Comparing the effect of IL-12 genetic adjuvant and alum non-genetic adjuvant on the efficiency of the cocktail DNA vaccine containing plasmids encoding SAG-1 and ROP-2 of Toxoplasma gondii

Abstract

Various methods are available for enhancing the potency of DNA vaccines, including employment of different forms of adjuvant. The current study was carried out to evaluate and compare the effects of genetic and non-genetic adjuvants on the immune response stimulated by DNA vaccine. Thus, two adjuvants, IL-12 (genetic adjuvant) and aluminum hydroxide (alum, non-genetic adjuvant), were used with cocktail DNA vaccine containing plasmids encoding complete rhoptry antigen 2 (ROP-2) and surface major antigen 1 (SAG-1) of Toxoplasma gondii. The efficacy of pcROP2+pcSAG1 in stimulation of the immune response against toxoplasmosis with and without adjuvant was evaluated in female BALB/c mice by measuring the level of total IgG antibody and cytokines. The results obtained indicated that after challenging the mice with the fatal RH strain of T. gondii, the survival rates of mice immunized with pcROP2+pcSAG1 (DNA cocktail), pcSAG1+pcROP2+alum, and pcSAG1+pcROP2+IL-12 were significantly greater than that of the control groups (p<0.05). Moreover, measurement of total IgG antibody indicated the significant difference between the control and experimental groups (p<0.05). Finally, the results obtained by measurement of cytokines (IFN-γ and IL-4) showed high levels of IFN-γ and low levels of IL-4 in groups vaccinated with pcROP2+pcSAG1 (DNA cocktail), pcSAG1+pcROP2+alum, and pcSAG1+pcROP2+IL-12 as the experiment groups, in comparison with the controls groups (PBS, pc-DNA3, alum+PBS, and pCAGGS-IL-12+pcDNA3). The results of the study showed that use of adjuvants (IL-12 and alum) coincident with DNA cocktail leads to significant change in the survival rates of the experiment groups in comparison with control groups. Also, there is no significant difference between adjuvants to induce immune responses.

DNA vaccination with a gene encoding Toxoplasma gondii Deoxyribose Phosphate Aldolase (TgDPA) induces partial protective immunity against lethal challenge in mice

“…In this investigation, our data demonstrated that both cell subtypes were significantly accumulated in response to immunization with TgDPA. This result corresponds with reports regarding immunological responses to T. gondii antigens [16, 68–72]. …”

Evaluation of the immune response in BALB/c mice induced by a novel DNA vaccine expressing GRA14 against Toxoplasma gondii

“…It is probably related with over stimulations of immune responses, caused by IL‐12. Additionally, in some of previous studies which used IL‐12 as an adjuvant, reported a lower immunogenicity …”

Partial Protective Effect of Intranasal Immunization with Recombinant Toxoplasma gondii Rhoptry Protein 17 against Toxoplasmosis in Mice

“…Currently, candidate vaccines that have been testing in mice are in the focus of protective antigen selections from membrane-associated surface antigens, excreted-secreted dense granule proteins, rhoptry proteins and micronemal proteins [6]–[8]. Of interests, rhoptry proteins (ROPs) excreted by rhoptries of the apical secretory organelles are involved in parasitic invasion [9].…”