Evaluation of Protective Immune Response Induced by a DNA Vaccine Encoding GRA8 against Acute Toxoplasmosis in a Murine Model

Abstract

Toxoplasma gondii is an apicomplexan zoonotic protozoan parasite that infects most species of warm-blooded animals, including humans. The heavy incidence and severe or lethal damage caused by T. gondii infection clearly indicate a need for the development of an effective vaccine. T. gondii GRA8 is a member of the dense granules protein family and is used as a marker of acute infection. In the present study, we evaluated the protective immunity induced by DNA vaccination based on a recombinant eukaryotic plasmid, pDsRed2-GRA8, against acute toxoplasmosis in mice. BALB/c mice were intramuscularly immunized with the pDsRed2-GRA8 plasmid and then challenged by infection with the highly virulent GFP-RH strain of T. gondii. The specific immune responses and protective efficacy against T. gondii of this vaccine were analyzed by measuring cytokine and serum antibody titers, splenocyte proliferation assays, and the survival times of mice after challenge. Our results showed that mice immunized with pDsRed2-GRA8 demonstrated specific humoral and cellular responses, induced higher IgG antibody titers with predominant IgG2a production; increased levels of IL-10, IL-12 (p70), IFN-γ, TNF-α, and splenocyte proliferation; and prolonged survival times compared to those of control mice. The present study showed that DNA immunization with pDsRed2-GRA8 induced humoral and cellular immune responses, and all immunized mice showed greater Th1-type immune responses and longer survival times than those of control mice. These results indicated that T. gondii GRA8 DNA immunization induces a partial protective effect against acute toxoplasmosis.

Evaluation of anti‐tick efficiency in rabbits induced by DNA vaccines encoding Haemaphysalis longicornis lipocalin homologue

“…After muscle injection, ELISA showed that the antibody level of anti‐TsE in the serum of mice immunized with pcDNA3.1‐TsE was significantly higher than those in the pcDNA3.1 group (Zhang et al, 2020). Moreover, BALB/c mice inoculated with recombinant eukaryotic plasmids expressing Toxoplasma gondii dense granules (GRA8) had higher IgG antibody titers (Chu et al, 2018). Meanwhile, high antibody levels were detected in host induced by pcDNA3.1‐HlLIP in our study, which was in accordance with the humoral immune results of endoparasite DNA vaccine.…”

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

“…T. gondii tachyzoite actively invades nucleated cells of the host, and surface antigens, micronemal proteins, dense granule proteins, and rhoptry protein family proteins all play important roles in this process. Researchers have investigated various types of vaccines based on invasion and virulence-related proteins, such as SAG1, SAG2, and SAG3; MIC1, MIC2, MIC3, MIC5, MIC6, and MIC8; GRA1, GRA2, GRA4, GRA6, GRA7, GRA24, and GRA25; and ROP2, ROP8, ROP17, ROP18, and ROP35 [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Compared to other vaccines, DNA vaccines offer many benefits of low cost, safety, and ease of preservation, among other things [ 19 ].…”