Open Access Highly Accessed Research article

Toxoplasma gondii cathepsin proteases are undeveloped prominent vaccine antigens against toxoplasmosis

Guanghui Zhao1, Aihua Zhou2*, Gang Lv1, Min Meng1, Min Sun1, Yang Bai1, Yali Han1, Lin Wang1, Huaiyu Zhou1, Hua Cong1, Qunli Zhao1, Xing-Quan Zhu3 and Shenyi He1*

Author Affiliations

1 Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province 250012, P R China

2 Department of Pediatrics, Provincial Hospital Affiliated to Shandong University, Shandong University School of Medicine, Jinan, Shandong Province 250021, P R China

3 State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, CAAS, Lanzhou, Gansu Province, P. R. China

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BMC Infectious Diseases 2013, 13:207  doi:10.1186/1471-2334-13-207

Published: 7 May 2013



Toxoplasma gondii, an obligate intracellular apicomplexan parasite, infects a wide range of warm-blooded animals including humans. T. gondii expresses five members of the C1 family of cysteine proteases, including cathepsin B-like (TgCPB) and cathepsin L-like (TgCPL) proteins. TgCPB is involved in ROP protein maturation and parasite invasion, whereas TgCPL contributes to proteolytic maturation of proTgM2AP and proTgMIC3. TgCPL is also associated with the residual body in the parasitophorous vacuole after cell division has occurred. Both of these proteases are potential therapeutic targets in T. gondii. The aim of this study was to investigate TgCPB and TgCPL for their potential as DNA vaccines against T. gondii.


Using bioinformatics approaches, we analyzed TgCPB and TgCPL proteins and identified several linear-B cell epitopes and potential Th-cell epitopes in them. Based on these results, we assembled two single-gene constructs (TgCPB and TgCPL) and a multi-gene construct (pTgCPB/TgCPL) with which to immunize BALB/c mice and test their effectiveness as DNA vaccines.


TgCPB and TgCPL vaccines elicited strong humoral and cellular immune responses in mice, both of which were Th-1 cell mediated. In addition, all of the vaccines protected the mice against infection with virulent T. gondii RH tachyzoites, with the multi-gene vaccine (pTgCPB/TgCPL) providing the highest level of protection.


T. gondii CPB and CPL proteases are strong candidates for development as novel DNA vaccines.

Toxoplasma gondii; Cathepsin proteases; Bioinformatics; Vaccine; Toxoplasmosis