Calcium-dependent protein kinases are potential targets for Toxoplasma gondii vaccine

Abstract

Toxoplasma gondii belongs to the Apicomplexa phylum that caused a widespread zoonotic infection in wide range of intermediate hosts. Over one-third of the world's population are latently infected with T. gondii and carry it. The complex life cycle of T. gondii indicates the presence of a plurality of antigenic epitopes. During the recent years, continuous efforts of scientists have made precious advances to elucidate the different aspects of the cell and molecular biology of T. gondii. Despite of great progresses, the development of vaccine candidates for preventing of T. gondii infection in men and animals is still remains a challenge. The calcium-dependent protein kinases (CDPKs) belongs to the superfamily of kinases, which restricted to the apicomplexans, ciliates, and plants. It has been documented that they contribute several functions in the life cycle of T. gondii such as gliding motility, cell invasion, and egress as well as some other critical developmental processes. In current paper, we reviewed the recent progress concerning the development of CDPK-based vaccines against acute and chronic T. gondii.

Keywords: Adjuvant; Calcium-dependent protein kinase; Immunization; Toxoplasma gondii; Vaccines.

Fig. 1. The biologic stages and the main transmission routes of Toxoplasma gondii. The only known definitive hosts for T. gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat's feces (1). Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts (2). Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites (3). Cats become infected after consuming intermediate hosts harboring tissue cysts (4). Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment (5). Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts (6); consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) (7); blood transfusion or organ transplantation (8); transplacentally from mother to fetus (9). Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens (10). Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as polymerase chain reaction (11) Adapted from Centers for Disease Control and Prevention [20].