Co-Immunization with DNA Vaccines Expressing SABP1 and SAG1 Proteins Effectively Enhanced Mice Resistance to Toxoplasma gondii Acute Infection

Abstract

Toxoplasma gondii (T. gondii) has many intermediate hosts, obligately invades nucleated cells, and seriously threatens human and animal health due to a lack of effective drugs and vaccines. Sialic acid-binding protein 1 (SABP1) is a novel invasion-related protein that, like surface antigen 1 (SAG1), is found on the plasma membrane of T. gondii. To investigate the immunogenicity and protective efficacy of DNA vaccines expressing SABP1 and SAG1 proteins against T. gondii acute infection, the recombinant plasmids pVAX1-SABP1 and pVAX1-SAG1 were produced and administered intramuscularly in Balb/c mice. Serum antibody levels and subtypes, lymphocyte proliferation, and cytokines were used to assess immunized mice’s humoral and cellular immune responses. Furthermore, the ability of DNA vaccines to protect mice against T. gondii RH tachyzoites was tested. Immunized mice exhibited substantially higher IgG levels, with IgG2a titers higher than IgG1. When the immune group mice’s splenocytes were stimulated with T. gondii lysate antigen, Th1-type cytokines (IL-12p70, IFN-γ, and IL-2) and Th2-type cytokine (IL-4) increased significantly. The combined DNA vaccine significantly increased the immunized mouse survival compared to the control group, with an average death time extended by 4.33 ± 0.6 days (p < 0.0001). These findings show that DNA vaccines based on the SABP1 and SAG1 genes induced robust humoral and cellular immunity in mice, effectively protecting against acute toxoplasmosis and potentially serving as a viable option for vaccination to prevent T. gondii infection.

Boosting Mouse Defense against Lethal Toxoplasma gondii Infection with Full-Length and Soluble SAG1 Recombinant Protein

“…2022111001). T. gondii RH tachyzoites were cultured in Vero cells, and total RNA extraction, Toxoplasma lysate antigen (TLA) preparation, and a mouse challenge experiment were all performed using these tachyzoites as previously described [26].…”

“…As previously described, splenocyte suspensions were taken from three mice in each group two weeks after the last immunization [26]. This was performed using the following steps: pushing the spleens through a wire mesh, purifying the suspensions by eliminating the red blood cells (RBCs) using an erythrocyte lysis solution, and resuspending them in 1640 medium with 10% FBS.…”

“…The splenocytes were cultured in 96-well plates to conduct a lymphocyte proliferation experiment as previously described [26]. These cells were then stimulated with TLA at a 20 µg/mL concentration.…”

“…The proportions of CD4 + and CD8 + T lymphocytes were determined by flow cytometry as previously described [26]. Splenocyte suspensions taken from three mice used for the spleen lymphocyte proliferation assay were labeled with fluorescently labeled monoclonal antibodies (mAbs), including FITC-conjugated anti-mouse CD45, Brilliant Violet 510TMconjugated anti-mouse CD3, APC-Cy7-conjugated anti-mouse CD4, and PE-conjugated anti-mouse CD8a (BioLegend, San Diego, CA, USA) for 30 min in the absence of light.…”

Vaccine Development against Infectious Diseases: State of the Art, New Insights, and Future Directions

“…Regarding protozoan parasites, papers have focused on three globally prevalent parasites: Toxoplasma gondii, Leishmania spp., and Plasmodium spp. In the case of Toxoplasma gondii, co-immunization with DNA vaccines expressing the SABP1 and SAG1 proteins has demonstrated significant potential in enhancing mice's resistance to acute Toxoplasmosis, suggesting DNA vaccines' promise in combating this widespread parasite and protecting both humans and animals [3]. In Leishmania research, the identification of immunodominant proteins in Leishmania (Viannia) naiffi subproteome paves the way for creating a pan-specific vaccine against this debilitating [4].…”