011) using Toxoplasma gondii heat shock protein 70 gene, Rabie et al (2003) using heat shock protein 70 gene, heat shock protein 30 and SAG genes and Angus et al (2000) using surface antigen incorporated within a plasmid vector in immunization of mice. On the other hand, a lower percentage of cyst reduction was reported by Martin et al (2004) using granular and rhoptery proteins in combination with alum as a vaccine adjuvant.…”

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

“…Our results showed that the level of anti-T. gondii IgG antibodies in mice immunized with pVAX-CDPK5 was statistically significantly elevated compared with levels in the three control groups. However, antibody titers in sera from the immunized mice, following three immunizations, were only twice as high as those in control mice, an antibody level which is much lower than those elicited by eukaryotic initiation factor 4A (eIF4A), rhoptry protein 18 (ROP18), microneme protein 6 (MIC6), and other T. gondii vaccine candidates (18,22,24,25,32,33). Because IgGdependent phagocytosis, cytotoxicity, or complement-mediated lysis effects are crucial mechanisms for resistance to tachyzoites (31), the relatively low antibody levels resulting from DNA immunization with pVAX-CDPK5 failed to prevent acute infection.…”

“…Our unpublished data and previous studies showed that both TgCDPK1 and TgCDPK3 (22) are promising vaccine candidates that can elicit protective immunity against acute and chronic T. gondii infection, but the immunogenicity of other CDPK members is not yet known.…”

“…In recent years, DNA vaccination has been demonstrated to elicit a predominantly Th1 immune response: inducing CD4 ϩ T-lymphocyte and CD8 ϩ cytotoxic T-lymphocyte (CTL) responses against the administered antigen (14, 16) and several T. gondii DNA vaccine candidates evaluated using this administration route (17,18,19,20,21,22) have shown effective protection against T. gondii infection. Also, DNA vaccines are promising tools in the development of safe and effective vaccines against T. gondii infection in both humans and animals (14), and thus it would be valuable to identify novel T. gondii antigens for use in DNA vaccination.…”

Low-level sequence variation in Toxoplasma gondii calcium-dependent protein kinases among different genotypes

“…In previous studies, TgCDPK1, TgCDPK3, and TgCDPK7 were shown to participate in parasite motility, such as host-cell invasion and egress, and parasite division and growth (Lourido et al, 2011(Lourido et al, , 2012McCoy et al, 2012;Morlon-Guyot et al, 2014). The important functions and the low variation of CDPKs in different T. gondii strains imply that they may be considered promising vaccine candidates, as the protective immunity induced by T. gondii CDPK3 revealed in our previous study showed the suitability of this protein family for development of new vaccines against T. gondii parasite infection (Zhang et al, 2013).…”