Toxoplasma gondii ADSL Knockout Provides Excellent Immune Protection against a Variety of Strains

Abstract

Toxoplasma gondii is a protozoan parasite, occurring worldwide, endangers human health and causes enormous economic losses to the Ministry of Agriculture. A safe and effective vaccination is needed to handle these problems. In addition, ideal vaccine production is a challenge in the future. In this study, we knocked out the adenylosuccinate lyase (ADSL) gene and found that the gene reduces the growth rate of T. gondii tachyzoites in vitro under standard growth conditions by plaque or replication experiments. Furthermore, mice that were immunized with tachyzoites of the ME49ΔADSL strain induced 100% protection efficacy against challenge with the type 1 strain RH, type 2 strain ME49 and type 3 strain VEG. All mice that were immunized with ME49ΔADSL had a survival rate of 100% when they were reinfected with wild-type strains, either 30 days or 70 days after immunization, and immunization was also protective against homologous infection with 50 T. gondii ME49 tissue cysts. In addition, the level of Toxoplasma-specific IgG was significantly elevated at 30 and 70 days after immunization. ME49ΔADSL induced high levels of Th1 cytokines (interferon gamma (IFN-γ), interleukin (IL)-12) at 4 weeks after immunization and spleen cell cultures from mice vaccinated for 150 days were able to produce robust INF-γ and IL-12 levels in the supernatant. The results of the present study showed that ΔADSL vaccination induced a T. gondii-specific cellular immune response against further infections. These results suggest that the ADSL-deficient vaccine can induce anti-Toxoplasma gondii humoral and cellular immune responses and has 100% immune protection against post-challenge by the type 1 strain RH, type 2 strain ME49 and type 3 strain VEG. It will be used as an excellent candidate for live vaccines and may contribute in a positive meaning to control human toxoplasmosis.

Advances in Toxoplasma gondii Vaccines: Current Strategies and Challenges for Vaccine Development

“…Immunizing mice with the α-amylase knockout type II ME49 mutant invoked both cellular and humoral immune response and inhibited parasite proliferation [ 92 ]. Mice immunized with the adenylosuccinate lyase-deficient ME49 were protected upon a challenge infection with the type I RH, type II ME49, and type III VEG strains [ 93 ]. Genetically engineering T. gondii using the CRISPR-Cas9 system to construct a T. gondii RH strain with a defective novel putative transporter 1 conferred heterologous protection and ensured 100% survival following a challenge infection with RH, PYS, and PRU strains [ 94 ].…”

Single- and duplex TaqMan-quantitative PCR for determining the copy numbers of integrated selection markers during site-specific mutagenesis in Toxoplasma gondii by CRISPR-Cas9

“…For positive selection of T. gondii mutant or transgenic strains that have successfully integrated an exogenous DNA coding for a modified dihydrofolate reductase-thymidylate synthase (mDHFR-TS), pyrimethamine (Pyr) is the drug of choice [15][16][17][18][19], since mDHFR-TS confers resistance to Pyr [20]. In the genome of WT T. gondii, a single-copy gene coding for DHFR-TS (WT-DHFR-TS) is expressed, but the enzyme is sensitive to Pyr [21].…”

Genomic Medicine and Advances in Vaccine Technology and Development in the Developing and Developed World

“…Zhang et al conducted a study on mice, highlighting that Toxoplasma gondii tyrosine hydroxylase (TgTH) could be highly immunogenic and, thus, be an interesting target antigen for a vaccine [ 24 ]. Another possible candidate in the development of a T. gondii vaccine is a knock-out strand, without the adenylosuccinate lyase gene, which seems to offer wide protection and should be used in clinical trials in humans this year, as discussed by Wang et al [ 25 ]. Another pathogen that often goes undetected in healthy adults but can be dangerous during pregnancy is cytomegalovirus (CMV); at the moment, there only are vaccinations that offer partial protection, but research aiming at achieving full protection is ongoing.…”