Background: Toxoplasma gondii, an obligate intracellular apicomplexan parasite, infects a wide range of warmblooded\r\nanimals including humans. T. gondii expresses five members of the C1 family of cysteine proteases,\r\nincluding cathepsin B-like (TgCPB) and cathepsin L-like (TgCPL) proteins. TgCPB is involved in ROP protein\r\nmaturation and parasite invasion, whereas TgCPL contributes to proteolytic maturation of proTgM2AP and\r\nproTgMIC3. TgCPL is also associated with the residual body in the parasitophorous vacuole after cell division has\r\noccurred. Both of these proteases are potential therapeutic targets in T. gondii. The aim of this study was to\r\ninvestigate TgCPB and TgCPL for their potential as DNA vaccines against T. gondii.\r\nMethods: Using bioinformatics approaches, we analyzed TgCPB and TgCPL proteins and identified several linear-B\r\ncell epitopes and potential Th-cell epitopes in them. Based on these results, we assembled two single-gene\r\nconstructs (TgCPB and TgCPL) and a multi-gene construct (pTgCPB/TgCPL) with which to immunize BALB/c mice\r\nand test their effectiveness as DNA vaccines.\r\nResults: TgCPB and TgCPL vaccines elicited strong humoral and cellular immune responses in mice, both of which\r\nwere Th-1 cell mediated. In addition, all of the vaccines protected the mice against infection with virulent T. gondii\r\nRH tachyzoites, with the multi-gene vaccine (pTgCPB/TgCPL) providing the highest level of protection.\r\nConclusions: T. gondii CPB and CPL proteases are strong candidates for development as novel DNA vaccines.
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