Low-level sequence variation in Toxoplasma gondii calcium-dependent protein kinases among different genotypes

The causative agent of toxoplasmosis, Toxoplasma gondii, can infect virtually all nucleated cell types of warm-blooded animals. In this study, we examined the sequence variation in calcium-dependent protein kinase 2 (CDPK2) genes among 13 T. gondii strains from different hosts and geographical locations. The results showed that the lengths of the complete CDPK2 DNA and cDNA sequences were 3671-3673 and 2136 bp, respectively, and the sequence variation was 0-0.9% among different T. gondii strains. Phylogenetic analysis based on the CDPK2 gene sequences revealed that T. gondii strains of the same genotypes were clustered in different clades. Further analysis of all the other T. gondii CDPK genes in genotype I (GT1), II (ME49), or III (VEG) strains indicated the T. gondii CDPK gene family is quite conserved, with sequence variation ranging from 0 to 1.40%. We concluded that CDPK2 as well as all the other CDPK genes in T. gondii cannot be used as proper markers for studying the variants of different T. gondii genotypes from different hosts and geographical locations, but their sequence conservation may be a useful feature promoting them as anti-T. gondii vaccine candidates in further studies.